China piping solution supplier: | Email: sales@epowermetals.comTel: +8618267732328

Complete guidance for piping systems

What are piping systems

Piping systems are used to transport fluids or other fluids required for chemical processes between various equipment and end users and consist of various components, such as valves, fittings, in-line measuring instruments, etc., called “piping systems”.

20220518134730 66905 - Complete guidance for piping systems

Piping components of the pipeline system

Mechanical components suitable for connection or assembly into pressurized fluid piping systems. Components include pipes, fittings, flanges, gaskets, bolts, valves and devices such as expansion joints, flexible joints, pressure hoses, storage bends, filters, tandem sections of instruments and separators.

What are the major components in a piping system?

There are many different types of piping systems including:

  • Pipe – This is the primary component of a piping system. It is used to convey fluids through the system. Pipe can be made out of different metal materials like steel, copper, plastic or fiberglass depending on its application and environment conditions it will work under.
  • Pipe supports: The pipe supports must be strong enough to withstand the weight of the pipe and any pressure that will be placed on them. It is difficult to predict if a support will fail so it is necessary to have backup supports in place.
  • Flanges: Flanges are used to join two pieces of piping together. They may also be used as an outlet or inlet for equipment such as valves or pumps.
  • Valves: Valves regulate the flow of fluid through a system by opening and closing at predetermined points along the line. They can control pressure or flow rate within a system and prevent backflow into an area where it could cause damage or injury.
  • Pumps: Pumps move fluids through pipes under pressure from one location to another using mechanical means such as pistons or gears driven by electric motors or diesel engines.
  • Fittings – Fittings are used to connect pipes together at different angles or positions as well as for other applications like expansion joints, reducers/expanders etc. In some cases fittings may not be necessary but in most cases they are required for connecting pipes together. Some common types of fittings include elbows, tees, reducers/expanders etc.
  • Heating Systems: Heating systems can be used for heating water in order to provide hot water for domestic use or industrial processes.

Piping Components



    • Butt Welded
    • Screwed
    • Socked Welded





Special Fittings

What is a pipe?

A pipe or tube is hollow, longitudinal product. ’A tube’ is a general term used for hollow product having circular, elliptical or square cross section or for that matter cross section of any perimeter.
A pipe is tubular product of circular cross-section that has specific sizes and thickness governed by particular   dimentional standard.
Pipe can be classified based on method of manufacture or based on their applications.
Method of Manufacture
Seamless pipes are manufactured by drawing or extrusion process.
ERW pipes (Electric resistance welded pipes) are formed from a strip which is longitudinally welded along its length. Welding may be by electric resistance, high frequency, or induction welding. ERW pipes can also be drawn for obtaining required dimensions and tolerances.
Pipes in small quantities are manufactured by EFW (Electric fusion welding) Process where in instead of electric resistance welding, the longitudinal seam is welded by manual or automatic electric arc process.
There are spiral seam welded pipes, which are large dia pipes 500 NB and above. And pipes are made by welding a spiral seam produced by forming continues steel skelp in to circular shape.
Centrifugally cast pipes are made by spraying molten metal along a rotating die where the pipes are cast in shape due to centrifugal action.
Classification based on Applications
Pipes are classified as:

  • Pressure Pipes or Process pipes
  • Line Pipes
  • Structural Pipes

Pressure pipes are those which are subjected to fluid pressure and or temperatures. Fluid pressure in generally internal pressure due to fluid being conveyed or may be external pressure (i.e. jacketed piping) and are mainly used as plant piping.
Line pipes are mainly used for conveying of the fluid and are subjected to fluid pressure. These are generally not subjected to high temperatures.
Structural pipes are not used for conveying fluids and therefore not subjected to fluid pressures or temperatures. They are used as structural components (e.g. handrails, columns, sleeves etc) and are subjected to static load only.
Pipes Dimensional Standards (ASME B 36.10, ASME B 36.19)
Diameters: Pipes are designated by Nominal size, starting from 1/8” Nominal size, and increasing in step.

  1. Pipes sizes increases in steps of 1/8” to ½” =1/8”,1/4”,3/8”,1/2”, Nominal size.
  2. Sizes in step of ¼” = ½”,3/4”,1”,1 ¼”,1 ½”
  3. In step of ½” up to 4” = 1 ½”, 2”, 2 ½”, 3”, 3 ½”,4”.
  4. In step of 1” up to 6” = 4”,5”,6”.
  5. In step of 2” up to 36” = 6”,8”,10”.

For the Nominal sizes up to including 12”, there is one unique O.D. (Different from nominal size) and I.D. would very depending on schedule number, For Nominal size 14” and above O.D. is same as Nominal size.
SCHEDULE No. : Pipes are designated by schedule number or weight designation like Std. (S) Extra Strong (XS) and Double Extra Strong (XXS)
Pipe schedule no is define as:

  • SCH. NO. S = 1000P/S

In the formula:

  • P = Internal Pressure (PSI)
  • S = Allowable tensile strength of material

Common pipe schedules are Sch 40, Sch 80, Sch 120, Sch 160, for larger pipe sizes intermediate Such numbers (Sch 20,Sch 30 etc)are also employed.
For carbon steel, Pipe wall thickness tolerance is 12 ½ % i.e. Pipe wall thickness can vary 12 ½% from thickness obtained from dimension chart.
For Stainless steels Schedule numbers are designated by suffix ‘S’ i.e. 10S, 20S, 40S, 80S etc.
Length: Pipes are manufactured in Standard length of 6 Meters to 7 Meters for easy transport of pipes.

What are pipe fittings?

Pipe fittings are used to connect pipe and tubing used in plumbing and pipe fitting installations. Their working is done in the form of a simple union or connection between two pipes of different shapes or dimensions. They come in many varieties with different functions which include tees, elbows and couplings. Pipe fittings are often made from metal materials such as copper, stainless steel or malleable iron/black iron. The type of material affects the price of the fitting but does not affect its function. They are used in water supply and waste management systems, fuel lines and natural gas distribution systems in commercial, industrial, residential and institutional buildings.

A pipe fitting is defined as a part used in a piping system, for changing direction, branching or for change of pipe diameter, and which is mechanically joined to the system.
There are many different types of fittings and they are the same in all sizes and schedules as the pipe.
Fittings are divided into three groups:

  • Buttweld (BW) Fittings – Butt welded fittings are pieces of pipe that are joined together by heating the metal and melting a thin layer of both pieces, causing them to flow together. Whose dimensions, dimensional tolerances etc, are defined in the ASME B16.9 standards. 
  • Socket Weld (SW) Fittings – Socket Welded/Socked Welded Fittings: These fittings are not as common, but offer high durability and strength for applications where a lot of pressure is being applied. Class 3000, 6000, and 9000 are defined in the ASME B16.11 standards. 
  • Threaded (THD) Fittings – This type of fitting has internal threads designed to seal against each other in order to keep weight low. Class 2000, 3000, and 6000 are defined in the ASME B16.11 standards.

Most Used Buttweld Fittings

Buttweld fittings are the most commonly used type of piping fitting, used in plumbing and heating applications. Buttweld fittings come in a variety of styles, including straight, 45-degree elbows and 90-degree elbows, as well as tees and crosses. They are manufactured from stainless steel materials.

20220518223820 92858 - Complete guidance for piping systems

Application of butt-weld fittings

  • Piping systems using butt-welded fittings have many inherent advantages over other forms.
  • Welding the fitting to the pipe means it is permanently leak-proof.
  • The continuous metal structure formed between the pipe and the fitting adds strength to the system.
  • Smooth inner surfaces and gradual directional changes reduce pressure loss and turbulence and minimize the effects of corrosion and erosion.
  • Welded systems utilize minimal space.

Bevelled ends

All butt weld fittings have beveled ends, for austenitic stainless steels with wall thicknesses over 4 mm and ferritic stainless steels with wall thicknesses over 5 mm. the shape of the bevel depends on the actual wall thickness. These bevelled ends need to be able to be “butt welded”.

Typical bevel types

20220518224538 68126 - Complete guidance for piping systems

ASME B16. 25 covers the preparation of butt welding ends of piping components connected to the piping system by welding. It includes requirements for welding groove, requirements for external and internal shaping of thick wall parts, and preparation of internal ends (including dimensions and dimensional tolerances). These weld edge preparation requirements are also incorporated into ASME standards (e.g. b16.9, B16.5 and B16.34).

Materials and properties

The most commonly used metal materials in the production of accessories are carbon steel, stainless steel, cast iron, aluminum, copper, glass, rubber and various types of plastics.
In addition, for pipe fittings and pipes for specific purposes, sometimes a material layer with completely different quality from the pipe fitting itself is equipped inside, which is “lined pipe fittings”.
The material of the joint is basically determined when selecting the pipe. In most cases, the material of the joint is the same as that of the pipe.

Butt welded pipe fittings: 45 °, 90 ° and 180 ° LR / SR elbows

The function of the elbow is to change the direction or flow in the piping system. By default, there are five opportunities, 45 °, 90 °, and 180 °, all of which are “long radius” versions. In addition, 90 ° and 180 ° elbows are “short radius” versions.
Long radius and short radius
Elbows are divided into two groups, and the distance they change direction is defined; The center line of one end to the face of the other end. This is called the “center to face” distance, which is equivalent to the radius of the elbow.
Long “radius elbow center to face distance, abbreviated as LR, always” 1 ½ X nominal pipe size (NPS) (1) ½ D) “And” short “radius elbow center to face distance, abbreviated as Sr, or even nominal pipe size.
For example, below, you will find the center to face distance of four 2-inch elbows (the “a” distance in the picture).
20220518224900 91937 - Complete guidance for piping systems

  1. Elbow 90° – 2″ – LR : = 1½ x (25,4 x 2)A = 76.2 mm
  2. Elbow 180° – 2″ – LR : = 1½ x(25,4 x 2) x 2A= 152.4 mm
  3. Elbow 90° – 2″ – SR : = 1 x (25,4 x 2 )A = 50.8 mm
  4. Elbow 180° – 2″ – SR : = 1 x (25,4 x 2) x 2A = 101.6 mm

45 ° elbow
The function of 45 ° elbow is the same as that of 90 ° elbow, but the measurement of dimension is different from that of 90 ° elbow.
45 ° butt welding elbow
20220518225343 84682 - Complete guidance for piping systems

The radius of the 45 ° elbow is the same as that of the 90 ° LR (1 ½ D)。 However, the center to face dimension is not equivalent to the radius as the 90 ° LR elbow. This is the measurement from each face to the intersection perpendicular to each other’s centerline. The distance on the image is B. This is due to less bending. Short radius 45 ° elbows do not exist.
The most widely used are 90 ° long radius and 45 ° elbow, while 90 ° short radius elbow is applied when the space is too small. The function of 180 ° elbow is to change the flow direction through 180 °. The center to center dimensions of LR and SR are twice that of the matched 90 ° elbow. These accessories are generally used in furnaces or other heating or cooling devices.
Reduced elbow
In addition to the defined elbow, there is also a reducing elbow, which is an elbow with different diameters at both ends. Because this elbow is not a standard item for many suppliers, it may have high price and long delivery time. If circumstances permit, using “ordinary” elbow with separate reducer is an option.
Butt welding reducing elbow
20220518225558 69708 - Complete guidance for piping systems

Elbows of other degrees can be processed from standard elbows. Longer radius types, such as center to face dimensions three times the nominal size (3D), are also available.
The dimensions and dimensional tolerances of long radius and short radius elbows are specified in ASME B16 9.
Wall thickness elbow
The weakest point on the elbow is the inner radius. ASME B16. 9 only center to face dimensions and some “perpendicularity” dimensional tolerances are standardized. The wall thickness at the welding line position is even standardized, but not through other parts of the elbow. The standard stipulates that the minimum tolerance will be within 12.5% of the minimum ordered wall thickness of the pipe. The maximum tolerance is specified only at both ends of the joint.

Butt welded pipe fittings: straight tee and reducing tee

The main purpose of tee is to make a 90 ° branch on the main road of the pipeline.
There are two possibilities for standard tee: equal tee and reduced tee. Equal tee (or straight tee) is used for branch pipes with the same diameter as the pipe. Reducing tee is generally used when the diameter of branch pipe is smaller than that of pipe.

20220520134410 28435 - Complete guidance for piping systems

Both tees are butt welded tees

Dimensions and standards
If we talk about a three inch tee, we mean an equal tee (straight tee).
3″ × 2 “tee means a reducing tee. Although the formal reducing tee will be represented by three diameters, i.e. A – B – C, similar to the picture of reducing tee.
A “represents the nominal pipe diameter (NPS) of the water inlet;” B “represents the NPs of the outlet and C” represents the NPs of the branch.
Therefore, some reducing tees have a size of 3 inches, C size of 3 inches and B size of 2 inches. This is the saying of three diameters. In a certain order, it is of course very important. Today, such tees and anomalies are difficult to obtain. Before choosing one, use a straight tee 3 “and a concentric or eccentric reducer 3” x2 “to do the same thing.
Straight pipe butt welded tees are obtained for all existing pipe diameters.
Reducing butt welding tee is not the case because many sizes are not produced or cannot be produced.
For example, 6 inches × The 4-inch tee is a standard item, but 16 inches × A two inch TEE may be nowhere to be found. It is not economical to use a 16 inch tee to connect a 2-inch branch pipe; In this case, a branch connector or a branch connection is used.

  • Formula = (header size / 2) – (1)

example. Header size = 10 inches, 2 inches branch connection is required.

  • Formula = (10 “/ 2) – (1) = 4” (up to 4 “branch connections)

Note – the same applies to all joints
In addition to the tee defined, there are straight pipe and reducing tee, that is, tee with two outlets. We never use this tee in ordinary pipes.
At least not in the petroleum and chemical industry.
Equal butt welding cross tee
20220520211943 13570 - Complete guidance for piping systems
Wall thickness tee
In the tee, the crotch radius (T) varies from manufacturer to manufacturer, but some have established their own requirements, which is 1.3 times the wall thickness to maintain the crotch.
Tee “crotch”.
20220520212402 75133 - Complete guidance for piping systems

Wall thickness tee
ASME B16. 9-2003 Section 2.2 joint design theory.
…… It is expected that some parts of the formed pipe fitting may be thicker than the pipe wall used for the pipe fitting.

Butt welded pipe fittings: Reducer

Reducer is used to change one direction of pipe diameter.
The standard has two possibilities, concentric reducers, which are usually used for vertical pipes, and eccentric reducers for horizontal pipes.

20220520213416 91001 - Complete guidance for piping systems
The plane of eccentric reducer is downward and upward
On the contour line, on the horizontal line, the eccentric reducer must be declared, or on the flat side of the bottom or top, it must be assembled.

20220520213239 38910 - Complete guidance for piping systems
The flat edge of the eccentric reducer is downward
For instance:

  • 1. The eccentric reducer with flat edge downward is often used on the pipe rack to keep the pipe at the same height after the pipe size is changed. When concentric or flat head eccentric reducers are used on pipe supports, their support details may change.
  • 2. Plane eccentric reducer is often used in the suction pipeline of pump to avoid the accumulation of cavitation. Eccentric reducers can avoid small “dead spots” behind concentric reducers.

Butt weld joint. Cover or end cap

Basically, a cover will be applied to close the end of a pipe. As shown in the figure below, the cover can be used for all pipe sizes and sometimes for other purposes.
20220520213330 81152 - Complete guidance for piping systems

Standard end cap


A Stub End always will be used with a Lap Joint flange, as a backing flange; both are shown on the image below.
20220520213852 18716 - Complete guidance for piping systems
Stub End
20220520213926 76727 - Complete guidance for piping systems
With a Stub End and Lap Joint Flange
This flange connection are applied, in low-pressure and non critical applications, and is a cheap method of flanging.
In a stainless steel pipe system, for example, a carbon steel flange can be applied, because they are not come in contact with the product in the pipe.
Stub Ends are available in almost all pipe diameters. Dimensions and dimensional tolerances are defined in the ASME B.16.9 standard.
ASTM Grades
Dimensions, dimensional tolerances of wrought carbon and alloy steel fittings are defined in several ASME standards. The material qualities for these fittings are defined in the ASTM standards.
These ASTM standards, define the specific manufacturing process of the material and determine the exact chemical composition of pipes, fittings and flanges, through percentages of the permitted quantities of carbon, magnesium, nickel, et cetera, and are indicated by “Grade”.
For example, a buttweld carbon steel fitting can be identified with Grade WPA or WPB, a buttweld stainless-steel fitting with Grade WP304 or Grade WP321
Below you will find as an example a table with chemical requirements for fittings according to ASTM A403 Grade WP304, WP304L, WP316L and a table with frequent Grades, arranged on pipe and pipe-components, which belong together as a group.

  • As you may be have noted, in the table below, ASTM A105 has no Grade. Sometimes ASTM A105N is described;
  • “N” stands not for Grade, but for normalized. Normalizing is a type of heat treatment, applicable to ferrous metals only. The purpose of normalizing is to remove the internal stresses induced by heat treating, casting, forming et cetera.

Chemical requirements composition, %


Grade WP304

Grade WP304L (A)

Grade WP316L (A, B)

Carbon, max




Manganese, max




Phosphorus, max




Sulfur, max




Silicon, max














ASTM Grades




Flanges, fittings, Valves



A106 Gr A

A234 Gr WPA


A216 Gr WCB



A106 Gr B

A234 Gr WPB


A216 Gr WCB



A106 Gr C

A234 Gr WPC


A216 Gr WCB




A335 Gr P1

A234 Gr WP1

A182 Gr F1

A217 Gr WC1



A335 Gr P11

A234 Gr WP11

A182 Gr F11

A217 Gr WC6



A335 Gr P12

A234 Gr WP12

A182 Gr F12

A217 Gr WC6



A335 Gr P22

A234 Gr WP22

A182 Gr F22

A217 Gr WC9




A335 Gr P5

A234 Gr WP5

A182 Gr F5

A217 Gr C5


A335 Gr P9

A234 Gr WP9

A182 Gr F9

A217 Gr C12




A333 Gr 5

A420 Gr WPL6

A350 Gr LF2

A352 Gr LCB


A333 Gr 3

A420 Gr WPL3

A350 Gr LF3

A352 Gr LC3




 A312 Gr    TP304

A403 Gr WP304

A182 Gr F304

A182 Gr F304



 A312 Gr   TP316

A403 Gr WP316

A182 Gr F316

A182 Gr F316




A312 Gr TP321

A403 Gr WP321

A182 Gr F321

A182 Gr F321



A312 Gr TP347

A403 Gr WP347

A182 Gr F347

A182 Gr F347



  • A106 = This specification covers carbon steel pipe for high-temperature service. 
  • A335 = This specification covers seamless ferritic alloy-steel pipe for high-temperature service. 
  • A333 = This specification covers wall seamless and welded carbon and alloy steel pipe intended for use at low temperatures. 
  • A312 = Standard specification for seamless, straight-seam welded, and cold worked welded austenitic stainless steel pipe intended for high-temperature and general corrosive service. 


  • A234 = This specification covers wrought carbon steel and alloy steel fittings of seamless and welded construction. 
  • A420 = Standard specification for piping fittings of wrought carbon steel and alloy steel for low-temperature service. 
  • A403 = Standard specification for wrought austenitic stainless steel piping fittings. 


  • A105 = This specification covers standards for forged carbon steel piping components, that is, flanges, fittings, valves, and similar parts, for use in pressure systems at ambient and higher-temperature service conditions. 
  • A182 = This specification covers forged or rolled alloy and stainless steel pipe flanges, forged fittings, and valves and parts for high-temperature service. 
  • A350 = This specification covers several grades of carbon and low alloy steel forged or ring-rolled flanges, forged fittings and valves for low-temperature service. 


  • A216 = This specification covers carbon steel castings for valves, flanges, fittings, or other pressure-containing parts for high-temperature service and of quality suitable for assembly with other castings or wrought-steel parts by fusion welding. 
  • A217 = This specification covers steel castings, martensitic stainless steel and alloys steel castings for valves, flanges, fittings, and other pressure-containing parts intended primarily for high-temperature and corrosive service. 
  • A352 = This specification covers steel castings for valves, flanges, fittings, and other pressure-containing parts intended primarily for low-temperature service. 
  • A182 = This specification covers forged or rolled alloy and stainless steel pipe flanges, forged fittings, and valves and parts for high-temperature service.

Definition and details of threaded fittings

According to ASME B16 11 standard
Overview of threaded joints
Threaded joints may represent the oldest method of connecting piping systems.
Like socket welded joints, threaded joints are mainly used for small diameter (small diameter pipes); It is generally used for pipes with nominal diameter of NPS2 or less.
Threaded pipes are often used in low-cost, non critical applications such as domestic water, fire protection and industrial cooling water systems.
Threaded fittings are usually made of gray iron or malleable cast iron, cast brass or bronze, or forged alloy and carbon steel.
They have three pressure levels: 2000lbs, 3000lbs and 6000lbs.
Types of threaded fittings by grade and size


Class Designation





Elbows 45 and 90 degrees
Tees, Crosses, Coupling
Half-Coupling, Cap

1/2 – 4

1/2 – 2

1/2 – 2


1/2 – 4

1/2 – 2

1/2 – 2


1/2 – 4

1/2 – 2

1/2 – 2

Pipe Wall

SCH 80 and XS

SCH 160



1. Threaded Elbow 90° 
 20220520215348 73096 - Complete guidance for piping systems
This Elbow makes 90° changes of direction in the run of pipe.
2. Threaded Tee
20220520215600 60140 - Complete guidance for piping systems
This Tee makes 90° branch from the main run of pipe.   

3. Threaded Cross

20220520215740 11588 - Complete guidance for piping systems

Threaded Crosses makes 90° branch from the main run of pipe.

4. Threaded Elbow 45°

20220520215908 21832 - Complete guidance for piping systems

This Elbow makes 45° changes of direction in the run of pipe.

5. Threaded Full-Coupling

20220520220002 20693 - Complete guidance for piping systems

Termed Coupling, joins pipe two pipe or to a nipple etc.

6. Threaded Cap (End Cap)

20220520220216 99776 - Complete guidance for piping systems

Seals the threaded end of pipe.

7. Threaded Half-Coupling

20220520220319 31210 - Complete guidance for piping systems

The Half Coupling can be directly welded to  the run pipe, to make a branch connection.                
8. Threaded Square Head Plug
20220520220437 73738 - Complete guidance for piping systems
9. Threaded Hex Head Plug
20220520220638 17233 - Complete guidance for piping systems
10. Threaded Round Head Plug
20220520220714 59163 - Complete guidance for piping systems

11. Threaded Hex Head Bushing

20220520220759 64953 - Complete guidance for piping systems

Can be used to reduce a threaded fitting.

12. Threaded Union (MSS SP-83)

20220520220840 11786 - Complete guidance for piping systems

Unions are primarily used for maintenance and installation purposes.
It is a screwed joint design and it consists of three interconnected pieces: two internally threads and a centerpiece that draws the ends together when rotated. 

Advantages and disadvantages of threaded fittings


  • The installation efficiency is moderate, and the requirements for professional installation skills are not high.
  • The integrity of leakage is good for low-pressure and low-temperature installation without vibration.


  • Due to the difference in thermal expansion between pipes and fittings, rapid temperature changes may lead to leakage.
  • Due to the high stress strengthening effect caused by the sharp notch at the bottom of the thread, the vibration may lead to the fatigue failure of the threaded pipe joint.
  • Socket welding is not acceptable in piping systems involving nuclear or radioactive services, or in corrosion services with solutions that promote stress corrosion cracking or concentrate cells. In general, butt welds are required for all sizes of pipes, and the welds are completely penetrated into the interior of the pipe.
  • In hazardous piping systems, threaded connections should be avoided if possible. They are vulnerable to fatigue damage, especially when exposed threads are corroded.

Note: in the minimum size, the wall thickness lost during threaded connection is actually equivalent to about 55% of the original pipe wall.

Definition and details of socket welded fittings

According to ASME B16 11 standard
Overview of socket welded pipe fittings
Socket weld is a pipe connection detail in which the pipe is inserted into a recessed area of a valve, fitting, or flange.
Different from butt welded pipe parts, socket welded pipe parts are mainly used for small diameter (small diameter pipe); It is generally used for pipes with nominal diameter of NPS2 or less.
In order to connect the pipe with the pipe of valves and fittings or other parts, fillet seal welding shall be used. When high leakage integrity and high structural strength are important considerations in design, socket welding structure is a good choice.
Due to the use of fillet welds and abrupt joint geometry, the fatigue resistance is lower than that of butt welded structures, but it is still better than most mechanical connection methods.

Some details of socket welded pipe fittings

Socket welded pipe is a kind of high-pressure pipe fitting, which is used in various industrial processes.
They are used for pipelines transporting flammable, toxic or expensive materials without any leakage, and are used to transport 300 to 600 psi steam.
They are only used with ASME piping and have the same size range.
They are permanent fields for pipeline engineering and are designed to provide good flow characteristics.
They are produced in accordance with several ASTM standards and in accordance with ASME B16 11 standard manufacturing. B16. The standard covers the pressure temperature class, dimensions, tolerances, marking and material requirements for Forged Carbon and alloy steels. Acceptable material forms include forgings, bars, seamless pipes and seamless pipes, which meet the chemical composition, melting method and mechanical properties of accessories in ASTM A105, A182 or A350.
They have three pressure levels. 3000lbs, 6000lbs and 9000lbs.
Types of socket welded pipe fittings by grade, size and wall thickness


Class Designation


3000 Lbs

6000 Lbs

9000 Lbs

Elbows 45 and 90 degrees, Tees, Crosses, Couplings, Half-Couplings, End or Pipe Caps

½ – 4

½ – 2

½ – 2


½ – 4

½ – 2

½ – 2


½ – 4

½ – 2

½ – 2

Pipe Size

by Wall Thickness

SCH 80 & XS

SCH 160


Advantages and disadvantages of socket welded pipe fittings

It is not necessary to chamfer the pipe during welding preparation.
Temporary tack welding does not require alignment because, in principle, the joint ensures correct alignment.
The welding metal shall not penetrate into the hole of the pipe.
They can be used instead of threaded joints, so the risk of leakage is much smaller.
Radiography of diagonal welds is unrealistic, so correct assembly and welding are very important. Fillet welds can be inspected by surface inspection, magnetic particle (MP) or liquid penetrant (PT) inspection.
Since there are no strict matching requirements and the special processing of butt weld end preparation is eliminated, the construction cost is lower than that of butt weld.

20220520221519 23491 - Complete guidance for piping systems
The welder shall ensure that there is a 1 / 16 inch (1.6 mm) expansion gap between the pipe and the socket shoulder.
ASME B31. Paragraph 1. 127.3 welding preparation (E) socket welding assembly.
In the joint assembly before welding, the pipe or pipe shall be inserted into the socket to the maximum depth, and then extracted about 1 / 16 inch (1.6 mm) away from the contact between the pipe end and the socket shoulder.
Expansion gaps and internal gaps left in socket welding systems promote corrosion and make them less suitable for corrosive or radioactive applications, where solid accumulation at joints can lead to operation or maintenance problems. In general, butt welds are required for all sizes of pipes, and the welds are completely penetrated into the interior of the pipe.
For ultra-high hydrostatic pressure (UHP) applications in the food industry, socket welds are unacceptable because they do not allow complete penetration and leave overlaps and gaps that are difficult to clean, resulting in virtual leakage.
The purpose of setting bottom gap in socket welding is usually to reduce the residual stress at the root of the weld, because residual stress may occur during the solidification of weld metal and allow differential expansion of mating elements.


1. SW Full-Coupling
20220520221826 92484 - Complete guidance for piping systems
Termed Coupling, joins pipe two pipe or to a nipple etc
2. SW Half-Coupling
20220520221912 79652 - Complete guidance for piping systems
The Half Coupling can be directly welded to the run pipe, to make a branch connection.
3. SW Reducing Coupling
20220520221952 79449 - Complete guidance for piping systems
Joints two different outside iameters of pipe.
4. SW Reducer Insert
20220520222038 94743 - Complete guidance for piping systems
Socket Weld Reducer Inserts are manufactured to MSS SP-79.
They enable quick and economic combinations of pipeline reductions to be made using standard socket weld fittings. 
5. SW Union (MSS SP-83)
20220520222114 66922 - Complete guidance for piping systems
Unions are primarily used for maintenance and installation purposes.
It is a screwed joint design and it consists of three interconnected pieces: two internally threads and a centerpiece that draws the ends together
When rotated. Unions should be screwed tight before the ends are welded 
To minimize warping of the seats. 
6. SW Elbow 90°
20220520222153 90568 - Complete guidance for piping systems
This Elbow makes 90° changes of direction in the run of pipe.
7. SW Elbow 45°
20220520222234 14197 - Complete guidance for piping systems
This Elbow makes 45° changes of direction in the run of pipe.
8. SW Tee
20220520222311 39508 - Complete guidance for piping systems
This Tee makes 90° branch from the main run of pipe.
9. SW Cross
20220520222355 34436 - Complete guidance for piping systems
SW Crosses makes 90° branch from the main run of pipe.
10. SW Cap (End Cap)
20220520222437 33719 - Complete guidance for piping systems
Seals the end of pipe.

What is a flange?

Flange is a part connecting shaft to shaft, which is used for the connection between pipe ends; it is also used for the connection between two equipment, such as reducer flange, on the inlet and outlet of equipment. Flange connection or flange joint refers to the detachable connection with flange, gasket and bolt as a group of combined sealing structure. Pipeline flange refers to the flange used for piping in the pipeline device, and for equipment, it refers to the inlet and outlet flange of the equipment. There are holes in the flange, and the bolts make the two flanges tightly connected. The flange is sealed with gasket. Flange is divided into threaded connection (threaded connection) flange, welding flange and clamp flange. Flange is used in pairs, low-pressure pipeline can use screw flange, more than four kilograms of pressure use welding flange. Add gasket between two flange plates, and then fasten them with bolts. The flange thickness of different pressure is different, and they use different bolts.

Material of flanges

Stainless steel
A182 F44(UNS31254),1.4404,1.4307,1.4541,1.4571
Duplex & Super Duplex
A812 F51/UNS1803,F53/UNS32750,F55/UNS32760,1.4426,1.4410
Carbon steel
20#,A105,A350 LF1/LF2/LF3,MSS SP44 & A694 F42/46/52/60/65/70
Alloy steel
A182 F1/F5a/F9/F11/F12/F22/F91
Copper-Nickle Alloy,Titanium,Aluminum,Monel,lnconel,Hastelloy and other special material
Manufacturing standard of flanges:
GB/T9112-9124,GB/T13402,GB/T3406,HG/T20615-20623,HG/T20592-20605,JPI-7S-15,DIN,AWWAC207,API,ASME B16.5/B16.47/B16.36/B16.48,JIS2220/2238,EN1092-1

Pressure rate of flanges

Many of the flanges in each standard are divided into “pressure classes”, depending on the different rates of pressure that are able to endure. The most common flanges pressure classes are #150, #300, #600, #900, #1500, #2500 and #3000 according to ASME designation. To other standards, as DIN, pressure classes are defined by the acronym PN, as for example, PN10, PN16, PN20, PN25, PN40, PN50, PN100, PN150, PN250 or PN420. Flanges from different pressure classes are not usually interchangeable.

Types of flanges


stainless steel weld neck flange 300x244 1 - Complete guidance for piping systems .    weld neck flange - Complete guidance for piping systems

A welding neck flange (“WN”)features a long tapered hub that can be welded with a pipe.

Welding Neck Flanges are easy to recognize at the long tapered hub, that goes gradually over to the wall thickness from a pipe or fitting.

The long tapered hub provides an important reinforcement for use in several applications involving high pressure, sub-zero and / or elevated temperatures. The smooth transition from flange thickness to pipe or fitting wall thickness effected by the taper is extremely beneficial, under conditions of repeated bending, caused by line expansion or other variable forces.

These flanges are bored to match the inside diameter of the mating pipe or fitting so there will be no restriction of product flow. This prevents turbulence at the joint and reduces erosion. They also provide excellent stress distribution through the tapered hub and are easily radiographed for flaw detection.

This flange type will be welded to a pipe or fitting with a single full penetration, V weld (Buttweld).


long weld neck flange - Complete guidance for piping systems

Long weld neck flanges (“LWN”) are similar to weld neck flanges, with the exception that the neck (tapered hub) is extended and acts like a boring extension.

Long weld neck flanges are generally used on vessels, columns or barrels. These flange types are available also in the heavy barrel (HB) and equal barrel (E) types.


slip on flange - Complete guidance for piping systems     slip on flange - Complete guidance for piping systems

A slip-on flange is connected to the pipe or the fittings by two fillet welds, one executed inside and one outside the cavity of the flange.

The calculated strength from a Slip On flange under internal pressure is of the order of two-thirds that of Welding Neck flanges, and their life under fatigue is about one-third that of the latter.

The connection with the pipe is done with 2 fillet welds, as well at the outside as also at the inside of the flange.

The X measure on the image, are approximately:
Wall thickness of pipe + 3 mm.

This space is necessary, to do not damage the flange face, during the welding process.

A disadvantage of the flange is, that principle always firstly a pipe must be welded and then just a fitting. A combination of flange and elbow or flange and tee is not possible, because named fittings have not a straight end, that complete slid in the Slip On flange.


Flanged joints made with slip-on flanges are, in the long run, a bit more fragile than connections made with welding neck flanges (in similar service conditions). This seems due to the following facts:

  • a welding neck flange features a tapered hub, absent in a socket weld flange, which distributes the mechanical stress between the pipe and the flange more evenly
  • a welding neck joint as only one welding area instead of two (socket weld flange).

Another advantage of the welding neck flange is that it can be connected either to pipes and fittings, whereas socket weld flanges suit pipes only.


threaded flange - Complete guidance for piping systems      threaded flange - Complete guidance for piping systems

Threaded flanges are joined to pipes by screwing the pipe (which has a male thread, generally NPT per ASME B1.20.1) onto the flange, without seam welds (in certain cases, though, small welds are applied to increase the strength of the connection).

Threaded Flanges are used for special circumstances with their main advantage being that they can be attached to the pipe without welding. Sometimes a seal weld is also used in conjunction with the threaded connection.

Although still available in most sizes and pressure ratings, screwed fittings today are used almost exclusively in smaller pipe sizes.

A threaded flange or fitting is not suitable for a pipe system with thin wall thickness, because cutting thread on a pipe is not possible. Thus, thicker wall thickness must be chosen…what is thicker ?

ASME B31.3 Piping Guide says:
Where steel pipe is threaded and used for steam service above 250 psi or for water service above 100 psi with water temperatures above 220° F, the pipe shall be seamless and have a thickness at least equal to schedule 80 of ASME B36.10.


socket weld flange - Complete guidance for piping systems .        socket weld flange - Complete guidance for piping systems

Socket weld flanges are connected to pipes using a single fillet weld executed on the outer side of the flange (different from the slip-on flange type that requires two welds).

Socket Weld flanges were initially developed for use on small-size high pressure piping. Their static strength is equal to Slip On flanges, but their fatigue strength 50% greater than double-welded Slip On flanges.

The connection with the pipe is done with 1 fillet weld, at the outside of the flange. But before welding, a space must be created between flange or fitting and pipe.

ASME B31.1 1998 127.3 Preparation for Welding (E) Socket Weld Assembly says:
In assembly of the joint before welding, the pipe or tube shall be inserted into the socket to the maximum depth and then withdrawn approximately 1/16″ (1.6 mm) away from contact between the end of the pipe and the shoulder of the socket.

The purpose for the bottoming clearance in a Socket Weld is usually to reduce the residual stress at the root of the weld that could occur during solidification of the weld metal. The image shows you the X measure for the expansion gap.

The disadvantage of this flange is right the gap, that must be made. By corrosive products, and mainly in stainless steel pipe systems, the crack between pipe and flange can give corrosion problems. In some processes this flange is also not allowed. I am not an expert in this matter, but on the internet, you will find a lot of information about forms of corrosion.

Also for this flange counts, that principle always firstly a pipe must be welded and then just a fitting.


laop joint flange - Complete guidance for piping systems lapjoint and stub end - Complete guidance for piping systems

Lap joint flanges feature a flat face and are always used in conjunction with a stub end.

Lap Joint Flanges have all the same common dimensions as any other flange named on this page however it does not have a raised face, they used in conjunction with a “Lap Joint Stub End”.

These flanges are nearly identical to a Slip On flange with the exception of a radius at the intersection of the flange face and the bore to accommodate the flanged portion of the Stub End.

Their pressure-holding ability is little, if any, better than that of Slip On flanges and the fatigue life for the assembly is only one tenth that of Welding Neck flanges.

They may be used at all pressures and are available in a full size range. These flanges slip over the pipe, and are not welded or otherwise fastened to it. Bolting pressure is transmitted to the gasket by the pressure of the flange against the back of the pipe lap (Stub End).

Lap Joint flanges have certain special advantages:

  • Freedom to swivel around the pipe facilitates the lining up of opposing flange bolt holes.
  • Lack of contact with the fluid in the pipe often permits the use of inexpensive carbon steel flanges with corrosion resistant pipe.
  • In systems which erode or corrode quickly, the flanges may be salvaged for re-use.


blind flange - Complete guidance for piping systems

Contrary to all the flange types seen above, blind flanges do not have a center hole, and are used to blind or seal a pipeline, a valve/pressure vessel and block the flow of the fluid.

Blind Flanges are manufactured without a bore and used to blank off the ends of piping, Valves and pressure vessel openings.

From the standpoint of internal pressure and bolt loading, blind flanges, particularly in the larger sizes, are the most highly stressed flange types.

However, most of these stresses are bending types near the center, and since there is no standard inside diameter, these flanges are suitable for higher pressure temperature applications.



Nipoflange1 - Complete guidance for piping systems

A Nipoflange is used for branch pipelines at 90 degrees and is a product manufactured by combining a welding neck flange with a forged Nipolet.

However, a Nipoflange is a solid single piece of forged steel and not two different products welded together.

To install a Nipoflange, the piping staff has to weld the Nipolet part of the device on the run pipe and bolt the flanged part on the flange of the branched pipe.

Nipoflanges are available in different materials, such as carbon steel ASTM A105 (high-temperature service), ASTM A350 (low-temperature carbon steel), ASTM A182 (stainless steel grades, including duplex and super duplex) and nickel alloys (Inconel, Incoloy, Hastelloy, etc).

Nipoflanges are also manufactured in the reinforced variant, which has additional mechanical strength compared to a standard Nipoflange.


weldoflange2 - Complete guidance for piping systems

A Weldoflange is conceptually similar to a Nipoflange, as that they are a combination of a weld neck flange and a branch fitting connection (a Weldolet in this case). Weldoflanges are made out of a single piece of solid forged steel, not by welding separate parts together.


Other less common types of flange Olets is the so-called Elboflange (a combination of a flange and an Elbolet) and “Latroflange” (combination of a flange with a Latrolet). Elboflanges are used to branch a pipeline at 45 degrees.

elbowflange - Complete guidance for piping systems


Swivel ring flanges facilitate the alignment of the bolt holes between the two mating flanges, a feature that is helpful in many circumstances, such as the installation of large diameter pipelines, subsea and offshore pipelines, pipe works in shallow waters and similar environments.Swivel flanges suit oil, gas, hydrocarbons, water, chemical and other demanding fluids in petrochemical and water management applications.

In the case of a large diameter pipeline, for instance, the pipe is fitted, at one end, with a standard welding neck flange, and with a swivel flange at the other end: by simply rotating the swivel flange on the pipe, the operators can achieve a perfect alignment of the bolt holes in a way easier and faster way.

The major standards for swivel ring flanges are ASME/ANSI, DIN, BS, EN, ISO, etc. The most common standard for petrochemical application is the ANSI/ASME B16.5 or ASME B16.47.

Swivel flange - Complete guidance for piping systems

Swivel flanges are available in all the standard shapes of common flanges, i.e. weld-neck, slip-on, lap-joint, socket weld etc, in all material grades and in a wide dimensional range (sizes can vary from 3/8” to 60” and pressure rating from 150 to 2500).

Swivel flanges can be manufactured in carbon steel (ASTM A105), alloy steel (ASTM A182 F1, A182 F5, A182 F9, A182 F91), and, stainless steel (ASTM A182 F304, A182 F304L, A182 F316, A182 F316L).


expander flange - Complete guidance for piping systems

Expanding flanges, or “expander flanges”, are used to increase the bore of the pipeline from a specific point to another or to connect pipes to other mechanical devices such as pumps, compressors, and valves that have different inlets sizes.

The expanding flange represented in the picture is a welding neck flange with a larger bore on the non-flanged end.

Expanding flanges can be used to increase the run pipe bore only by one or maximum two sizes and not more (example: from 2 to 3 or maximum 4 inches).

Expander flanges are a cheaper (and lighter) solution compared to the combination of a buttweld reducer and a standard flange (which is the standard solution for pipe bore increases above 2 sizes).

The most common materials for expanding flanges are A105 (high-temp. carbon steel), A350 (LTCS) and ASTM A182 (stainless steel and above).
Pressure ratings and dimensions of expanding flanges are in accordance with the ANSI/ASME B16.5 specification and are available with raised or flat face (RF, FF).

expanding flange - Complete guidance for piping systems
The drawing of an ASME expanding flange.


reducer flange - Complete guidance for piping systems

Reducer flange

Reducing flanges, otherwise called reducer flanges, have an opposite function than expander flanges seen above, i.e. they are used to decrease the bore of a pipeline.

The bore of the run pipe can be safely reduced by only 1 or 2 sizes (otherwise a solution based on the combination of a butt weld reducer and a standard flange has to be used).

Reducing flanges are available in most sizes and material grades, and are not generally available from stock.

Reducing flanges follow the same considerations in terms of specifications, sizes and material grades as expander flanges.


Another important parameter to define a flange is the flange faces. Exist five principal types of flange faces who its possible to see below.

flanges product 3 en - Complete guidance for piping systems

  • Flat Face (FF): The Flat Face flange has a gasket surface in the same plane as the bolting circle face. Applications using flat face flanges are frequently those in which the mating flange or flanged fitting is made from a casting.
  • Raised Face (RF): The Raised Face flange is the most common type used in process plant applications, and is easily to identify. It is referred to as a raised face because the gasket surfaces are raised above the bolting circle face. This face type allows the use of a wide combination of gasket designs, including flat ring sheet types and metallic composites such as spiral wound and double jacketed types.
  • Ring-Type Joint (RTJ): They have grooves cut into their faces which steel ring gaskets. The flanges seal when tightened bolts compress the gasket between the flanges into the grooves, deforming the gasket to make a metal to metal seal.
  • Tongue-and-Groove (T&G): The Tongue and Groove faces of this flanges must be matched. One flange face has a raised ring (Tongue) machined onto the flange face while the mating flange has a matching depression (Groove) machined into it’s face.
  • Male-and-Female (M&F): With this type the flanges also must be matched. One flange face has an area that extends beyond the normal flange face (Male). The other flange or mating flange has a matching depression (Female) machined into it’s face.

Production process of flange

Flange production process is mainly divided into forging, casting, cutting, rolling these four.
(1). Cast flange and forged flange
The shape and size of the casting blank are accurate, the machining amount is small and the cost is low, but there are casting defects (porosity, crack and inclusion); the internal structure streamline of the casting is poor (if it is a cutting part, the streamline is worse);
Forged flange is generally lower carbon content than cast flange and is not easy to rust. The forging has good streamline, compact structure and better mechanical properties than cast flange;
If the forging process is not proper, there will be large or uneven grains, hardening cracks, and the forging cost is higher than that of casting flange.
Forgings can bear higher shear force and tensile force than castings.
The advantages of casting are that it can produce more complex shape and lower cost;
The forging has the advantages of uniform internal structure and no harmful defects such as pores and inclusions in the casting;
The difference between casting flange and forging flange is different from the production process. For example, centrifugal flange is one of the casting flange.
Centrifugal flange is a kind of flange produced by precision casting. Compared with ordinary sand casting, the structure of centrifugal flange is much finer and its quality is improved. It is not easy to have loose structure, porosity, sand hole and other problems.
First of all, we need to know how the centrifugal flange is produced. The process and products of centrifugal casting to make flat welding flange are characterized by the following process steps:

  • ① put the selected raw material steel into medium frequency electric furnace for smelting, so that the temperature of molten steel can reach 1600-1700 ℃;
  • ② preheat the metal mould to 800-900 ℃ and keep constant temperature;
  • ③ start the centrifuge, inject the steel water in step ① into the metal mold after preheating in step ②;
  • ④ the casting is naturally cooled to 800-900 ℃ and kept for 1-10 minutes;
  • ⑤ cool with water to near normal temperature, demould and take out the casting.

Let’s learn about the production process of forged flange:

flanges process 1 - Complete guidance for piping systems flanges process 6 - Complete guidance for piping systems
The forging process is generally composed of the following processes: blanking, heating, forming and cooling after forging. The forging process includes free forging, die forging and die forging. In production, different forging methods are selected according to the forging quality and production batch.
Free forging has low productivity and large machining allowance, but the tool is simple and versatile, so it is widely used to forge single piece and small batch forgings with simple shape. The free forging equipment includes air hammer, steam air hammer and hydraulic press, which are suitable for the production of small, medium and large forgings respectively. Die forging has the advantages of high productivity, simple operation, mechanization and automation. Die forgings have high dimensional accuracy, small machining allowance and more reasonable fiber structure distribution, which can further improve the service life of parts.
Basic process of free forging: during free forging, the shape of forgings is gradually forged into blanks through some basic deformation processes. The basic process of free forging includes upsetting, drawing, punching, bending and cutting.

  • 1. Upsetting and upsetting is the process of forging the original billet along the axial direction to reduce its height and increase its cross section. This process is often used to forge gear blanks and other disc forgings. Upsetting can be divided into full upsetting and partial upsetting.
  • 2. Drawing length is a forging process that increases the length of the blank and reduces the cross-section. It is usually used to produce shaft parts, such as lathe spindle, connecting rod, etc.
  • 3. Forging process of punching through hole or through hole on blank with punch.
  • 4. Forging process of bending the blank to a certain angle or shape.
  • 5. The forging process in which one part of the billet rotates at an angle to the other.
  • 6. Forging process of cutting split blank or cutting head.

(2). Die forging
Die forging is called model forging. The heated blank is placed in the forging die fixed on the die forging equipment for forging.

  • 1. Basic process of die forging process: blanking, heating, pre forging, final forging, punching and connecting skin, trimming, tempering and shot peening. Common processes include upsetting, drawing, bending, punching and forming.
  • 2. Common die forging equipment: die forging hammer, hot die forging press, flat forging machine, friction press, etc.
  • Generally speaking, the quality of forged flange is better. Generally, it is produced by die forging, with fine crystal structure, high strength and high price.

Both cast flange and forged flange are common manufacturing methods of flange. According to the strength requirements of components to be used, if the requirements are not high, turning flange can also be selected.
(3). Cutting flange
The inner and outer diameter and thickness of the flange are directly cut out on the middle plate, and then the bolt hole and water line are processed. The flange produced in this way is called cut flange. The maximum diameter of such flange is limited to the width of the middle plate.
(4). Rolled flange
The process of using the middle plate to cut the sliver and then roll it into a circle is called rolling, which is mostly used in the production of some large flanges. After coiling, welding, flattening and processing of waterline and bolt hole are carried out.

What is a valve?

valve is a device used in a fluid system to control the direction, pressure, and flow of a fluid. It is a device that allows a steel pipeline or a medium (liquid, gas, powder) to flow or stop and control its flow.

The valve is a control component in the fluid transmission pipeline system. It is used to change the passage section and the flow direction of the medium, and has the functions of diversion, cutoff, throttling, check, diversion or overflow relief. Valves for fluid control, from the simplest shut-off valves to the wide variety of valves used in extremely complex automatic control systems, the variety and specifications of the valve, the nominal diameter of the valve from a very small instrument valve to a diameter of up to 10m Valves for industrial piping. It can be used to control various types of fluids such as water, steam, oil, gas, mud, various corrosive media, liquid metal and radioactive fluid. The working pressure of the valve can be from 0.13MPa to 1000MPa. The working temperature can be C-270 ° C ultra-low temperature to 1430 ° C high temperature.
The valve can be controlled by various transmission methods, such as manual, electric, hydraulic, pneumatic, turbo, electromagnetic, electromagnetic hydraulic, electrohydraulic, gas-hydraulic, spur gear, bevel gear drive, etc.; can be under pressure, temperature Under the action of other forms of sensing signals, according to predetermined requirements, or simply open or close without relying on the sensing signal, the valve relies on a driving or automatic mechanism to cause the opening and closing member to be lifted, slid, swiveled or swiveled. Movement, thereby changing the size of its flow path area to achieve its control function.

Valve materials

Common materials of valves

  • 1. Gray cast iron: gray cast iron is suitable for water, steam, air, gas, oil and other media with nominal pressure PN ≤ 1.0MPa and temperature of – 10 ℃ ~ 200 ℃. Common grades of gray cast iron are: HT200, HT250, HT300 and ht350.
  • 2. Malleable cast iron: suitable for water, steam, air and oil media with nominal pressure PN ≤ 2.5MPa and temperature – 30 ~ 300 ℃. Common brands include kth300-06, kth330-08 and kth350-10.
  • 3. Ductile iron: suitable for water, steam, air, oil and other media with PN ≤ 4.0Mpa and temperature of – 30 ~ 350 ℃. Common brands are: QT400-15, QT450-10, QT500-7.
  • In view of the current domestic process level, the factories are uneven, and it is often difficult for users to test. According to experience, it is recommended that PN ≤ 2.5MPa, steel valve is still safe.
  • 4. Acid resistant high silicon ductile iron: suitable for corrosive media with nominal pressure PN ≤ 0.25MPa and temperature lower than 120 ℃.
  • 5. Carbon steel: suitable for water, steam, air, hydrogen, ammonia, nitrogen, petroleum products and other media with nominal pressure PN ≤ 32.0mpa and temperature – 30 ~ 425 ℃. Common brands include WC1, WCB, ZG25, high-quality steel 20, 25, 30 and Low-Alloy Structural Steel 16Mn.
  • 6. Copper alloy: suitable for water, seawater, oxygen, air, oil and other media with PN ≤ 2.5MPa and steam media with temperature of – 40 ~ 250 ℃. The common brands are zgnsn10zn2 (tin bronze), H62, HPb59-1 (brass), qaz19-2 and qa19-4 (aluminum bronze).
  • 7. High temperature copper: suitable for steam and petroleum products with nominal pressure PN ≤ 17.0mpa and temperature ≤ 570 ℃. Common brands include ZGCr5Mo, 1cr5m0.zg20crmov, zg15gr1mo1v, 12CrMoV, wc6 and wc9. The specific selection must be in accordance with the regulations of valve pressure and temperature specification.
  • 8. Low temperature steel: applicable to media with nominal pressure PN ≤ 6.4Mpa, temperature ≥ – 196 ℃ (such as ethylene, propylene, liquid natural gas, liquid nitrogen and other media, common brands include ZG1Cr18Ni9, 0Cr18Ni9, 1Cr18Ni9Ti and zg0cr18ni9)
  • 9. Stainless acid resistant steel: it is applicable to nitric acid, acetic acid and other media with nominal pressure PN ≤ 6.4Mpa and temperature ≤ 200 ℃. The common brands are zg0cr18ni9ti, zg0cr18ni10 < < resistance to nitric acid >, zg0cr18ni12mo2ti, zg1cr18ni12mo2ti < < resistance to acid and urea >
  • 10. In addition to the above metal valves, there are plastic valves and ceramic valves for special applications.

Types of valves

Ball Valve

Evolving from plug valves, ball valves are a kind of quarter-turn valves whose disc is ball shape. They are mainly used for blocking off, distributing and changing the direction of flow, of which, ball valves with V-type opening have a better flow rate moderating function.


  • The lowest flow resistance (zero).
  • Ball valves won’t get stuck during working even without lubricant, so they are reliable for controlling the flow of corrosive and low-boiling-point media.
  • Fully sealed ability under conditions with relatively high pressure and temperature.
  • Fast shut-off (speeds of some structures are merely 0.05-0.1s), no impact when automatic system operating.
  • The disc can automatically position on the margin.
  • When fully opening or closing, the sealing surfaces of the ball and valve body are separated with the medium, so the sealing surfaces won’t be eroded when the medium is speedily passing the valve.
  • Compact structure, lightweight – so it is considered as the most suitable valve for low-temperature system.
  • Symmetrical shape, especially welded body, being able to withstand the pressure from pipeline.
  • Disc can withstand high-pressure difference when closing.
  • Ball valves with all-welded valve body can directly be buried in the ground, and prevent the inner part of valves from being eroded. Ball valves, whose service life can reach to 30 years, are an ideal option for petroleum, natural gas pipelines.


The major material of the sealing ring of valve body is PTEF, which won’t have chemical reactions with almost all other materials. In addition, PTEF has characteristics such as small friction coefficient, stable performance, aging resistance, being able to withstand a wide range of temperature, excellent sealing performance. But, its physical properties, including large expansion coefficient, cold stream sensitivity, poor thermal conductivity, restrain the design of valve body. As the material of sealing ring hardens, its sealing ability weakens. Moreover, PTEF is unable to with high temperature and can’t be used in conditions with temperature higher than 180℃, otherwise the sealing part will deteriorate. 

Weak adjustment performance compared to globe valves, especially pneumatic or electric valves.

Under what circumstances are ball valves used?

Ball valves are used to prevent fluid circulation. A ball valve is a ball with a drilled hole, usually the same diameter as the pipe. It is a quarter turn valve, which has the advantage that it will not hinder the flow of fluid in the open position. When the hole diameter on the valve ball is the same as the pipe diameter, it is called “full flow” valve. In the closed position, this type of valve provides a good sealing system.
This valve is used for liquids (water, oil, etc.) and gases.
Some ball valves are also equipped with conical plugs.
Ball valves can also be used as three-way or four-way valves. In this case, they are also called sector valves.

Plug Valve

It is a rotary valve whose disc is plunger shape (cylindrical shape or conical shape), which can be rotated to control the flow of media. The working principle of plug valves is basically the same with that of ball valves, which evolves from plug valves and mainly used in oil field exploitation, and petrochemical field.

Relief Valve

It is a protective device for pressure vessel, equipment, or pipeline. When the pressure of equipment, vessel or pipeline exceeds the allowed value, the valve will automatically open and discharge media, so as to prevent the pressure continue to go up. If the pressure is lower than the allowed value, valve should close automatically and timely in order to guarantee safe operation of equipment, vessel or pipeline.

Steam trap valve

Media like vapor, compressed air will generate condensate water during transporting that needs to discharge in time for stabilizing the working efficiency and operation of devices.
Steam traps have the following functions:

  • To prevent vapor leakage
  • To discharge air, or other incondensable gases

Check Valve

Check valves, which are also known as non-return valves, one-way valves, reflux valves, can be divided into swing type and lift type. They are a kind of automatic valves that open and close by the force produced by the flow of media. The main function of check valves is to prevent media from flowing backward, pumps and drive motor from reversing, vessel media from venting. 

Gate Valve

It is a valve that vertically moves along the axis of tunnel, and is used for on/off control of the flow of medium rather than moderating flow rate. Gate valves are able to withstand high or low temperature or pressure and convey a wide range of media, but not including mud type media generally.


  • Small flow resistance force.
  • Small torque required for on/off control.
  • The direction of flow is not restricted – gate valves can be used in a bidirectional loop network.
  • The impact of erosion caused by media is less than that of globe valves when gate valves are fully open.
  • Simple structure, good manufacturability.
  • Short structural length.


  • Relatively large installation space – big external dimension, long open length required.
  • High-frequency rubbing during opening and closing; Scrapes may occur in high-temperature conditions.
  • Generally, gate valves have two sealing surfaces, which bring a little more difficulty to machining, grinding and maintenance.
  • Long on/off time.

Butterfly Valve

Butterfly valves are a kind of valves that block off or moderate the flow of medium by quarter-turning (the disc is rotated a quarter turn).


  • Simple structure, volume, lightweight, low material consumption.
  • Quick shut-off, small flow resistance.
  • Being able to be used in controlling the flow of media with suspended solid, or, according to the solidity of the sealing surface, powdery or granular media. Butterfly valves are suitable for blocking off and moderating flow (bi-direction) in ventilating and dedusting pipeline, as well as gas pipe, waterway in metallurgy industry, light industrial field, power plant, petrochemical system.


  • Small scope of flow moderating – 95% of flow won’t be blocked off even the valve is only open 30%.
  • Being unable to withstand pipeline system with high temperature and pressure due to the restriction of its structure and sealing surface materials (temperature ≤ 300℃, pressure ≤ PN40).
  • Poor sealability compared with ball valves, globe valves (So it can only be installed on places where require low sealabilty.)

Under what circumstances should Butterfly Valves be used?

Butterfly valve is mainly used to control the flow of fluid. Depending on the material of the valve, it can be used for different types of fluids: chemically neutral fluids, such as water or oil, sludge, food or drug fluids, and some butterfly valves can be specially used for corrosive fluids. However, butterfly valves cannot be used for fluids containing solid particles to avoid complete closure of the valve.
Butterfly valves are “quarter turn” valves. It needs to be rotated 90 ° between the open and closed positions to operate. For large diameters, a drive system equipped with a gearbox may be required to compensate for the pressure directly applied to the butterfly valve.
Butterfly valves are designed to ensure a good sealing system. Large diameter butterfly valves are usually flange mounted. For example, butterfly valves for heating circuits are usually screw in valves. Butterfly valve is usually the most space-saving, especially compared with ball valve.

Globe Valve

It is a valve whose disc moves along the center line of valve body. According to this kind of movement mode, the variation of the opening of valve body is proportional to disc travel. Besides, the fact that the valve stem of globe valve has a relatively short travel of opening and closing, its reliable blocking-off function, these three factors are why globe valves are a suitable option for flow moderating, blocking off, and throttling.


  • Wear resistance – small friction compared with gate valves during the processes of opening and closing.
  • Short open length (a quarter of the channel within the valve body).
  • Only one sealing surface, good manufacturability, easy maintenance.
  • High-temperature resistance – Globe valves’ packing materials are normally asbestos and graphite.


Because globe valves will change the flow direction of medium, their minimum flow resistance is higher than that of most other valves.

Under what circumstances are globe valves or piston valves used?

The working principle of stop valve and piston valve is the same. The end of the piston rod has a dished part or piston, which is lowered into the valve to prevent fluid flow. This valve is particularly suitable for regulating the fluid according to the pressure in the pipeline. Many stop valve actuators contain an adjusting spring that adjusts the opening of the valve according to the pressure.
The main disadvantage of this valve is the large head loss. In addition, when the fluid pressure is too high, it is difficult to operate the valve in the closed position. They can also close quickly, resulting in water hammer. This valve can also be used as a three-way valve.

Reducing Valve

Reducing valves are used for reducing the upstream pressure to the required downstream pressure and stabilizing the downstream pressure by consuming the energy of medium.

Under what circumstances should Needle Valves be used?

Needle valves are especially used to regulate low flow liquids or gases.
This is a small diameter valve designed for low pressure applications. It is often called “faucet”. Generally, it needs to be started manually. They are very common in home applications and fluid sampling operations. Needle valves are cheaper, which explains why they are so popular.
Important features:

  • Low flow;
  • It usually needs to be started manually;
  • Low cost.

Under what circumstances should Diaphragm Valves be used?

Diaphragm valves are mainly used for sanitary and aseptic processes, i.e. when the circulating fluid must be isolated from any potential contamination.
This valve mainly operates in open / closed mode, although in some cases it can be used for fluid regulation. In the open position, the diaphragm valve is called “full flow”, and there is little pressure drop because the closed diaphragm completely clears the fluid flow. This valve has a very good seal because there is no direct contact between the fluid and the valve stem, but they need regular maintenance to ensure that the diaphragm is in good condition, especially when the fluid contains solid particles. The diaphragm material is required to be able to fully adapt to the operating temperature and pressure conditions to avoid premature wear.
Diaphragm valves are mainly used in food and pharmaceutical industries. They are also often used in the chemical industry and ultrapure applications, depending on the materials they use, especially diaphragms. Diaphragm pumps are also suitable for sludge and highly viscous liquids.
This type of valve is not suitable for large diameter circuits: generally, their manufacturing width does not exceed DN350.
Important features:

  • Limited head loss;
  • Good sealing performance;
  • Application in food, medicine, chemical industry and other industries;
  • Compatible with fluids containing particles.


  • Regular maintenance is required;
  • Small nominal diameter.

When to use knife gate valve?

Knife gate valve is often used in mining, power plant, papermaking, chemical industry, food and other industries. Knife gate valves have the advantage of being very compact due to the linear movement of the closing baffle (the plate that prevents fluid flow in the closed position). Knife gate valve is mainly a stop valve, although it can also be used as a control valve when the valve is in the partially open position.
Knife gate valves can be used for fluids containing solid particles, such as wastewater or sludge. In general, knife gate valves are designed to be sealed on the upstream side of the circuit (fluid inlet side), but some valves are sealed on both sides. Therefore, knife gate valves can be used regardless of the fluid flow direction. In the open position, the head loss is very low because the valve will not cause a change in fluid direction.

However, closing and opening times can be long and regular maintenance is required to correct wear between the valve and the seal.

What is a multi-way valve?

Multi way valve refers to a valve with multiple inlets and / or outlets. The most common is a three-way valve, usually a ball valve. This valve is usually used to regulate the flow of fluid in equipment between two different circuits. It can also be used to mix two liquids. There are also four-way, five-way and six-way valves. Valves with more channels than these are very rare.


Valve installation requirements

  1. Before installing the valve, carefully check whether the model and specifications of the valve used are consistent with the design;
  2. According to the model of the valve and the factory manual, check whether the valve can be applied under the required conditions;
  3. When the valve is hoisted, the rope should be tied to the flange connection between the valve body and the valve cover, and should not be placed on the hand wheel or the valve stem to avoid damage to the valve stem and the hand wheel;
  4. When installing the valve on the horizontal pipe, the valve stem should be vertical upwards, and the valve stem should not be installed downward;
  5. When installing the valve, it is forbidden to use the forced-to-mouth connection method of pulling and pulling hard to avoid damage caused by uneven force;
  6. The open gate valve should not be installed in the wet place in the ground, so as to avoid valve stem corrosion.

Valve assembly requirements

The cleaned parts must be sealed and stored for installation.
The requirements for the installation process are as follows:

  1. The installation workshop must be clean, or set up a temporary clean area, such as the use of newly purchased color strips or plastic film to prevent dust from entering during the installation process.
  2. The assembly workers must be dressed in clean cotton overalls, wearing a cotton cap, hair can not leak, wear clean shoes, hand wearing plastic gloves, skim.
  3. The assembly tool must be degreased and cleaned before assembly to ensure cleanliness.

Valve specifications

  1. The model number of the valve should indicate the national standard number requirement. If it is an enterprise standard, the relevant description of the model number should be indicated.
  2. The working pressure of the valve requires ≥ the working pressure of the pipeline. Under the premise of not affecting the price, the working pressure of the valve should be greater than the actual working pressure of the pipeline.
  3. Valve manufacturing standards, should be based on the national standard number, if it is an enterprise standard, the procurement contract should be accompanied by corporate documents.

Valve performance testing requirements

  1. When a certain specification of a valve is manufactured in batches, an official agency shall be entrusted to carry out the following performance tests: 1 the opening and closing torque of the valve under the working pressure condition; 2 the detection of the flow resistance coefficient of the valve under the condition of pipeline water delivery.
  2. The valve should be tested before leaving the factory: 1 valve in the open condition, the valve body should withstand the internal pressure of the valve pressure value twice; 2 valve in the closed condition, the two sides respectively with 11 times the valve pressure Value, no leakage; but the metal-sealed butterfly valve, the leakage value is not greater than the relevant requirements.

Valve sealing requirements

The sealing performance of the valve refers to the ability of the sealing parts of the valve to prevent the leakage of the medium. It is the most important technical performance index of the valve. There are three sealing parts of the valve: the contact between the sealing surface of the opening and closing parts and the valve seat; the joint of the packing with the valve stem and the stuffing box; the connection between the valve body and the valve cover. The leak in the former place is called endoleak, which is commonly referred to as the lack of tightness, which will affect the ability of the valve to cut off the medium. For shut-off valves, internal leakage is not allowed. The latter two leaks are called leaks, that is, the medium leaks from the valve to the outside of the valve. External leakage can cause material loss, pollute the environment, and cause accidents in severe cases. For flammable, explosive, toxic or radioactive media, external leakage is not allowed, so the valve must have a reliable sealing performance.

Other requirements for valves

  1. The assembled valve is purged with nitrogen for at least 1 minute.
  2. The airtight test must be pure nitrogen.
  3. After the airtight test is passed, encapsulation is carried out, sealed with a clean polyethylene cap, and the polyethylene cap is soaked with an organic solvent before use and wiped clean.
  4. Then seal with a vacuum bag.
  5. Fnally packing.
  6. Measures should be taken during transportation to ensure that the envelope is not damaged.

The valve parts are few, the structure is simple, the precision is general, and it is a simple component in the mechanical industry, but the core sealing part of the valve is required to be particularly high. The valve manufacturing process is complicated and the technical difficulty is also great.

What process characteristics do we need to pay attention to?

1. Valve manufacturing materials

Due to the variety of valve specifications, such as general valves have gate valves, globe valves, check valves, ball valves, butterfly valves, hydraulic control valves; industrial valves have solenoid valves, regulating valves, pressure reducing valves, high temperature and high pressure valves, low temperature valves and other special valves They are used in various fields of the national economy, and their use occasions vary widely, such as high temperature and high pressure, low temperature cryogenic, flammable and explosive, highly toxic, strong corrosive medium and other working conditions, which imposes stringent requirements on the material of the valve.
In addition to cast iron, carbon steel and alloy structural steel, the valve manufacturing materials also use CrNi stainless steel, CrMoAl nitrided steel, CrMoV heat resistant steel, CrMnN acid resistant steel, precipitation hardened steel, duplex stainless steel, low temperature steel, titanium alloy and Mongolian. Nyle alloy, Inconel alloy, Hastelloy and G0CrW cemented carbide. The casting, welding and processing properties of these high-alloy materials are very poor, which brings great difficulty to the manufacturing process. In addition, most of these materials are high-alloy, high-strength, high-hardness precious materials, and there are many difficulties in material selection, preparation, and procurement. Some materials are difficult to purchase due to their small amount of use.

2. Structure of the cast blank

Most of the valve blanks are made of thin shell castings with complex structure, which not only requires good appearance quality, but also has dense internal quality and good metallographic structure. It cannot have defects such as pores, shrinkage holes, sand inclusions, cracks, etc. . Therefore, the casting process is complicated and the heat treatment technology is difficult. In the machinery industry, the casting of pressure-bearing thin-shell casting blanks of valves is much more complicated and difficult than castings of other mechanical components.

3. Mechanical processing technology

Because most of the high-strength, high-hardness, high-corrosion materials have poor cutting performance, such as high-alloy stainless steel and acid-resistant steel, they have the disadvantages of high toughness, high strength, poor heat dissipation, large chip viscosity and strong work hardening tendency. Difficult to achieve the required dimensional accuracy and finish, it presents certain difficulties for machined tools, processes and equipment. In addition, the valve sealing surface is also very high in machining accuracy, mating angle, smoothness and matching sealing pair, which brings great difficulty to machining.

4. Process arrangement of valve parts

The number of main parts of the valve is small, the structure is relatively simple, the processing precision of most sizes is not high, and the outside is rough, which gives the impression of being a simple machine. In fact, the heart seal of the valve can be extremely precise, the “three degrees” (flatness, smoothness, hardness) of the sealing surface is very high, and the sealing degree of the sealing faces composed of two sealing surfaces must reach zero to zero. To meet the zero leakage of the airtight test. This rough reference to ensure the precise zero-to-zero requirements of the heart is the biggest process difficulty in valve processing.

5. Valve test and inspection

The valve is an important opening and closing and regulating component of the pressure pipeline, and the working conditions of the pressure pipeline are different, high temperature and high pressure, low temperature cryogenic, flammable and explosive, highly toxic and strong corrosion. However, the test and inspection conditions for valve manufacturing are unlikely to meet the same requirements for working conditions. The international and domestic various valve test standards are tested under the condition of near normal temperature with gas or water as the medium. There is a fundamental hidden danger, that is, the valve products that have passed the normal factory test may have difficulty in meeting the requirements of use due to problems such as material selection, casting quality and sealing damage under severe actual working conditions. Quality accident. It is no wonder that some old valve experts who have worked for a lifetime are more and more cautious and more worried.

Manufacturing process of valves

The first step: valve body manufacturing

Valve body (casting, sealing surface surfacing)
Casting purchase (according to standard) into factory inspection (according to standard) ➱ surfacing welding ➱ ultrasonic flaw detection (according to the pattern) ➱ surfacing and post-weld heat treatment ➱ finishing ➱ grinding sealing surface ➱ sealing surface hardness test, coloring flaw detection.

The second step: the valve internals manufacturing process

A. Internal parts such as valve discs, valve seats, etc.

Purchasing raw materials (according to the standard), entering the factory inspection (according to the standard), making blanks (round steel or forgings, according to the technical requirements of the drawings), roughing the ultrasonic flaw detection surface (when the pattern is required), roughing the surfacing, welding, welding and welding Post-heat treatment ➱ Finishing of all parts ➱ grinding sealing surface ➱ sealing surface hardness test, coloring flaw detection.

B. Valve stem

Purchasing raw materials (according to standards), entering the factory inspection (according to the standard), making blanks (round steel or forgings, according to the technical requirements of the drawings), roughing, surfacing, welding, post-weld heat treatment, finishing, machining, grinding, grinding ➱ valve stem surface treatment (nitriding, quenching, electroless plating) ➱ final treatment (polishing, grinding, etc.) ➱ grinding sealing surface ➱ sealing surface hardness test, coloring flaw detection.

C. Do not need to weld the inner surface of the sealing surface, etc.

Purchasing raw materials (according to the standard), entering the factory inspection (according to the standard), making blanks (round steel or forgings, according to the technical requirements of the drawings), roughing the ultrasonic inspection surface (when the drawings are required), finishing the various parts.

The third step: fastener manufacturing

Fastener manufacturing standard DL439-1991.
Purchasing raw materials (according to standards), entering the factory inspection (according to the standard), making blanks (round steel or forgings, according to the technical requirements of the drawings) and sampling for necessary inspection, roughing, finishing, and spectral inspection.

The fourth step: final assembly

After receiving parts, cleaning, cleaning, rough assembly (according to the drawings), water pressure test (according to drawings, processes), after passing, disassembling, wiping, final assembly, and electrical installation or actuator debugging (for electric valves) The package is shipped.
1504662865119111 - Complete guidance for piping systems
Valve product production and inspection flow chart

Step 5: Valve product production and inspection process

  1. The company purchases raw materials of various specifications.
  2. The material is tested by a spectrum analyzer, and the raw material material test report is printed for backup.
  3. Raw material cutting with a cutting machine.
  4. The inspector checks the diameter and length of the raw material cut.
  5. The forging workshop processes the raw materials by forging.
  6. The inspector performs various dimensional inspections of the blank for forming.
  7. The worker is cutting the waste edge.
  8. The sand blaster sandblasts the surface of the blank.
  9. The inspector performs surface treatment inspection after sandblasting.
  10. Workers carry out rough machining.
  11. Valve body sealing thread processing—Employees are inspected after processing by the inspection and inspection personnel.
  12. The valve body is connected to the thread for machining.
  13. Middle hole machining.
  14. The inspector conducts a general inspection.
  15. Qualified semi-finished products are sent to the semi-finished warehouse.
  16. Semi-finished products are plated.
  17. Semi-finished plating surface treatment inspection.
  18. Inspection of various accessories (ball, valve stem, sealed seat).
  19. Product assembly in the assembly shop—assembly line inspection personnel inspect the product.
  20. The assembled product is subjected to pressure testing and drying to the next process.
  21. The assembly shop is responsible for product packaging—-packaging line inspection personnel to check the sealing, appearance and torque of the product. Unqualified products must never be packaged.
  22. Qualified products are packaged and sent to the finished product warehouse.
  23. All inspection records will be stored in the computer for easy access.
  24. Qualified products are sent to and from the country through containers.

Valve cleaning step

Valve components must be processed through the following processes before assembly:

  1. According to the processing requirements, some parts need to be polished, and the surface cannot be processed with burrs;
  2. All parts are degreased;
  3. After the degreasing is completed, the acid washing passivation is carried out, and the cleaning agent does not contain phosphorus;
  4. After pickling and purification, rinse with pure water, there can be no drug residue, carbon steel parts save this step;
  5. Dry the parts one by one with a non-woven fabric, and do not leave the surface of the parts such as wire wool, or blow dry with clean nitrogen;
  6. Use a non-woven fabric or a precision filter paper to analyze the pure alcohol and wipe each component one by one until there is no dirty color.

Daily maintenance of valves

  1. The valve storage environment should be noted. It should be stored in a dry and ventilated room and block both ends of the passage.
  2. The valve should be regularly inspected, and remove the dirt on it, apply anti-rust oil on its surface.
  3. Install the applied valve and perform regular maintenance to ensure its normal operation.
  4. Check the valve sealing surface for wear and repair or replace it according to the situation.
  5. Check the trapezoidal thread wear of the stem and stem nut, whether the packing is out of date, etc., and make necessary replacements.
  6. Test the sealing performance of the valve to ensure its performance.
  7. The valve in operation should be in good condition, the bolts on the flange and the bracket are complete, the thread is not damaged, and there is no looseness.
  8. If the handwheel is lost, it should be timely and cannot be replaced with a spanner wrench.
  9. The packing gland is not allowed to be skewed or has no pre-tightening clearance.
  10. If the valve is used in a harsh environment and is susceptible to dirt such as rain, snow, dust, sand, etc., a protective cover should be installed for the valve stem.
  11. The scale on the valve should be kept intact, accurate and clear, and the valve seals and caps.
  12. The insulation jacket should be free from dents and cracks.
  13. the valve in operation, to avoid hitting it, or supporting heavy objects.

Valve connection

Flange connection

This is the most used form of connection in the valve. According to the shape of the joint surface, it can be divided into the following types:

  1. Smooth type: used for valves with low pressure. More convenient processing
  2. Concave and convex type: high working pressure, can use medium hard washer
  3. Gutter type: It can be used with gaskets with large plastic deformation. It is widely used in corrosive media and has good sealing effect.
  4. Trapezoidal trough type: use oval metal ring as a gasket, used for valves with working pressure ≥ 64 kg / cm 2 , or high temperature valves.
  5. lens type: the gasket is a lens shape, made of metal. For high pressure valves with working pressure ≥100 kg/cm 2 or high temperature valves.
  6. O-ring type: This is a newer form of flange connection, which developed with the appearance of various rubber O-rings, it is in the form of a sealed connection.

Clip connection

A connection form in which the valve and the two pipes are directly clamped together by bolts.

Butt weld connection

A connection that is directly welded to the pipe.

Threaded connection

This is a simple connection method and is often used for small valves. There are two cases:

  1. Direct sealing: The internal and external threads directly seal. In order to ensure that the joints are not leaking, they are often filled with lead oil, wire hemp and polytetrafluoroethylene raw material tape; among them, the polytetrafluoroethylene raw material tape is widely used; this material has good corrosion resistance and excellent sealing effect. It is easy to use and store. When disassembling, it can be completely removed, because it is a non-stick film, which is superior to lead oil and wire.
  2. Indirect sealing: the force of screwing is transmitted to the gasket between the two planes, so that the gasket acts as a seal.

Card sleeve connection

The ferrule connection, the connection and sealing principle is that when the nut is tightened, the ferrule is subjected to pressure, and the blade portion bites into the outer wall of the tube, and the outer tapered surface of the ferrule is tightly pressed against the tapered surface of the joint body under pressure, thereby It can reliably prevent leakage.

The advantages of this form of connection are:

  1. Small size, light weight, simple structure, easy assembly and disassembly;
  2. Strong connection, wide range of use, can withstand high pressure (1000 kg / cm), high temperature (650 ° C) and shock vibration
  3. Can choose a variety of materials, suitable for anti-corrosion;
  4. Processing accuracy requirements are not high; easy to install at high altitude.
  5. The ferrule connection form has been adopted in some small diameter valve products in China.

Clamp connection

This is a quick connection method that requires only two bolts for low pressure valves that are often removed.

Self-tightening connection

All of the above connection forms use external force to offset the medium pressure and achieve sealing. The following describes the connection form that uses the medium pressure for self-tightening. Its sealing ring is installed at the inner cone, at an angle to the opposite side of the medium, the medium pressure is transmitted to the inner cone, and is transmitted to the sealing ring. At a certain angle of the cone surface, two component forces are generated, one and The centerline of the valve body is parallel to the outside and the other is pressed against the inner wall of the valve body. The latter part of the force is self-tightening. The greater the medium pressure, the greater the self-tightening force. Therefore, this type of connection is suitable for high pressure valves. It is more connected to the flange and saves a lot of material and manpower, but it also requires a certain pre-tightening force, so that it can be used reliably when the pressure inside the valve is not high. Valves made using the principle of self-tightening are generally high pressure valves.

There are many forms of valve connections, such as small valves that do not have to be removed, welded to the pipe; some non-metallic valves, socketed connections, and so on. Valve users should be treated according to the circumstances of the break.

What are the different piping systems?

Piping systems can be divided into two main groups: Mechanical Piping Systems (MPS) and Process Piping Systems (PPS).

  1. Mechanical Piping Systems (MPS) are the pipes and fittings that convey water and other fluids within a building or facility. They are part of the mechanical system, along with such things as heating and air conditioning systems, electrical wiring, and elevators.
  2. Process Piping Systems (PPS) carry fluids through industrial processes such as chemical plants and manufacturing plants. PPS is typically made up of more complex piping networks than MPS, usually consisting of pipes, valves, pumps, heat exchangers and instrumentation.

What is the purpose of piping system?

Piping systems used to transfer media from one place to another.
These can include water, air or steam. A piping system is usually composed of several parts including the following:

  • Piping material (metal, plastic, etc.)
  • Flange: This is where two pipes come together and make a seal. The flange prevents fluid from escaping around the pipe joints when they are bolted together; metal flanges may be removable or bolted on permanently.
  • Joints: These are used to join pipes together at various angles and sizes depending on your project needs.

To integrate the whole process in an industry

Piping systems are used to integrate the whole process in an industry.
The purpose of piping systems is to provide a means for transporting raw materials, intermediate products, and finished goods throughout an industrial facility.
Piping systems are divided into two major categories, the distribution system and Collection System.
In a professional tone:
Piping systems are divided into two major categories, the distribution system and Collection System.
Piping systems are usually made from different materials, ranging from thermoplastic to metal.
The material used depends on the application, which can range from very hot to cold and wet environments. For example, if you’re in a factory that needs to process hot liquids or gases at high temperatures, then stainless steel piping is typically used for its durability and resistance to corrosion. On the other hand, if you need pipes for your home’s plumbing system and it will be exposed to water over time, then PVC pipes would be suitable because they’re more flexible than metal ones—and less expensive too!
The choice of material also affects how easily the piping can be installed into place when building a new structure or replacing old sections within an existing one (such as in your house). In general though it’s best practice when choosing PVC instead of copper because:

  • PVC has better longevity;
  • It’s lighter weight;
  • It won’t corrode as easily under certain conditions (like saltwater exposures).

Piping systems are integral parts of any industrial process.
They transfer heat, fluids, gases and even electricity from one point to another.
This is done using various components such as pipes and valves which can be made out of metal or plastic depending on the type of liquid being transported. This allows for a wide range of products to be manufactured at high temperatures and pressures without compromising their quality or safety standards.

How does a pipeline system work?

Pipeline systems are a network of pipelines which are typically used for transporting liquids or gases over long distances.
Pipeline transportation is used when trucking or shipping the material is not possible due to high volume, long distance or safety risk.
Pipelines may be buried underground in trenches, or they may lie above ground on pylons (as gas lines do) in order to protect them from damage by traffic. The word “pipeline” comes from its original meaning: an underground channel for liquid (water) transport. It has since come to refer to any pipe with one end open at both ends through which material can flow continuously under pressure without loss due to leakage or evaporation. In this article we will discuss how pipelines work and how they are built so that you can understand what goes on behind the scenes when you enjoy your favorite beverage!
A pipeline system has multiple uses, including oil, water, sewage and other liquids and gases.
The lines can be large or small in diameter (the pipe’s width), depending on the type of material being transported. In the U.S., most pipelines are buried underground to avoid damage from construction equipment or accidents with vehicles at road crossings.
Pipelines can be pressurized (filled with a liquid or gas under pressure) or unpressurized (filled with a liquid that doesn’t expand much as it warms up). The two types of pipeline systems are:

  • Transportation pipelines – used to transport oil and gas from production sites to refineries where it is processed into gasoline, diesel fuel or other products for consumers; also used for transporting natural gas from production sites to distribution points where it is sent through distribution lines for home heating and cooking; provide access for maintenance workers; carry hazardous materials such as chemicals into industrial plants
  • Distribution networks – convey drinking water directly from a treatment plant to homes/businesses through pipes buried underground within a city’s rights-of-way.

The pipeline is used to transport the materials from one place to another such as an oil refinery to a port.
Examples of materials transported by pipelines:

  • Oil and gas
  • Water
  • Liquids

Pipeline systems are often used for transporting oil and gas extracted from mines.
Pipelines are a common method of transporting oil and natural gas extracted from mines. Once the oil or natural gas has been extracted, it can be transported to refineries via pipeline systems.
The pipe diameter can vary depending on the liquid or gas transported through it.
Pipe diameters can vary depending on the liquid or gas being transported. Materials used in pipelines include PVC, copper, galvanized steel and stainless steel. Pipe sizes may be as small as 2 mm (0.08 in) or as large as 4 meters (13 ft).
Pipeline transportation is used when trucking or shipping the material is not possible due to high volume, long distance or safety risk.
It can be used in situations where there are multiple points of origin and destination, but it’s often more cost-effective than trucking or shipping.
Pipeline transportation has advantages over other methods because it avoids traffic congestion and doesn’t require parking lots at every stop along the way. This makes it especially useful for transporting large quantities of hazardous materials across long distances quickly without inconveniencing local residents by creating backups on roads that may be narrow.
Pipelines are a great way to transport liquids and gases.
Pipelines are a cost-effective, energy efficient and safe way to transport liquids and gases.
Pipeline systems offer a number of benefits over other methods of transportation including:

  • Low environmental impact. Pipelines can be designed with minimal environmental impact by avoiding sensitive areas and operating in conditions that avoid ecological stress such as spills or contamination from leaks.
  • Quick installation times. The pipeline system is typically assembled from sections that are built offsite before being installed on site by skilled workers who then complete the installation process by connecting each section together in an assembly line fashion. This method allows for quick installation times when compared to other modes of transportation which require extensive planning and construction periods prior to use (e.g., railroads).
  • The end result is an efficient method for transporting both liquids and gases across land masses without much disruption to the surrounding environment or population centers along its route(s).

Source: China Piping Solutions Provider – Yaang Pipe Industry Co., Limited (

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at [email protected]



Leave a Reply



Inquery now



WhatsApp Skype

Wechat: 8618267732328

  • Email me
    Mail to us