What are valves solutions?
Table of Contents
- What are valves?
- Types of valves
- Manual valves
- Specification of manual valves
- Control valves
- Globe Control Valve
- Angle Control Valves
- Three-Way Control Valve
- V-Notch Control valve
- Butterfly Control valve
- Pressure Regulator
- Design and Manufacturing of control valves
- Assembly and Inspection of control valves
- Flange Dimension of control valves
- Face To Face of control valves
- Characteristics of the valve
- Materials of valves
- Standard of valves
- Manufacturing Process of Valves
- Installation of valves
- Operation of valves and precautions
- Common failures of valves and prevention
- How to obtain cost-effective valve solutions?
In fluid piping systems, valves are control elements whose main functions are to isolate equipment and piping systems, regulate flow, prevent backflow, and regulate and discharge pressure.
Valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, slurries, oils, liquid metals and radioactive media. As it becomes very important to select the most suitable valve for the piping system, it becomes vital to understand the characteristics of the valve and the steps and basis for selecting the valve.
Types of valves
Valves in general can be divided into two main categories.
Valves that rely on the ability of the medium (liquid, gas) itself and act on its own. Such as check valves, safety valves, control valves, traps, pressure reducing valves, etc.
The ball valves are normally used as positive shut off valves. The positive shut off is attained because of the soft seats. Special design is also available with ball having shaped port for regulation. Metal seated ball valves are also available for high temperature service.
According to structural features, ball valve is classified into: floating ball valve, trunnion mounted ball valve, multi way ball valve.
According connection, ball valve is classified into: flanged ball valve, fully welded ball valve and socket welded ball valve, ring type jointed (RTJ) ball valve.
According to materials used for body, ball valve is classified into casting ball valve, forged ball valve, stainless steel ball valve, etc.
Butterfly valve, also called as flap valve is a valve that has simple structure, used for media having low pressure. The closure member of butterfly valve is a disc which can swing along with valve shaft. Operation is similar to that of a ball valve, which allows for quick shut off. A butterfly valve is from a family of valves called quarter-turn valves. In operation, the valve is fully open or closed when the disc is rotated a quarter turn. There are different kinds of butterfly valves, adapted for different pressures and different usage.
Based on materials used for sealing face, butterfly valve is classified into soft sealing butterfly valve, hard sealing butterfly valve.
Based on types of sealing, butterfly valve is classified into forced sealing butterfly valve, pressurized sealing butterfly valve and automatic sealing butterfly valve.
Based on working pressure, butterfly valve is classified into vacuum butterfly valve, low pressure butterfly valve, medium pressure butterfly valve, high pressure butterfly valve and ultra-high pressure butterfly valve.
Based on connection, butterfly valve is classified into wafer butterfly valve, flanged butterfly valve, lug type butterfly valve and welded butterfly valve.
Check valve, also called as clack valve, non-return valve or one-way valve is a valve normally allows media (liquid or gas) to flow through it in only one direction. Check valve is two-port valve, which means that there are two openings in the body of check valve, one for media to enter and the other for media to leave. There are various types of check valve used in a wide variety of applications. Accordingly, most of check valves do not have any valve handle or stem. Plastic or metal can be used for bodies (external shells) of the check valve. Typically, check valve is designed for and can therefore be specified for a specific cracking pressure.
Based on structure, check valve is classified into lift check valve, swing check valve and butterfly check valve.
Based on materials, check valve is classified into cast iron check valve, brass check valve, stainless steel check valve, carbon steel check valve and forged steel check valve.
Based on connection, check valve is classified into threaded check valve, flanged check valve and welded check valve.
Diaphragm valves offer many combinations of body materials and elastomeric diaphragm materials. The valve design is abrasion-resistant and non-clogging. When the diaphragm, which is connected to the stem of the valve by a compressor, is pulled away from the bottom of the valve body, the path of the fluid has a smooth, streamlined flow. Slurries at low pressure that would normally clog most other valve designs easily pass through a diaphragm valve. The valve has a top-entry design, allowing in-line maintenance; it is suitable for throttling and on/off service in applications ranging from water treatment to chemical abrasion processes. Diaphragm valves are operated manually, electrically, or pneumatically.
The main advantage of a diaphragm valve is the almost full flow opening and hence very low head loss. Diaphragm valves are good for controlling flow, normally they are used for compressed air, seawater or freshwater and in a great number of other applications. Full flow also means less wear and tear compared to other valves, giving longer lifetime and reduced need for maintenance.
Gate Valves made By Yaang are a Total solution to your industrial Gate Valve needs. Yaang Gate Valves are available in various sizes, ranging from ½” – 80”. Yaang Gate Valves are available manufactured with various materials, such as: Carbon Steel, Stainless Steel, Cast Iron, Forged Steel and available in different types Gate Valves. If you Need special Gate Valve specifications, please contact us to inquire about your Gate Valve requirements.
Globe Valves made By Yaang are the best solution to your industrial Globe Valve needs. Yaang Globe Valves are available in various sizes, ranging from 2” – 80”. Yaang Globe Valves are available manufactured with various materials, such as: Cast Steel, Stainless Steel, Cast Iron, Alloy Steel, Forged Steel and available in different types Globe Valves. If you Need special Globe Valve specifications, please contact us to inquire about your Globe Valve requirements.
Plug Valves made By Yaang are the best solution to your industrial Plug Valve needs. Yaang Plug Valves are available in various sizes, ranging from ½” – 24”. Yaang Plug Valves are available manufactured with various materials, such as: Cast Iron, Cast Steel, Stainless Steel, and available in different types Plug Valves. If you Need special Plug Valve specifications, please contact us to inquire about your Plug Valve requirements.
Needle valves are valve designs that are constructed with a small opening accompanied by a plunger that looks a great deal like a common sewing needle. The purpose of this type of valve is to create a means of controlling the flow of liquids or gases through the valve mechanism. It is possible to easily adjust the flow rate to any specific amount desired, making the needle valve useful in a number of applications, including engines.
Like all industrial valves, needle valves are used to control flow. They are similar in construction to globe valves, but are most often used for the precision regulation of relatively low flow rates. Many needles valves tend to be smaller in size for the finest flow control. They are widely used for instrumentation control, line shut-off, and pressure regulating for a wide variety of applications.
Strainer is an indispensable device on the transmission medium pipeline. It is usually installed at the inlet of pressure reducing valve, pressure relief valve, constant water level valve, square strainer and other equipment. The strainer is composed of cylinder, stainless steel strainer screen, sewage part, transmission device and electrical control part. After the water to be treated passes through the strainer cartridge of the strainer screen, its impurities are blocked. When it needs to be cleaned, just take out the removable strainer cartridge and reinstall it after treatment. Therefore, it is very convenient for use and maintenance.
Safety valve is a special valve whose opening and closing parts are normally closed under the action of external force. When the medium pressure in the equipment or pipeline rises beyond the specified value, it can prevent the medium pressure in the pipeline or equipment from exceeding the specified value by discharging the medium outside the system. Safety valves are automatic valves, which are mainly used in boilers, pressure vessels and pipelines. The control pressure does not exceed the specified value, which plays an important role in protecting personal safety and equipment operation. The safety valve can only be used after pressure test.
Specification of manual valves
• API 6D, API 600, API 599, API 598, API 608, API 602, BS 1873, ASME B16.10, ASME B16.5, ASME B16.47 (Serie A and Serie B) and MSS SP44 are the key specifications covering the dimensions and the manufacturing tolerances of valves.
• ASTM A105, A182, A216, A217, A351, A352, A494 are the common materials related to valves.
• MSS SP25 covers the marking system.
• ASTM A 703 /A 703M IS Speciﬁcation for Steel Castings, General Requirements, for Pressure-Containing Parts.
• ASTM A 487 /A 487M is Speciﬁcation for Steel Castings Suitable for Pressure Service
• ASTM A 985 /A 985M is Speciﬁcation for Steel Investment Castings General Requirements, for Pressure-Containing Parts.
• API 6F is About recommended practice for fire test for valves.
Pressure Test of manual valves
• Normally, valves are pressure tested by the factory to check for leaks before they’re shipped. The type and method of testing conforms to one or more of many different standards. The purpose of these tests and the expected results are often misunderstood and misapplied, resulting in unnecessary delays and unanticipated costs. The most common standard for pressure test is API D and API 598.
Disadvantage of manual valves
• Valves are the most sensitive item comparing with other piping material so should be chosen carefully, for every services the engineering team should chose right type and right material in order to avoiding any failure.
• For flange end valves, Each flange connection can leak (some people claim that a flange connection is never 100 percent leak proof).
Cost of manual valves
• Comparing with other piping components (flange, fittings and pipe), valve is the most expensive one because of internal parts and different manufacturing process.
Size of manual valves
• FROM 0.5″ TO 72″.
• Conformity with the customers drawing.
Other Properties of manual valves
• Valves vary widely in form and application. Sizes typically range from 0.1 mm to 60 cm. Special valves can have a diameter exceeding 5 meters.
• Valve costs range from simple inexpensive disposable valves to specialized valves which cost thousands of US dollars per inch of the diameter of the valve.
• Disposable valves may be found in common household items including mini-pump dispensers and aerosol cans.
• A common use of the term valve refers to the poppet valves found in the vast majority of modern internal combustion engines such as those in most fossil fuel powered vehicles which are used to control the intake of the fuel-air mixture and allow exhaust gas venting.
With the help of manual, electric, hydraulic, pneumatic to manipulate the action of the valve. Such as gate valves, globe valves, throttle valves, butterfly valves, ball valves, plug valves, etc.
Globe Control Valve
Globe valves are the best solution for throttling service in oil, gas, petrochemical and other industrial purposes. It provides optimal solutions to control from general service fluids to corrosive,
Cryogenic, high temperatures fluids under severe service conditions containing erosion, corrosion and high pressure drops.
High Cv to body size ratio, which allows for smaller and more cost effective valve size selection;
High Cv to valve weight ratio;
Optimized streamlined flow;
Excellent flow control rangeability.
• Modular construction design.
• All trim components are replaceable from the top for easy maintenance.
• Wide range of supplementary cavitation & noise.
• Inherently characterized trim offered in equal.
Percentage, linear, quick opening and modified parabolic.
Multi trim sizes are available.
• Full range of body and trim material options.
• Full range of bonnet and packing designs to suit.
Various temperatures and fluids.
Angle Control Valves
Angle valves are widely accepted for controlling fluid of high differential pressure, slurry, high viscosity, or adhesive. They are provided with a number of features such as low resistance of passage, anti-wear quality within the valve, and easy maintenance and inspection.
• High Cv to body size ratio.
• High Cv to valve weight ratio.
• Excellent flow control rangeability.
• Modular construction design available with a range of different connections and styles.
• All trim components removable from the top for easy maintenance.
• Wide range of supplementary noise control options.
Inherently characterized trim offered in equal percentage, linear, quick opening and modified parabolic (options). Multi trim sizes available.
• Full range of body and trim material options.
• Full range of bonnet and packing designs to suit various temperatures and fluids.
Three-Way Control Valve
Three-way type control valves are used For controlling the fluids mutually to three directional pipings, i.e., mixing service or diverting service.
• High Cv to body size ratio.
• High Cv to valve weight ratio.
• Excellent flow control rangeability.
• Modular construction design available with a range of different connections and styles.
• All trims components removable from the top for easy maintenance.
• Wide range of supplementary noise control options. Inherently characterized trim offered in equal percentage, linear, quick opening and modifiedparabolic (options).
• Multi trim sizes available.
• Full range of body and trim material options.
• Fully rationalized and interchangeable features.
• Full range of bonnet and packing designs to suit various temperatures and fluids.
V-Notch Control valve
V-notch ball valves are Top Entry, Full Bore, Trunnion, and stem ball type, which are exclusively designed for excellent proportional control.
We supply special shape of ball which is suitable for accurate throttling control and on-off service not only general fluids but also critical conditions in powders, slurry, gummy, fibrous material and other fluids with special characteristics.
• High Cv body size ratio (Full bore).
• Controls through 90° rotat ion.
• Excellent control range ability.
• Easy maintenance.
• ISO standard Mounting Design Flexibility.
• Direct mounting actuator design flexibility.
• Control any fluids.
• Full range of body and vane material options with availability of hard facings.
• Seat changeability.
• Equal or Linear characteristics available.
• Self-cleaning and tight seating.
• Double-eccentric disc options.
Butterfly Control valve
Butterfly control valves have been developed for a large number of applications throughout process industries.
this high performance butterfly valves are mainly used for isolation or on-off applications but also suitable for control, especially on high-flow, low-pressure applications. It offers additional advantages such as simple structure and low cost.
• High Cv to valve weight ratio compared to conventional control valves.
• Throttling controls 60° rotation, on-off controls 90° rotation.
• Excellent flow control range ability.
• Triple-offset design.
• Metal / Laminated / Soft seat available.
• Actuator mounting flange dimensions in accordance with ISO 5211.
• Swing through and tight shut-off seated trim design.
• Flange types are available.
• Full range of bonnet and packing design to suit various temperatures and fluids.
• Provides fire safe sealing, which combines a soft seal ring and metal seal ring.
• Full range of body and vane material options. Hard facing available.
Pressure regulating valves are designed for controlling pressure of liquid s& gases in various industrial applications.
• Direct operated / Pilot operated.
• Easy setting / Fast action.
• Low cost maintenance.
• Wide spring selection range.
• Various types of pressure regulating valves for liquids & gases.
• Pressure reducing type (P2 control).
• Back pressure/Relief type (P1 control).
• Tank blanketing type.
Save fuel with optimized process control. In a situation where the controlled outlet temperature is higher than the saturation temperature and steam is to be used for heating application. It is absolutely necessary that for such applications the outlet steam temperature should be as close as possible to its saturation temperature. The sole reason for this is the saturated steam is the best conductor of heat and as the degree of Superheat increases, the heat transfers become inefficient. Superheated steam contains a large amount of heat energy, this energy is in three forms; 25% of enthalpy of water, 66% of enthalpy of evaporation (latent heat) and 9% of enthalpy of superheat. The coefficient of heat transfer when using superheated steam as the heating medium is variable, low and difficult to quantify accurately. This makes accurate sizing and control of heat transfer equipment difficult, and will also result in a larger and more expensive heat exchanger. Desuperheater can help you to optimize your process control can save fuel and in turn save investment cost.
To ensure temperature stability of the conditioned steam and to prevent thermal shock in downstream lines, the cooling water should ideally be fully atomized. There should also be a correct mix of superheated steam and cooling water.
● Size: Steam 1½”to 50”, Water 1½”to 2”.
● Forged/Casting construction.
● Venturi nozzle type.
● Low pressure loss over the desuperheater station.
● Water pressure marginally above steam pressure.
Typical Desuperheater Designs
● Fixed-Geometry Nozzle Design.
● Variable-Geometry Nozzl e Design.
● Self-Contained Design.
● Steam-Atomized Design.
● Geometry-Assisted Wafer Design.
Materials of Construction
● ASTM SA 105, SA 182F11 or SA 18 2 F22F (Forged).
● ASTM A217 Gr WC6 (Casting).
● DIN C22.8, 1.7335 or 1.7380.
● Other materials upon request.
● ASME / ANSI B16.34 class 150 to 2500.
● DIN 2401 class PN 25 to 400.
● Butt-weld connections to ANSI B16.25 or DIN 2559.
Actuators are designed to control the flow, level and the pressure of fluid to respond to demand for fine process control and various plant systems.
A common control valve accessory is the valve position controller, also called a positioner. The fundamental function of a positioner is to deliver pressurized air to the valve actuator, such that the position of the valve stem or shaft corresponds to the set point from the control system.
Design and Manufacturing of control valves
• ANSI/ISA-75.01.01 (60534-2-1 MOD): Industrial-Process Control Valves – Part 2-1: Flow capacity – Sizing equations for fluid flow under installed conditions
This standard includes equations for predicting the flow of compressible and incompressible fluids through control valves. The equations for incompressible flow are based on standard hydrodynamic equations for Newtonian incompressible fluids. They are not intended for use when non-Newtonian fluids, fluid mixtures, slurries or liquid-solid conveyance systems are encountered. The equations for incompressible flow may be used with caution for non-vaporizing multi-component liquid mixtures. Refer to Clause 6 for additional information.
• ANSI/ISA-75.05.01: Control Valve Terminology
This document contains terminology for control valves.
• ISA-75.17: Control Valve Aerodynamic Noise Prediction
This standard establishes a method to predict the noise generated in a control valve of standard design by the flow of compressible fluid and the resulting noise outside of the pipe and downstream of the valve. The transmission loss (TL) equations are based on a rigorous analysis of the interaction between the sound waves that exist in the pipe and the many coincidence frequencies in the pipe wall. Commercial pipe specifications allow a relatively wide tolerance in pipe wall thickness. This limits the value of the very complicated mathematical methods required for a rigorous analysis; calculations prove that a simplified expression is justified.
The equations in this standard make use of the valve sizing factors defined in ANSI/ISA-S75.01 and ANSI/ISA-S75.02. This method was developed from the fundamental principles of acoustics, fluid mechanics, and mechanics.
Assembly and Inspection of control valves
• ANSI FCI 70.2: Control valve Seat Leakage
This standard establishes a series of seat leakage classes for control valves and defines the test procedures.
Selection of a leakage class is not restricted as to valve design, but acceptable values for various commercially available designs are suggested for each class under Section
• IEC 60534.4: Inspection and routine testing
This part of IEC 60534 specifies the requirements for the inspection and routine testing of control valves manufactured in conformity with the other parts of IEC 60534.
This standard is applicable to valves with pressure ratings not exceeding Class 2500. The requirements for actuators apply only to pneumatic actuators.
This standard does not apply to the types of control valves where radioactive service, fire safety testing, or other hazardous service conditions are encountered. If a standard for hazardous service conflicts with the requirements of this standard, the standard for hazardous service should take precedence.
• ANSI/ISA-75.19.01: Hydrostatic Testing of Control Valves
This standard applies to control valves having bodies, bonnets, cover plates, and bottom flanges made of carbon steel, low alloy and high alloy (stainless) steel, nickel-base alloy, cast iron, and ductile iron.
• ASTM E 165: Standard Test Method for Liquid Penetrant Examination
This practice2 covers procedures for penetrant examination of materials. Penetrant testing is a nondestructive testing method for detecting discontinuities that are open to the surface such as cracks, seams, laps, cold shuts, shrinkage, laminations, through leaks, or lack of fusion and is applicable to in-process, final, and maintenance testing. It can be effectively used in the examination of nonporous, metallic materials, ferrous and nonferrous metals, and of nonmetallic materials such as nonporous glazed or fully densified ceramics, as well as certain nonporous plastics, and glass.
• ISA 75.02.01: Control valve Capacity Test Procedure
This test standard utilizes the mathematical equations outlined in ANSI/ISA-75.01.01 (IEC 60534-2-1 Mod)-2007, Flow Equations for Sizing Control Valves, in providing a test procedure for obtaining the following:
a) Valve flow coefficient, C (Cv, Kv)
b) Liquid pressure recovery factors, FL and FLP
c) Reynolds Number factor, FR
d) Liquid critical pressure ratio factor, FF
e) Piping geometry factor, FP
f) Pressure drop ratio factor, xT and xTP
g) Valve style modifier, Fd
This standard is intended for industrial process control valves used in flow control of Newtonian fluids. See 4.2 for more information regarding specific valve styles.
• ISA-75.25.01: Test Procedure for Control Valve Response Measurement from Step Input
This standard defines the testing and reporting of step response of control valves that are used in throttling closed loop control applications. A control valve consists of the complete, ready-to-use assembly of the control valve body, actuator, and any required accessories. The most probable accessory is a valve positioner. For background, refer to technical report ISA-TR75.25.02-2000 (R2010), Control Valve Response Measurement from Step Inputs.
Flange Dimension of control valves
• ASME B 16.5: Pipe Flanges and Flanged Fittings.
This Standard establishes requirements for wrought copper and wrought copper alloy braze-joint seamless fittings designed for use with seamless copper tube conforming to ASTM Standard Specification, B88 (Water and General Plumbing Systems), B280 (Air Conditioning and Refrigeration Service), and B819 (Medical Gas Systems). This Standard covers joints assembled with brazing materials conforming to ANSI/AWS A5.8.
This Standard is allied to ASME standards B16.18 and B16.22. It provides requirements for fitting-ends suitable for brazing. This Standard covers
- (a) pressure–temperature ratings
- (b) abbreviations for end connections (c) size and method of designating openings of fittings
- (d) marking
- (e) material
- (f) dimensions and tolerances
- (g) testing
• ANSI B16.10: Face to Face & End to End Dimensions of Valves
This Standard covers face-to-face and end-to-end dimensions of straightway valves, and center-to-face and center-to-end dimensions of angle valves. Its purpose is to ensure installation interchangeability for valves of a given material, type, size, rating class, and end connection.
• ASME B16.47: large diameter steel flanges: nps 26 through nps 60 This Standard covers pressure–temperature ratings, materials, dimensions, tolerances, marking, and testing for pipe flanges in sizes NPS 26 through NPS 60.
Included are flanges with rating class designations 75, 150, 300, 400, 600, and 900 with requirements given in both SI (Metric) and U.S. Customary units, with diameter of bolts and flange bolt holes expressed in inch units. This Standard is limited to
(a) flanges made from cast or forged materials (b) blind flanges made from cast, forged, or plate materials. Also included in this Standard are requirements and recommendations regarding flange bolting, flange gaskets, and flange joints.
Face To Face of control valves
• ISA S75.12: Face-to-Face and End-to-End Dimensions of Valves
This standard applies to socket weld-end globe-style control valves, sizes 1/2 in (15 mm) through 4 in (100 mm), and screwed-end globe-style control valves, sizes 1/2 in (15 mm) through 2 1/2 in (65 mm), having top, top and bottom, port, or cage guiding.
• ANSI/ISA-75.08.01: Face-to-Face Dimensions for Integral Flanged Globe-Style Control Valve Bodies (Classes 125, 150, 250, 300, and 600)
This standard applies to integral flanged globe-style control valves, sizes 15 mm (1/2 inch) through 400 mm (16 inches), having top, top and bottom, port, or cage guiding.
• ANSI/ISA-75.08.02: Face-to-Face Dimensions for Flanged and Flangeless Rotary Control Valves (Classes 150, 300, and 600, and PN 10, PN 16, PN 25, PN 40, PN 63 and PN 100)
This standard applies to flanged and flangeless rotary control valves using a full ball or a segment of a ball and other rotary-stem control valves, sizes (20 mm) 3/4 inch through (600 mm) 24 inches for Classes 150 through 600, and for PN 10, PN 16, PN 25, PN 40, PN 63, and PN100.
• ANSI/ISA-75.08.03: Face-to-Face Dimensions for Socket Weld-End and Screwed-End Globe-Style Control Valves (Classes 150, 300, 600, 900, 1500, and 2500)
This standard applies to socket weld-end globe-style control valves, sizes 1/2 inch (15 mm) through 4 inches (100 mm), and screwed-end globe-style control valves, sizes 1/2 inch (15 mm) through 2 1/2 inches (65 mm), having top, top and bottom, port, or cage guiding.
• ANSI/ISA-75.08.08: Face-to-Centerline Dimensions for Flanged Globe-Style Angle Control Valve Bodies (Classes 150, 300, and 600) This standard aids user in their piping design by providing Classes 150, 300, and 600 raised-face flanged globe-style angle control valve face-to-centerline dimensions without giving special considerations to the equipment manufacturer to be used.
• ANSI/ISA-75.08.09: Face-to-Face Dimensions for Sliding Stem Flangeless Control Valves (Classes 150, 300, and 600)
1.1 This standard applies to sliding stem flangeless control valves, sizes 20 mm (3/4 inch) through 600 mm (24 inches) for Classes 150, 300, and 600.
1.2 The face-to-face dimensions listed apply only to control valves that will be bolted between flanges.
1.3 This standard is not intended to include rotary valves, such as butterfly valves.
• ANSI/ISA–75.15: Face-to-Face Dimensions for Buttweld-End Globe-Style Control Valves (ANSI Classes 150, 300, 600, 900, 1500, and 2500)
This standard applies to buttweld-end globe-style controls valves, sizes 15 mm (1/2 inch) through 450 mm (18 inches) for ANSI Classes 150 through 2500, having top, top and bottom, port, or cage guiding.
• ANSI/ISA–75.16: Face-to-Face Dimensions for Flanged Globe-Style Control Valve Bodies (ANSI Classes 900, 1500, and 2500) This standard applies to flanged control valves, sizes 15 mm (1/2 inch) through 450 mm (18 inches), having top, top and bottom, port, or cage guiding.
According to the structural characteristics, according to the direction of movement of the closing member relative to the valve seat can be divided into:
- Shutter-gate shape: the closing member moves along the center of the valve seat.
- Gate shaped: the closing member moves along the center of the vertical valve seat.
- Rotary plug and spherical: the closing member is a plunger or ball, rotating around its own centerline.
- Swivel-shaped: the closing member rotates around an axis outside the valve seat
- Disc-shaped: the closing member is a disc that rotates around an axis inside the valve seat.
- Sliding valve shape: the closing member slides in a direction perpendicular to the passage.
According to the use, according to the different uses of the valve can be divided into:
- Open: used to connect or cut off the pipeline media, such as globe valves, gate valves, ball valves, butterfly valves, etc.
- Check: used to prevent the backflow of media, such as check valves.
- Adjustment: used to adjust the pressure and flow of the medium, such as regulating valves, pressure reducing valves.
- Distribution: used to change the direction of media flow, distribution of media, such as three-way plug, distribution valve, slide valve, etc.
- Safety valve: in the media pressure exceeds the specified value, used to discharge excess media to ensure the safety of piping systems and equipment, such as safety valves, accident valves.
- Other special purposes: such as traps, venting valves, drain valves, etc.
According to the drive mode, according to the different drive modes can be divided into:
- Manual: with the help of handwheels, handles, levers or sprockets, etc., with human drive, transmission of larger torque is equipped with worm gears, gears and other reduction devices.
- Electric: With the help of electric motors or other electrical devices to drive.
- Hydraulic: driven with the help of (water, oil).
- Pneumatic: driven by compressed air.
By pressure, according to the nominal pressure of the valve can be divided into:
- Vacuum valve: absolute pressure <0.1Mpa that is 760mm mercury column high valve, usually expressed in mm mercury column or mm water column pressure.
- Low pressure valve: nominal pressure PN ≤ 1.6Mpa valve (including PN ≤ 1.6MPa steel valve)
- Medium pressure valve: nominal pressure PN2.5-6.4MPa valve
- High pressure valves: valves with nominal pressure PN10.0-80.0MPa
- Ultra-high pressure valves: valves with nominal pressure PN ≥ 100.0MPa
According to the temperature of the medium, according to the temperature of the medium when the valve works can be divided into:
- Ordinary valve: applicable to the medium temperature -40 ℃ ~ 425 ℃ valve.
- High temperature valves: applicable to the medium temperature 425 ℃ ~ 600 ℃ valve.
- Heat-resistant valves: applicable to the medium temperature of 600 ℃ or more valves.
- Low-temperature valves: applicable to the medium temperature -150 ℃ ~ -40 ℃ valve.
- Ultra-low temperature valve: applicable to the medium temperature -150 ℃ below the valve.
According to the nominal diameter points, according to the nominal diameter of the valve can be divided into:
- Small diameter valves: nominal diameter DN < 40mm valves.
- Medium diameter valves: nominal diameter DN50 ~ 300mm valves.
- Large diameter valves: nominal diameter DN350 ~ 1200mm valves.
- Extra large diameter valves: nominal diameter DN ≥ 1400mm valves.
According to the way of connection with the pipeline, according to the valve and the pipeline connection can be divided into:
- Flange connection valve: valve body with a flange, and the pipeline flange connection valve.
- Threaded connection valve: valve body with internal or external threads, and the pipeline using a threaded connection valve.
- Welded connection valve: the valve body with a welded mouth, and the pipeline using a welded connection of the valve.
- Clamp connection valve: the valve body with a clamp port, and the pipeline using the clamp connection valve.
- Ferrule connection valves: valves connected to the pipeline using a ferrule.
Characteristics of the valve
There are two general types of valve characteristics, use characteristics and structural characteristics.
- It determines the main performance and use of the valve, belonging to the valve use characteristics are.
- The type of valve (closed-circuit valves, regulating valves, safety valves, etc.)
- The type of product (gate valve, globe valve, butterfly valve, ball valve, etc.).
- The material of the main parts of the valve (valve body, valve cover, valve stem, valve flap, sealing surface).
- Valve transmission mode, etc.
It determines the valve installation, repair, maintenance and other methods of some structural characteristics, which belong to the structural characteristics are:
- The structural length and overall height of the valve, the form of connection to the pipeline (flange connection, threaded connection, clamped connection, male threaded connection, welded end connection, etc.)
- the form of the sealing surface (inlaid ring, threaded ring, overlay welding, spray welding, valve body body)
- The form of valve stem structure (rotary stem, lift stem), etc.
Materials of valves
Forged Carbon Steel, Stainless Steel and Duplex
Forged carbon Steel valves: ASTM A105/ A105M, 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. Materials shall be subjected to heat treatment (annealing, normalizing, tempering, or quenching). Material shall conform to carbon, manganese, phosphorus, sulfur, silicon, copper, nickel, chromium, molybdenum and vanadium contents. The forgings shall be subjected to tension, hardness and hydrostatic tests, with the latter applicable when required. Material shall adhere to tensile strength, yield strength, elongation, reduction of area, and hardness requirements. Guidelines for retreatment, repair by welding, and product marking are given.
Forged carbon Steel valves For low Temprature Service: ASTM A350/ A350M (LF1, LF2, LF3, LF5, LF6, LF9, LF 787), This specification covers several grades of carbon and low alloy steel forged or ring-rolled flanges, forged fittings and valves for low-temperature service. The steel specimens shall be melt processed using open-hearth, basic oxygen, electric furnace or vacuum-induction melting. A sufficient discard shall be made to secure freedom from injurious piping and undue segregation. The materials shall be forged and shall undergo heat treatment such as normalizing, tempering, quenching and precipitation heat treatment. Heat analysis and product analysis shall be performed wherein the steel materials shall conform to the required chemical compositions of carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, copper, columbium, vanadium, and nitrogen. The materials shall also undergo tension tests and shall conform to the required values of tensile strength, yield strength and elongation. Impact tests shall also be performed and the steel materials shall conform to the required values of minimum impact energy, temperature, and minimum equivalent absorbed energy. Hardness and hydrostatic tests shall also be performed.
Forged Alloy Steel and Stainless Steel valves For High Temprature Service: ASTM A182/ A182 M-98ª(F 304, F 304H, F 304L, F 304N, F304 LN, F 309H, F310, F 310H, F 310 MoLN, F 316, F 316H, F 316L, F 316N, F 316LN, F 317, F 317L, F 347, F 347 H, F 348, F 348 H, F 321, F321 H), This specification covers forged or rolled alloy and stainless steel pipe flanges, forged fittings, and valves and parts for high-temperature service. After hot working, forgings shall be cooled to a specific temperature prior to heat treatment, which shall be performed in accordance with certain requirements such as heat treatment type, austenitizing/solution temperature, cooling media, and quenching. The materials shall conform to the required chemical composition for carbon, manganese, phosphorus, silicon, nickel, chromium, molybdenum, columbium, titanium. The material shall conform to the requirements as to mechanical properties for the grade ordered such as tensile strength, yield strength, elongation, Brinell hardness. All H grades and grade F 63 shall be tested for average grain size.
Forged carbon Steel valves: ASTM A105/ A105M Forged carbon Steel valves For low Temprature Service: ASTM A350/ A350M (LF1, LF2, LF3, LF5, LF6, LF9, LF 787)
Forged Alloy Steel and Stainless Steel valves For High Temprature Service: ASTM A182/ A182 M-98ª(F 304, F 304H, F 304L, F 304N, F304 LN, F 309H, F310, F 310H, F 310 MoLN, F 316, F 316H, F 316L, F 316N, F 316LN, F 317, F 317L, F 347, F 347 H, F 348, F 348 H, F 321, F321 H)
Forged Duplex Steel valve : ASTM A182 (F 50, F 51, F 52, F 53M F 54, F 55, F 57, F 59, F 60, F 61, F 904L)
Low Temperature Steel
ASTM A352/ A352M (LCA, LCB, LCC, LC1, LC2, LC2-1, LC3,LC4, LC9(J31300), CA6NM)
This specification covers steel castings for valves, flanges, fittings, and other pressure-containing parts intended primarily for low-temperature service. Several grades of ferritic steels and one grade of martensitic steel are covered. All castings shall receive a heat treatment proper to their design and chemical composition. It should be recognized that liquid quenching of the ferritic grades is normally required to meet the mechanical properties of heavier sections. The steel shall conform to the requirements as to chemical composition specified. Tensile test and impact test shall be made to conform to the requirements specified.
ASTM A351/ A351 M (CF8(F304), CF3(F304L), CF3M(F316L), CF8M(F316))
This specification covers austenitic steel castings for valves, flanges, fittings, and other pressure-containing parts. The steel shall be made by the electric furnace process with or without separate refining such as argon-oxygen decarburization. All castings shall receive heat treatment followed by quench in water or rapid cool by other means as noted. The steel shall conform to both chemical composition and tensile property requirements.
High Temperature Steel
ASTM A217/ A217 M-98a( WC1, WC4, WC5, WC6, WC9, WC11, C5, C12, C12A
Standard specification for steel casting, martensitic stainless and alloy, for pressure-containing parts, sutable for high-temprature service.
ASTM A351/ A351 M (CN7M, CD4MCu, CG8M, CK3MCuN)
ASTM A351/ A351 M (CN7M, CD4MCu, CG8M, CK3MCuN), This specification covers austenitic steel castings for valves, flanges, fittings, and other pressure-containing parts. The steel shall be made by the electric furnace process with or without separate refining such as argon-oxygen decarburization. All castings shall receive heat treatment followed by quench in water or rapid cool by other means as noted. The steel shall conform to both chemical composition and tensile property requirements.
ASTM A890/ A890 M, This specification covers castings, iron-chromium-nickel-molybdenum corrosion-resistant, duplex(austenitic/ferritic) for general application. Castings shall be heat treated in accordance with the required procedure and heat-treat temperature. Proper heat treatment of these alloys is usually necessary to enhance corrosion resistance and in some cases to meet mechanical properties. Minimum heat-treat temperatures are specified; however, it is sometimes necessary to heat-treat at higher temperatures, hold for some minimum time at temperature and then rapidly cool the castings in order to enhance the corrosion resistance and meet the required mechanical properties. The steel shall conform to the required chemical composition for carbon, manganese, silicon, phosphorus, sulfur, chromium, nickel, molybdenum, copper, tungsten, and nitrogen. Castings shall be marked for material identification with the specification designation and grade.
SA-494/ SA-494 M(UNS N02100, UNS N24135, UNS N04020, UNS N24030, UNS N24025, UNS N24130, UNS N30012, UNS N30007, UNS N30003, UNS N06040, UNS N30002, UNS N30107, UNS N26455, UNS N26625, UNS N26055, UNS N30003, UNS N26022, UNS N08826, UNS N26059)
This specification covers nickel, nickel-copper, nickel-copper-silicon, nickel-molybdenum, nickel-chromium, and nickel-molybdenum-chromium alloy castings for corrosion resistant service. The castings shall be heat treated. When Class 1 is specified, grades CY40 and M25S shall be supplied in the as-cast condition. When Class 2 is specified, grades CY40 and M25S shall be supplied in the solution treated condition. When Class 3 is specified, grade M25S shall be supplied in the age-hardened condition. The chemical composition requirements of the alloys are presented. The tensile property requirements including the heat treatment procedure for the castings are presented in detail. It is required that one tension test shall be made from each master heat except for grades M25S and CY5SnBiM when the master heat is used to pour the castings. One tension test shall be made from each melt except for grades M25S and CY5SnBiM. Test results shall conform to the specified tensile requirements.
Standard of valves
Piping Codes and Valve Standards: As with every intended use for valves, piping carries its own set of standards that valve companies and users need to understand. This article provides an overview of the codes (it does not necessarily cover detailed requirements for specific services).
Most codes covering piping in non-water service have tables that list valves covered by the code. Non-listed valves need case-by-case analysis.
The typical piping codes used in the valve industry (excluding the water industry) are ASME B31.1 for Power Piping 2014, ASME B31.3 for Process Piping 2014, ASME B31.4 for Pipeline Transportation Systems for Liquids and Slurries 2012, and ASME B31.8 for Gas Transmission and Distribution Piping Systems 2014.
In each of these codes, valves are listed in tables. When that’s the case, no additional requirements are generally placed on the valve manufacturer and supplier besides the valve product standards (e.g., API 6D, ASME B16.34, etc.). Although special cases exist, such as class M in B31.3, they are not discussed in this general overview.
The question also arises about what happens in situations that call for non-listed valves. These situations vary from piping code to code so they should be examined on a case-by-case basis.
The ASME B31.1 code lists three valves standards, excluding cast iron and bronze valves. The standards are: 1) ASME B16.34, Valves–Flanged, Threaded, and Weld End; 2) MSS SP67–Butterfly Valves; and 3) MSS SP68–High Pressure Butterfly Valves with Offset Design. As stated in B31.1, para 107.1, “Valves not complying with above [the list] shall be of a design, or equal to the design, that the manufacturer recommends for the service as stipulated in para. 102.2.2. Such valves shall be pressure tested in accordance with MSS SP-61.”
This puts the responsibility on the valve manufacturer to recommend the design for the service and compounds the issue when valves are supplied through distribution. Rarely will the valve manufacturer know the actual service, since that manufacturer is not responsible for the piping system. Therefore, it is essential that the designer of the piping system clearly understands what is offered when the valve is unlisted. This is especially important with respect to pressure/ temperature ratings. The piping designer should always check the suitability of the valve for the service.
The ASME B31.3 code lists four valve standards, again excluding cast iron and bronze valves. The standards are: 1) ASME B16.34, Valves–Flanged, Threaded and Welding End; 2) MSS SP72–Ball Valves with Flanged or Butt-Welding Ends for General Service; 3) API 608–Metal Ball Valves with Flanged, Threaded and Welding Ends; and 4) API 6D–Specification for Pipeline and Piping Valves.
The API 6D standard was added in the 2014 edition of this code with a caveat that the design of valves comply with ASME B16.34. (Therefore, it does not really add anything to the 2012 edition list).
In the 2014 edition of ASME B31.3, the designer has to be satisfied that composition, mechanical properties, method of manufacture and design are suitable for the intended service. The pressure/temperature ratings should be established in accordance with rules in paragraph 304. The change from the 2012 edition to the 2014 edition caused the onus to fall on designers. This is because the 2012 edition states that pressure design shall be verified in accordance with paragraph 304 of the code; however, the latest edition states the designer has to be satisfied the design is suitable for the intended service. The situation is similar to what happens with B31.1 since the manufacturer rarely knows the service.
ASME B31.4 lists eight valve standards, once again excluding cast iron and bronze valves.
These valve standards, which are more comprehensive than the previous codes, are:
• ASME B16.34, Valves–Flanged, Threaded, and Welding End
• MSS SP68–High Pressure Butterfly Valves with Offset Design
• MSS SP72–Ball Valves with Flanged or Butt-Welding Ends for General Service
• API 600–Steel Gate Valves-Flanged and Butt-Welding Ends, Bolted Bonnets, Twelfth Edition
• API 602–Steel Gate, Globe and Check Valves for Sizes DN 100 and Smaller for the Petroleum and Natural Gas Industries
• API 603–Corrosion-resistant, Bolted Bonnet Gate Valves-Flanged and Butt-Welding Ends
• API 6D–Specification for Pipeline and Piping Valves
• API 6A–Specification for Wellhead and Christmas Tree Equipment
In this code, special valves not on the list are permitted, provided the valve design is of at least equal strength and tightness, the valves are capable of withstanding the same test requirements as covered in the above standards, and the valve’s structural features satisfy the material specification and test procedures of the valves in similar service set forth in the standards. These requirements are stricter than previous codes, requiring the designer to make the valve with equal strength and tightness.
The ASME B31.8 code lists five valve standards, excluding cast iron and thermoplastic valves. These standards are:
1) ASME B16.33–Manually Operated Metallic Gas Valves for Use in Gas Piping Systems up to 175 psi (Sizes NPS1/2 Through NPS 2);
2) ASME B16.34 Valves–Flanged, Threaded and Welding End;
3) ASME B16.38–Large Metallic Valves for Gas Distribution: Manually Operated, NPS 21 .2 (DN 65) to NPS 12 (DN 300), 125 psig (8.6 bar) Maximum; 4) API 6D–Specification for Pipeline and Piping Valves; and 5) API 6A–Specification for Wellhead and Christmas Tree Equipment.
ASME B31.8 does not have criteria for unlisted valves. It states that “Valves shall conform to standards and specifications referenced in this Code and shall be used only in accordance with the service recommendations of the manufacturer.” This means that with the 31.8 code, one must only use valves that are listed.
The common standard for valves is ASME B16.34. While this standard has several aspects that are positive, it is not really a design code like ASME BPVC section VIII, where material strength, corrosion allowance and formula for irregular shapes are taken into account. For this reason, designs should be cross checked against a pressure vessel code.
While compliance with the piping codes is necessary in almost all cases, compliance with national laws is obligatory.
API 6D, API 600, API 599, API 598, API 608, API 602, ASME B16.10, ASME B16.5, ASME B16.47 (Serie A and Serie B) and MSS SP44 are the key specifications covering the dimensions and the manufacturing tolerances of Control valves body.
Specification for Pipeline Valves. API Specification 6D is an adoption of ISO 14313: 1999, Petroleum and Natural Gas Industries-Pipeline Transportation Systems-Pipeline Valves. This International Standard specifies requirements and gives recommendations for the design, manufacturing, testing and documentation of ball, check, gate and plug valves for application in pipeline systems.
Bolted Bonnet Steel Gate Valves for Petroleum and Natural Gas Industries – Modified National Adoption of ISO 10434:1998.
Metal Plug Valves – Flanged, Threaded and Welding Ends. A purchase specification that covers requirements for metal plug valves with flanged or butt-welding ends, and ductile iron plug valves with flanged ends, in sizes NPS 1 through NPS 24, which correspond to nominal pipe sizes in ASME B36.10M. Valve bodies conforming to ASME B16.34 may have flanged end and one butt-welding end. It also covers both lubricated and no lubricated valves that have two-way coaxial ports, and includes requirements for valves fitted with internal body, plug, or port linings or applied hard facings on the body, body ports, plug, or plug port.
The API STANDARD 598: VALVE INSPECTION AND TESTING, covers the testing and inspection requirements for gate, globe, check, ball, plug & butterfly valves. It has acceptable leakage rates for liquid as well as gas testing. All valves built to the various API standards are required to meet API-598 leakage criteria prior to shipment from the manufacturer or supplier.
Compact Steel Gate Valves – Flanged, Threaded, Welding, and Extended-Body Ends. The standard covers threaded-end, socket-welding-end, butt-welding-end, and flanged-end compact carbon steel gate valves in sizes NPS4 and smaller. BS 1873
British Standard Institute: Specification for steel globe and globe stop and check valves (flanged and butt-welding ends) for the petroleum, petrochemical and allied industries.
Face to Face & End to End Dimensions of Valves.
ASME B16.5 Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24 Metric/Inch Standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, testing, and methods of designating openings for pipe flanges and flanged fittings. Included are: flanges with rating class designations 150, 300, 400, 600, 900, and 1500 in sizes NPS 1/2 through NPS 24 and flanges with rating class designation 2500 in sizes NPS 1/2 through NPS 12.
ASME B16.47 (Serie A and Serie B), MSS-SP44
Large Diameter Steel Flanges, NPS 26 through NPS 60 Metric/Inch Standard, Weld Neck, Slip-On, Blind. Class 150 to Class 900.
ASTM A703/ A703M
This specification covers steel castings, general requirements, for pressure-containing parts. The steel shall be made by open-hearth or electric-furnace process, with or without separate refining such as argon-oxygen-decarburization (AOD), unless otherwise designated by the individual specification. Ferritic and martensitic steel shall be cooled after pouring to provide substantially complete transformation of austenite prior to heat treatment to enhance mechanical properties. The material shall conform to the specified chemical composition requirements. An analysis of each heat shall be made by the manufacturer to determine the percentages of the elements specified. The mechanical test methods and definitions are presented in details. One tension test shall be made from each heat, and shall conform to the tensile requirements specified. Test coupons shall be cast from the same heat as the castings represented, except that for investment castings, the test coupons shall be cast in the same type of mold as the castings. After machining, each casting shall be tested under specified hydrostatic shell test pressures in the applicable steel rating for which the casting is designed.
ASTM A487/ A703M
This specification covers low-alloy steel and martensitic stainless steels in the normalized and tempered, or quenched and tempered conditions, suitable for pressure-containing parts. All castings shall receive the specified heat treatment requirement: austenitizing temperature, medium, quenching cool, and tempering temperature. Preliminary heat treatment and multiple tempering are permitted. Recording-type pyrometers shall be used to control the furnace temperature. The steel shall conform to the required chemical composition for carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, vanadium, boron, and copper. Residual elements include: copper, nickel, chromium, tungsten, molybdenum, and vanadium. Tensile properties of the steel shall conform to the requirements for tensile strength, yield strength, elongation, reduction of area, hardness, and maximum thickness. Product analysis tolerance is specified. Repair by welding may be done.
ASTM A985/ A985M
This specification covers a group of common requirements that are mandatory for steel castings produced by the investment casting process for pressure-containing parts. Master heats shall be made by the electric furnace process with or without separate refining such as argon-oxygen-decarburization (AOD), vacuum-oxygen degassing (VOD), vacuum-induction-melting (VIM). Ferritic and martensitic steel shall be cooled after pouring to provide complete transformation of austenite prior to heat treatment to enhance mechanical properties. Chemical, heat, and product analyses shall be performed and the chemical composition thus determined shall conform to the prescribed values in carbon, manganese, silicon, phosphorus, sulfur, nickel, chromium, molybdenum, vanadium, tungsten, copper, and aluminum. Tensile testing shall be done on the castings and shall meet the required yield and tensile strength, elongation, and reduction of area. Each casting shall also be tested after machining to hydrostatic shell pressure test and shall not show any leaks.
API 6F is About recommended practice for fire test for valves.
Valve Types and Typical Applications
• DC = Directional Change
• IOS = Isolation or Stop
• PR = Pressure Relief
• TH = Throttling
1. Only angle-globe valves can be used for a 90-degree change in direction of flow.
2. Check valves (other than the stop-check valves) stop flow only in one (reverse) direction. Stopcheck valves can be and are used as stop, block, or isolation valves, in addition to being used as a check valve.
3. Some designs of ball-and-plug valves (contact the valve manufacturer) are suitable for throttling service.
4. Multiport ball-and-plug valves are used for changing the direction of flow and mixing flows.
Control Valve Arrangement
The image below shows how a control valve can be used to control rate of flow in a line. The “controller” receives the pressure signals, compares them with pressure drop for the desired flow and if the actual flow is different, adjusts the control valve to increase or decrease the flow.
Comparable arrangements can be devised to control any of numerous process variables. Temperature, pressure, level and flow rate are the most common controlled variables.
Manufacturing Process of Valves
All valves are indispensable parts of any industrial system, but not all valves are created in the same way. For example, some valves are forged and other valves are cast, Forging and casting are two of the most common ways to create high-quality valves. The biggest difference between forging vs casting valve methods is how they’re carried out.
Manufacturing Process of Forging Valves
Forged valves are created using a forging method that involves shaping metals and alloys while they’re in their solid form. Heat and industrial-size tools deliver compressive forces to bend the metals and alloys, and dies are used to cut and shape the materials to create specific valves. Forging can be performed in most temperatures depending on the metals used.
Forging valves presents many benefits for industrial companies. For example, companies don’t have to worry about wasted materials. Since forged valves are shaped into one solid piece, little effort is needed to rework the material to achieve the proper shape and size.
Forged valves have a reputation for being strong, which make them ideal for handling high-pressure and high-temperature systems. During the forging process, the metal’s grain structure becomes more refined. This leads to an increase in impact and overall strength. Also, forging boosts its resistance to common issues such as cracks, shrinkage, and porosity.
On top of that, forging can create valves with less wall thickness. This helps to reduce the likelihood of thermal fatigue during valve operation. This also means that forged valves can be heated and cooled more quickly, which allows them to adequately handle the stresses of systems that continuously cycle through start-up and phase-down processes.
Manufacturing Process of Casting Valves
Unlike forging, casting uses the liquid form of metal to create valves. These metals are melted into a molten liquid and poured into various molds. Once the liquid cools and solidifies, it’s broken out of or ejected from the mold.
One of the biggest benefits of casting is that it can create valves with complex shapes, patterns, and sizes. Using a mold to manufacture these devices gives you more freedom to make different types valves with more intricate parts.
Casting valves are also a great cost-effective solution for many companies. It allows you to make valves using more types of metals and alloys. Plus, since it doesn’t require as much labor as forging valves, casting helps to reduce machining costs, especially when creating valves of complex shapes.
Most importantly, casting valves provides an easier and less time-consuming way to make replacement parts when a system’s current valves break down and deteriorate.
- Purchasing Raw Material and Standard Parts→Material Inspection→Machining→Body Assembly→Painting→Mounting & Calibrating required Accessories→Final Test→Packing & Marking→Delivery
1. Purchasing Raw Material and Standard Parts
(Cast , Forge, Bar, Sheet)
• Cast Materials generaly used for size over 2”
• Forge & Bar materials generaly used for size below 2” and internal trim parts
– Internal Inspection
• Raw Material & Material Certificate Check
• Quantity Check
• Visual & Dimension Check (VT)
2. Material Inspection
• Chemical Analysis Check
• Preservation Analysis Certificate
• Positive Material Identification
• Dye Penetrant Exams
• Magnetic Particle Exams
• X and Gamma Rays Exams
• Ultrasonic Exams
• NDE (RT/UT/PT/MT)
• Visual and Dimensional Exams
• Body & Bonnet
• Internal Trim Part
• Dimension Inspection after machining (according to approved drawing and related standards)
• Hydrostatic Test
4. Body Assembly
• Assembling of Internal Trim Part,
• Bonnet Assembly
• Valve Body Paiting
• Visual Check
• Dry film thickness check of painting
• Adhesion check of painting
6. Mounting & Calibrating required Accessories
• Air Filter Regulator
• Solenoid valve
• Limit Switch
• Volume Booster
7. Final Test
• Visual & Dimension inspect
• Stroke test,
• Seat Leakage test
Function & Performance test of full assebmly of body, actuator and accessories
8. Packing & Marking
• Packing Inspection
• Pre Shipment Inspection (PSI)
Installation of valves
General requirements for valve installation.
- (1) flange type threaded connection of the valve should be in the closed state.
- (2) welding valve and pipe welding to be primed with argon arc welding to ensure its internal smoothness and flatness. When welding, the valve should be in the open state to prevent local overheating deformation. Welding high-pressure water injection valve to open the valve body, the rubber gasket pick out to prevent the rubber ring is hot.
- (3) before installing the valve, according to the direction of media flow, determine its installation direction.
- (4) installed in the horizontal pipeline valve, to vertical up, horizontal up or down tilt 45 °, its centerline should be taken as flush as possible.
- (5) installation of cast iron valves (black, silver), shall prevent damage caused by strong connection or uneven force.
Installation of valves when the location and direction of choice
The location of the valve installation, must be convenient for operation; even if the installation is temporarily difficult, but also for the sake of the long-term work of the operator. The best valve handwheel and chest to take flush (generally 1.2m from the operating floor), so that opening and closing the valve is less effort. Landing valve handwheel to face up, do not tilt, so as not to operate twisted. The valve against the wall machine against the equipment, but also to leave room for the operator to stand. To avoid operating on your back, especially acid and alkali, toxic media, etc., otherwise it is very unsafe.
Gate valve should not be installed upside down (i.e. handwheel down), otherwise the medium will be left in the valve cover space for a long time, easy to corrode the stem, and forbidden by certain process requirements. At the same time the replacement of packing is extremely inconvenient. Open stem gate valve, do not install in the ground, or due to moisture and corrosion of the exposed stem.
Lift check valve, installation to ensure that its valve flap vertical, in order to lift flexible. Swing check valve, installation to ensure that its pin level, in order to spin open flexible.
Many valves have directional, such as stop valves, throttle valves, pressure reducing valves, check valves, etc., if installed backwards, will affect the use of the effect and life (such as throttle valves), or simply does not work (such as pressure reducing valves), or even cause danger (such as check valves). General valve, there are directional signs on the valve body; in case there is no, should be correctly identified according to the working principle of the valve.
Stop valve cavity left and right asymmetric, the fluid to let it from the bottom up through the valve mouth, so that the fluid resistance is small (determined by the shape), open to save effort (due to the media pressure up), close the media does not pressure packing, easy access to maintenance. This is the reason why the shut-off valve can not be a reverse. Other valves also have their own characteristics.
Pressure reducing valve should be installed upright on the horizontal pipeline, do not tilt in all directions.
Maintenance of valves
Maintenance of the valve, can be divided into two cases; custody maintenance and use maintenance.
(A) custody maintenance
Improper storage is one of the important reasons for damage to the valve.
Valve storage, can not be stacked, small valves on the shelves, large valves can be neatly arranged on the ground in the warehouse, do not let the flange connection surface contact the ground. Protect the valve from touching bad.
Short-term temporary non-use of the valve, asbestos packing should be removed to avoid electrochemical corrosion, damage to the valve stem.
The valve just into the warehouse, to check, such as in the process of transport into the rain or dirt, to wipe clean, and then stored.
Valve import and export should be sealed with wax paper or plastic sheet to prevent the entry of dirty things.
Can rust in the atmosphere of the valve processing surface to be coated with anti-rust oil, to protect.
Placed outside the valve, must be covered with linoleum or sheeting and other rainproof, dustproof items. The warehouse where the valve is stored should be kept clean and dry.
(B) the use of maintenance
The use of maintenance is to extend the life of the valve and ensure reliable opening and closing.
Stem threads often friction with the stem nut, to apply a little grease or graphite powder, play a lubricating role.
Infrequent opening and closing of the valve, to regularly turn the handwheel, the stem threads with lubricant to prevent bite.
Outdoor valves, to add a protective sleeve to the stem to prevent rain, snow, dust and rust stains.
If the valve is mechanically driven, add lubricant to the gearbox on time and keep the valve clean.
Do not rely on the valve to support other heavy objects, do not stand on the valve.
The valve stem, especially the threaded part, should be cleaned frequently and new lubricant should be added to prevent hard debris in the dust from wearing the threads and stem surface and affecting the service life.
Operation of valves and precautions
For the valve, not only to be able to install and maintain, but also to operate.
(A) manual valve opening and closing
Manual valve is the most widely used valve, its hand wheel or handle, is designed in accordance with ordinary human power, taking into account the strength of the sealing surface and the necessary closing force. Some people are accustomed to use the plate hand, should be strictly noted, do not use too much force too hard, otherwise it is easy to damage the sealing surface, or plate broken handwheel, handle.
Open and close the valve, the force should be smooth, not impact. Certain impact opening and closing of high-pressure valve components have been considered this impact force and general valve can not be equivalent.
For steam valves, before opening, should be pre-heated, and exclude condensate, open, should be as slow as possible to avoid the phenomenon of water strike.
When the valve is fully opened, the handwheel should be reversed a little so that the threads are tightened between them to avoid loose damage.
For the open stem valve, remember the position of the stem when fully open and fully closed to avoid hitting the upper dead center when fully open. And it is easy to check whether it is normal when fully closed. If the valve office off, or spool seal embedded between the larger debris, the fully closed stem position to change.
When the pipeline is first used, more internal dirt, the valve can be slightly open, the use of high-speed flow of media, will be washed away, and then gently closed (not fast closed, closed, to prevent residual impurities pinch sealing surface), open again, so repeat many times, flush clean dirt, and then put into normal operation.
Always open the valve, the sealing surface may be stuck with dirt, close the above method should also be used to flush it clean, and then formally close the tight.
If the handwheel, handle damaged or lost, should be immediately equipped, not to use the live plate hand instead, so as not to damage the valve stem quadrilateral, opening and closing does not work, so that accidents occur in production.
Certain media, cooling after the valve is closed, so that the valve shrinkage, the operator should be closed again at the appropriate time, so that the sealing surface does not leave a slit, otherwise, the media from the slit high-speed flow through, it is easy to erode the sealing surface.
When operating, if you find that the operation is too laborious, you should analyze the reason. If the packing is too tight, can be properly relaxed, such as the valve stem is skewed, should notify the personnel repair. Some valves, in the closed state, the closing piece of thermal expansion, resulting in opening difficulties; such as must be opened at this time, the valve cover threads can be loosened by half a turn to a turn, eliminate the stem stress, and then plate hand wheel.
- 1. More than 200 ℃ high temperature valves, due to installation at room temperature, and after normal use, the temperature rises, the bolt heat expansion, the gap increases, so it must be tightened again, called “hot tight”, the operator should pay attention to this work, otherwise it is easy to leak.
- 2. Cold weather, the water valve closed for a long time to stop, the valve should be removed after the water. Steam valve after stopping steam, but also to exclude condensate. The bottom of the valve has such as silk plug, it can be opened to drain.
- 3. Non-metallic valves, some hard and brittle, some lower strength, operation, open and close the force can not be too large, especially not to make a strong force. Attention should also be paid to prevent objects from bumping.
- 4. The use of new valves, packing do not press too tightly to not leak, so as not to pressure the stem too much, speeding up wear and tear, and opening and closing effort.
Common failures of valves and prevention
(A) the general valve
Stuffing box leakage
This is the main aspect of running, bubbling, leakage, often seen in the factory. The following causes of stuffing box leakage.
- 1. Packing and working medium corrosive, temperature, pressure does not fit;
- 2. Filling method is not correct, especially the whole packing spare spin into, most likely to produce leakage.
- 3. The stem processing accuracy or surface finish is not enough, or there is ovalness, or scored.
- 4. The stem has been pitting, or rust due to the lack of protection in the open air.
- 5. The stem is bent.
- 6. The packing has been used for too long has been aging.
- 7. The operation is too violent.
Leakage of closing parts
Usually the stuffing box leakage is called external leakage, the closing piece leakage is called internal leakage, closing piece leakage, in the valve in, not easy to find.
Closure piece leakage, can be divided into two categories; one is the sealing surface leakage; the other is the seal root leakage:
Causes of leakage are:
- 1> poorly ground sealing surface.
- 2> seal ring and valve seat, valve office with a tight fit.
- 3> valve flap and valve stem connection is not secure.
- 4> valve stem bending, so that the upper and lower closing pieces are not centered;
- 5> closing too fast, the sealing surface contact.
- 5> close too fast, the sealing surface contact is not good or long damaged.
- 6> improper choice of materials, can not withstand the corrosion of the medium.
- 7> the globe valve, gate valve for regulating the use of sealing surface can not withstand the impact of high-speed flow of media.
- 8> certain media, after the valve is closed gradually cooled, so that the seal surface slit, will also produce erosion phenomenon.
- 9> certain seals and valve seat, valve office between the use of threaded connections, easy to produce oxygen concentration difference battery, corrosion loosening.
- 10> because of welding slag, rust, dust and other impurities embedded in the production system, or the production system has mechanical another piece off blocking the spool, so that the valve can not be closed tight.
The valve stem lift failure
The causes are:
- 1> operation is too violent so that the thread damage.
- 2> lack of lubricant or lubricant failure.
- 3> valve stem bending.
- 4> insufficient surface finish.
- 5> inaccurate tolerances and overbite.
- 6> stem nut tilt.
- 7> improper choice of material; for example, the stem and stem nut are of the same material, easy to bite.
- 8> thread wave media corrosion (refers to the concealed stem valves or valves with the stem in the lower part).
- 9> open-air valves lack of protection, stem threads sticky with dust and sand, or rusted by rain, frost and snow, etc.
Valve body cracking: generally caused by freezing. When it is cold, the valve should have insulation and heating measures, otherwise the valve and the water in the connecting pipeline should be drained after the shutdown (if there is a silk plug at the bottom of the valve, you can open the silk plug to drain).
Handwheel damage: impact or long lever fierce operation caused by. As long as the operator or other relevant personnel pay attention, it can be avoided.
Packing gland fracture: uneven force when pressing the packing, or the gland is defective. To compress the packing, rotate the screw symmetrically, not to be skewed. Manufacturing should not only pay attention to the large and key parts, but also pay attention to secondary parts such as gland, otherwise it will affect the use.
Stem and gate connection failure: gate valve using stem rectangular head and gate T-slot connection form more, T-slot sometimes not processed, so that the stem rectangular head wear faster. Mainly from the manufacturing side to solve. But the use of the unit can also make up the T line groove processing, so that she has a certain degree of finish.
Double gate valve gate can not be pressed tight cover: double gate tension is generated by the top wedge, some gate valve, the top wedge material is not good (low grade cast iron), the use of soon wear or break. The top wedge is a small piece, replace the original cast iron parts.
(B) automatic valve
Spring-loaded safety valve
One of the faults, sealing surface leakage. Causes are: sealing surface between the debris trapped; sealing surface damage.
This failure to rely on regular maintenance to prevent. Failure of the second, the sensitivity is not high. Causes are: spring fatigue; improper use of springs.
Spring fatigue, no doubt should be replaced. Improper use of springs, is the user does not pay attention to a nominal pressure of the spring-type safety valve, there are several pressure segments, each with a corresponding spring. Such as nominal pressure of 16 kg/cm2 safety valve, the use of pressure is 2.5 – 4 kg/cm2 pressure section, installed 10 – 16 kg/cm2 of the spring, although it can also be opened, but high and low, very insensitive.
Long seen failures are: valve flap broken; media backflow.
Caused by the valve to break the reason is: check valve before and after the medium pressure is in close balance and each other “saw” state, valve to do often with the valve seat beat, some brittle materials (such as cast iron, brass, etc.) made of valve to be broken. Prevent the way is to use the valve office for the tough material check valve.
Media backflow causes are: sealing surface damage; entrapped impurities. Repair the sealing surface and remove impurities, you can prevent backflow.
The above description of common failures and prevention methods can only serve as inspiration, in actual use, will encounter other failures, to achieve active and flexible prevention of valve failure, the most fundamental one is familiar with its structure, material and action principle.
Valves are mechanical devices that control the flow and pressure of fluids in a hydraulic or air system. Valves are an important part of piping systems that carry liquids, gases, steam, sludge, etc.
There are many different types of valves to choose from, each with different characteristics, capacities and uses.
Before selecting a valve, you need to determine what it will be used for. Will the valve be used to regulate the fluid or to stop the flow of fluid?
Then you need to determine the type of media circulating in the system: is it a gas or a liquid? Is the medium corrosive, chemically neutral, a food product or a medical fluid requiring special sanitary conditions?
When it comes to the operating system of the valve, it is necessary to know whether it is manual or automatic. In the first case, someone must be on site to operate the valve, while in the other case, the valve can be operated remotely, for example from a control station.
Finally, it is important to know how the valve will be integrated into the system and the type of assembly or installation used, especially if welding, bolting through flanges or screwing in is required.
Once these different elements have been identified, you can then focus on the technical characteristics of the installation, in particular the flow and pressure, used to size the valve.
In order to calculate the size of a valve, you need to know the parameters related to the operation of the circuit.
Parameters for sizing valves.
- Flow rate
Pressure is an important factor that must be taken into account, on the one hand to avoid undersizing the valve, which could lead to problems in valve leakage or rupture, and on the other hand to avoid oversizing the valve.
The operating temperature, i.e. the temperature of the circulating medium, and the ambient temperature around the valve body need to be determined. It is important to know the temperature extremes that the valve needs to withstand in order to be able to select the valve that can be used to operate under these conditions, especially the materials used to manufacture the body, shut-off system and seals.
The operating pressure, i.e., the pressure at which the medium circulates through the valve.
Flow rate and velocity of the fluid. The flow rate and rated velocity are essential elements to help you select the right valve, especially for regulating that flow. The flow coefficient (Kv) is a theoretical value specified by the manufacturer that allows you to calculate the nominal flow rate of the valve. It can be expressed in liters per minute (l/min) or cubic meters per hour (m3/h). The valve manufacturer provides charts to determine this coefficient based on the required flow rate and nominal diameter.
The nominal diameter (DN) of the circuit in which the valve is located. This is essential to avoid oversizing the valve, which may lead to unstable operation of the equipment, or to avoid undersizing, which may lead to a significant pressure drop and rapid valve damage.
How to choose chemical valves under corrosive media conditions?
Valves in corrosive media conditions, anti-corrosion is the most critical part of chemical equipment, if you can not properly select the metal material of chemical valves, a slight inadvertence, light damage to equipment, or even cause accidents or disasters. According to relevant statistics, about 60% of the damage to chemical equipment is caused by corrosion, so in the selection of chemical equipment should first pay attention to the scientific nature of the selection of materials. Usually there is a misconception that stainless steel is a “universal material”, regardless of what media and environmental conditions are held out of stainless steel, which is incorrect, but also very dangerous. The following for some commonly used chemical media to talk about the key points of material selection:
1. Sulfuric acid media
As one of the strong corrosive medium, sulfuric acid is a very wide range of important industrial raw materials. Different concentrations and temperatures of sulfuric acid on the material corrosion differences, for concentrations above 80%, the temperature is less than 80 ℃ of concentrated sulfuric acid, carbon steel and cast iron have better corrosion resistance, but it is not suitable for high-speed flow of sulfuric acid, not suitable for pump valve materials; ordinary stainless steel such as 304 (0Cr18Ni9), 316 (0Cr18Ni12Mo2Ti) for sulfuric acid medium is also limited. Therefore, pump valves for conveying sulfuric acid are usually made of high silicon cast iron (casting and processing difficulties), high alloy stainless steel (No. 20 alloy). Fluorine plastic has better resistance to sulfuric acid, the use of fluorine lined pump valve (F46) is a more economical choice. If the pressure is too high, the temperature rises, the plastic valve with the point of impact, you have to choose much more expensive than it is ceramic ball valve.
2. Hydrochloric acid media
Most metal materials are not resistant to hydrochloric acid corrosion (including a variety of stainless steel materials), molybdenum-containing high silicon iron can only be used for 50 ℃, 30% below hydrochloric acid. Contrary to metal materials, most non-metallic materials have good corrosion resistance to hydrochloric acid, so rubber-lined pumps and plastic pumps (such as polypropylene, fluorine plastic, etc.) is the best choice for conveying hydrochloric acid. But such a medium if the temperature exceeds 150 ℃, or pressure greater than 16 kg, any plastic (including polypropylene, fluorine plastic or even PTFE) will not be able to do the job, and there is not yet a very ideal valve on the market, but you can try the emerging ceramic ball valve, the advantages of this valve is self-lubricating, small torque force, not aging, the life of the valve is much longer than the average, its The disadvantage is that the price is much higher than the plastic valve.
3. Nitric acid media
Most of the general metal in nitric acid is rapidly corroded and destroyed, stainless steel is the most widely used nitric acid-resistant materials, all concentrations of nitric acid at room temperature have good corrosion resistance, it is worth mentioning that molybdenum-containing stainless steel (such as 316, 316L) on nitric acid corrosion resistance is not only not better than ordinary stainless steel (such as 304, 321), and sometimes even worse. For high-temperature nitric acid, titanium and titanium alloy materials are usually used.
4. Acetic acid media
It is one of the most corrosive organic acids, ordinary steel in all concentrations and temperatures of acetic acid will be seriously corrosive, stainless steel is excellent acetic acid resistant materials, containing molybdenum 316 stainless steel can also be applied to high temperature and dilute acetic acid vapor. For high temperature and highly concentrated acetic acid or containing other corrosive media and other demanding requirements, high alloy stainless steel or fluorine plastic pumps can be used.
5. Alkali (sodium hydroxide)
Steel is widely used in sodium hydroxide solution below 80 ℃, 30% concentration within, there are also many petrochemical plants at 100 ℃, 75% below when still using ordinary steel, although corrosion increases, but the economy is good. Ordinary stainless steel corrosion resistance of lye compared with cast iron has no obvious advantages, as long as the medium allows a small amount of iron admixture, stainless steel is not recommended. For high-temperature lye more titanium and titanium alloy or high-alloy stainless steel.
6. Ammonia (ammonia hydroxide)
Most metals and non-metals in liquid ammonia and ammonia (ammonia hydroxide) corrosion are very slight, only copper and copper alloy should not be used.
7. Chlorine (liquid chlorine) most of the metal valve corrosion resistance of chlorine is very limited, especially chlorine with water, including a variety of alloy valves, in this case, tetrafluoro valve is a very good choice, but the production of chlor-alkali chemical plants will find: tetrafluoro valve with a slightly longer period of time, the torque increases, tetrafluoro aging problem will come to the fore, the leakage in this case is fatal. The leakage in this case is fatal. Consider replacing the original ordinary PTFE-lined valve with a PTFE-lined ceramic ball core, using the self-lubricating nature of ceramic and PTFE corrosion resistance will have perfect results.
8. Salt water (seawater)
Ordinary steel in sodium chloride solution and seawater, salt water corrosion rate is not too high, generally must be protected by coatings; all types of stainless steel also has a very low uniform corrosion rate, but may cause localized corrosion due to chloride ions, usually using 316 stainless steel is better.
9. Alcohols, ketones, esters, ethers
Common alcohol media are methanol, ethanol, ethylene glycol, propanol, etc., ketone media are acetone, butanone, etc., ester media are a variety of methyl ester, ethyl ester, etc., ether media are methyl ether, ether, butyl ether, etc., they are basically not corrosive, commonly used materials can be applied, the specific choice should also be based on the properties of the medium and related requirements to make a reasonable choice. It is also worth noting that ketones, esters, ethers have solubility to a variety of rubber, to avoid mistakes in the selection of sealing materials.
Source: Network Arrangement – China Valves Solutions Supplier – Yaang Pipe Industry (www.epowermetals.com)
(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.)
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