China piping solution supplier:

Manufacturing process flow of pipe fittings

Raw materials

  1. The selection of materials shall comply with the relevant standards of the pipe production country and the raw material standards required by the owner.
  2. After entering the factory, the inspectors first verify the original material certificate issued by the manufacturer and the material inspection report of the import manufacturer. Check whether the identification on the material is complete and consistent with the quality certificate.
  3. The newly purchased materials shall be rechecked, and the chemical composition, length, wall thickness, outer diameter (inner diameter) and surface quality of the materials shall be strictly inspected according to the requirements of ASME and din17175 standards, and the batch number and pipe number of the materials shall be recorded. Materials that do not meet the requirements are not allowed to be put into storage and processed. The internal and external surface of the steel pipe is not allowed to have cracks, folding, rolling, scab, separation layer and hairline. These defects shall be completely removed, and the removal depth shall not exceed the negative deviation of the nominal wall thickness, and the actual wall thickness at the cleaning position shall not be less than the minimum allowable wall thickness. On the inner and outer surface of the steel pipe, the allowable defect size shall not exceed the relevant provisions in the corresponding standards, otherwise it will be rejected. The oxide scale on the inner and outer surface of the steel pipe shall be removed and treated with anti-corrosion treatment, which shall not affect the visual inspection and can be removed.

In order to ensure that the materials meet the specified specifications, the following tests shall be carried out for the materials specially required by customers:

  1. The mechanical properties meet the requirements of din17175 and ASME respectively. For alloy steel pipe, transverse mechanical property test (including transverse impact test) is carried out. The impact test is Charpy V test, and the inspection times are the same as tensile test.
  2. Process performance.
  • 100% ultrasonic nondestructive testing shall be conducted for steel pipes one by one according to sep1915, and standard samples for ultrasonic flaw detection shall be provided. The defect depth of standard sample shall be 5% of wall thickness, and the maximum defect depth shall not exceed 1.5mm.
  • Flattening test for steel pipe 3. The actual grain size of finished alloy steel pipe shall not be coarser than grade 4, and the grade difference of steel pipe with the same heat number shall not exceed grade 2. The grain size inspection shall be conducted in accordance with ASTM I 12-95, and the inspection times shall be once for each heat treatment batch.


  1. It is necessary to consider many factors such as the thickness of the tube, the thickness of the tube before and after the pipe fitting is calculated, such as the thickness of the pipe fitting, the thickness of the pipe fitting, the thickness of the pipe fitting, the thickness of the pipe fitting, etc Whether the enhancement coefficient is in line with the design stress coefficient of the pipeline and the flow area of the pipeline. The radial material compensation and shoulder material compensation should be calculated for hot pressing tee.
  2. Cold cutting method is adopted for cutting high alloy metal pipe materials by gantry band saw cutting machine. Flame cutting is generally avoided for other materials, but band saw is used to prevent hardening layer or cracks caused by improper operation.
  3. According to the design requirements, the external diameter, wall thickness, material, pipe number, furnace batch number and pipe blank serial number of raw materials shall be transplanted during cutting and blanking, and the low stress steel seal and paint spraying method shall be adopted for identification. And record the operation content on the production process flow card.
  4. After the first piece is laid off, the operator shall carry out self inspection and report to the special inspection personnel of the testing center for special inspection. After passing the inspection, the blanking of other parts shall be carried out, and each piece shall be inspected and recorded.

Hot pressing (pushing) molding

  1. The hot pressing forming process of high-pressure pipe fittings (especially TEE) is an important process, and the billet can be heated by oil heating furnace. Before the billet is heated, the scrap angle, oil, rust, copper, aluminum and other low melting point metals on the surface of the billet are cleaned with hammers and grinding wheels. Check whether the identification of the blank meets the design requirements.
  2. Clean up the sundries in the furnace hall, and check whether the heating furnace circuit, oil circuit, trolley and temperature measurement system are normal and whether the oil is sufficient.
  3. The blank is heated in the heating furnace. Refractory bricks are used to isolate the workpiece from the furnace hearth for 20. The heating speed is strictly controlled at 150 ℃ / h according to different materials. The heat preservation is more than 1 hour when heated to 30-50 ℃ above material AC3. In the process of heating and heat preservation, digital display or infrared thermometer is used to monitor and adjust at any time.
  4. When the blank is heated to the specified temperature, the pressing is completed by 2500 ton press and pipe fitting die. During pressing, the temperature of the workpiece is measured by infrared thermometer, and the temperature is not less than 850 ℃. When the workpiece is not pressed at one time and the temperature is too low, the workpiece is returned to the furnace for reheating and heat preservation before pressing.
  5. The hot forming of the product fully considers the metal flow law of the thermoplastic deformation in the forming process of the finished product. The molding mold tries to reduce the deformation resistance generated by the hot processing of the workpiece, and the pressing tire mold is in good condition. According to the requirements of ISO9000 quality assurance system, the tire mold is verified regularly to control the thermoplastic deformation of the material, so as to make the actual wall of any point on the pipe fitting The thickness is greater than the minimum wall thickness of the straight pipe connected.
  6. For large diameter elbow, medium frequency heating push molding is adopted, and large elbow pushing machine is selected as pushing equipment. In the pushing process, the heating temperature of the workpiece is adjusted by adjusting the power of the intermediate frequency power supply, which is generally controlled at 950-1020 ℃, and the pushing speed is controlled at 60-100 mm / min.

Heat treatment

  1. For finished products made of 10CrMo910, 12Cr1MoV and other materials, our company carries out heat treatment in strict accordance with the heat treatment system specified in din17175 and ASME standard. Generally, the heat treatment of small pipe fittings can be carried out in resistance furnace, and the heat treatment of large diameter pipe fittings or elbows can be carried out in fuel oil heat treatment furnace.
  2. The furnace hall of the heat treatment furnace shall be clean and free of oil, ash, rust and other metals different from the treatment materials.
  3. Heat treatment shall be carried out in strict accordance with the heat treatment curve required by “heat treatment process card”. The temperature rise and fall speed of alloy steel pipe parts shall be controlled to be less than 200 ℃ / h.
  4. The automatic recorder records the temperature rise and fall at any time, and automatically adjusts the temperature and holding time in the furnace according to the preset parameters. In the heating process of pipe fittings, the fire wall is used to block the flame, so as to prevent the flame from directly spraying on the surface of the pipe fitting, so as to ensure that the pipe fittings will not overheat and burn during the heat treatment process.
  5. After heat treatment, metallographic examination shall be carried out for alloy pipe fittings one by one. The actual grain size of alloy shall not be coarser than grade 4, and the grade difference of pipe fittings with the same heat number shall not exceed grade 2.
  6. Carry out hardness test on the heat-treated pipe fittings to ensure that the hardness value of any part of the pipe fittings does not exceed the range required by the standard.
  7. After heat treatment of pipe fittings, the oxide scale on the inner and outer surfaces shall be removed by sandblasting until the metallic luster of the material is visible. For the defects such as scratches and pits on the material surface, the grinding wheel and other tools shall be used to smooth them. The local thickness of the polished pipe fittings shall not be less than the minimum wall thickness required by the design.
  8. Fill in the heat treatment record according to the pipe fitting number and identification, and re write the incomplete identification on the surface of the pipe fitting and the flow card.

Groove processing

  • The groove processing of high-pressure pipe fittings is carried out by mechanical cutting. Our company has more than 20 sets of various lathes, power heads and other machining equipment. According to dl869 welding technical specification of thermal power plant, GD87 typical design manual of steam water pipe parts and components in thermal power plant, DL / t695-1999 steel butt welding pipe fittings for power station, and double-V-shaped pipe fittings for various thick wall pipe fittings required by the bid inviting party can be processed Or U-shaped groove, inner groove and outer groove can be processed by the company according to the groove drawing and technical requirements provided by the bid inviting party, so as to ensure that the pipe fittings are easy to operate and weld in the welding process.
  • After the pipe fitting groove is completed, the inspection personnel shall inspect and accept the overall dimensions of the pipe fittings according to the drawing requirements, and rework the products with unqualified geometric dimensions until the products meet the design dimensions.


  1. The welding of pipe fittings such as “welded tee” and “welded elbow” to be welded shall be carried out by professional welders with many years of welding experience. Appropriate welding procedure qualification shall be made according to the requirements, and mechanical property test shall be carried out on the weld, and welding production shall be conducted under the guidance of appropriate process specification. Qualified welding procedure qualification shall be adopted in the welding process, and the procedure qualification shall comply with the provisions of ASME Boiler and pressure vessel code section IX welding and brazing procedure qualification, and the welder shall be qualified according to this assessment. In the welding process, the welding items of the welder are not consistent with the items passed the examination, so welding is not allowed. During the welding process, the quality assurance engineer shall monitor and measure the stop point and witness point of the welding process to ensure that there are no defects and problems in the key process of welding. The welding parameters such as interlayer temperature, preheating temperature and welding pass number shall be strictly controlled and the interlayer cleaning shall be carried out carefully. Tempering treatment shall be carried out immediately after welding to ensure that the performance of welded joint meets the specification requirements.
  2. The welding process shall be carried out in strict accordance with the “welding process guidance card” formulated by the company. During the welding process, the defects such as incomplete penetration, air hole, slag inclusion, crack and undercut shall be avoided.
  3. The post weld heat treatment of pipe fittings can be carried out in resistance furnace, oil furnace or far-infrared heating furnace to ensure that the mechanical properties and other technical indexes of welded joints are similar to those of base metal.
  4. The welds of welded pipe fittings shall be subject to 100% X-ray or ultrasonic testing. According to jb4730-2005 standard, the ultrasonic wave reaches grade I and the ray reaches grade II.


  1. All high pressure pipe fittings shall be tested according to dl869, dl5031 and other standards before delivery. According to the requirements of ASME b31.1, all kinds of tests shall be completed by professional inspectors with corresponding qualifications approved by the State Bureau of technical supervision.
  2. Magnetic particle (MT) testing shall be carried out on the external surface of high-pressure tee, elbow and reducer, ultrasonic thickness measurement and flaw detection shall be conducted for the outer arc side of elbow, tee shoulder and reducer, and radiographic inspection or ultrasonic flaw detection shall be conducted for weld joint of welded pipe fittings. Ultrasonic testing is carried out on the blank of forged tee or elbow before machining.
  3. Magnetic particle inspection shall be carried out within 100 mm of the groove of all pipe fittings to ensure that there are no cracks and other defects in the groove caused by cutting process.
  4. Surface quality. The inner and outer surface of the pipe fitting is not allowed to have any defects such as crack, shrinkage cavity, ash slag, sand sticking, folding, missing welding, double skin, etc. the surface shall be smooth without sharp scratch, the depth of depression shall not exceed 1.5mm, and the maximum size of depression shall not be greater than 5% of the circumference of the pipe and shall not be greater than 40mm. There shall be no cracks, pores, craters and spatters on the weld surface, and there shall be no undercut. The inner corner of tee joint shall be smooth transition. All pipe fittings shall be subject to 100% surface appearance inspection. The cracks, sharp corners, pits and other defects on the surface of the pipe fittings shall be polished with a grinder, and the magnetic particle inspection shall be carried out on the polished parts until the defects are eliminated. The thickness of the polished pipe fittings shall not be less than the minimum design thickness.
  5. The following tests shall be carried out for the pipe fittings with special requirements of customers:
  • Hydraulic test all pipe fittings can be tested with the system (the hydrostatic test pressure is 1.5 times of the design pressure, and the time is not less than 10 minutes). If the quality certification documents are complete, the pipe fittings can be delivered without hydrostatic test.
  • Actual grain size: the actual grain size of finished pipe fittings shall not be coarser than grade 4, and the grade difference of pipe fittings with the same heat number shall not exceed grade 2. The grain size inspection shall be conducted in accordance with the method specified in Yb / t5148-93 (or ASTM e112-95), and the inspection times shall be once for each heat number and heat treatment batch.
  • Microstructure: the manufacturer shall carry out microstructure inspection in accordance with relevant provisions of GB / t13298-91 (or corresponding international standards) and provide microstructure photos. The inspection times are each heat number + size (diameter × wall thickness) + heat treatment batch once.

Packaging and marking

The surface of the pipeline shall be coated with anti rust primer, and the surface shall be painted with different colors according to different pipes. The paint shall be uniform, without bubbles, wrinkles and peeling, and the groove shall be treated with special antirust agent. Small forged pipe fittings or important pipe fittings are packed in wooden cases, while large ones are usually bare. The nozzles of all pipe fittings are firmly protected by rubber (plastic) ring, so as to protect the pipe fittings from damage. Ensure that the final products are free from any defects such as cracks, scratches, tensile marks, double skin, sticking sand, interlayer and slag inclusion. Mark the pressure, temperature, material, diameter and other pipe fittings specifications on the obvious parts of pipe fittings. Low stress steel seal is used.

Transportation of pipe fittings

The transportation of pipe fittings should be based on the actual situation. Generally, domestic pipe fittings are transported by truck. In the process of vehicle transportation, it is required to use high-strength soft packing tape to firmly bind the pipe fittings with the car body. Collision and friction with other pipe fittings are not allowed during vehicle driving, and rainproof and moisture-proof measures shall be taken. When the pipe fittings are delivered, the delivery status of alloy steel pipe parts is: normalizing + tempering; the delivery status of carbon steel is: normalizing.

Available technical documents

Before delivery, all kinds of quality records, reports and technical documents shall be reviewed according to regulations, which can be reviewed by the owner before delivery. The documents to be submitted with the goods include: the design parameters of the processed parts of the quality assurance certificate, the design drawings, the inspection report of the pipe fittings (including a raw material re inspection report; B-ray flaw detection report; C heat treatment report; D ultrasonic flaw detection report; e magnetic particle inspection report; F dye penetration inspection report; G geometric dimension inspection report; h and various reports formulated through consultation with the user) the material and weight of the pipe fittings Other necessary documents.
The factory configuration of pipeline is as follows:

Piping design

  • 1. Design the pipeline direction and girth weld position, relative distance from platform and hole, relative position of straight pipe section of elbow, various holes of elevator block, nozzle seat, etc., factory weld and site weld.
  • 2. Design the groove form of pipeline and pipeline, valve, equipment, flow measurement device, etc., weld C value or corresponding inner diameter value at groove, minimum design wall thickness and weld coefficient at groove.
  • 3. Design the section beginning and size of various weld metal filling, and specify the forming requirements of inner wall of girth weld and welding reinforcement of outer wall. For example, the structural dimensions and relevant data of the nozzle seat such as venting and venting at thermal measuring points are designed. The area compensation method is used for the design of the nozzle seat. The full penetration fillet weld of the pipe socket is designed according to the method of asmeb31.1 power pipe.
  • 4. For the branch pipe with opening hole, such as safety valve socket, the calculation method of thermal pipe socket can not be used simply. In the design, the calculation method of thick wall tee is required to calculate the groove height of each section of branch pipe, and the fillet height of full penetration fillet weld of each section shall be designed according to asmeb31.1 power pipeline.
  • 5. Assist the Design Institute in drawing the installation drawing and piping drawing after the slope cutting calculation of the pipeline, and mark the drainage slope of the pipeline and the calculation angle of the pipe fittings in the piping installation drawing. Therefore, on the premise of complying with the design, the factory piping engineer should understand the actual habits and installation conditions of the construction company, calculate the angle of pipe fittings and the elevation of each node after slope cutting, and consider the influence of pipe fittings on pipe size after cold tightening.
  • 6. The factory understands the specification requirements of thermal engineering, chemistry and other specialties of the Design Institute, manufacturers and performance debugging units for various measuring points, and reflects the requirements of these specifications in piping design.
  • 7. According to the requirements of the pipeline installation Atlas of the Design Institute, design and select the supports and hangers, clamp blocks, supports, stop blocks and other accessories in the piping design drawing.
  • 8. According to the technical requirements of cold tightening and installation sequence, determine the relevant technical requirements of pipeline adjustment section.
  • 9. Each piping product shall be uniquely identified according to the piping system diagram (PID) or the pipeline product identification number (KKS code). So as to realize the management of pipeline product information and traceability.
  • 10. Mark the weld number on the piping drawing (girth weld, all kinds of fillet weld, etc.) according to the provisions of weld identification. These numbers can meet the requirements of metal supervision and management and meet the needs of relevant metal management software. These welds are classified and marked with factory joints and construction site welds.

Pipe welding

1. Before combined welding, confirm that the welding of various materials is supported by welding procedure qualification, and have welders with corresponding welding qualification.
2. The combined welding shall be carried out according to the requirements of the following documents:

  • (1) Combined working drawing;
  • (2) Welding operation instruction;
  • (3) Welding process card;
  • (4) Material list and surplus material list.

3. After the assembly is completed, the special inspector and the team shall check the main geometric dimensions, alignment misalignment, relative position of components, and the position of accessories. Welding can only be carried out after confirming that the requirements of drawings and welding standards are met, and this process can be controlled as the stop point of the factory.
4. For pipes that need to be preheated, electric heating shall be used for preheating, and the heating width on each side shall not be less than 3 times of the thickness of the weldment.
5. The heating rate of preheating shall be calculated as 250 * 25 / wall thickness ℃ / h, and shall not be greater than 300 ℃ / h. There are recorded curves for welding preheating for verification.
6. For alloy pipe welding, the inner wall of the pipe shall be filled with argon for protection, and shall be fully sealed to ensure that the oxygen content at the edge of inner groove is lower than the standard requirements.
7. Weld welding shall be carried out in strict accordance with the requirements of welding process parameters on the welding process card. During the welding process, the welding inspectors shall supervise on site, and the welding engineer shall conduct spot check at any time.
8. The shape of fillet weld shall be concave butt joint or 45 ° straight transition, and the welding height shall take into account the allowance for non-destructive testing after grinding.
9. After the circumferential weld and fillet weld are welded, the welder’s steel seal and weld joint number shall be marked.
10. For the alloy welded joint, after welding, the temperature drops below 100 ℃, and the argon elimination treatment shall be carried out immediately. Specific methods to implement the process requirements, and automatic temperature recording.
11. Inspection items and execution standards after welding:

  • Appearance quality inspection: 100% DL869-2004 welding section;
  • Main dimension inspection: 100% 0-10 mm;
  • Vt flaw detection of circular welded junction: ultrasonic inspection of 100% sd67-83 pipeline welds;
  • NDT for fillet weld: 100% OD ≤ 4 ‘(101.6) Pt 0d > 4’ (101.6) MT;
  • Spectrum of fillet weld of alloy pipe: 100% meet material requirements.

The weld appearance size after grinding shall not be less than the design size. If it is smaller than the design size, repair and re flaw detection shall be carried out.

Post weld heat treatment

  • (1) After welding, the welded joints of A335P22, 12Cr1MoV and 10CrMo910 shall be subject to stress relief annealing at 720-750 ℃ after welding, and those of A335P22, 12Cr1MoV and 10CrMo910 shall be subject to stress relief annealing at 585-620 ℃. Tempering treatment of welded joint integral tempering treatment of assembly parts
  • (2) The welded joints in the factory shall be heat treated in the furnace as a whole.
  • (3) Heat treatment and heat treatment curve of welded joint shall be stored in quality department after being confirmed as qualified by special inspection personnel and heat treatment engineer.

The inspection items and qualification standards after heat treatment are as follows:

  1. VT inspection of girth welds: 100%
  2. Fillet weld MT flaw detection: 100%
  • OD≤4’(101.6)PT
  • OD>4’(101.6)MT


  • 1. The surface of all pipes, fittings and accessories will be sandblasted
  • 2. The qualified standard of surface sandblasting is: remove more than 98% oxide scale on the surface, and there is no oil stain, burr, welding spatter and other impurities. If there are impurities that cannot be removed by sand blasting, use grinding wheel to clean them.


  • 1. The paint required by the design blueprint will be used, and only primer will be applied in the factory.
  • 2. The air temperature during painting shall not be greater than 80%, and there shall be no large dust.
  • 3. Paint the pipe hole wall within 8 hours after sandblasting.
  • 4. Apply transparent paint to the place with steel seal and yellow paint frame around it.
  • 5. Painting is not allowed for groove and groove edge within 20 mm.
  • 6. The groove shall be coated with anti-oxidation anti rust coating which does not affect the welding quality.
  • 7. The qualified standard of paint is: no mud crack, no adhesion, peeling, blister, rust on the base, pit, buried powder and other defects on the surface.
  • 8. Measure the paint film thickness after the paint is dry, and the paint thickness meets the design requirements.
  • 9. The defective paint parts shall be repaired by grinding the defects to remove the defects, and then repainting the defective areas with the original paint.


  • 1. Both ends of the pipe shall be sealed with blind plug. The type of blind plug can be iron plug, rubber plug, plastic plug and wood plug according to the situation, but it can protect the groove and seal the inner wall of the pipe.
  • 2. Before plugging the pipe, a certain amount of desiccant should be added to protect the inner wall of the pipe. The desiccant should be roasted before loading.
  • 3. If the pipe socket is equipped with screw thread, the matching bolt shall be processed for blocking to protect the screw thread. After the rest of the pipe seat is blocked with wood block, it shall be wrapped with tape. If the pipe seat is slender, protective measures shall be taken to prevent damage during transportation.
  • 4. For non pipeline materials, appropriate packaging measures such as box loading and rack loading should be taken to ensure that they are not damaged during transportation.


  • 1. The use unit, specification, material, pipe number, flow direction and manufacturing unit of the pipe shall be marked by spraying. In order to facilitate on-site search, the marks will be marked on two sides of the pipe diagonally opposite.
  • 2. In order to facilitate on-site search, the number of the pipe shall be marked at the plugging opening at both ends of the pipe.

Deliver goods

  • 1. According to the nature of the goods and the convenience of receiving the goods on site, the factory will take appropriate transportation methods such as train, car and mail to ensure the timely and accurate delivery of goods to the site.
  • 2. The factory will make a transportation plan and inform the receiving unit one month in advance for them to receive the goods. The factory will provide sufficient quality records to prove the product quality according to the factory’s quality assurance system and user’s requirements. The specific items will be determined by both parties.

Source: Network Arrangement – China Pipe Fitting Manufacturer – Yaang Pipe Industry (

(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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