Manufacturing process specification for steel pipe fittings
The manufacturing process for steel pipe fittings typically involves several steps to ensure the production of high-quality, durable fittings that meet industry standards.
The “Manufacturing Process Specification for Steel Pipe Fittings” specifies the basic parameters, raw materials, manufacturing process, material properties, geometric dimensions and allowable deviations, process quality and defect repair, inspection and experimentation, marking, coating and protection, quality certificate and shipping requirements for the production of steel pipe fittings made of L245N, L360M, L450M for pipe fittings procurement projects.
This MPS document shall be used together with GB/T 12459-2005 “Steel Butt-Welding Seamless Pipe Fittings“, GB/T 13401-2005 “Butt-Welding Pipe Fittings made of Steel Plate“, GB/T 19326-2012 “Steel Socket Welding, Threaded and Butt-Welding Olets” standard and D1630D-GI00-PR01-SP14 “Technical Specification of Pipe Cleaning Tee”. Where there are conflicting provisions with GB/T 12459-2005 “Steel Butt-Welding Seamless Pipe Fittings”, GB/T 13401-2005 “Butt-Welding Pipe Fittings made of Steel Plate”, GB/T 19326-2012 “Steel Socket Welding, Threaded and Butt-Welding Branch Pipe Holder” standard and D1630D-GI00-PR01-SP14 “Pipe Cleaning Tee Technical Specification”, the strictest shall prevail. Stringent shall prevail.
2. Normative references
The clauses in the following documents become the clauses of this document by reference to this document. All subsequent change orders (excluding errata) or revisions of dated references do not apply to this document. However, parties entering into agreements based on this document are encouraged to investigate the possibility of using the most recent versions of these documents. Where a document is cited without a date, the latest version applies to this document.
- GB 150: Steel pressure vessels
- GB/T 223: Methods of chemical analysis of steel and alloys
- GB/T 228: Room temperature tensile test methods for metallic materials
- GB/T 229: Charpy pendulum impact test method for metallic materials
- GB/T 232: Bending test method for metallic materials
- GB/T 9711-2011: Steel pipes for the pipeline transportation system in the oil and gas industry
- GB/T 10561: Method for micro-assessment of non-metallic inclusions in steel
- GB/T 12459-2005: Seamless butt-welded pipe fittings made of steel
- GB/T 13401-2005: Butt-welded pipe fittings made of steel plate
- GB/T 19326-2012: Socket weld, threaded and butt-welded branch pipe seats made of steel
- GB 50251: Design specification for gas pipeline engineering
- GB 50253: Design Code for Oil Pipeline Engineering
- NB/T 47008-2010: Carbon and alloy steel forgings for pressurized equipment
- NB/T 47013-2015: Non-destructive testing of pressurized equipment
- NB/T 47014-2011: Welding process for pressurized equipment
- JB/T 4711: Coating and transportation packaging for pressure vessels
- SY/T 0609: Specification for high-quality steel butt-welded pipe fittings
- Q/SY GJX106: Technical conditions for pipe fittings DN400 and above for oil and gas transportation pipeline projects
- ISO 9001: Quality Management System Requirements
- API SPEC 5L: Specification for Line Pipe
- ASTM A370: Methods and Definitions for Testing Mechanical Properties of Steel Products
- ASNT No.SNT-TC-1A: Qualification and Accreditation of Non-Destructive Testing Personnel
- ASTM E45: Method for Determining Inclusion Content in Steel
- TSG Z6002-2010: Special equipment welding operator assessment rules
3. Manufacturing process
Manufacturing process of butt-welding elbow made of steel plate: Finished elbow
1. Raw materials into the factory; 2. Inspection and acceptance of raw materials; 3. Steel plate material; 4. Blank heating in the furnace; 5. Pressing molding; 6. Drawing line cutting; 7. Grouping; 8. Welding *; 9. Shaping; 10. Heat treatment *; 11. Beveling; 12. Surface treatment; 13. Non-destructive flaw detection; 14. Dimensions and appearance of the test; 15. Paint; 16. Marking; 17. Bevel protection; 18. Storage and shipment
Note: * for special processing procedures.
Manufacturing process of hot push elbow: Finished elbow (thermoforming)
1. Raw materials into the factory; 2. Inspection and acceptance of raw materials; 3. Steel pipe undercutting; 4. Push forming; 5. Heat treatment *; 6. Beveling; 7. Surface treatment; 8. Non-destructive flaw detection; 9. Size and appearance inspection; 10. Painting; 11. Marking; 12. Bevel protection; 13. Storage and shipment
Note: * for special processing procedures.
Cold push elbow manufacturing process: Finished elbow (cold molding)
1. Raw materials into the factory; 2. Inspection and acceptance of raw materials; 3. Steel pipe material; 4. Pushing into shape; 5. Heat treatment *; 6. Drawing line cutting flush; 7. Beveling; 8. Surface treatment (carbon steel, alloy steel fittings sandblasted to remove rust, stainless steel fittings acid pickling and passivation); 9. Non-destructive flaw detection; 10. Size and appearance inspection; 11. Painting (carbon steel pipe fittings); 12. Marking; 13. Beveling protection; 14. Storage and shipment
Note: * for special processing procedures.
Manufacturing process of molded tee: Finished tee (cold molding)
1. Raw materials into the factory; 2. Inspection and acceptance of raw materials; 3. Material; 4. Compression molding; 5. Shaping; 6. Pipe end cutting; 7. Heat treatment *; 8. Beveling; 9. Surface treatment (carbon steel, alloy steel fittings sandblasted to remove rust, stainless steel fittings acid pickling passivation); 10. Non-destructive flaw detection; 11. Size and appearance inspection; 12. Painting (carbon steel fittings); 13. Marking; 14. Beveling Protection; 15. Storage and shipment
Note: * for special processing procedures.
Manufacturing process of molded tee: Finished tee (thermoforming)
1. Raw materials entering the factory; 2. Inspection and acceptance of raw materials; 3. Steel pipe discharging; 4. Heating and flattening; 5. Pressing drum package; 6. Drum package opening; 7. Heating and drawing; 8. Shaping; 9. Pipe end cutting; 10. Heat treatment*; 11. Beveling; 12. Surface treatment; 13. Non-destructive flaw detection; 14. Dimension and appearance inspection; 15. Painting; 16. Labeling; 17. Bevel protection. 18. Storage and shipment; 18. Storage and shipment
Note: * for special processing procedures.
Manufacturing process of pipe cap
1. Raw materials into the factory; 2. Inspection and acceptance of raw materials; 3. Material of pipe fittings; 4. Heating; 5. Pressing; 6. Shaping; 7. Pipe end cutting; 8. Heat treatment *; 9. Beveling; 10. Surface treatment (carbon steel, alloy steel fittings sandblasted to remove rust, stainless steel fittings acid pickling and passivation); 11. Non-destructive flaw detection; 12. Size and appearance of the inspection; 13. Paint (carbon steel fittings); 14. Marking; 15. Bevel protection; 16. Storage and shipment
Note: * for special processing procedures.
Manufacturing process of butt-welding reducer made of steel plate: Finished reducer (steel plate)
1. Raw materials into the factory; 2. Inspection and acceptance of raw materials; 3. Steel plate discharging; 4. Coiled tube welding*; 5. Shaping; 6. Tube end cutting; 7. Heat treatment*; 8. Beveling; 9. Surface treatment; 10. Non-destructive testing; 11. Size and appearance inspection; 12. Painting; 13. Marking; 14. Beveling protection; 15. Storage and shipping
Note: * for special processing procedures.
Manufacturing process of weldolet
1. Raw materials into the factory; 2. Inspection and acceptance of raw materials; 3. Steel sheet material; 4. forging; 5. Heat treatment *; 6. Non-destructive testing; 7. Turning; 8. Wire cutting; 9. Surface treatment (carbon steel, alloy steel fittings sandblasted to remove rust, stainless steel fittings acid pickling and passivation); 10. Non-destructive flaw detection; 11. Dimensions and appearance of the inspection; 12. Marking; 13. Protection; 14. Storage and shipping
Note: * for special processing procedures.
Manufacturing process of clear pipe tee
1. Raw materials into the factory; 2. Inspection and acceptance of raw materials; 3. Steel pipe feeding; 4. Opening; 5. Heating and drawing; 6. Shaping; 7. Pipe end cutting; 8. Heat treatment *; 9. Beveling; 10. Surface treatment; 11. Non-destructive testing; 12. Size and appearance inspection; 13. Corrosion protection; 14. Marking; 15. Bevel protection; 16. Storage and shipping
Note: * for special processing procedures.
4. Basic parameters of pipe fittings
The basic production parameters of pipe fittings shall meet the requirements of the bidding documents of pipe fittings of the Pipe Fittings Procurement Project. Clear pipe tee priority GB50251, GB50253, ASME B31.3, ASME B31.8 or nationally recognized pressure vessel or pressure piping code to determine the calculation and analysis methods for strength design, but also in accordance with SY/T 0609-2006 Chapter 6 “Design Verification Tests” method of design to determine the wall thickness. Design to determine the wall thickness. The permissible strength value of clear pipe tee manufactured according to this specification shall be calculated according to GB50251 and GB50253 by using seamless pipe (or welded pipe with welded joint coefficient equal to 1.0) of the same steel grade (or steel number), equal diameter and wall thickness subjected to internal pressure.
5. Raw material requirements
5.1 Raw materials used for the manufacture of pipe fittings shall be fully sedated steel smelted by oxygen blowing converter or electric furnace with required toughness and heat treatment condition, and suitable for on-site welding with pipe fittings, flanges and tubes conforming to the requirements of corresponding standards such as the standard for pipes used in pipeline engineering.
5.2 Manufacture of raw materials for pipe fittings should be seamless steel pipe, steel plate, forgings. Its chemical composition and mechanical properties should be in line with the requirements of the raw material standards, chemical composition of the test equipment shown below.
Figure 5.2.1 Mobile read-only spark spectrometer (chemical composition analysis)
Figure 5.2.2 Silicon manganese phosphorus analyzer
5.3 In addition to the provisions of the technical specification of the cleaning tee, the mechanical properties of pipe-cleaning tee steel shall meet the requirements of parts 10, 12 and 13 of SY/T 0609. Cleaning tee steel should have good welding performance of carbon steel or high-strength low alloy steel. Materials of the following standards may be used (but not limited to): GB/T 9711.
5.4 Raw materials should have quality certificate and their inspection items should be in line with the provisions of relevant standards or ordering requirements. Steel without marking, lot number, quality certificate or incomplete quality certificate items cannot be used. The use of low-priced and inferior materials is not allowed. The Owner shall approve the source of materials and shall not be used without written approval.
5.5 After the raw materials are imported into the factory, our company shall accept them according to their quality certificates and carry out sampling inspection on the appearance, size and physical and chemical properties of the raw materials.
5.6 The surface of raw materials shall be free of oil and dirt, and shall not be allowed to come into contact with low melting point metals (Cu, Zn, Sn, Pb, etc.) during manufacturing, handling, loading and unloading. Otherwise, it shall be removed by appropriate methods (e.g., Sandblasting).
6. Manufacturing process requirements
6.1 Pipe forming process
6.1.1 Steel plate butt-welding elbow molding process: (carbon steel, alloy steel elbow)
1) Undercutting with gas cutting gun in accordance with the layout plan;
2) Single-piece pressing;
- a) Heating temperature: carbon steel pipe fittings 850-900 ℃, alloy steel pipe fittings 900-950 ℃; heat preservation 1-1.5min/mm out of the furnace;
- b) Equipment: heating furnace, forklift, hydraulic press;
- c) Tooling: elbow mold;
- d) Pressing speed ：120mm/min-240mm/min;
- e) Pressing before the first workpiece positioning: The elbow piece of the inner arc center and mold spacing is greater than the elbow piece of the outer arc center and mold spacing of about 80mm.
3) Elbow single-piece cutting
- a. Drawing lines in accordance with the process dimensions;
- b. Equipment: elbow cutting machine.
4) Grouping, welding
- a. Butt spot weld the two pieces of pressed elbows with their weld joints spaced 50-100mm apart.
- b. Spot welding of the amount of misalignment shall not exceed 8% wall thickness and shall not be greater than 1.6mm; otherwise, make the necessary traction. Welding repair methods are not allowed to repair the misalignment exceeding the standard.
- c. Weld and pipe body should be a smooth transition; weld height should be within the range of 0-3mm.
- d. Butt welds shall be made by manual arc welding process and all butt welds shall be fully welded through. Fillet welds shall have full weld throats and if not otherwise specified, the two weld legs shall be approximately equal in length. If welding support is used, it shall be removed before heat treatment. The quality of the weld shall conform to the provisions of GB150: the surface of the weld shall be smooth and free from defects such as arc pits, cracks, pores, slag, biting edges and so on.
6.1.2 Elbow thermoforming process: (carbon steel, alloy steel elbow)
(1) According to the requirements of the size of the material to be undercut with a band saw;
2) Elbow push molding
- a) Adjust the medium-frequency power supply to heat the core head; as the billet advances, the heating current should be gradually increased, and monitor the billet heating temperature with a thermometer; process billet heating temperature: carbon steel pipe fittings 850-900 ℃, alloy steel pipe fittings 900-950 ℃;
- b) Equipment: medium-frequency induction heating ring, elbow push breaking machine.
6.1.3 Elbow cold forming process: (carbon steel, alloy steel, stainless steel elbow)
(1) According to the size of the sample, undercut with a band saw machine for undercutting and according to the undercutting sample adjust the angle of the saw machine.
(2) Elbow push into shape
- a. Open the mold will be coated with a lubricant workpiece into the mold cavity guide section.
- b. Pressure cylinders to press the upper and lower mold; side push cylinder will be pre-positioned in the mold guiding section of the pipe blank into the molding cavity and molded in the mold core. The following figure shows the hydraulic press.
Figure 18.104.22.168 YL32-2000 four-column hydraulic machine
6.1.4 Tee cold forming process: (carbon steel, alloy steel, stainless steel tee)
(1) Under the material
According to the requirements of the tee undercutting parameter table with a band saw machine for undercutting.
- a) Equipment: pipe fittings cold forming molds, presses;
- b) Put the surface of raw material which is qualified by inspection into the inner cavity of the mold by brushing molybdenum disulfide or putting on the plastic film, and then close the baffle;
- c) Setting the pressure to carry out the pipe fittings one-time molding pressing process.
(3) The use of band saws to excise the tee branch pipe end cap, according to the standard among the tee size requirements, each end of the 2mm-3mm machining allowance, in order to process the bevel. The figure below shows the tee cold forming hydraulic press and tee mold.
Figure 22.214.171.124 YK65-1600 type frame tee cold extrusion molding hydraulic machine
Figure 126.96.36.199 YKST65-400T type frame tee cold extrusion molding hydraulic machine
Figure 188.8.131.52 Cold forming stamping tee molds
6.1.5 Tee hot forming process: (carbon steel, alloy steel tee)
1）Using a band saw machine for undercutting according to the requirement of undercutting size;
- a) Heating temperature: carbon steel pipe fittings 850-900 ℃, alloy steel pipe fittings 900-950 ℃, insulation 1-1.5min/mm out of the furnace.
- b) Equipment: heating furnace, forklift, hydraulic press;
- c)Press down 100-150mm according to the pipe fitting workpiece;
- d) Tee weld should be placed in the 180º position of the support port.
3) Pressing bulge
- Heating temperature: carbon steel fittings 850-900 ° C, alloy steel fittings 900-950 ° C, insulation 1-1.5min/mm out of the furnace.
- Equipment: heating furnace, forklift, hydraulic press;
- Tooling: tee forming mold.
The heated flattened pipe section is lifted out of the furnace, and one side of the workpiece is immersed in the water for cooling and the depth of immersion is between 1/2 and 2/3 of the oval-long axis of the flattened pipe section. Cooling will be completed with workpiece lifting to the tee mold, placed to the top and bottom of the vertical, left and right, red hot side in the lower part.
Press the upper slide down, pressing until the pre-set stroke.
Observe more during the pressing process, and stop the press when you find wrinkles.
Will be pressed after the completion of the workpiece reloading furnace, reloading furnace heating and insulation, repeat the above steps 4 and 5 operations until the three-way upper and lower mold together.
4）Bulging and opening
- Equipment: Cutting gun, forklift;
- Opening size: see opening list for opening size.
- Heating temperature heating temperature: carbon steel pipe fittings 850-900 ℃, alloy steel pipe fittings 900-950 ℃, insulation 1-1.5min/mm out of the furnace.
- Equipment: heating furnace, forklift, hydraulic press.
- Tooling: Tee drawing mold (branch mouth facing down).
- Check the pressure and start drawing after working normally.
- Lift the heated tee out of the furnace, place it on the tee mold, put it into the branch pipe drawing mold, and draw the mouth.
- Pressing down the upper slide of the press to complete the first drawing.
- The tee, after the completion of the press, is reloaded into the furnace, reload the furnace heating and insulation and the 5 and 6 steps of the operation, in turn, to do the second, third and fourth mold drawing.
- The maximum pressure allowed in the drawing process is 10MPa.
- The maximum speed allowed in the drawing process is 50mm/min.
6.1.6 Pipe cap molding process:
(1) Undercutting with cutter gun according to the undercutting layout drawing.
- a. Blanks are heated according to the specified requirements, heating temperature: carbon steel, alloy steel 850-900 ℃, stainless steel 1050 ℃-1100 ℃. Heating of the billet should ensure that the temperature is uniform and hold 1-1.5min/mm out of the billet so that the temperature of all parts of the billet is consistent.
- b. Equipment: heating furnace, forklift, hydraulic press;
- c. Tooling: pipe cap forming mold;
- d. Pressing speed: 120mm/min-240mm/min.
6.1.7 Steel plate butt-welding reducer joint molding process: (carbon steel fittings)
(1) Under the material coil pipe
- Undercutting with gas cutter gun according to layout drawing.
- Equipment: Cutting gun, pipe coiling machine.
- Bevel the cut steel plate blank by hot cutting method for butt weld, bevel angle: 30º, blunt edge: 1-2mm.
- The cut steel plate billet is rolled on the pipe coiling machine.
- a. Welded seam of the wrong side of the counterpart b ≤ 10% of the thickness of the steel plate and shall not be greater than 2mm.
- b. Welded seam and pipe body should have a smooth transition and welded seam height should be within the range of 0-3mm.
- c. Butt welding shall be performed by manual arc welding process and all butt welds shall be fully welded through. If welding support is used, it shall be removed before heat treatment. The quality of the weld shall comply with the provisions of GB150: the surface of the weld shall be smooth and free of defects such as arc craters, cracks, pores, slag entrapment, biting edges and so on.
- d. After welding the inner diameter and thickness of the steel pipe testing, the steel pipe outside diameter should be consistent with the receiver; the wall thickness should not be less than the receiver wall thickness.
6.1.8 Clear pipe tee molding process:
1) Undercutting with a band saw machine according to the requirement of undercutting size;
2) Open the hole
- i. Equipment: cutting gun, forklift;
- ii. Opening size: see opening list for opening size;
- iii. Tee weld should be placed at 180º position of the opening of the support port.
- Equipment: forklift, 3000T hydraulic press;
- Tooling: Tee drawing mold (branch port facing up);
- Check the pressure and start drawing after working normally;
- Place the tee on the tee mold, the opening area to maintain a neutral flame heating, temperature: 1050-1100 ℃;
- After the heating reaches the specified temperature, turn on the press to pull out the core mold to complete the extraction;
- The maximum permissible pressure in the drawing process is 10MPa.
- The maximum speed permitted in the drawing process is 50mm/min.
After the pipe fittings are molded, the pipe end diameter should be detected first; if it is too poor, then use the hydraulic press, shaping tires to straighten the mouth, and the roundness of the pipe end diameter after shaping should not exceed the provisions of GB/T 12459-2005, GB/T 13401-2005, GB/T 19326-2012 standard, D1630D-GI00-PR01-SP14 “Clear Pipe Tee Technical Specification”.
6.3 Heat treatment
6.3.1 Heat treatment of normalizing + tempering shall be carried out after pipe fittings are formed; no heat treatment is required after machining of forged pipe fittings. Fig. 6.3.1 and Fig. 6.3.2 show MTL-350 and MTL-2000 heat treatment furnaces, respectively, which are suitable for heat treatment of pipe fittings of various specifications.
Figure 6.3.1 MTL-350 heat treatment furnace (5.6 m × 3.2 m × 3 m)
Figure 6.3.2 MTL2000 (14.5 m × 4.5 m × 3.5 m)
6.3.2 Pipe tees shall be final heat-treated after completion of the baffle welding. The pipe-cleaning tee shall be delivered in normalized condition (air-cooled). The heat treatment process of quenching and tempering allowed by SY/T 0609 can also be adopted. We provide a length of 200mm short section for the welding process evaluation test. The material of the short section is the same as that of the pipe cleaner tee, and the heat treatment conditions are the same.
6.4 Surface hardness test in production
A portable hardness tester inspects the external surface of all pipe fittings. Inspection position: Tee main pipe body (including the abdomen and shoulder), branch pipe body, weld and heat-affected zone; elbow inner arc side, outer arc side and neutral zone, weld and heat-affected zone; top and end of the cap; reducer joints, big end, small end, weld and heat-affected zone, each position should be taken 3-5 points to be measured and then take the average value of the readings and form a hardness inspection report in production. Formation of hardness test report in production, hardness value should meet: material L245N, L360M ≤ 255HV10; material L450M ≤ 265HV10. Hardness testing equipment has a bouvier hardness tester, such as Figure 6.4.1.
Figure 6.4.1 Brinell hardness tester
(1) Fittings welding end face should be machined molding, the implementation of GB/T 12459-2005 and GB/T 13401-2005 standard fittings, the blunt edge size and bevel angle should be in line with the requirements of Figure 1. For the pipe fittings implementing GB/T 19326-2012 and other standards, the bevel form should meet the provisions of the implementation standards. The end bevel of the pipe cleaning tee should follow the relevant provisions of GB 50251 and other standards and match with the welded pipeline. The beveling details should be indicated on the processing drawing of the pipe cleaning tee and submitted for design review.
Figure 1 Beveling type of pipe fittings
2) Our beveling equipment has 7 sets of machines for making bevels, a few of which are listed in the following figure for bevel processing.
Fig. 6.5.1 1200 electric beveling machine
Figure 6.5.2 920 beveling machine
Figure 6.5.3 CNC lathe machine
6.6 Surface Treatment
Before the NDT of each carbon steel and alloy steel fittings, sandblasting, grinding and other methods should be used to remove the oxide skin and other dirt on the surface of the fittings and ensure that the surface roughness can meet the requirements of MT, UT and RT inspection. The following figure shows our automatic sand blasting room and staff on site for sandblasting, ultrasonic testing and penetration testing.
Figure 6.6.1 Automatic sand blasting room
Figure 6.6.2 Sandblasting
Figure 6.6.3 Ultrasonic testing
Figure 6.6.4 Penetration testing
6.7 Non-destructive testing
After heat treatment, non-destructive testing should be carried out on each pipe fitting; the methods and criteria are described in clause 12 — non-destructive testing of this MPS document.
6.8 Appearance inspection and repair see Clause 10 Quality of artistry and treatment of defects of this MPS document.
6.9 Dimensional Inspection
Carry out full-size inspection, geometric dimensions and form deviations shall comply with the provisions of Article 9 of this MPS document.
6.10 Manufacturing process confirmation
6.10.1 The dimensions of pipe fittings must meet the provisions of the standard.
6.10.2 Before obtaining the ordering contract to provide pipe fittings according to these technical conditions, our company shall submit to the owner the requirements of material properties (including welding properties) and manufacturing process documents (MPS), inspection and test reports, etc.; once confirmed by the owner, it shall not be changed arbitrarily. Manufacturing will only be permitted with the written approval of the Owner.
6.10.3 After the contract award, any changes in the content of our submitted manufacturing process specifications shall be reported immediately to the Owner for approval. Failure to report and receive approval on time shall be considered a basis for refusal to execute the contract.
6.11.1 Qualified welders shall complete all welds (including reworked welds) in accordance with the assessed welding process. Welding process evaluation shall be carried out in accordance with JB 4708, and welder examination shall be carried out in accordance with Rules for Examination and Management of Boiler Pressure Vessel and Pressure Pipe Welders.
6.11.2 The welding material used in the product after heat treatment, the tensile properties of welded joints and Charpy impact toughness should meet the requirements of the relevant provisions of Chapter 7.
6.11.3 All butt joints shall adopt an all-welded structure. Welding method should be used melting welding process, preferred submerged arc welding. The welding method is preferred to double-sided welding; if single-sided welding is used, a pad ring should not be used. Our company has 10 licensed welders, 20 sets of ZX7-400 welding machines, and 2 sets of WZ-1200 submerged arc welding machines, as shown below. It can fully meet the production requirements of our company.
Figure 6.11.1 WZ-1200 submerged arc welding machine
7. Performance requirements
7.1 Tensile properties
The tensile properties of the pipe fittings shall comply with the requirements of Table 7.1.
Table 7.1 Tensile Properties Requirements
|Strength grade||Yield strength Rt0.5||Tensile strength Rm||Elongation A|
|L245N||245-450||415-760||Regulations that meet the technical requirements of raw materials|
7.2 Charpy impact toughnes
Specimens of the specified parts of the pipe fittings should be carried out through the charpy impact test, test method see GB/T 229-2007, the test results should be consistent with the raw material standards; forged fittings are exempted from this test.
Clear pipe tee at the specified temperature of the standard specimen Charpy V-notch impact test should be satisfied with the base material of the average of the three tests ≥ 60J and the minimum value of a single specimen ≥ 45J; weld and the heat-affected zone of the average of the three specimens ≥ 40J and the minimum value of a single specimen ≥ 30J.
7.3 Guided bending test of welded seam (only for pipe fittings with seams)
For pipe fittings with butt welds, the weld shall be subjected to a transverse-oriented bending test. After the bending test, there shall not be any crack with a length greater than 3.18 mm at the weld seam, heat-affected zone and base material; cracks originating at the edge of the specimen shall have a crack length of not more than 6.35 mm in any direction.
The hardness value shall satisfy the provisions of clause 6.4.
7.5 Metallographic organization and grain size inspection
7.5.1 Metallographic specimens on transverse sections of pipe bodies and welds of pipe fittings shall be examined at low magnification. They shall not contain cracks or other defects exceeding those specified in the standards for raw materials and welds.
7.5.2 Transverse cross-section of the pipe body near the inner and outer surfaces, wall thickness of the center of the inclusions grade and grain size inspection, steel A, B, C, D non-metallic inclusions level limitations as shown in Table 7.5 (according to ASTM E45 method A test). The pipe body’s original austenite grain size should be GB/T 6394-2002 provisions of the 6 level or finer; a photo should accompany the inspection report.
Table 7.5 Non-metallic inclusions level limits
8. Geometric size, shape, allowable deviation
8.1 Implementation of GB/T 12459-2005, GB/T 13401-2005 standard pipe fittings, its geometric dimensions, shape and location tolerance requirements are shown in Table 8.1. implementation of GB/T 19326-2012 standard pipe fittings, its geometric dimensions, shape and location tolerance should be in line with the requirements of its corresponding standards.
8.2 The permissible tolerance of outer diameter, inner diameter, wall thickness and weight of the pipe fittings shall meet the requirements of 8.1, and no negative deviation is allowed. The inner diameter of the pipe-cleaning tee shall have a deviation of not more than 3% from the nominal inner diameter of the inner diameter of the connected pipeline. Clear pipe tee branch pipe M value and main pipe C value in accordance with SY/T 0609-2016 medium diameter (reducer) tee chart to determine the size values given.
8.3 All pipe fittings must meet the requirements of the receiver material, caliber, specifications, etc., and be manufactured in accordance with the control inner diameter (the inner diameter of the pipe fittings is required to be the same as the inner diameter of the connected pipe).
8.4 For All fittings (tees, sizes, elbows, etc.) at any point, the minimum wall thickness shall not be less than the minimum wall thickness of the connected pipe.
8.5 Pipe fitting’s bevel type and size should be consistent with the requirements of 6.5.
Table 8.1 Pipe fitting tolerance (GB/T 12459-2005, GB/T 13401-2005) unit: mm
|All pipe fittings||90 º elbow and tee center to end face dimensions A, B, C, M||Reducer F, H||Total length of pipe cap E||Geometric tolerance|
|Nominal diameter||End outer diameter ac||Wall thickness b||90 º Elbow, Tee, Reducer Q||90 º elbow and tee P|
|15–65||+1.6～-0.8||Not less than 87.5% of the nominal wall thickness||±2||±2||±3||1||2|
a. Is the sum of the absolute values of the positive and negative deviations of roundness;
b. The nominal wall thickness shall be specified by the purchaser;
c. When it is necessary to increase the wall thickness of pipe fittings to meet internal pressure resistance requirements, this tolerance may not apply to local areas of formed pipe fittings.
- a. For the roundness of the sum of the absolute value of positive and negative deviations;
- b. The purchaser specifies the nominal wall thickness;
- c. When it is necessary to increase the wall thickness of the fittings to meet the requirements of resistance to internal pressure, the tolerance may not apply to localized areas of the formed fittings.
9. Quality of Workmanship and Handling of Defects
9.1 Surface Quality
9.1.1 Cracks, overheating, overburning, and hard spots shall not be present on the surface of the tubing.
9.1.2 The internal and external surfaces of the fittings shall be smooth and free from defects detrimental to strength and appearance, such as knots, scratches, heavy skin and other defects.
9.2 Handling of defects
9.2.1 The pipe body of the sharp notch, chisel marks and other scratches that can cause greater stress concentration should be repaired and smooth transition. After grinding should be repaired and grinding parts of the use of penetration or magnetic particle method of flaw detection to confirm that the defects have been eliminated, and ultrasonic method of grinding parts of the thickness measurement, the remaining wall thickness shall not be less than the provisions of 8.1. Smooth, isolated round bottom marks may not be repaired.
9.2.2 Welding is not permitted to repair any defects in the pipe body.
9.2.3 Welding filler welds shall be made of low hydrogen type welding consumables. The strong toughness technical index of welding consumables shall be in accordance with the requirements of the corresponding standards, and the filler welds shall be carried out before heat treatment.
9.2.4 Patching welding should be used before the appropriate method to the existence of defects completely removed; patching welding should be patched according to the requirements of 10.4 non-destructive testing of the welding area. A maximum of two touch-up welds shall be allowed for the same defective area.
10. Inspection and test
10.1 Mechanical performance test and metallographic examination
10.1.1 The buyer should confirm physical and chemical performance test unit has the appropriate qualifications for the unit to undertake.
10.1.2 Test frequency: formal production should be drawn from the same heat treatment furnace batch of pipe fittings for mechanical properties and metallurgical testing.
10.1.3 Sample: mechanical properties and metallurgical test specimens should be taken from the final heat treatment of the pipe or the production of fittings with the melting batch, the same thermal process and heat treatment conditions, wall thickness difference of not more than 6mm of steel pipe or steel plate produced by the connection in the heat treatment of fittings at the appropriate location of the sample. If the heat treatment of the same batch of products is carried out in a number of different heat treatment furnaces, test pieces should be taken from each heat treatment furnace.
10.1.4 Plate tensile specimens, guided bending test with a test block from the pipe fittings sample pipe cut from the specified location, can be cold pressed flat. The cylindrical tensile specimen centerline should be located in the center of the wall thickness; the test block is not allowed to flatten. Charpy impact test blocks are not allowed to flatten.
10.1.5 Tensile specimen size and processing according to GB/T 2975. Specimen size should be as large as possible when the size of the fittings is small and cannot process the minimum specimen specified in the standard with a transverse specimen. Tensile performance test according to GB/T 228.1-2010 method.
10.1.6 Each specified position of the Charpy impact test should take a group of three specimens; the specimen centerline should be located in the sample 1/2 wall thickness or 25mm from the outer surface of the pipe body, both of which take the value of a small position, notch orientation should be perpendicular to the surface of the material. The center of the weld and heat-affected zone Charpy impact specimen notch location should be Figure 10.1.6 position using the immersion method to determine the notch should be through the upper surface of the specimen and the intersection of the outer weld line of fusion; notch orientation should be perpendicular to the surface of the material.
Figure 10.1.6 Weld centerline and heat-affected zone impact specimen notch location
10.1.7 Charpy impact specimen should be in accordance with the method specified in GB/T 229, as far as possible, using 10mm × 10mm standard Charpy V-notch specimen. When the test material wall thickness is not enough to prepare a full-size specimen, in accordance with GB/T 229, can be processed into a proportion of the specimen for the test, the impact absorbed work required by the thickness of the proportional reduction in the specimen using a transverse specimen. Impact test with the following equipment can do low-temperature impact test.
Figure 10.1.7.1 Impact test equipment
Figure 10.1.7.2 XT-50 impact specimen notch projector
10.1.8 Weld-oriented bending test shall take a face and back bending specimen with a width of 38.1 mm and a length of at least 152.4 mm, with the weld located in the middle of the specimen, and the test results shall satisfy the provisions of clause 7.3.
10.1.9 Hardness test Cross-sectional specimens shall be intercepted from the specified position of the fitting and after polishing and etching (etching shall be for weld specimens only), shall be subjected to a Vickers 10kg load hardness test at the position specified in Figures 10.1.9.1 and 10.1.9.2.
10.1.10 Metallographic specimen cross-sections of pipe bodies and welds shall be examined for defects or flaws using appropriate magnification, particularly for macro and microscopic cracks on the surface. Metallographic examination of the pipe body should also be organized, grain size and inclusions checked, grain size according to the provisions of GB/T 6394-2002 for evaluation, and inclusions level according to the provisions of GB/T 10561 for evaluation.
10.1.11 If all the tests of the sample pieces representing a batch of pipe fittings are in accordance with the provisions of 7.1-7.5, the batch of pipe fittings is qualified. Suppose a sample representing a batch of pipe fittings of any of the test items failed, the pipe fittings are allowed to double the unqualified test items for re-inspection, or the batch of pipe fittings to re-examine a heat treatment, take a sample of all of the above tests. In that case, re-heat treatment is allowed to be carried out only once.
10.1.12 For any batch of product specimens, when the test specified in 10.1.11 cannot meet the requirements, shall be taken from the same batch of twice the number of fittings to re-examine the test. If all specimens meet the requirements, the batch is considered to be satisfactory except for those products that could not pass the previous test.
Figure 10.1.9.1 Position of Vickers hardness test point of the pipe body
Figure 10.1.9.2 Welded joint Vickers hardness test point location
10.2 Inspection of geometric dimensions
All pipe fittings shall be geometrically tested in accordance with GB/T 12459-2005 “Steel Butt-Welding Seamless Pipe Fittings”, GB/T 13401-2005 “Butt-Welding Pipe Fittings made of Steel Plate”, GB/T 19326-2012 “Steel Socket Welding Olets, Threaded Olets and Butt-Welding Olets” standard and D1630D-GI00-PR01-SP14 “Clear Pipe Tee Technical Specification”. The geometric dimension test is carried out in accordance with the standard for socket welded, threaded and weldolet and D1630DGI00-PR01-SP14 Technical Specification for Clear Pipe Tee.
10.3 Product hardness test
Hardness tests shall be carried out on alloy steel pipe fittings piece by piece. Pipe fittings sampled in the production of portable Richter hardness tester in the specified parts of the macro-hardness inspection, each position to take 3-5 equally spaced hardness point readings for the average value.
10.4 Non-destructive testing
10.4.1 Our company shall submit the non-destructive testing methods and process protocols used in writing to the owner and obtain approval before production.
10.4.2 The non-destructive testing (NDT) personnel shall be assessed at least according to GB/T 9445, ASNT No. SNT-TC-lA or other equivalent standards and the organization where the personnel works shall qualify for testing. The qualification of the last assessed inspector shall be re-assessed if they have not engaged in the NDT work for more than 12 months. Non-destructive testing (NDT) shall be carried out by level I, II or III personnel. The evaluation of the displayed results shall be carried out by level Ⅰ personnel under the supervision of level Ⅱ or Ⅲ personnel or directly by level Ⅱ or Ⅲ personnel.
10.4.3 Clear pipe tee main and branch pipe transition area shall be 100% ultrasonic testing plus 100% magnetic particle testing to confirm that no hazardous defects exist. The longitudinal butt joints of the process evaluation test pieces shall be subjected to 100% ultrasonic testing and 100% radiographic testing, with ultrasonic testing level I qualified and radiographic testing level II qualified.
10.4.4 After final heat treatment, 100% magnetic particle or penetration testing shall be carried out on the surface of the pipe body of each pipe fitting according to the relevant provisions of NB/T 47013-2015. Magnetic particle test, choose A-30/100 or C-15/50 standard specimen, grade Ⅰ qualified.
10.4.5 After final heat treatment, the body area of each pipe fitting shall be probed for crack defects by ultrasonic inspection. Manual ultrasonic inspection equipment shall be able to continuously and uninterruptedly inspect the pipe body area of the fitting that can be inspected, and the equipment shall display defects with sufficient sensitivity. The sensitivity of the inspection equipment shall be calibrated using a comparison specimen at least once at the beginning and halfway through each shift (8h). Comparison specimens shall be taken from pipe fittings having the same process, the same outside diameter or radius of curvature, and the same wall thickness of the straight section of pipe as the pipe being inspected. Comparison specimen should be drilled along the wall thickness of 1.6mm diameter vertically through the hole (or in the comparison of the internal and external surfaces of the standard block along the circumference of the processing of the N5 groove, drilling or groove by the company’s choice). 1.6mm diameter holes for calibration equipment cannot be interpreted as the smallest size of the equipment can detect the shortfall. If the signal generated by the defect is greater than or equal to 100% of the height of the echo generated by the 1.6mm through-hole of the comparison specimen, it is considered a defect.
10.4.6 Inspection found sharp yawning or defects should be repaired grinding, grinding should be rounded transition. After resharpening, the resharpened parts shall be probed by penetration or magnetic particle method to confirm that the defects or flaws have been eliminated. And use the ultrasonic method to measure the thickness of the repaired and ground parts, and the minimum remaining wall thickness shall comply with the provisions of 8.1 and 8.2.
10.4.7 All butt welds of each pipe fitting shall be subjected to 100% ray testing and 100% ultrasonic testing after final heat treatment in accordance with the relevant provisions of NB/T 47013-2015. The ray testing shall be qualified at level Ⅱ, and the ultrasonic testing shall be qualified at level I. The welds of each pipe fitting shall be subjected to 100% ray testing, and the ultrasonic testing shall be qualified at level Ⅰ after final heat treatment. All the welds that rays cannot detect can be detected by magnetic particle or ultrasonic, and the detection method and acceptance standard shall be in accordance with the relevant provisions of NB/T 47013-2015, Grade I qualified.
10.4.8 The straight pipe section of each pipe fitting shall be inspected by longitudinal wave manual ultrasonic or other effective ultrasonic methods approved by the Owner for delamination within a length of 100mm from the pipe end, and no delamination or inclusion defects with a size exceeding 19.0mm shall be allowed to exist.
10.4.9 The beveled surface of pipe ends shall be inspected for delamination by magnetic particle or liquid immersion methods, and no delamination shall be permitted to exist with a single length exceeding 6.4 mm or with a cumulative length exceeding 6.4 mm over a 50 mm period and no filler repair shall be permitted to be made to it.
10.4.10 Magnetic particle inspection or liquid penetrant inspection of pipe fitting repairs shall not permit the presence of defects of any size.
10.4.11 Before the nondestructive testing of each pipe fitting, the oxide skin and other dirt on the surface of the fittings shall be removed by shot blasting and grinding, and the surface roughness shall be ensured to meet the requirements of PT, MT and UT testing.
10.4.12 The ultrasonic inspection equipment used shall be intact, and our company shall submit the specification for inspection and instrument calibration, as well as the method of confirming the defects found, location and size. The ultrasonic calibration method shall be submitted for the Owner’s approval including a detailed description of the comparison specimen and the calibration method.
10.5 Purchaser’s Inspection
10.5.1 We shall provide the inspection process and the qualifications of the inspectors, as well as submit relevant documents developed in accordance with ISO 9001 requirements for review.
10.5.2 The Owner will designate inspectors to enter the plant as representatives for matters relating to inspection and acceptance during production.
10.5.3 The Owner’s representative will conduct audits and inspections to check whether the quality management system and MPS documents, etc., meet the requirements of this document, as deemed necessary by the Owner’s representative.
10.5.4 We shall allow the Owner’s personnel or their representatives to review reports and specimens of all tests made as part of production control during the production of the fittings.
10.5.5 The Owner will be entitled to reject the fittings if they are oily on the inside and outside surfaces, producing visible rust and corrosion.
10.5.6 Any fittings found to be defective during installation in the shop or at the site may be rejected and notified to us. The Owner’s authorized inspection representative will have the right to reject any fittings that do not conform to this document.
11. Design verification tests
11.1 The tests required
As a basis for design, design verification tests shall be made in accordance with this document. A record of the design or a record of a successful verification test shall be available for inspection by the purchaser in our product files. Unless otherwise agreed between the supplier and purchaser, the only verification test shall be a burst test.
11.2 Test Samples
Fittings selected for testing shall be inspected for geometry in accordance with this document and the results shall conform to the requirements specified herein and shall be labeled with the fittings’ material, strength class, furnace lot number, and heat treatment status.
11.3 Test assemblies
The theoretically calculated burst strength of each cap, seam or seamless straight pipe section in the test assembly shall be at least 105% of the calculated burst strength of the test fitting.
In the welding process, when the test fittings, straight pipe sections and pipe caps, two and two mutually butt straight pipe sections at the end of the inner wall of the wrong side of the amount greater than 1.5mm, the pipe end should be in accordance with the technical requirements of the slope is not more than 1:3 boring processing, smooth transition. The length of the straight pipe short section welded between pipe fittings and header shall be at least twice the outer diameter of the straight pipe short section.
A shorter length of straight pipe section may be used when the following conditions are met:
- a) The test assembly shall be capable of withstanding at least 105% of the strength calculated in accordance with equation (1) in 11.5;
- b) For pipe fittings DN350 and below, the minimum length of the straight section shall be one times the outside diameter of the pipe;
- c) For fittings DN350 and above, the minimum length of the straight section shall be 0.5 times the outside diameter of the pipe but not less than 355.6 mm.
11.4 Fluid medium
The test medium can be water or other hydraulic test fluid.
11.5 Strength calculation for verification test
Pipe fittings verification test strength calculation should be determined in accordance with the formula (1):
In the formula:
- p – calculated minimum proof test strength in megapascals (MPa);
- αb – the actual tensile strength of the pipe fittings (on behalf of the test fittings measured on the specimen tensile strength), in MPa (MPa) (when the actual tensile strength of the pipe fittings is less than the same strength connecting the standard minimum tensile strength of the tube, according to the standard minimum tensile strength of the connecting tube);
- t – the nominal wall thickness of the pipe connected with the fittings in millimeters (mm);
- D – the outside diameter of the pipe of the same strength connected with the fitting, in millimeters (mm).
11.6 Test procedure
11.6.1 Test assembly assembly and testing
Pipe burst test assembly welding and assembly are completed in accordance with the requirements of the standard NB/T 47013-2015. All the test components of the parent material and welds were selected ultrasound, ray, magnetic particle or penetration and other means of non-destructive testing, qualified and then injected into the test assembly of water or other fluids used in the hydraulic pressure test in preparation for bursting pressurization test.
11.6.2 Verification test
During the hydraulic test process, continuous pressure should be applied until the pipe fittings burst. The measured strength during the burst of the test component should be at least the calculated burst strength verified by equation (1). If during the test, the capacity of the testing machine cannot reach sufficient strength to cause any part of the structural specimen to burst, but when the final test strength reaches 105% of the calculated burst strength value according to equation (1), the test can be considered qualified.
11.7 Availability of Test Results
It is optional to test all combinations of different sizes, wall thicknesses, and materials individually. A satisfactory verification test on a representative fitting may be used to verify other fittings of the same type within the following ranges:
11.7.1 Material Strength Grades
Testing of fittings of one strength class may verify the design of other geometrically similar fittings.
11.7.2 Geometric dimensions
The results of a successful fitting verification test may be representative of other fittings within the range described below.
- a. Similar fittings with outside diameters not less than 0.5 times the diameter of the test fitting and not more than 2 times the diameter of the test fitting;
- b. Unreduced test fittings can be verified for similar fittings that are reduced in size;
- c. The t/D ratio of similar fittings must not be less than 0.5 times the t/D ratio of the test fittings, nor greater than 3 times;
- d. Test fittings with a short radius of curvature may verify fittings with a longer radius of curvature, provided that they comply with the provisions of the standard.
12.1 All pipe fittings supplied in accordance with this Technical Specification shall be marked with a white marking sprayed or steel stamped in sequence on their outer walls, clearly indicating the following:
- a) Standard number;
- b) Material grade;
- c) Specifications (outside diameter and wall thickness expressed in inches);
- d) Our company’s name or trademark;
- e) Date of production.
12.2 All clear pipe tees supplied in accordance with this Technical Specification shall be marked on their outer walls by stencil spray brushing or low-stress impressions and clearly marked with the following:
- a) Dimensions;
- b) Nominal thickness of the beveled end of the clear pipe tee;
- c) Steel grade symbol;
- d) Steel grade symbol and melt lot identification number;
- e) Manufacturer’s name or trademark;
- f) Clearance tee number.
13. Protection and packaging
13.1 The surface of pipe fittings shall be thoroughly cleaned before painting until the original color of the metal is visible, and flying edges, burrs, oil stains, etc. It shall be eliminated. After sandblasting and descaling, the pipe cleaner tee shall be painted with antirust primer (not within 100mm from the welded end), and the top coat shall be painted together with other equipment in the station. The welding bevel of the pipe cleaning tee should be protected by effective measures to prevent it from being damaged during transportation. The end of the pipe should be effectively protected during packing to ensure that the pipe cleaning tee is not subject to mechanical damage and environmental erosion during transportation and storage.
13.2 The antirust paint film should be uniform, without bubbles, wrinkles and skinning.
13.3 A packing list and certificate of product quality should be attached to the packing box.
13.4 The content of the packing list should include.
- ① Our company name or trademark;
- ② Factory date and number;
- ③ Product name, specification, quantity and net weight;
- ③ Product name, specification, quantity, net weight, etc;
- ④ Owner’s name and contract number;
- ⑤ Name and number of attached documents.
The packing list of the products shall have the official seal of the packing department of our company, the date of packing and the signature of the inspector.
14. Certificate of Product Quality Conformity
According to the standard production of pipe fittings, each batch should have a certificate of product quality. Certificate of quality should include the following:
- ① The name of the company and the date of manufacture;
- ② Quality inspector’s signature and date of inspection, quality inspection department seal;
- ③ Product name, specifications, manufacturing standard number;
- ④ Chemical composition and mechanical properties of raw materials;
- ⑤ Specified inspection test results.
Remarks: Matters not covered should meet the provisions of the corresponding standards and technical specifications.