This standard applies to grey cast iron pipe fittings with socket and flange connections for conveying water and coal gas. GB 3420-1982 Grey cast iron pipe fittings GB3420-1982 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
GB3420-1982
Grey cast iron pipe fittings
Cast 4
1983-11-01
1982-12-31Approved
National Bureau of Standards
Page 1
1 Dimensions, shape, weight
2 Technical requirements
3 Test methods
4 Inspection rules||t t||5 Marking, quality certificate, transportation and storage M
Page 2
This standard applies to grey cast iron pipe fittings with socket and flange connections for conveying water and gas. The use of cast iron pipe fittings should refer to relevant pipeline design and construction specifications. National
Page 3
1.1 Size and shape
1 Size, shape, weight
1.1.1 The name and graphic marking of pipe fittings shall comply with the provisions of Table 1. Other types, specifications and sizes of pipe fittings not listed in the table can be produced by negotiation between the supply and demand parties, but their connection dimensions must be consistent with this standard.
1.1.2 The shape and size of pipe fittings shall conform to the provisions of Figures 1 to 27 (omitted) and Table 530. Number
Socket short pipe
Insert short pipe
Double socket bend pipe
Double socket bend pipe
22 Double socket bend pipe
11 Double socket bend pipe
Full socket T-tube
Full socket cross pipe
Double socket bend pipe
Double socket BendbZxz.net
Three-plate T-tube
Blind flange
Double-sleeve T-tube
Graphic marking
Nominal diameter Dg, mm
75~1500
75～1500
751500
75~1500
75~1500
75～1500
7 51500
75~1500
200~1500
751500
75~300
75~1500|| tt||75~1500
75~1500
75~1500
75~1500
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0-1982
Socket-and-spigot reducer
Socket-and-spigot reducer
Socket-and-spigot elbow
45° socket-and-spigot elbow
22 Socket-and-spigot elbow
11 Socket-and-spigot elbow
B-shaped pipe
Socket-and-spigot single-disc exhaust pipe
Socket-and-spigot drain pipe
*Socket-and-spigot single-disc exhaust pipe can be used as a fire hydrant T-shaped pipe. 1.2 Dimensional deviation
1.2.1 Deviation of the outer diameter of the socket and the inner diameter of the socket
The deviation of the outer diameter of the socket and the inner diameter of the socket shall comply with the provisions of Table 2. 751500
751500
75~700
75～700
75~700
150~1500
700～1500
Nominal diameter
75～200
250~900
1000~1500
1.2.2 Allowable deviation of socket depth
Allowable deviation of socket of cast iron pipe fittings:
Nominal diameter is 75~500mm..·.
Nominal diameter is equal to and greater than 600mm
...±5mm;
±10mm.
30～32
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1.2.3 Wall thickness tolerance
The negative deviation of the wall thickness of the pipe fitting is (1.5+0.05T) mm. The negative deviation of the wall thickness of the socket is (1.5+0.05T) mm. 1.2.4 Length tolerance
The length tolerance of cast iron pipe fittings is mm.
1.2.5 Pipe plate machining and drilling tolerance1.2.5.1 The center of each screw hole on the pipe plate must correspond to the center of the pipe fitting, and the deviation of the center circle diameter of the screw hole is ±1mm. 1.2.5.2 The deviation of the distance between the centers of adjacent screw holes is ±0.5mm. 1.2.5.3 Thickness deviation after tube coil processing: Nominal diameter less than or equal to 300mm
Nominal diameter equal to or greater than 350mm*
1.2.5.4 The diameter deviation of the protruding part of the tube coil is ±2%. -2mm;
-3mm.
1.2.5.5 The deviation between the center of the inner diameter of the tube coil and the center of the screw hole should not be greater than the provisions of Table 3. Table 3
Nominal diameter D
≤150
200~500
≥600
1.3 End face
The end face of the pipe fitting should be perpendicular to the axis of the pipe fitting.
1.4 Weight and its allowable deviation
Allowable deviation
1.4.1 Pipe fittings are delivered according to theoretical weight. When calculating the weight, the specific gravity of cast iron is 7.20. 1.4.2 The weight deviation of each pipe fitting is ±8%, of which the weight deviation of elbows, multi-branch pipe fittings and non-standard pipe fittings is ±12%.
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2.1 Chemical composition
2 Technical requirements
The phosphorus content of cast iron pipe fittings should not be greater than 0.40%, and the sulfur content should not be greater than 0.12%. 2.2 Mechanical properties
2.2.1. The tensile strength of cast iron pipe fittings should not be less than 14kgf/mm2.2.2 When cast iron pipe fittings are difficult to cut and drill and objections occur, hardness tests should be carried out. The surface hardness of pipe fittings should not be greater than HB230, and the hardness of the main core part of the pipe fittings should not be greater than HB215. 2.3 Process performance
2.3.1 Water pressure test
The water pressure test of pipe fittings should comply with the provisions of Table 4. Table 4
Nominal diameter D
≤300
≥600
2.3.2 Air tightness test
Test pressure, kgf/mm
When the pipe fittings are used for gas pipelines, if an air tightness test is required, the test method shall be agreed upon by the supply and demand parties. 2.4 Organization
2.5 Surface quality
The inner and outer surfaces of the pipe fittings must be smooth, and cracks, cold shuts, honeycombs and any other obvious defects that hinder use are not allowed.
Casting defects that are limited and affected by the casting process but do not affect use are allowed to exist. There should be no more than 2 local weak points on the pipe fittings. The thickness after local thinning should not be less than the minimum thickness of the same diameter centrifugal straight pipe G grade in GB3421-82 "Sand mold centrifugal cast iron pipe". The area affected by the reduced wall thickness should be less than 1/10 of the cross-sectional area of ​​the inner cavity.
With the consent of the South African party, local defects can be repaired. However, the repaired pipe fittings must be retested with water pressure according to this standard.
2.6 Coating
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2.6.1 The inner and outer surfaces of the pipe fittings can be coated with asphalt or other anti-corrosion materials. If the inner surface is not required to be coated, it shall be negotiated by the supply and demand parties.
2.6.2 The coating should be insoluble in water and should not cause odor and taste in the water. The content of harmful impurities should comply with the relevant provisions of the Ministry of Health for drinking water.
2.6.3 Before coating, the inner and outer surfaces should be smooth and free of rust and iron flakes. 2.6.4 After the coating is applied, the inner and outer surfaces should be smooth, the coating should be uniform, adhere firmly, and not change due to the hot or cold climate.
Page 8
3 Test method
3.1 The size of the pipe fittings shall be measured with a caliper or a sample and a measuring tool with sufficient accuracy. 3.2 The surface quality and coating quality of the pipe fittings shall be checked with the naked eye. 3.3 Chemical analysis shall be carried out in accordance with the provisions of GB223 (1~8)-81, GB223.9~223.24 "Chemical Analysis Methods for Steel and Alloys" W
and YB35 (1~6)-78 "Chemical Analysis Methods for Steel" W
3.4 ​​Tensile test shall be carried out in accordance with the provisions of GB228-76 "Metal Tensile Test Method". si
Tensile test bars are cast in the same sand mold using the same furnace molten iron. 3.5 The hardness test shall be carried out in accordance with the provisions of GB231-63 "Metal Brinell Hardness Test Method". C
3.6 The water pressure test must be carried out before coating. When the specified pressure is reached, the pressure shall be maintained for no less than 30 seconds, and the pipe fitting shall be tapped lightly with a 0.75kg steel hammer. There shall be no leakage. 口
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Cast iron pipe fittings shall be inspected and accepted in batches. Each batch of pipe fittings produced from the same furnace of molten iron and the same molding process M
4 Inspection rules
The inspection and acceptance of cast iron pipe fittings shall be carried out by the supplier's technical quality supervision department. 4.3.4 Tensile test Take 2 samples per shift (8h). The test results represent all pipe fittings produced during that shift. 4.3.3 Take 2 samples from each furnace for chemical analysis. Chemical analysis must be carried out when the charge is changed. C
4.3.5 Hardness test Take 2 samples per shift (8h). The test results represent all the pipe fittings produced during the shift. When any of the chemical composition, tensile test and hardness test is unqualified, double the number of samples should be taken from the batch of pipe fittings for re-inspection of the unqualified item. If the re-inspection result is qualified, the batch of pipe fittings can be judged as qualified. If the re-inspection result is still unqualified, the batch of pipe fittings should be scrapped. At this time, the supplier can also inspect each one and deliver the qualified ones. 4.2 Batch rules
4.3 Sampling quantity
composition.
4.3.6 Pipe fittings should be subjected to water pressure test one by one. 4.3.7 The weight of pipe fittings shall be randomly checked.
4.4 Re-inspection and judgment rules
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5 Marking, quality certificate, transportation and purchase and storage 5.1 The manufacturer's name or trademark and pipe fitting specifications shall be cast on the pipe fittings. 5.2 Each batch of pipe fittings shall be accompanied by a certificate when leaving the factory, including: a. Name of the foundry;
b. Product name and specifications;
c Water test pressure;
d. This standard number;
e. The results of various tests required by this standard. 5.3 During the transportation of cast iron pipe fittings, it is strictly forbidden to touch or drop them to avoid bruises and damage. 5.4 The floor of the warehouse where pipe fittings are stored must be soft and flat. Table 5 Socket section of special-shaped pipe fittings
Socket size
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3420-1982
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