Some standard content:
National Standard of the People's Republic of China
Sand-Mold Centrifugal Cast Iron Pipe
Cast-Iron Pressure Pipe Centrifugally Cast in Sand-llned Molds
This standard applies to sand-molded centrifugal cast iron straight pipes for conveying water and gas. The use of cast iron pipes should refer to relevant general road design and construction specifications. 1 Grading
UDC621.643.22
GB 3421—82
Sand-molded centrifugal cast iron pipes are divided into two grades, P and G, according to their wall thickness. If other thickness pipes are required, they can be produced by changing the inner diameter. 2 Dimensions, shape, weight
2.1 Dimensions and shapes
2.1.1 The shape and dimensions of the socket straight pipe shall comply with the provisions of Figure 1, Table 1 and Table 2. 2.1.2 If a straight pipe with a flexible rubber ring interface or other interface forms is required, it can be produced by negotiation between the supply and demand parties. 2.1.3 The cut length of cast iron pipes shall comply with the effective length specified in Table 2. The weight of short-length pipes shall not exceed 2% of the delivery quantity (excluding the pipes for cutting samples). The allowable shortened lengths are: 500, 1000, 1500 and 12000 mm. 1=24
75-450
500 and above
National Bureau of Standards 1982-12-31
R-C+ER,-CR,-E
1983-11-01 implementation
Nominal diameter
2.2 Appearance
1067-0
GB3421—82
Bearing size
The curvature of cast iron pipes shall not exceed the provisions of Table 3. 2.2.1
The end face of cast iron shall be perpendicular to the axis.
Table 2 Wall thickness and weight of sand-cast centrifugal cast iron pipes Nominal diameter
Wall thickness, mm
Inner diameter, mm
Note: When calculating the weight, the specific gravity of cast iron is 7.20. Effective length, mm
Total weight, kg
Weight of straight section 1 meter
Total weight = weight of straight section 1 meter × effective length·weight of socket convex part (calculated result is rounded off to three significant figures). G grade
Nominal diameter Dg
200~450
L in the table represents the effective length of the pipe in meters. 2.3 Dimensional deviation
2.3.1 Deviation of the outer diameter of the spigot and the inner diameter of the socket
GB 3421-82
The deviation of the outer diameter of the spigot and the inner diameter of the socket shall comply with the provisions of Table 4. Table 4
Nominal diameter
500~800
2.3.2 Socket depth deviation
Outer diameter of socket
For nominal diameter less than 600mm, it is ±5mm, and for others, it is ±10mm. 2. 3.8 Wall thickness deviation
The negative deviation of pipe body wall thickness is (1+0.05T) mm. The negative deviation of socket wall thickness is (1+0.05C) mm. Xiequ
Inner diameter of socket
Note: The local thinning thickness shall not exceed (1.5+0.05?) mm. If the local thinning is more than 3 places, it shall comply with the provisions of Table 5. Table 5
Nominal diameter
200 450
500~800
900~1000
2.3.4 Length deviation
The length deviation of cast iron pipe is ±20mm.
2. 4 Weight and deviation
Maximum length of local thinning
Minimum distance between each other
Cast iron pipes are delivered according to theoretical weight. Cast iron pipes from which samples are cut are accepted according to the complete length. The negative deviation of the weight of each cast iron pipe is 5%. 2.5 Marking example
The sand mold centrifugal cast iron pipe with a nominal diameter of 500mm, a wall thickness of grade P and an effective length of 6000mm is marked as: Centrifugal pipe P-500-6000GB3421-82
Technical requirements
3.1 Chemical composition
The phosphorus content of the sand mold centrifugal cast iron pipe should not be greater than 0.30%, and the sulfur content should not be greater than 0.10%. 3.2 Mechanical properties
The bending strength of the pipe ring should comply with the provisions of Table 6. 3.3 Process performance
3. 3. 1 Water pressure test
The water pressure test should comply with the provisions of Table 7.
Nominal diameter Dg, mm
350~70
Type of straight pipe
3.3.2 Air tightness test
GB 8421 --82
Bending strength of pipe ring, kgf/mm2
Nominal diameter Dg, mm
Not less than
Test pressure, kgf/cm2
When cast iron pipes are used for gas pipelines, if air tightness tests are required, the test methods shall be agreed upon by both parties. 3.4 Organization
Cast iron pipes shall be grey cast iron with dense organization and easy to cut and drill. 3.5 Surface quality
3.5.1 There shall be no cracks and 1 Severe moire on the inner surface of the pipe, and there shall be no defects that affect the use or can be avoided by the manufacturing method. 8.5.2 The sand on the inside and outside of the socket must be scraped off, and the local protrusions must be flattened. The sand on other parts shall not exceed 2mm, and the height of the local protrusions shall not exceed 5 mm.
3.6 Coating
3.6.1 The inner and outer surfaces of the pipe body can be coated with asphalt or other anti-corrosion materials. If cement mortar lining or no coating on the inner surface is required, it shall be provided by the supplier. It needs to be agreed by both parties.
8.6.2 The coating should not be insoluble in water, and should not cause water to have odor and taste. The content of harmful impurities should comply with the relevant regulations of the Ministry of Health for drinking water. 3.6.3 Before coating, the inner and outer surfaces should be smooth and free of rust. 3.6.4 After coating, the inner and outer surfaces should be smooth, the coating should be uniform and firmly adhered, and no abnormality should occur due to hot or cold weather. 4 Test method
4.1 The size of the cast iron pipe is measured with a caliper or a sample and a measuring tool with sufficient accuracy. 4.2 The surface quality and coating quality of the cast iron pipe are checked with a meat gum. 4.3. Chemical analysis shall be conducted in accordance with the provisions of GB223 (1~7)--81, GB223.8~223.24-82 "Methods for Chemical Analysis of Iron and Steel and Alloys".
4.4 The pipe ring bending strength test shall be sampled at the spigot end of the cast iron pipe with qualified surface quality. Sample size: For cast iron pipes with a nominal diameter less than or equal to 350mm, the pipe ring width is half of the average diameter; for cast iron pipes with a nominal diameter equal to or greater than 400mm, the pipe ring width is 200mm. During the test, place the sample on a hard pad and use a testing machine to test, as shown in Figure 2. A Enlarged
In Figure 2: Nominal diameter <300 mm
Nominal diameter 350～600…
Nominal diameter 7(0mm-
The bending strength of the pipe ring is calculated according to the following formula:
Bending strength of pipe ring, kgf/tm
[Positive loss load, kgt
Average diameter of pipe ring, mm,
Wall thickness, mm
Width of pipe ring, mm.
GB 421-82www.bzxz.net
4-13mm
α=25mm;
a= 60mm.
4.5 The water pressure test must be carried out before coating. When the specified pressure is reached, the pressure stabilization time shall be no less than 30s, and the arm body shall be tapped lightly with a 0.75kg steel bar. There should be no leakage.
5 Inspection rules
5.1 Inspection and acceptance
The inspection and acceptance of cast iron pipes shall be carried out by the supplier's technical supervision department. 5.2 Batch rules
Cast iron pipes shall be inspected and accepted in batches. Each batch shall consist of cast iron pipes with the same nominal diameter, the same wall thickness grade, a certain length and the same chemical analysis results. 5.3 Sampling Quantity
5.3.1 The size, surface quality and coating quality of cast iron pipes shall be checked one by one. 5.3.2 Chemical analysis Two samples shall be taken for testing every shift (within 8 hours), but samples must be taken at any time during the charge change. 5.3.3 Mechanical test shall be carried out on various cast iron pipes in the same furnace. Samples shall be taken once when 50 pipes are poured or equal to 50 pipes per shift (8 hours), and samples shall be taken twice when more than 50 pipes are poured (4 hours apart, once for large pipes and once for small pipes). 5.3.4 Water pressure test shall be carried out on each cast iron pipe. 5.3.5 The weight of cast iron pipes shall be sampled.
5.4 Re-test and judgment rules
If any one of the test results of the bending strength and hardness of the pipe ring does not meet the requirements of this standard, the root pipe shall be scrapped, and double samples can be taken from the same batch of cast iron pipes for re-testing of the unqualified items. If the re-test results are still unqualified, the batch of straight pipes shall be reported. At this time, the manufacturer can also submit them for acceptance one by one.
If the chemical composition is unqualified, samples can be taken from the pipe body of the batch of cast iron pipes represented by the samples for re-testing. If the re-test results are still unqualified, the batch of cast iron pipes shall be scrapped.
6 Marking, packaging and quality certificate
GB 8421-82
6.1 The name or trademark of the manufacturer, year, month and thickness grade symbol "P" or "G" shall be cast on the socket of the cast iron pipe. 6.2 Cast iron pipes with a nominal diameter of 200 mm or less should be tightly wrapped with straw ropes at the spigot end, with a width of not less than 100 mm and a height of not less than 12 mm.
When there are many loading and unloading times in vehicle-ship transport or long-distance transport, a rubber ring or plastic ring should be put on the spigot end, with a width of not less than 50 mm and a height of not less than 15 mm.
6.3 Each batch of straight pipes should be accompanied by a quality certificate. The following contents should be indicated on it:
body. Manufacturer name:
Product name, specification, thickness level:
Test water pressure,
Quantity per batch:
e, standard number:
f. Various analysis and test results required by this standard. 7 Transportation and storage
7.1 Cast iron straight pipes should be protected from damage during transportation. 7.2 When loading cast iron straight pipes, the part protruding from the vehicle body shall not exceed one-fourth of the length of the pipe. 7.3 The ground on which the pipes are placed shall be flat, and wooden blocks shall be placed on the hard ground. 7.4 Each layer of cast pipes on the pipe stack shall be covered with wooden blocks, and the directions of the two adjacent layers of pipes above and below shall be 90°, and the sockets and spigots of each layer of pipes shall be placed alternately. 7.5 The height of the pipe stack shall not exceed 3 m, and pillars shall be set beside the stack to prevent the pipes from rolling. Additional remarks:
This standard was proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard was drafted by Anshan Iron and Steel Company.
The main drafters of this standard are Li Xinsheng and Guo Fuqing. From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB 428-64 "Cast Iron Straight Pipes and Pipe Fittings" shall be invalidated.
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