【正文】 of steel pipe in mm。R —— Allowable stress in MPa, 60% of minimum value of plastic elongation strength specified in Table 4. Under test pressure, the standup pressure time should not be less than 10s and steel pipes are not allowed to leak. According to requirements of the purchaser, other test pressure is allowed to be applied to hydraulic test after negotiation between a supplier and a purchaser and being indicated in contract. The supplier can substitute hydraulic test with ultrasonic flaw detection or eddy current flaw detection. When adopting ultrasonic flaw detection, pared artificial defect of sampling pipes should be in conformity with acceptance level L3 of GB/T 5777–2008。 when applying eddy current flaw detection, pared artificial defect of sampling pipes should be in conformity with acceptance level A of GB/T 77352004. Processing Property Flattening TestAccording to requirements of the purchaser, flattening test can be conducted to pipes with wall thickness of no more than 10 mm after negotiation between a supplier and a purchaser and being indicated in contract. Sample should be flattened to the result that clearance between two flat plates is H, which is calculated based on formula (3). After being flattened, no crack or chick is allowed on outside of bending position. ……………(3)Of which:H — distance between two flat plates and its unit is mm。 S — wall thickness of steel pipes and its unit is mm。 D — nominal outer diameter of steel pipes and its unit is mm。 a — deformation coefficient of per unit length. It is for austenite steel pipes and for other types of steel pipes. Expansion TestAccording to requirements of the purchaser, expansion test can be performed to steel pipes, whose outer diameter is no more than 150 mm and wall thickness is not over 10 mm, after negotiation between a supplier and a purchaser and being indicated in contract. Intercrystalline Corrosion TestIntercrystalline corrosion test should be carried out to austenite steel pipes. Method of intercrystalline corrosion test should be in pliance with GB/T 4334 – 2008. Other intercrystalline corrosion test methods could be employed after negotiation between a supplier and a purchaser and being indicated in contract. Surface Quality No crack, folding, fluting, delamination and scab are allowed on inner and outer surface of steel pipes. These defects should all be removed. Removed depth should not be above 10% of wall thickness. And actual wall thickness at removed position should be not less than minimum allowable wall thickness. GB/T 149762012 Allowable depth of straight scratch inner and outer surface of steel pipes should in keeping with the following rules: — hot rolled (extruded, expanded) steel pipes: not exceed 5% of wall thickness. And maximum allowable depth of straight scratch on pipes with a diameter of no more than 140 mm is , while maximum allowable depth of straight scratch on pipes with a diameter of more than 140 mm is 。 — cold drawn (rolled) steel pipes: not exceed 4% of wall thickness and maximum depth is , but maximum allowable depth of straight scratch on pipes with a wall thickness of less than mm is mm。 Other local defects that do not exceed negative deviation of wall thickness are allowed. Nondestructive Inspection According to requirements of the purchaser, ultrasonic flaw detection and eddy current flaw detection can be conducted to steel pipes through negotiation between a supplier and a purchaser. When adopting ultrasonic flaw detection, pared artificial defect of sampling pipes should be in conformity with acceptance level L3 of GB/T 5777。 when applying eddy current flaw detection, pared artificial defect of sampling pipes should be in conformity with acceptance level A of GB/T 7735. 7. Test Method Dimensions and shape of steel pipes should be measured one by one with measuring tools that meet accuracy requirements. Visual inspection should be performed to inner and outer surface of steel pipes one by one under the condition of sufficient lamination. Test methods and sampling methods for other inspection items of steel pipes should be in line with Table 5. Table 5 Inspection Item, Test Method and Sampling Quantity of Steel PipesNo.Inspection ItemSampling QuantitySampling MethodTest Method1Chemical position Take 1 sample each furnaceGB/T 20066GB/T 223, GB/T 11170, GB/T 20123, GB/T 201242Tensile test Take 1 sample on two pipes of each batchGB/T 2975GB/T 3Flattening testTake 1 sample on two pipes of each batchGB/T 246GB/T 246 4Expansion testTake 1 sample on two pipes of each batchGB/T 242GB/T 2425Hydraulic testOne by oneGB/TGB/T 2416Ultrasonic inspection One by oneGB/T 577720087Eddy current inspection One by oneGB/T 773520048Intercrystalline corrosion testTake 1 sample on two pipes of each batchGB/T 43342008GB/T 433420088 Inspection Rules Inspection and Acceptance Inspection and acceptance of steel pipes should be carried out by quality technical supervision department of a supplier. Lot Grouping RulesSteel pipes should be inspected and accepted according to batches. Each batch should be posed by steel pipes of the same grade, same furnace no. same specification, same heat treatment system (furnace batch). And quantity of each batch of pipes should not exceed the following rules: — Outer diameter ≤76 mm and wall thickness ≤3 mm, 500 pieces?！?Outer diameter 351 mm, 50 pieces。 — Other dimensions, 200 piecesGB/T 149762012 Sampling Quantity Sampling quantity of various items for each batch of pipes should be in line with Table 5. Reinspection and Decision RulesReinspection and decision rules of steel pipes should be in accordance with relative regulations of GB/T 2012.9. Packing, Signs and Quality CertificatePacking, signs and quality certificate of steel pipes should b