Section 2 Seamless pressure pipes

2.1.1 Provision is made in this Section for seamless pressure pipes in carbon, carbon-manganese and low alloy steels.

2.1.2 Where pipes are used for the manufacture of pressure vessel shells and headers, the requirements for forgings in Ch 5, 7 Forgings for boilers, pressure vessels and piping systems are applicable where the wall thickness exceeds 40 mm.

2.2.1 Pipes are to be manufactured by a seamless process and may be hot or cold finished.

2.2.2 The method of deoxidation and the chemical composition of ladle samples are to comply with the appropriate requirements given in Table 6.2.1 Chemical composition of seamless pressure pipes.

2.3.1 Pipes are to be supplied in the condition given in Table 6.2.2 Heat treatment.

2.4.1 All pipes are to be presented in batches as defined in Ch 6, 1 General requirements.

2.4.2 Each pressure pipe selected for test is to be subjected to tensile and flattening or bend tests.

2.4.3 The results of all mechanical tests are to comply with the appropriate requirements given in Table 6.2.3 Mechanical properties for acceptance purposes: seamless pressure pipes (maximum wall thickness 40 mm), see 2.1.2 .

2.5.1 Values for nominal minimum lower yield or 0,2 per cent proof stress at temperatures of 50°C and higher are given in Table 6.2.4 Mechanical properties for design purposes: seamless pressure pipes and are intended for design purposes only. Verification of these values is not required, except for materials complying with National or proprietary specification where the elevated temperature properties used for design are higher than those given in Table 6.2.4 Mechanical properties for design purposes: seamless pressure pipes.

2.5.2 In such cases, at least one tensile test at the proposed design or other agreed temperature is to be made on each cast. The test specimen is to be taken from material adjacent to that used for tests at ambient temperature and tested in accordance with the procedures given in Ch 2 Testing Procedures for Metallic Materials. If tubes or pipes of more than one thickness are supplied from one cast, the test is to be made on the thickest tube or pipe.

2.5.3 As an alternative to Ch 6, 2.5 Mechanical properties for design 2.5.2, a manufacturer may carry out an agreed comprehensive test program for a stated grade of steel to demonstrate that the specified minimum mechanical properties at elevated temperatures can be consistently obtained. This test program is to be carried out under the supervision of the Surveyors, and the results submitted for assessment and approval. When a manufacturer is approved on this basis, tensile tests at elevated temperatures are not required for acceptance purposes, but at the discretion of the Surveyors occasional check tests of this type may be requested.

2.5.4 Values for the estimated average stress to rupture in 100 000 hours are given in Table 6.2.5 Mechanical properties for design purposes: seamless pressure pipes - Estimated values for stress to rupture in 100,000 hours (units N/mm²) and may be used for design purposes.