4.3　Inspection of Pipe Fittings

4.3.1　Before the pipe construction with the working pressure no less than 5.88MPa and the working temperature no less than 400℃,the following items shall be confirmed to meet the current national or industrial standards against the quality certificate from the manufacturer.

1　Metallographic analysis result of alloy steel pipe fittings.

2　Non-destructive testing result of high-pressure pipe fittings.

4.3.2　The flange sealing surface shall be bright,clean and smooth without any run-through grooves,porosity,cracks,burrs or other defects reducing the strength and connection reliability.

4.3.3　The flange with male and female face or ring shall be inlaid naturally.The height of convex surface shall be no less than the depth of concave surface.

4.3.4　The supporting surface of connecting bolts on the flange end surface shall be parallel to the flange joint face.It shall be stressed uniformly after fastening.

4.3.5　The dimension of the flange connecting with the equipment shall be checked.The dimension tolerance of flange shall meet the requirements of GB/T 9124 Technical Conditions of Steel Pipeline Flange Seal,in which the tolerance of the flange thickness represented by C shall meet the requirements of Table 4.3.5.

Table 4.3.5　Tolerance of the flange thickness　unit:mm

4.3.6　The material of flange gasket shall meet the design requirements.When the design has no specific requirements,the gasket material shall be selected according to Appendix C.

4.3.7　The surface of metal gasket shall have no defects such as cracks,burrs,run-through scratches or rusts.Its hardness shall be less than flange hardness.

4.3.8　Gasket covered by outer ring metal and spiral wound gasket shall have no defects such as radial scratches or looseness.