Gasket modification issue
Thread Content
During the initial nitrogen gas airtightness test (2.0 MPa) of the paraffin oil hydroprocessing unit, a leak was detected in the flange of the oil and gas outlet at the top of the thermal high-pressure separator. Upon pressure relief inspection, it was found that a deep groove had been formed in the seal groove of the flange due to the pressure exerted by the gasket. Design pressure/temperature of the thermal high-pressure separator: 15.4 MPa/350°C, manufactured by Shanghai Boiler Factory. According to tests conducted by the Project Quality Management Center, the hardness of the flange on the head of the thermal high-pressure separator is low (average value: 111 HB). Design material for the top elbow of the thermal high-pressure separator: the body is made of 2 1/4Cr1Mo, with TP347 welded on top; the gasket is designed to be made of 0Cr18Ni10Ti ； Is it possible to use 00Cr12 as the material for the gasket?
No, for materials exposed to high-pressure hydrogen, selection should be based on the NALSON curve; 00Cr12 is definitely not suitable – stainless steels containing Ti or Nb should be used instead.
It is absolutely not feasible; the applicable temperatures for the two materials are different, and there are specific requirements for selecting materials that can be used in hydrogen-rich environments. The selection of materials must be made in accordance with relevant standards. Sinopec has standards that can be referred to.
Could you please explain it to me more clearly? Thank you!