We are being asked by a Refinery client to modify some 6" and 8" gate valves by adding a tap. MSS SP-45 is a spec showing tap locations for drains and by-passes on valves. We would tap by boring a hole at location A or B on figure 5 of MSS SP-45 and welding in a nippolet. The valve will then be pressure tested as required by API 600.My question is if the valve is a NACE trim valve will the need any additional PWHT or testing? The welding procedure has to be qualified for the maximum allowable hardness (refer to NACE MR 0175) and probably the testing of the weld for composition and hardness, in order to maintain the 'NACE' rating of the valve. The PWHT depends on the material and thickness and the additional code requirements.

MORE NEWS