Considerations for Installation Model 476 Type 1 & Type 2 Model 477 Type 1
Pipe Flow Considerations Flow of line content during field installation has direct impact on the quality of the weld process. High flow rates in the system at the time of field welding can cause weld “under bead” cracking of the weld to the pipe. Under bead weld cracks severely diminish the quality of the weld and lead to future weld failure. Flow rates should be at a minimum - 0 flow rate and maximum of 3 feet per second flow. With water application temperature below 70 o F (21 o C) and a flow rate beyond 3 feet per second, a special water backed weld procedure should be qualified and implemented in the field. Fitting field welding test inspection process: After the fitting has been welded to the host run, it should be tested for welding quality. This test is strictly a leak test, NOT a fitting design or structural test. This was determined by the fitting design criteria. Repair weld as required. If the fitting is to be hydro- tested the test MUST NOT EXCEED pipeline operating pressure at the time of testing. This is to be certified by a pipeline pressure gauge. Exceeding the actual operating condition increases the possibility of “damaging the pipe” inside the split teed fitting. Testing weld quality by magnetic particle or dye penetrate process are acceptable methods. Fitting support after installation and testing All hot tap or line stop fittings should be properly supported under bottom of the fitting. Horizontal or off the side hot tap fittings should have support under the bottom of the fitting AND at the flanged outlet where the valve is to be mounted. All side outlet taps MUST have the tapping machine supported at the back of the tapping machine. This is to prevent additional bending moments being placed on the tapping branch outlet connections. Fitting Design Hot tap and line stop fittings should be in accordance with pipe branch outlet area reinforcement calculations per ASME B31 Pipe Code Specifications. Field Welder Qualifications The field welder should be qualified to an American Welding Society (AWS) procedure as a minimum. Additionally, qualified to and ASME Code per Section IX fore Pipeline Under Pressure with 6-G Weld Test Certification.
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