Field welding of Weld Neck flanges to Line Pipe
has occurred for years and as long as the joined assemblies of pipe
and flanges has service pressure well below flange rated pressure,
the assemblies give little trouble. As the oilfield has matured and
higher pressures have become a prominent issue, all potentially
pressurized assemblies should now receive pressure tests to 1.5 times
working pressure when first weld assembled, and to full rated working
pressure with each movement of the assembly.
API Flange Specifications prescribe strength of
material and chemistry limits for
but leave the operators choice of pipe strength unspecified.
API Specification 5L specifies pipe of
various sizes and wall thicknesses, many of which will match up to
Flange Weld Necks, and
this line pipe has many strength grades (see
API 5L Line Pipe
Physical Properties) but API Spec 5L does not designate working pressures for
any sizes or strength grades.
WOODCO USA uses a formula consistent with API Spec 6A 20th Edition,
Para. 126.96.36.199 Distortion energy theory. Our formula makes no
allowance for defects in material, variation in wall thickness, etc.
You can use the calculator below, inputing your pipe wall and yield
strength for the pipe selected. Users will have to determine the safety
factors they want to use for the variation they expect to encounter in
practice including considerations for corrosion, internal erosion, and welding variation.
provided below, will allow users to estimate the
working pressure of selected sizes and strength grades of pipe, (see
Carbon Steel Pipe Dimensions and Weights for Pipe O.D.'s, I.D.'s,
and wall Thicknesses).