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Thread Ratings

Thread Ratings

Thread Ratings

(OP)
Does anybody know the pressure ratings, over temperature ranges, for tapered and parallel threads?

RE: Thread Ratings

Fawkes,

Here are some figures I have to hand (from the UK):


Pipe Fittings to BS143 & 1256:1986

Both Malleable Cast Iron and Cast Copper Alloy fittings generally have screw threads to BS21.

Malleable Cast Iron fittings have permissible working pressure of 25 bar (-20 to 120 deg C) to 20 bar (300 deg C).

Cast Copper Alloy  fittings have permissible working pressure of 16 bar (-20 to 120 deg C) to 10 bar (300 deg C).

For 120 deg C to 300 deg C, linear interpolation is allowed.

Design test pressures are;

MCI:    100 bar (1/4 to 4 inch)
MCI:    64 bar (5 & 6 inch)
CCA:    64 bar  (1/4 to 4 inch)

Hope this helps,

Brian

RE: Thread Ratings

What materials are used for the threaded parts?

RE: Thread Ratings

If it is pipe threads, then calculate the wall thickness per B31.? with a wall thickness deduction for the thread depth.

Or, are you referring to bolts?

RE: Thread Ratings

(OP)
I'm referring to pipe threads, but I'm interseted in the the maximum allowable pressure so that the threads does not shear because of the hydrostatic force and so that the thread seals properly.

This also needs to cover a range of temperatures. Most data I've found only seems to realte to atmospheric conditions.

The materials are mainly carbon, stainless or duplex steels.

RE: Thread Ratings

Check Thread378-49291
To determine the force required to pull the pipe apart at the thread requires calculating the tensile stress area.If you just want to know about thread length failure (the least likely on tubular threaded material) take the length of the thread and use a shear strength of the weakest material to obtain a number.
The Machinery’s Handbook has information about tensile stress area and shear. For pipe or tubular  threads you must deduct the ID area to find the actual tensile stress area. Multiply the tensile stress area by the yield strength of the material to obtain a number. With all of these calculations be sure to use a safety factor and test to failure if possible.

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