Tapered Pipe Threads 1

[ADH]

Hi,

I am looking for information concerning basic stress/strain calculations for tapered pipe threads (in a plastic drain pan). The threads will take a threaded PVC elbow (nothing fancy). Anyhow, everything I can find concerns bolt (flat) threads, nothing on tapered threads.

Is there a conservative approach to using these calculations? What do you suggest? Thanks in advance.

ADH

 

[FINN_imported]

You may wish to look at NPTF dryseal USA standard taper pipe thread (Class 1) for both internal and external threads. According to the Machinery's Handbook, this gives the best seal for fluids as well as the strongest thread connection in tapered threads due to interference of threads over the full length of the taper.
As for finding stress calculations for the threads...I can only assume you are looking for a tightening torque for the fitting. You may wish to try a modification of the standard tightening torque equation T=KDP where:

T=tightening torque

K=0.15 (for light oil between threads)

D=tensile stress area (must try at different diameters along the taper)

P=clamping load in pounds (I can only assume this to be the amount of force to start deforming the port of the plastic drain pan.

We have some equipment with steel tapered plugs into plastic tanks where we have used a steel band around the port of the plastic tank to prevent deformation of the plastic tank to the point of failure.

I realize this is very vague, but I also hope it helps.

-FINN