hydraulic cylinder internal threads

[duk748]

hello all - small question here - i have a design problem that i am not sure of the correct formula to use for the stripping of threads - i have a gland threaded into the body of a hydraulic cylinder that has a burst presure of 9000 p.s.i. - the tube is made of a572 steel & the threaded gland out of 80-60-05 ductile iron - i have used the thread stripping formula out of machinery handbook & found what the length of engagement should be but am not sure how the 9000 pounds force plays into the formula - any info would be appreciated - thank you

 

[MikeHalloran]

The 9000 is pounds per square inch of surface area, which can become a very large force on a surface with more than a square inch of area. I.e., to estimate the force trying to push the gland out of the threads, you multiply the 9000 by the net affected area, which is the area of a circle at the thread pitchline ... minus the area of the rod that goes through the gland.

A less conservative approach would use the same area, but the actual maximum system pressure times an appropriate safety factor, not the burst pressure of the cylinder tubing.



Mike Halloran
Pembroke Pines, FL, USA

 

[EdStainless]

One thing to double check is how much the cylinder will swell under pressure. In some cases this reduces the thread engagement enough to reduce the thread strength, with predictably unpleasant results.

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