Flat end caps on a hydraulic cylinder
Flat end caps on a hydraulic cylinder
(OP)
Hi,
I am designing a hydraulic cylinder that will have a flat end cap and need to figure out the thickness it will need to be. I was wondering if anyone could provide me with a formula? The ID=6" and will be under a pressure of 3000psi. TIA.
I am designing a hydraulic cylinder that will have a flat end cap and need to figure out the thickness it will need to be. I was wondering if anyone could provide me with a formula? The ID=6" and will be under a pressure of 3000psi. TIA.





RE: Flat end caps on a hydraulic cylinder
d bolt PCD inch
p pressure psi
s unit stress psi
K 0.162 for plates bolted rigidly to flanges.
That should give you a start.
You should check the Code for the latest data and qualifiers.
RE: Flat end caps on a hydraulic cylinder
RE: Flat end caps on a hydraulic cylinder
For a welded cap use the formula of johnp taking:
d=inner pipe diameter (cap should be inserted into the cylinder and the weld done on the extra cylinder length projecting beyond the cap, otherwise take the pipe outer diameter)
K=0.33
s=15000 psi (typical for low carbon steel)
If the cap may be welded also on inner side, the thickness could be slightly reduced (down to using K=0.2 if the cylinder wall is thicker than the minimum required) but this doesn't seem very important for such a small cap.
Of course you will require a heavy weld, with an effective depth equal to cap thickness.
Note that for your conditions (high pressure, small diameter) the code is quite conservative, especially for the weld.
prex
motori@xcalcsREMOVE.com
http://www.xcalcs.com
Online tools for structural design
RE: Flat end caps on a hydraulic cylinder
RE: Flat end caps on a hydraulic cylinder
As you don't want to use the code you might take 2/3 of the yield strength (except for very high strength steels).
For the weld you can calculate it in shear using an allowable shear stress equal to 70% of the allowable in tension.
All this is for building a prototype and testing it. Note that if you are designing an equipment that shall go to the market, you should hire someone to do a professional calculation.
prex
motori@xcalcsREMOVE.com
http://www.xcalcs.com
Online tools for structural design
RE: Flat end caps on a hydraulic cylinder
What I don’t understand is why the calculated stress can’t go up to 1.5 x design stress as the stress comes from bending? But no code that I know will allow this.