hydraulic cylinder

Mrezaaeemi posted this question in thread " calculating thickness of hydraulic cylinders" and I am posting reply by Abdel Halim Galala's post # 236.

Please don't thank me. Thank Mr.Abdel Halim Galala.

" You can use the following equatin with a good accuracy:

t = P D / (2 S E) + CA

Where,

t = Nominal Cylinder Wall Thickness, Inch

P = Internal Design Pressure, PSI (at the most severe condition)

D = Cylinder Inside Diameter, Inch

S = Allowable Tensile Strength of Cylinder Material, PSI (at Design Temperature)

E = Joint Efficiency, dimensionless (E=1 in case of Seamless Cylinder)

CA = Corrosion,Erosion, Wear, .... etc. tolerances, Inch

Note : If the Cylinder is subjected to external pressure, you have to check the calculated thickness at that pressure using another technique

The equation shown is for longitudinal joints (circumferential or what we called "hoop stresses" resulting due to internal pressure) which are the most severe stresses compared with longitudinal stresses.

Note : In case of circumferential joints (longitudinal stresses) : t1 = P D /4 SE + CA, and it is easy to find that t = 2 t1 by neglecting CA.

According to ASME Code, Section VIII, Division 1, the equation can be applied up to : t <= D/2 (not D/20 as you mentioned), or P <= 1.25 SE.

Otherwise the equation for "thick wall tubes", can be applied in accordance with ASME Code.

Can you please provide me the name of Code which states the condition of D/t > 20?

I prefer to select a Design Code and apply its rules and recommendations. For E, refer to ASME Code. Also refer to ASME Code to find S (allowable tensile strength of tube material). Thank you for your question related with factor E.

E is a Joint Efficiency multiplied by S (allowable tensile strength) to lower the allowable tensile strength of cylinder material. E depends on if there is a seam weld (longitudinal weld) in the cylinder or not. If yes, did you radiographed that weld or not. For each case there is a different value for E, but in no case E >1.

Also E may be specified as Casting Quality Factor with a symbol "F" (instead of E) which depends on the type of cylinder material and its procedure of production."

A small piece of advice to save everybod's time including yours too - there is a "search" everywhere and even in CR4. Just put in your words and do some searching, it will solve many of your questions.

Am I right to assume that the force against the walls will be function of the surface? In this case, there should be a PI factor in your equation.

Regards,

Here is the link to the thread that Ducon referred to ---

Calculating the Thickness of a Hydraulic Cylinder