Hydraulic Cylinder Codes

[DBCox]

This may seem like an odd question, but I have always operated under the assumption that hydraulic cylinders should be designed and manufacturered to ASME Section VIII code since I consider them to be pressure vessels. I have worked for a cylinder manufacturer and we desgined per VIII code, but the weld procedures were not written/approved with section VIII in mind. Upon discussing this with a weld engineer today, Section VIII requires that anything over 15 PSI and material over 3/4" thick be post weld heat treated. I do not know any cylinder manufacturer's who PWHT. So, that leads me to the question:

When writing and qualifying weld procedures for hydraulic cylinders, what code(s) should be considered?

 

[schlebb]

Although it is not a bad idea to design cylinders to the ASME Code, strictly speaking these are not pressure vessels. If they are used for hydraulic purposes they are exempt from the code.
Most cylinder manufacturers build to the standards published by the National Fluid Power Association.
You can purchase these on their website.

http://www.nfpa.com/Standards/Standards_StandardsLocator.asp?pid=355

The standards you are looking for are ANSI(NFPA) T3.6...

 

[Cockroach]

PWHT is typically mandatory in the valve industry, which adheres to the pressure vessel code. You are correct, the wall thickness criteria is 3/4 inches.

Look at CSA Z245.15, API 6D for reference on this. The first is particularly good with Figure 12 showing the required butt weld geometry and materials discussing PWHT as a means of stress relieve at the welded joint.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[unclesyd]

Here is the online catalog from Cylinder Repair Company and I see no mention of any fabrication codes on any of the cylinder components. The only thing mentioned are some material specifications.

You might give the a call to see if they have to comply with any codes.

http://www.crconline.com/

 

[EdDanzer]

Hydraulic cylinder welding is different than ASME pressure vessels as distortions will destroy the function of the product, DOM tube is a cold worked steel and the yield strength can be reduced if too much heat is applied.

Worry less about codes and more about procedures that make a successful product. If you are not sure of what to do contact a welding engineer with fluid power experience.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[kmosier]

Refer to the National Fluid Power Association. Most manufacturers we have dealt with for custom cylinder design adhere to their guidelines.

Project Engineer

http://www.cognidyn.com/