cam and groove hose couplings

[akagdis]

I am using a cam and groove hose coupling at the end of a 1- 1/2" ball valve attached to a metal braid hose, ~6ft in length. The female end is on a vessel rated a MAWP of 75PSI @ 360F. The cam and groove coupling is rated for 250psi @ 72F. My maximum working pressure is ~70psi @ 200F, and I don't see us going any higher than 212F, and the pressure will not go above 70PSI. Do you see any problem with using cam and groove couplings rather than Swagelok npt-like couplings in this situation. I have some engineers here saying that I shouldn't use cam/groove style couplings because they leak. Is there any truth in what he is saying or is it a matter of personal preference, operating under the conditions outlined above?

 

[Latexman]

The ears that are pushed down to engage the cam into the groove are notorious for being knocked loose by accident or vibrated loose. Even if you require them to be wired or cable tied down, be prepared for the fittings to come apart one day and have a spill. It'll happen.

Good luck,
Latexman

 

[moltenmetal]

Cam and groove couplings are very useful for transfer hoses and other temporary connections, but are troublesome in long-term/semi-permanent services. They rely on rubber gasketing to work properly. The cams apply such a minimal amount of gasket seating stress that an elastomeric gasket is a necessity- nothing else will work. A coupling rated for 250 psig at 70 F will probably leak at 70 psig if you take the temperature up to 200-212 F simply because the rubber gasket will be getting quite soft at those temperatures. Talk with the mfg and see if they have any pressure/temperature recommendations for their systems. Cold MAWPs are useless when you're dealing with materials which soften rapidly with increasing temperature.

Ditto the note about pinning the cam levers and/or wiring them in place so they don't vibrate loose.

 

[akagdis]

Thanks for your responses, I should clarify that these are used in a temporary situation, as the vessels need to be moved on a routine basis. The gasket I am using is of Viton material, rated -40° to +400° F, and the ears have a locking mechanism to prevent accidental un-latching. Wish me luck!