Failed Propane Acme Connector

[wsmurdoch]

This spring in the Bahamas while cooking breakfast the stove went out. Checking in the propane locker I was surprised to see the cylinder pressure was zero. The 20 pound tank should have been half full. When I began to unscrew the Acme (QCC) connector I saw the problem. The plastic connector was cracked partially separating the threaded barrel of the connector from its end. Ten pounds of propane had leaked from the cracked fitting and spilled into the propane locker. Luckily, the overboard drains and lack of an ignition source prevented a possible catastrophe. The connector had been tightened by hand. I’m a 135 pound, 63 year old fellow, so I don’t think it was over-tightened. The connector is green and marked, “Use with type 1, UL, MAX WP 250 PSI, 250-325 kBTU/h, RECA”.
I took this photo of the failed connector at home so you can see the crack.

Has anyone else seen this sort of failure?

[a64pilot]

I'd replace it with the all brass one that screws internally to the valve, I guess it's probably the "old" way as it requires a wrench, I think it's left hand threads too.

[a64pilot]

Apparently what I'm talking about can be had with a plastic part the doesn't require a wrench, but when the plastic fails, no leak will occur
Tractor Supply Co. - Enjoy searchingropane fittings

[a64pilot]

More specifically, this one
Mr. Heater Propane Fitting P.O.L. with Handwheel - Tractor Supply Co.

[wsmurdoch]

My temporary fix was to replace the plastic Acme (QCC) fitting and its pigtail with a brass POL fitting and a short length of hose. I had the short length of hose with a POL fitting on each end onboard. I use it to decant propane from one bottle to another. It comes in handy when the only available propane is cylinder exchange. I don't want to give up one of my 20 lb aluminum cylinders. Back in the US, I replaced the POL fitting and hose with another Acme fitting and pigtail.

The newer Acme fitting has some additional safety features, "Acme nuts contain a thermal bushing, which will melt in a fire, and prevent the escape of gasses from the tank. When it melts, it allows the new OPD spring activated shut off valve, which will only allow the flow of gas if a fitting is attached, to pop out and completely shut the flow down. They also have an improved excess flow check valve, compared to the valve in the old POL fitting" (and my POL fittings have no valve -- they are bored straight through, and the quote was from the internet).

Anyway, since no one has seen another Acme connector fail, I'm "pretty" happy with it.