Gas off at the tank

[tsmwebb]

I'm drinking cold coffee as I type this. I staggered up to the LPG locker to turn on the gas this morning as I usually do. Turned the valve and gas started venting through the pig-tail hose. The hose was fine yesterday and nothing has touched it since then... It looks perfect. I'm not even sure where the break is but it must be in that length of hose... I suppose they can just die. Even though the solenoid was off, if I had left the tank valve open the entire tank would have vented into the locker. Sure the locker is vented over the side, but... At any rate, I'm glad that we turn the gas off at the tank each time we're done with it.

--Tom.

 

[Ross]

Check for rodents. The squirrels sometimes chew through my gas grill hose. I trained as a welder in my youth and always turn off the valve at the tank.. I have a pressure gauge at the tank and and each time I turn the gas on I shut it off again and observe the gauge for a minute. If the gauge holds I turn the gas on for the day.

 

[tsmwebb]

Check for rodents. The squirrels sometimes chew through my gas grill hose. I trained as a welder in my youth and always turn off the valve at the tank.. I have a pressure gauge at the tank and and each time I turn the gas on I shut it off again and observe the gauge for a minute. If the gauge holds I turn the gas on for the day.

No obvious rodents or rodent spore. The hose has a SS mesh cover and there's no sign of nibbling on it. I suspect age and maybe thermo loading. It is getting on for 10 years on the hose and it is getting up into the 90's here already. Still, the hose lives inside and looks like new. Of course, with the cover on I can't see the hose.

I've been to the two little marine shops here in San Carlos and they don't have anything. So, I'll bus into Guaymas and see about it. Of course, the system was assembled in Australia and I don't know if the pluming fittings are 1/4" or metric... Bummer. But mostly I'm unhappy that I didn't get my morning coffee and glad I didn't blow up!

My hose goes from the tank to the solenoid and then the gauge so I can test for leaks on the stove side of the system but not the tank side -- if that makes sense. But we have always turned the gas on and off at the tank each time we use the stove. It is possible that we've had a slow leak in the pigtail for some time and it just got bad enough to notice... It's scarily obvious now. Maybe the system should have two gauges so we can check the solenoid to gas link...

--Tom.

 

[Ross]

I favor the gauge at the tank. Remember that the gas pressure is measured in inches of water column. Usually less than 6 inches, that translates to about a quarter psi. Just plain generic all fuel hose or propane/natural gas hose and a bottle of very soapy water to test for leaks at the connections. The steel armour is just rodent proofing. A sharp bend could have been the fault.

 

[tsmwebb]

A sharp bend could have been the fault.

I don't think so in this case. It runs in a nice easy curve from the fitting. The odd thing to me is that it failed without being touched. It wasn't leaking noticeably when I turned the gas off. I didn't touch the hose at that point. It sat for a day in the absolutely still water at the slip and then when I opened the valve, again without so much as looking hard at the hose, it failed dramatically.

--Tom.

 

[Ross]

When you get a replacement do a post mortem on the old one. sorta sounds like old age deterioration.

 

[Dan]

The odd thing to me is that it failed without being touched.

Happened to me too. I got a frantic call from the dockmaster telling me there was a strong odor from my boat (he thought it was my holding tank, at first). Turns out my propane hose just gave out. I hadn't used the tank in over a year.

 

[tsmwebb]

When you get a replacement do a post mortem on the old one. sorta sounds like old age deterioration.

I'll do that. The hose is crimped on with seriously large SS crimps. So, I'll have to dremel it off. The damage from that might make finding the original problem problematic... I'm wondering if the failure might the o-ring on the bit that screws into the tank. Still don't know why it would fail w/o any warning. It looks like there is a check valve that I can disassemble, too. Though I don't know how that could be the problem...

--Tom.

 

[Ross]

I would want to know why before I put it back the same.

Edit to add: if you can get the failed hose off intact then pressurize it in soapy water and isolate the leak so that when you do start cutting you won't ruin the evidence. It seems to me that the pressure is too low to blow an O-ring. The regulator is right at the tank,YES? the leak was on the low pressure side of everything?

 

[tsmwebb]

I would want to know why before I put it back the same.

Edit to add: if you can get the failed hose off intact then pressurize it in soapy water and isolate the leak so that when you do start cutting you won't ruin the evidence. It seems to me that the pressure is too low to blow an O-ring. The regulator is right at the tank,YES? the leak was on the low pressure side of everything?

Yes, I want to know what happened.

Getting the hose off is no big deal -- in fact, it is sitting right next to me. Getting the hose off the fittings is the hard part. It is a pretty hefty bit of construction. The mesh hose, and presumably the rubber gas hose inside it, hare attached to the fittings with half in long crimps on heavy SS collars. I just replaced the o-ring and tested it and it still leaks. Since it has a check valve in one end I suppose I can put it in a bucket, pump air into it and see if there are bubbles. But, since I can't see the pressure hose at all I'm no sure what I'll learn.

The hose that failed is between the bottle and the regulator so it is high pressure. The regulator is on the bulkhead.

--Tom.

 

[Ron20324]

Yeah, go for the first likely test- the soapy water.

 

[Ross]

I would move the regulator. The domestic propane setups use copper tubing and POL fittings between the tank and the regulator and flare fittings on the low pressure side but I don't like anything flexible between the tank and the regulator on a boat. My tanks are tied down at two points and will stay in place if the boat is smashed.

 

[tsmwebb]

I would move the regulator. ...I don't like anything flexible between the tank and the regulator on a boat.

That makes some sense. I've got a fairly typical two tank, one regulator set-up. I move the pigtail to the tank in use rather than having a valve. In the realm of human factors this is a good set-up. It gives very strong feedback to me when I have to shift tanks so I'm not likely to forget to fill the reserve. But, it does mean I've got a run of high pressure flexible hose.

I just got a new pig-tail from the "local" hardware store -- 5 miles walking through the desert with buzzards flying over-head and trolling for snakes (beer is being applied as I type). Have put it all back together and soap tested it. Will pressure test it this evening. I think I'll dissect the old hose in the morning.

Still bothers me a lot that the old hose busted without any warning signs at all. Certainly a good reason to shut the tanks off!

In the it ain't broke but might not be ideal category: my solenoid is in front of the regulator. It works there, but is it best practice?

--Tom.

 

[Ross]

In the it ain't broke but might not be ideal category: my solenoid is in front of the regulator. It works there, but is it best practice?

--Tom.

The low pressure side? That is good.

 

[tsmwebb]

The low pressure side? That is good.

It goes tank, pigtail, solenoid, regulator. (wish I had a fast enough connection for pictures!). So, it's high pressure. It works for sure -- we test it every time we use the stove -- and it keeps most of the pipe connections downstream of the solenoid. Seems to me that with a properly rated solenoid, the solenoid should be as close to the tank as possible. But I pulled Calder off the shelf and his drawings show regulator and then solenoid... So, I'm confused.

--Tom.

 

[Ross]

I Jjust checked the west catalog. They sell high pressure pigtail hoses UL certified but their solenoids are all on the low pressure side of the regulator. The marine regulators have a built in high pressure gauge they sell a high pressure gauge for non marine regulators.

 

[tsmwebb]

Just finished the postmortem:

1) the outer SS covering was in lovely shape. Looked beautiful and was a bugger to cut off.

2) the hose inside was old, harding and showing lots of cracks.

3) there is no non-destructive way to inspect this hose.

4) I don't see a burst point, but given the state of the hose the leak could be anywhere in the length.

5) this was a first quality hose, it never saw any UV, it was well secured at both ends and it was less than 10 years old. It looked brand-new on the outside.

CONCLUSION: This suggests to me that pigtails should be changed out pro-actively. I have no idea what the MTBF is, but based on a sample population of one I'd suggest a replacement interval of around 5 years. Also, I very strongly suggest turning the gas off at the tank when the stove is not in use.

I took some before and after shots and if I get to a 'net cafe or someplace with a little quicker connection I'll upload them.

--Tom.

 

[Don12364]

Sure its the hose??

Regulators are made in cast aluminium. I have had one corrode through underneath where the drips gather.
I would paint soapy water round everything before disassembling anything.

 

[sailingdog]

Generally, it is recommended that you replace the hose in LPG installations about every five years..