Letby on gas cylinders

[krclink]

Took my van for a habitation service and was told that because there was letby on my refillable gas cylinders, the firm doing the service would not test the gas system. I bought two new cylinders, as the old ones were about 6 months away from their 10 year renewable date, and went for a retest with another service engineer. Got told that the new cylinders had letby as well. Just wondered if anybody has had a similar experience

 

[Emmit]

Go on, I'll ask.
"Letby"?

 

[joka250]

Go on, I'll ask.
"Letby"?

Beat me to it.

 

[Emmit]

"Letby"

I've tried a few online dictionaries.

Zilch

 

[Odd-no-more]

Let by is "not shutting fully off"

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[Reallyretired]

Let-by test is a test for gas tightness (google is your friend)
Presumably the OPs system is leaking somewhere and the problem isn't the gas bottles. Possibly a misunderstanding with the gas blokes, not that they won't test, but they have tested and it has failed.

 

[Odd-no-more]

Let-by test is a test for gas tightness (google is your friend)
Presumably the OPs system is leaking somewhere and the problem isn't the gas bottles. Possibly a misunderstanding with the gas blokes, not that they won't test, but they have tested and it has failed.

The way we test is to charge system with gas and then shut off the supply and test to see if the pressure drops. The first part of the test is to check the valve is fully shutting of, if it fails to fully shut off the rest of the test cannot be carried out. We call this letby. Because the valve is "letting by"

 

[Reallyretired]

Seems strange that the replacement bottles have the same problem as the originals.

 

[Jimbohorlicks]

Seems strange that the replacement bottles have the same problem as the originals.

It's not the bottles that's the problem, once the system is pressurised the bottles are switched off if the system pressure falls then there is a leak somewhere along the pipework, appliances.we have just had gas maIns renewed at home renewed at home and this is also the test they do beyond the meter, switched off, to test house pipework etc.

 

[Spriddler]

Surely the obvious step is to brush some soapy water around all the joints to identify the location of leak?

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[canopus]

Let by is "not shutting fully off"

Thought you'd gone back to work?

 

[Just smiffy]

A habitation service is just that, isn’t it..! Service and repair if required..?
think I would take my business elsewhere if their incapable....

A habitation check is nothing I can’t do whenever I get my van ready for a trip.....

 

[Reallyretired]

The fault, if it is letby, is that the shut off valves on one or both bottles are failing to close properly. As its more likely to be just one of them rather than both they need to be removed to test them separately.
I agree a habitation check is a waste of money, as all items apart from the damp check are things you would naturally check anyway, and a damp meter costs less than most are charging for this superfluous check.

 

[Spriddler]

The fault, if it is letby, is that the shut off valves on one or both bottles are failing to close properly. As its more likely to be just one of them rather than both they need to be removed to test them separately.

Agreed, but the OP already said he has replaced both of the bottles but it hasn't cured the letby/leak.

 

[krclink]

Thanks for all your inputs guys. The letby problem concerns only the cylinders and not the rest of the system. Having been in touch with the suppliers of the cylinders and the second engineer, it was decided that the only way to sort this is to return the cylinders with the van to the supplier, who has said that they would check obviously the cylinders, and the rest of the system. I must say that I did do the soap bubble test on the cylinders, and the soap film remained in place for at least 1 minute on one cylinder and about 20 seconds longer on the second, bearing in mind that it was carried out beside the van which was parked outside on a relatively calm day.

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[Odd-no-more]

Thought you'd gone back to work?

Back.next week, 3 days a week

 

[nicholsong]

Back.next week, 3 days a week

A fool and his fun are easily separated!

 

[Pausim]

Do you have a filter between the bottle and the regulator? I had a similar problem, the pressure tester could not be used because when the bottles were turned off there was still pressure in the system, on the high pressure side of the regulator. Turned out to be a puddle of oily lpg in the filter housing which was slowly gassing after the bottles had been turned off. Easily cleaned out with a bit of kitchen towel and the problem was solved.

Also proves the value of the filter because if the oily residue had reached the regulator it would have damaged it.

 

[Odd-no-more]

Thought you'd gone back to work?

Back.next week, 3 days a we

A fool and his fun are easily separated!

It's 5 weeks to Christmas, so 15 extra days in all. And the extra cash helps

 

[Minxy]

Is it the cylinders or could it actually be the hoses?

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[TheBig1]

in the back of my mind a bit, but wasn't there a batch of cylinders with faulty valves reported and a recall in place?

 

[krclink]

Update to original. post. Have taken van to supplier of bottles to carry out gas checks. He did a mamometer check with gas bottles turned off and no gas in system. Mamometer got a reading of 12mbar which may have suggested that there was let by, but after approx 15 minutes the AES fridge tried to relight. This had the affect of reducing the pressure to zero, and it stayed like that for another 10 or so minutes. Seemingly the reason for the apparent reading is that the Truma regulator plus the gas filters I had fitted have a residual pressure buildup, and this is what in simple terms causes the apparent let by . Net result is that the cylinder's are both fine.

 

[Basildog]

Small lpg systems are notoriously difficult to test as even the slightest thing like temperatures etc can give some very weird results.
Letby test is needed before you start any tightness test because imagine you have a tiny seep of gas whether it’s lpg or natural into the system from the supply valve that maintained the test pressure of the system despite their being a leak .
Letby test pressure is between 7 to 10 mbar .
Let-by is now tested at 7 to 10 mbar for one minute.
• Should the let-by test fail it
may be necessary to test
the cylinder supply control valve with LDF. If the valve is satisfactory, additional time should be allowed until a stable reading is obtained. It may
be difficult to achieve a stable reading on an installation with a small pipework volume or
if the pipework is exposed to direct sunlight.
So not sure how a qualified guy would not follow the simple way of diagnosing a faulty cylinder shut off valve !

 

[Basildog]

Seems strange that the replacement bottles have the same problem as the originals.

Unbelievable that someone who is carrying out a gas test didn’t bother to follow industry standards

 

[Basildog]

Took my van for a habitation service and was told that because there was letby on my refillable gas cylinders, the firm doing the service would not test the gas system. I bought two new cylinders, as the old ones were about 6 months away from their 10 year renewable date, and went for a retest with another service engineer. Got told that the new cylinders had letby as well. Just wondered if anybody has had a similar experience

As per my previous post it seems unbelievable that you have had 2 different gas bods fail to correctly identify whether or not a cylinder shut off valve is fully closing or not ( letting by ).
Do you know if either one actually is qualified ? ?

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