pneumatic compressor gas tightness question.

[SH]

I have a Stanley air compressor with a 25 litre storage vessel.

when I start it, it pumps up to 120 psi and then the motor cuts out.

Over typically 5 minutes, the air pressure will decay slowly to 80 psi whereby the compressor motor restarts.

This happens when I am not using any air tools.

I have used a can of gas leak detector and tested all unions and joints and I can confirm there are no leaks.

This then leaves the compressor pump bit itself... are they actually gas tight or do they have a normal amount of leakage back to the air inlet port?

[Tim Lamb]

In message <s1in5t$vog$ [e-mail]>, SH [e-mail] writes

I have two compressors with the same feature. I think you are expecting too much for a modestly priced device. 5 minutes for 40 psi is rather a lot although the initial pressure will drop as the compressed air cools.

Is your household insurer aware that you have a pressure vessel subject to annual testing at your home?:-)

[SH]

good question but I have never seen any small print to say that domestic grade compressors must have their pressure vessels checked annually.....

That would also mean party balloons & bicycle tyres would have to be checked as they are also technically pressure vessels! :-)

[Steve Walker]

So is your pressure cooker - and that's a proper one with even a "testable" safety valve.

[T i m]

I have noticed 'leaks' from a couple of places in the past. One being the water drain screw underneath and the other the pressure release valve in the starter solenoid or the non return valve.

If you put the end of the outlet hose in a jar of water you should see if it's leaking 'from' the system or leaking 'past' any non-return / start back-pressure release valves etc (the one that goes 'Psssthhh!' when the compressor shuts off when at full pressure).

Cheers, T i m

[Tim Lamb]

Don't insure with the NFU mutual is another answer:-)

[John]

My understanding is that the requirement for annual testing is when the pressure x volume exceeds 250 bar.litres

120 psi is less than 10 bar so no inspection in this case

John

[T i m]

<snip>

AFAIK there is no (mandatory) requirement to have such placed under the regulations if it's under 250 bar/l.

So, if the OP's compressor is 25l and 120psi (8.3 bar) then it's only

210 bar/l so well under the threshold (and likely why the regulations are set at that level or compressors are made to that spec).

It looks like the regulation applies to all pressure cookers though. ;-)

Cheers, T i m

[Matthias Czech]

Am 01.03.2021 um 15:29 schrieb T i m: [..]

nitpicking: Bar*l not bar/l

[T i m]

Thanks, the '/' wasn't indented to indicate 'divide (or per) but just as a separator between bar and it but could be confusing if not seen along with the formal regs etc.

In the linked regs it was generally written out as 'bar litres'.

Cheers, T i m

[John Rumm]

That sounds rather excessive...

(I have a similar compressor, and it will typically not refire in many many hours (days even) with no air demand.

However it does not take much of a leak to cause what you are seeing. Typically if I have a nailer hooked up to it, and put it down on the workbench between uses - sometimes you get a slight leak from the quick connect PCL connector - depending on hose angle etc, and then a few mins of that leak will be enough to prompt it to recharge.

Did you check the drain valve?

It it an "oil free" using? If not has it got (enough) oil in it? Have you checked all the hoses as well as the joins?

[Harry Bloomfield, Esq.]

SH submitted this idea :

You have a leak somewhere, check the drain valve at the bottom of the tank; any airlines you have attached. Tap water, with a drop of Fairly liquid and a soft paint brush makes finding a leak easy.

My DIY garage compressor normally holds full pressure for days, with nothing connected to it.

[Tim Lamb]

In message [e-mail], John [e-mail] writes

Hmm.. £120/yr. potential saving. I'll check my volumes...

>

[Brian Gaff (Sofa]

Everything leaks. I think back in the 60s our school had some small air lines and they ran cyclicly even if nothing was going on. Therse were introducing the 6th form to air powered tools as I recall. Brian

[Brian Gaff (Sofa]

Yes, lots of dangerous stuff in the home. Remember CRTs? Now its more likely a lithium battery burning the house down, or an exploding electrolytic capacitor taking an eye out if you are working on an open PC. Brian

[newshound]

I don't recall them having such a restriction on my house insurance.

I was mildly amused on shifting my car insurance to them that one of their questions was "Would you ever carry more than 3000 shotgun cartridges in your car".

I imagine it might be quite exciting if that quantity went off.

[newshound]

IME CRTs don't go off very spectacularly. Long long ago my father sought to make one safe (while I watched) by wrapping it in multiple layers of blankets and sacking, then lobbing bricks at it from a distance. After a number of failed attempts, the gun extension just snapped off with no detectable "bang". (By the end of the war he was training people in how to blow stuff up. He won't have done a "stored energy" sum and, on thinking about it, there's not much stored energy even in an old-style

45 degree tube).

[Tim Lamb]

I think somewhere there is a limit related to carrying ammunition in a shoot vehicle.

Not sure if Tim would be pleased but there are moves afoot to cease using lead for shot.

[Tim Lamb]

In message [e-mail], John [e-mail] writes

Sadly my two are 100L and 150L if I have the sums right.

[Fredxx]

I'm surprised its still in use. Certainly been banned for fishing for quite a while.

What alternative, depleted uranium? I guess the Rolls Royce solution will be Tungsten.