compressor unloader valve issue

[finyuk2005]

just got my compressor up and running after a few years and i tentatively let it get up to full pressure which is 150psi, when it finally cut off the unloader valve seemed to stay open for too long and the pressure dropped to 120psi,
i think its the unloader anyway, but it had stopped before i could run out to see where the air was coming from!

does that sound like the unloader, or could the pressure switch do that?
might be worth me taking the unloader off and stripping it down and cleaning it,
might lower the cut off pressure too, dont really need 150psi,

any one have any ideas on the subject?

cheers!

 

[mtt.tr]

What type of compressor?

 

[finyuk2005]

What type of compressor?

its a clarke industrial, 200l 4hp piston type

 

[finyuk2005]

just watching some yootoob videos, looks like it could also be the check valve? might take that off too and make sure its all cleaned up

 

[wyn]

It does sound like the check valve not sealing.

 

[finyuk2005]

It does sound like the check valve not sealing.

i'll have a go at that then,
cheers!!

 

[wyn]

I'm sure they are just a bit of a spring loaded soft plastic disc.

 

[brightspark]

I'm sure they are just a bit of a spring loaded soft plastic disc.

some are some are neoprene. just fill the tank and slacken the pipe from the pump to the tank if it leaks it will hiss if it doesnt its working ok

 

[finyuk2005]

some are some are neoprene. just fill the tank and slacken the pipe from the pump to the tank if it leaks it will hiss if it doesnt its working ok

just stripped it down and have it in the ultrasonic horrible noise maker,
it looks like a fairly chunky rubber stopper thing with a spring behind it, didnt look too dirty but there was an o ring in there that was very hard and fell apart! i will refit and see how it goes,
might pull the pressure switch off, there might be the actual unloader valve on that,
there is also a valve thing of some kind on the head just next to the outlet i might give a clean too

 

[timgunn1962]

The odds are the "rubber stopper" thing is the problem (I've always known them as a "pastille") in the check valve. Inspect it closely for damage. They used to be dead easy to get hold of from any decent pneumatics supplier, but they've got a lot harder to find over the last 20 years or so. If it's passing, you'll usually get a continuous bleed-off of air from the bottom of the pressure switch. If it's fine, you'll just get a pulse as the compressor switches off. Sometimes, the pastilles are reversible.

 

[MoreWellie]

o ring in there that was very hard and fell apart!

that sounds like a guilty part

There is an "over pressure" emergency release valve which could have started venting at a lower pressure than expected which is probably the "valve kind of thing" don't think they are serviceable but, once the compressor stops, you should be able to hear where the hissing is coming from as it must take some time to go down from 150 to 120

 

[finyuk2005]

I think i might have found the reason, i have made a slightly different pipework arrangement for a cooling coil before the air enters the tank,
i think the reason for the longer than usual unloader valve opening could just be because there is a huge amount more air in the delivery line to get rid of,
also, i now need to nip back to town to get a proper hydraulic hose made up, i think that might cope better, as the first one i tried just burst at the crimp as it comes out the compressor head... bugger

 

[MoreWellie]

i think the reason for the longer than usual unloader valve opening could just be because there is a huge amount more air in the delivery line to get rid of,

Well that sounds reasonable from a longer hiss point of view but the tank pressure still shouldn't drop from 150 to 120 as the non return valve should stop the air leaking back

when the unloader has finished hissing there shouldn't be any appreciable pressure in the pipe to the head which is what makes it easier for the motor to restart when the tank pressure drops

 

[finyuk2005]

Well that sounds reasonable from a longer hiss point of view but the tank pressure still shouldn't drop from 150 to 120 as the non return valve should stop the air leaking back

when the unloader has finished hissing there shouldn't be any appreciable pressure in the pipe to the head which is what makes it easier for the motor to restart when the tank pressure drops

that what i wondered, didnt think the tank should drop as well, could the spring thats meant to close the check valve be too weak?
will get a new pipe mad up and have another play around!

 

[finyuk2005]

got a new pipe for the outlet of the pump to the start of my cooler made up, proper 2 wire hydraulic hose this time and a 90 degree elbow to take a slight bend out the hose,
all seems to work grand now, and cleaning up the check valve seemed to work, the tank no longer drops any pressure when the unloader does its thing!

happy days!, now to make the cooling coil up in a 1000l IBC and get some gutters up to direct the rainwater into it!

 

[MoreWellie]

Good news on the hose and check valve

now to make the cooling coil up in a 1000l IBC

Have you thought about how you are going to empty any water that condenses out into the bottom of this coil? Normally on air coolers you have drop legs where the water collects so it doesn't block the air flow and can be vented out when appropriate

 

[finyuk2005]

Good news on the hose and check valve

Have you thought about how you are going to empty any water that condenses out into the bottom of this coil? Normally on air coolers you have drop legs where the water collects so it doesn't block the air flow and can be vented out when appropriate

i have 7 drop legs in the system in total, so think it should be ok!

 

[Farside]

i have 7 drop legs in the system in total, so think it should be ok!

Get it out of the system before the final drop legs and it will be far better overall.

 

[finyuk2005]

Get it out of the system before the final drop legs and it will be far better overall.

well the coil is between the pump and the tank and has a good sized drop one end of the coil,
hopefully that will catch most of it, i figure if i can keep as much water out the tank its a bonus!

 

[finyuk2005]

finally got some guttering up around my shed and 3 IBC's rigged up for rainwater harvesting, managed to cram 25 odd meters of pipe into one of them, and a drop leg with a ball valve at the end of the coil,
after running the compressor all the way up to pressure the outlet pipe out of the pump head was 95 degrees and the inlet into the compressor tank was just 10 degrees!! id say thats a pretty great result!
Opened the ball valve after the unloader valve had stopped hissing and got a good few ml's of water out, water that hasnt made it to the tank or the rest of the system which is good!
Might look for an automatic drain instead of the ball valve, as that would empty every time the unloader valve releases the pressure