re: Airmaster 6mm bleed pipe problem

[cobra148]

Airmaster 8/35 tiger turbo 6mm bleed pipe problem.
Hi, I purchased a new pressure switch from ebay, for the airmaster, it came with a hex nut and olive for the 6mm bleed or blow off pipe.

I cut the pipe off the old switch as it had a blue plastic connector, and the 6mm
pipe would not come out. The new switch had a hex nut connector for the 6mm pipe. Anyway I put the olive onto the 6mm pipe and tightened up very slowly and carefully.

I then powered up the compressor, no air leaks are present, and motor runs untill 120 psi tank pressure is reached, then there is a long hiss from under the pressure switch area and keeps hissing untill pressure in the tank reduces to 90 psi then motor restarts although seeming to struggling to start.

This cycle keeps going until I manualy switch off and release all the tank pressure through the outlet tap.I think it should only hiss for a second or two
I cant remember. So I removed the brass nut on 6mm pipe under the pressure switch and noticed the olive was crushed and pinching the black plastic 6mm pipe almost shut, the olive looked more mangled than compressed.

I cant understand this as this olive came with the switch ,and seems to fit the 6mm pipe really well. And tightening it up slowly should not have crushed
it badly enough to crush the pvc pipe.

Anyway what I need to know is what type of new olive and fittings do i need
to ask for to replace this ?, there seems to be all sorts available gas/water ect.

Also can I use a copper pipe and fittings here instead of the pvc pipe ?.

photo of switch attached

Regards

 

[the snooper]

sounds like the non return valve is stuck open where the delivery pipe enters the air receiver

the 6mm pipe is there to unload the pressure in the delivery pipe and should not be able to empty the receiver take the valve apart and clean it.
make sure all pressure has gone of course

unless of course you have been supplied a faulty pressure switch

 

[the snooper]

even if you disconnect the nylon pipe with pressure in the receiever no air should come from it and the fact the it struggles to re sart suggets there is a problem with the valve shown in the picture

 

[cobra148]

Hi, thanks for that, I will check this in the morning and report back.
If I clean this non return valve and get it to operate correctly, do I have to connect the black 6mm pipe or can I leave it unconnected permanently ?.

Thanks

 

[the snooper]

no you will have to reconnect it otherwise the compressed air will flow from it when the compressor is running, its there to release pressure so the motor can start easily when there is pressure in the receiver

 

[cobra148]

Ok will do, just need to source some olives for the pipe.

Thanks

 

[the snooper]

plumbing shop will have the olives if they are just a standard 6mm

 

[rtbcomp]

You shouldn't use olives with plastic pipe.

You really need a push-fit connector, you may be able to take the one out of the original switch.

To release the pipe you push the ring that the pipe goes through. (Or is it pull? It's ages since I used one - someone will clarify!)

If you can't get a push fit then a bit of copper pipe inserted in the end of the plastic should do the trick.

 

[Robotstar5]

To release the pipe you push the ring that the pipe goes through. (Or is it pull? It's ages since I used one - someone will clarify!)

You push the ring towards the body of the fitting to release the pipe, it also helps to push the pipe forward to help it "unlock".

 

[gavuk]

You shouldn't use olives with plastic pipe.

Its not as common now with push fit being far easier but we used plastic pipe and olives for years in industry ,trouble was always selecting the correct olive for the fittings,as there were a few types from leading manufacturers...

 

[cobra148]

@ the snooper Big thanks for your help.
The non return valve was indeed bunged up with goo, the rubber piston that closes the air off to the bleed pipe was stuck. So I removed it and cleaned it up.

Went to local DIY store for some 6mm olives and Now the compressor stops
motor at 120 psi with just a short hiss . I repeatedly let air out of outlet tap
and motor restarted at 90 psi every time with no struggle to start.

So A big thanks to you buddy , and other poster's.
Oh by the way only went with olive method as the airmaster had one on the plastic pipe from new.

I know what the other guys mean though, as the olive will always try to crush the pvc pipe. I dont think there would be any reason for not swapping this pvc pipe for a 6mm copper pipe with olives and fittings.

I do have a 200L GGA 520/A compressor 3.5HP but fixing the airmaster is great as It's handy for small repairs and tyre inflating ect.

Thanks Guys

 

[rtbcomp]

Glad you got it going, we always appreciate being told of outcomes.

 

[the snooper]

glad to be of help
a good description of the problem always helps

 

[Rob Colver]

Thank you so much @the snooper . I've struggled with a similar problem for months. In my case the return valve was stuck because the rubber 'piston' had expanded. I pared it down until it could move smoothly and now it works a treat :-)

 

[the snooper]

Thank you so much @the snooper . I've struggled with a similar problem for months. In my case the return valve was stuck because the rubber 'piston' had expanded. I pared it down until it could move smoothly and now it works a treat :-)

Good that old posts are still of use to people

 

[timgunn1962]

The pastilles for Non Return Valves are usually quite readily available from decent pneumatics suppliers. Cost is usually something around a fiver and I tend to change them every year or two, at about the same time as I change air filters in a non-dusty environment.

On typical workshop compressors running fairly low duty cycles, they seem to last a long time. With a protracted period of heavy use: continuous or near-continuous running for several hours, they seem to get hot and degrade much faster, becoming brittle and prone to cracking, then not sealing properly. A complete NRV is normally a pain to change, but the pastille is usually a doddle. On most of the 3HP compressors I come across, it's a 1/2" NRV with a 24mm hex on the brass plug. It's not very deep, so any relief on the inside of the socket you use reduces the engagement on the hex significantly. I have a socket ground down to give full engagement and I've had no problem since I've been using it. Mauling about with open-ended spanners, and particularly adjustables, has led to some complete NRVs needing to be replaced and that's too much like work, hence the ground-down socket.