Snap-On HP12 Compressor Operation and Maintenance

[Bill Edwards]

Just about any thick paper is fine, don't worry too much about it being advertised as 'gasket' paper. Folder dividers are good, though the thickness may not be the same.
However, you did say that you thought the gasket currently fitted was homemade, looking at the state condition of the machine overall I wouldn't be surprised if the previous gasket make just used whatever was nearest at that time, and it could be too thick.

Personally I always fit just about all gaskets using Blue Hylomar. It's great stuff, but use it very sparingly on this as you do not want any to squeeze out when you tighten it down, getting that stuck in the valves will not help it work!
A very thin smear, not quite to the very edge of the paper for safety.

 

[JonnyAlpha]

Ok so Iv'e made the gasket, anyone know whether the head needs to be Torqued down? and if so to what tightness. I have tracked down that the head is similiar to an ABAC B3000. According to this publication the Torque settings for the head on the B3000 are 18 - 20 Lbs / Feet what do you reckon?

 

[Bill Edwards]

In the absence of accurate figures just do them to be ordinary 'spanner tight' as feels right, nothing excessive.
You won't do any harm to do it diagonally in more than one stage.

Don't forget to rotate the compressor by hand once it is all torqued down before powering it up with the motor, to make sure everything is OK.

 

[eil]

What thickness did you use Jonny.

 

[JonnyAlpha]

What thickness did you use Jonny.

The original was about 1.8mm, I managed to get some from a local Engine refurb company that was 0.9mm so I doubled it up to achieve the same spacing, two gaskets basically.

 

[JonnyAlpha]

Here's the gasket material, it was coated in graphite on one side, made hell of a mess :-)

Here's the two gaskets:

And here's the valve plate back together:

I put some Hylomar between the gaskets and on either side, only a very thin small amount.

Its all bolted down now and will test in the morning (by hand first as suggested).

 

[eil]

I was asked to "take a quick look at this compressor for me" jobs today and took the head off and measured the gasket thought it would be a good guide for you.

 

[Wallace]

One of the used gaskets off my Clarke SE16C measured 0.8mm compressed.

 

[JonnyAlpha]

Mmm well the guy down the Engine Shop measured the gasket with a set digital calipers and it was 1.8mm, the recess on the outlet side of the valve plate that allows the reed valve to move and pass air is that very deep. With the gasket fitted the pins that hold the reed valve still locate in the pin holes on the opposite side, if the gasket was too thick this would not be the case. Not sure if the gasket was home made and thicker than the original but I'll go with it now as its the same as was in it before and i'll post back the results, hopefully it will be an improvement?

 

[eil]

Mmm well the guy down the Engine Shop measured the gasket with a set digital calipers and it was 1.8mm, the recess on the outlet side of the valve plate that allows the reed valve to move and pass air is that very deep. With the gasket fitted the pins that hold the reed valve still locate in the pin holes on the opposite side, if the gasket was too thick this would not be the case. Not sure if the gasket was home made and thicker than the original but I'll go with it now as its the same as was in it before and i'll post back the results, hopefully it will be an improvement?

If he measured the old ones up then that's ok then, I just thought it might be helpful for you or someone else who might be searching in future

 

[JonnyAlpha]

After a dry test turning the flywheels and all was smoot I just fired up the compressor and tested it.

It too 50 seconds to get up to 50 PSI, 1min 50sec to reach 100PSI and a fabulous 3min 17secs to reach cut out which is set to 140PSI not 150 as I first thought.

That's a 100% improvement on the previous testing so success :-)

Just off to haggle with the guy on the original price :-)

 

[brightspark]

After a dry test turning the flywheels and all was smoot I just fired up the compressor and tested it.

It too 50 seconds to get up to 50 PSI, 1min 50sec to reach 100PSI and a fabulous 3min 17secs to reach cut out which is set to 140PSI not 150 as I first thought.

That's a 100% improvement on the previous testing so success :-)

Just off to haggle with the guy on the original price :-)

dont forget to tell a few porkies and tell him its a bit worn and down on power none of its good points

 

[eil]

Haggle on £50 ?, you tight ****

 

[JonnyAlpha]

Got it for £30 :-)

 

[brightspark]

Got it for £30 :-)

good man thats the way to go

 

[Bill Edwards]

That's OK, but I'd have haggled it down a bit more

 

[brightspark]

That's OK, but I'd have haggled it down a bit more

and if it had been me selling id have told u to sling your hook and wouldnt have sold u it for any price