Compressor cylinder inspection question

[wdeutsch]

Background info: I just picked up a used Hypres horizontal compressor that was surplussed from a local fire department. While they *say* they maintained it well, I have some questions about that. It's got 1400 hours on it, and once the outside layer of filth/grime/oil was cleaned off, it looks pretty good. No rust. Motor and compressor flywheel turn easily. There's a rumor of an issue with the 3rd stage pressure relief valve, but I won't know about that until I fire it up.

Before I fire it up and send my first air sample for testing, I'd like to make sure there's not a bunch of buildup on the cylinder walls from poor upkeep or the switchover from mineral to synthetic oil that they did.

The Primary Question: If I remove the heads to inspect the cylinder walls, do I have to replace the head gaskets? From my experience in auto repair, it's 100% that you have to do this, but I'm hearing hints that this may not be the case in the world of breathing air compressors. If I will need to replace them, I'll get an order going so they are on hand. If it's more normal to be able to re-use, I'll give it a shot without the spares on hand. Thoughts/experience?

While we're at it, any other PM I should plan on that I haven't picked up on from reading here?

Done/To-Do includes:

1. Thorough scrub-down of the whole unit, including detailed clean of finned final stage cooling coil
2. Cleaning filter housing interiors, replacing filters, cleaning sintered separator
3. Replacing intake filter
4. Oil change. Compressor has synthetic oil in it currently, I'll replace/refresh with the same kind.
5. Air testing
6. Installation of in-line CO monitoring

 

[iain/hsm]

Before any of that consider the following :

1. Make a note of the Model and the Serial number NA-9 NA12 NA18
2. Quote only the model when asking questions on a public forum
3. Quote both model and serial number only when pricing and or ordering parts
4. Get a copy of both the operator manual and the service repair manual
5. Get a price list of the spare service parts
6. Check the data plate on the motor
7. Check your power supply for compatibility
8. Remove the Fan Belt (Drive Belt) Record size and type, Check for wear/cracking
9. Run the compressor electrics/ motors fans etc only without turning the block or making pressure
10. Photo everything so not to forget. Don't Forget

By doing this your checking all the running gear without risking the pump assembly
Then you can concentrate on removing the dead flies out of the air intake filter
and making a judgement call if you want to lift the lids

Only the 1st stage has the head gasket on the NA's and as it seals the valve plate I would leave it be.
The only call is if the pump was inhibited or so dry it scores the rings on start up

 

[wdeutsch]

Before any of that consider the following :

1. Make a note of the Model and the Serial number NA-9 NA12 NA18
2. Quote only the model when asking questions on a public forum
3. Quote both model and serial number only when pricing and or ordering parts
4. Get a copy of both the operator manual and the service repair manual
5. Get a price list of the spare service parts
6. Check the data plate on the motor
7. Check your power supply for compatibility
8. Remove the Fan Belt (Drive Belt) Record size and type, Check for wear/cracking
9. Run the compressor electrics/ motors fans etc only without turning the block or making pressure
10. Photo everything so not to forget. Don't Forget

By doing this your checking all the running gear without risking the pump assembly
Then you can concentrate on removing the dead flies out of the air intake filter
and making a judgement call if you want to lift the lids

Only the 1st stage has the head gasket on the NA's and as it seals the valve plate I would leave it be.
The only call is if the pump was inhibited or so dry it scores the rings on start up

Thanks, Iain!

Items 1-8 are completed or waiting for info from the manufacturer. I appreciate the heads up on #9. Great idea that I would not have thought about. #10 is my way if life. At my age, my phone camera is my auxilliary memory backup.

I don't have reason to suspect there is any inhibition/friction within the pump itself, as the flywheel turns silky smooth and quietly when spun by hand. I also don't think it's been run dry, as the oil level looks appropriate and the oil that's in there looks mostly clean.

I mostly worry that the previous owners may not have kept up on some of the details, as I know they switched from mineral to synthetic oil and made no mention of any cleanup afterwards. That, and they swore the filters would be useable and they were.... far from that. Add on that this was supposed to be a fire department breathing air compressor and their final filter was NOT rated for that purpose. So, I have concerns and want to peek under the hood.

Based on what you say, I'll take a look at cylinders 2 and 3 and see what they show and make a decision about #1 after that.

Thanks again!

 

[iain/hsm]

Thanks, Iain!

Items 1-8 are completed or waiting for info from the manufacturer.

Is that on your list or mine LOL

I appreciate the heads up on #9. Great idea that I would not have thought about. #10 is my way if life. At my age, my phone camera is my auxilliary memory backup.

No Problem we can discuss detail later but it's a good start.
I should be able to post a manual and parts list with drawings if you get stuck.

I don't have reason to suspect there is any inhibition/friction within the pump itself, as the flywheel turns silky smooth and quietly when spun by hand. I also don't think it's been run dry, as the oil level looks appropriate and the oil that's in there looks mostly clean.

So far so good with the air intake filter, the oil and the spin test. But one of the considerations with unknown blocks you need to make before going main engine start is with the oil pump.
My rule is always fit an oil pump pressure gauge its more important than any of the interstage gauges or the final discharge pressure gauges in the first 30 seconds of start .

Without fitting your own known working gauge the risk you take is making a start the oil pump fails and the low oil cut out has been disconnected. It's very unlikely with a fire station sale more the sort of thing you get from an EBay rip off practice. The other "Star Stunt" they play is when checking the oil its brand new and never used.

Oh and check the paint on the socket bolts on each of the stage heads just to make sure they haven't been removed by the Allen Key in the past if and you really want to check the piston liners those are the heads I would check first.

You should have a direction arrow on the Block and if the motor is 3 phase another reason for removing the belts and doing an electrical and rotation check out if the phase wires are swapped on re installing

I mostly worry that the previous owners may not have kept up on some of the details, as I know they switched from mineral to synthetic oil and made no mention of any cleanup afterwards. That, and they swore the filters would be useable and they were.... far from that. Add on that this was supposed to be a fire department breathing air compressor and their final filter was NOT rated for that purpose. So, I have concerns and want to peek under the hood.

Based on what you say, I'll take a look at cylinders 2 and 3 and see what they show and make a decision about #1 after that.

Thanks again!

As far as I aware I think the NA series were all synthetic but again I will check the manuals
If you like you could post pictures they sometimes help I can see a heat exchanger fitted back to front from 30 yards.