Piston rings butt gap clearence

[adamsmitqc]

Anyone got much experiance on piston ring clearences on air compressors, just been checking mine and top ring is giving 25 thou at the top of its travel.. Seems excessive to me, I always thought about 5 thou of clearence per inch of cylinder diameter? It's a 60 mm diameter piston.

 

[adamsmitqc]

I was expecting 10 to 15 thou

 

[Wallace]

Maybe it was 0.0010"-0.0015" and with wear has opened the gap to 0.0025"?

 

[adamsmitqc]

yeah this is what I'm thinking Wallace!

 

[normspanners]

I would have expected 10 thou as well, I have a newish compressor stripped at the moment I will check for you tommorow

 

[mike 109444]

Are you measuring it with a used (worn) ring in a worn bore? If the ring AND the bor are worn then double bubble of ware

 

[adamsmitqc]

The piston bore could be worn as could be the rings... Don't have new rings (suspect I'll be getting some). I hope it's the rings and not the cylinder bore! I might remove all the rings and then check the clearence with the piston fitted back into the cylinder bore, rings removed, should help give me an idea if the bore is worn.

 

[brightspark]

The piston bore could be worn as could be the rings... Don't have new rings (suspect I'll be getting some). I hope it's the rings and not the cylinder bore! I might remove all the rings and then check the clearence with the piston fitted back into the cylinder bore, rings removed, should help give me an idea if the bore is worn.

if the bore is worn there will be a lip at the top . just measure the wear on that if there isnt a lip its not worn . then just fit a ring in the bore and measure the clearance with feeler gauges to see what the gap is

 

[the snooper]

is this your erp compressor ? if so they are built in hull so parts are easy to obtain

 

[eil]

I have a broomwade ac13 which has a bore of 66.6mm and in its specs it states a piston ring gap of 0.002" to 0.007" its got a cast iron cylinder, which means a bit tighter than an engine in retrospect.

 

[adamsmitqc]

if the bore is worn there will be a lip at the top . just measure the wear on that if there isnt a lip its not worn . then just fit a ring in the bore and measure the clearance with feeler gauges to see what the gap is

No lip at the top of the cylinder so that's a bonus, I've already fitted a ring in the bore and that's where I got the 25 thou from!

Gonna ring up ERP tomorrow and get a price for 4 new rings (two on each cylinder), have already changed the oil scrapers. Need a new non return valve, the rubber has degraded to almost nothing on mine, has actually split in two!

 

[adamsmitqc]

I have a broomwade ac13 which has a bore of 66.6mm and in its specs it states a piston ring gap of 0.002" to 0.007" its got a cast iron cylinder, which means a bit tighter than an engine in retrospect.

Interesting, I'll bear these figures in mind when I check the gap on the new rings!

 

[Wallace]

yeah this is what I'm thinking Wallace!

I have a City & Guilds certificate in "Stating The Bleeding Obvious"!

 

[adamsmitqc]

I have a City & Guilds certificate in "Stating The Bleeding Obvious"!

Not to worry, I have an NVQ in "missing / overlooking the obvious"

 

[MUKESH GUPTA]

Yes the safest and general gap clearance is 0.004" ( 0.10 mm) per inch ( 25mm )

 

[MUKESH GUPTA]

I am not very sure for AIR COMPRESSOR piston rings gap clearance . i personally think it should be lesser as there is no heat

 

[jordan1]

I am not very sure for AIR COMPRESSOR piston rings gap clearance . i personally think it should be lesser as there is no heat

The cylinders on my compressors get quite hot if run for any length of time.

 

[dannyp]

meausere it at the bottom of the bore as well they dont wear much if at all there. in my pesronal experiance rings/ piston and bore wear don't seem to be a compressor issue, valves and big ends are the usual failures well they are here anyway

 

[addjunkie]

meausere it at the bottom of the bore as well they dont wear much if at all there. in my pesronal experiance rings/ piston and bore wear don't seem to be a compressor issue, valves and big ends are the usual failures well they are here anyway

I agree with this, id mike the bore, same as any cylinder looking for wear. My money would be on valves too, but most of my compressor experience is on much larger multi stage machines.

 

[dannyp]

i would actualy think it's more than likely under the bench still wating for a round tuit to arrive