View Full Version : grasso compound compressor

26-04-2013, 08:04 PM
got one of these giving me issues,it built up head pressure initially now it wont ,I suspect the device inside the compounding cylinder there appears to be excessive noise as its going thru its loading stage think the model is rc 3111

26-04-2013, 09:40 PM
Hi Cadwalader.
Let me get this right.
Yours is a 3/1-11, so you have three LP cylinders and 1 HP.
From memory within the HP cylinder there is a relief valve within the btm liner locating ring.
Which bleeds the HP pressure back through this valve into the crankcase (Suction pressure).
This may be passing / faulty?

Alternatively you could have a misaligned suction or Discharge ring.
Although I suspect with your proven knowledge of these comps that's way to simple.

Other things like incorrect suction loading pin clearance, passing non return valve in the discharge line
Can you give a few more clues as to what is happening?

26-04-2013, 10:45 PM
judging by the noise it sounds like the relief valve because crankcase pressure/intermediate pressure is none existant and shows very close to suction pressure,and the head pressure will not build up although it did once it had stood overnight turned off,when it loads the cylinder once the oil pressure picks up 30/60 seconds thats when you can hear what i can only describe as a clatter.

27-04-2013, 01:34 AM
Something has broken internally, valve plates or similar, hole in piston, dropped a rod. Sounds messy and expensive. The joys of compounded recip compressors and inter-cooler injection. Great when running in design envelop, disaster when goes wrong.

27-04-2013, 06:40 AM
I'm with Magoo!
Time for an internal my friend.
I initially thought you just had gasses passing. But a "clatter" (sharp intake of breath!), that's a different matter.

27-04-2013, 09:39 PM
off with its head on monday or heads!

27-04-2013, 09:40 PM
anyone got gaskets for this beast?

06-05-2013, 12:42 AM
got this bitch running yesterday,all sorts of probs liquid inj,oil trap blocked,cleaned valves reeds etc main problem was oil pump worn.

06-05-2013, 08:32 AM
Well done.
Especially for working over a B/Holiday weekend.
I hope you "Filled your boots"?
Finacially that is.
So the clatter likely was due to the lower than needed oil pressure.
So that assumidly the suction unloading pins were not being withdrawn fully?
Hence the clatter?

06-05-2013, 10:02 PM
thank god for the manual,went back today think we need some more gas very hot on site today water on the condensor trick we now seem to have little liquid injection.

07-05-2013, 07:30 PM
still more problems with this machine,oil pressure to cylinder loaders is erratic? the machine is running at -25c the question is which oil mineral of coarse but what viscosity 160/or 300 seem to think it used to run on clavus 68

07-05-2013, 09:14 PM
Hi Cad.
Stick to 68 viscosity,
Of which there are a few options.
The oil pumps are relatively easy to rebuild. I am not saying the spares are cheap mind!
I have in the past made up a mandrel from an old oil pump gear/ spindle.
When pushing the new bushes into place you have to ensure that they are flush with their housing.
So that the 2 gears don't bind against their end plate.

Which needs to be inspected for wear and grooving. Which is a result of lateral movement of both or either of the gear wheels.

On the outside of the oil pump body is a 6mm ermeto fitting.

The capped end can have Gauge fitted to it to monitor the available oil pressure developed by the pump.
Which dependant upon the pressure developed will tell you whether the issue is indeed the oil pump or mechanical wear elsewhere.

Don't make the mistake I once did and having been advised that I needed a 25bar gauge.
I fitted a 25 bar one,ran the errant compressor and later that night.
Donned a full Ammonia chemical suit to go in and shut down the compressor. Having to wade through a plant room floor full of liquid ammonia in the process.
What Grasso had failed to tell me was that on start up the oil pump can develop way more than 25bar.
When the comp re-started, having gone off on temp. the start-up pressure had burst the steel bourdon tube within the gauge.
Spewing first oil and the Ammonia liquid / vapour from the system wet return.

I may be teaching you to suck eggs!
But have you regulated the oil pressure using the reg valve 21 psi diff seems to ring bell?
Having Also checked the amount of oil being returned to the sump through the site glass.

Lastly the loading gear piston O rings are easy enough to replace.
I used to unbolt them, Using a air nozzle fitted to a Nitrogen bottle / regulator and a small low pressure.
Say 5 to 10psi.
Pop out the piston and replace their o rings.


charlie patt
07-05-2013, 09:35 PM
Eurofrigo 01788544561

08-05-2013, 12:20 AM
this has a guage fitted with a shut off valve,but when it starts the pressure does not go as high as you say it takes its time to get to 14 bar,we are on r22 and this 14 bar pressure comes when our pressure on the suction guage reads about 2 bar,we seem to be stable when delivery /head pressure is around 14 bar also?

08-05-2013, 12:21 AM
Eurofrigo 01788544561 thanks buddy

charlie patt
08-05-2013, 08:06 PM
if the condensor neck is cracked or snapped you can buy the mod kit or basically fit a new burgaflex hose and loop it to give it some flex we also braise a bracket on the new condensor the necks are just to long and vibrate and crack

18-05-2013, 03:35 PM
got the grasso singing last week the main fault turned out to be the intercooler/heat exchanger gaskets,along with the oil pump,liquid inj txv,moisture in system and some ****head has taken the schraders out of the test points on system which made diagnosis long winded we had to recover 80% of the charge to strip things down,why o why would the schraders be removed!

18-05-2013, 11:29 PM
Seems you have system sorted, thanks for up-dates. Good result.