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  1. #1
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    Grasso M-1 oil pressure



    Hi all,
    I need some advice on recommended oil pressure setting for a Grasso M-1. I dont have any other information on the compressor other than the serial number and this is the only one I have ever seen. This compressors oil pump is bolted onto the compressor and driven off the female rotor, there is a oil regulator/dump valve available to set the oil pressure, all other oil pressure is supplied by system differental. The oil presssure appears to be only used for loading, must have a spring for the slide to return to minimum. Running on NH3, LP = 3bar, HP = 10bar. Oil cooling via thermosyphen. Fixed speed at 3000rpm.

    Thanks



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    Re: Grasso M-1 oil pressure

    Superfridge,
    The ones I know of have no oil pressure adjustment with oil pump om
    n end of compressor.
    It may be a relief valve preventing excess pressure.
    Ensure good oil level, clean or new oil filter.
    I would think 2-3 bar above discharge is normal on these, with minimum of 1 bar.
    What pressure do you have?
    Oil relief is under capacity control block & preset.
    Have seen a small piece of debris upset oil pressure if under seal.
    Have also seen worn oil pumps which are not really repairable (very expensive, gold cheaper).
    They are only 9 l/m.
    Oil filter housing is downstream of oil filter, so it must be very clean.
    Will send you a bit of what I have to your email, maybe helps a bit.
    If slow to load/unload, there is usually adjustment screws on capacity control block.

  3. #3
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    Re: Grasso M-1 oil pressure

    Hi,

    Control oil pressure 6 bar (above discharge)

    Like Ranger - a couple of times I've replaced the Overflow valve (6 bar) underneath the valve block

    On VSD I've also had to tinker with the integrated orifice bedded in the valve block - oil pressure was following motor speed

    Generally Pump should be good for 10+ years (but not forever)

    Depressurise the package & push nitrogen (with a gauge & hose) into the Capacity Block (where the oil Pump delivery line connects) - slowly dial up the pressure from zero, the gauge should rise readily to 6 bar with only a trickle of nitro
    Last edited by HVACRsaurus; 18-01-2018 at 11:03 AM.
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  4. #4
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    Re: Grasso M-1 oil pressure

    Thanks for the replys and the information sent.

    I have 4.5 bar oil pressure which I thought was excessive if the oil pressure was just used to load/unload but not in this case and maybe should be higher. The oil pressure control valve is not adjustable. My other concern is the high frequency vibration emmitting from the pipework around the oil pump which has caused the oil pressure gauge line to crack leading me to think the pumped oil pressure was excessive. From the info Ranger1 sent through;

    1.5.5 Oil pump (integrated into the compressor) The oil pump is directly driven by the compressor and runs during the entire compressor operation. The oil pump provides sufficient oil pressure for capacity control. The unused oil supplied by the oil pump flows via an oil pressure control valve (spring-held check valve) to the oil supply channel in the screw compressor. The check valve (integrated into solenoid valve block for capacity control) regulates a pressure difference of (6 0,5 bar) between the discharge and suction sides of the oil pump.

    This paragraph seems to explain it well enough.
    Last edited by Superfridge; 19-01-2018 at 08:57 AM.

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    Re: Grasso M-1 oil pressure

    Superfridge,
    Maybe consider changing oil filter if you have not already.
    Also how many hours on compressor since major service or overhaul?
    Slide valve guide wear/turning has been an issue in these in the past.
    I would suggest overhaul 20-30,000 hrs, interesting what others think, they mention thrust bearing checks every 5-8000 hrs & inspections up to 8 years, can't find anything specific on overhaul hours.
    It's not always thrust bearings that are the problem, but slide valve.
    Oil pump is tiny straight cut gears, maybe also causing vibration, consider flexible hose if keeps happening, but oil pressure could be indicating some kind of wear in it if filter clean, oil temperature in limits & relief valve, could also check oil injection, if open to much causing oil compression/vibration.
    Last edited by RANGER1; 19-01-2018 at 08:44 PM.

  6. #6
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    Re: Grasso M-1 oil pressure

    Cheers for your help RANGER1

    You know when you see something for the 1st time and it isn't the norm you have to try find out why. Normal pumped oil pressure on the screws we look after is 2-3bar not 6bar or even 4.5bar. I don't know why 6bar is the norm for this machine but thats what the manual states.

    A lack of recorded history with this machine on site but it has been overhauled in the last 3-4 years. Someone for some reason replaced the oil pump last shut, my next step is to find out why. The machine receives yearly servicing, the oil filter is good.

    Yes, it's the oil pump causing the vibration. If you have ever pumped oil into a skid while running and noticed the portable oil pump tune changing with the increased pressure that is what it is like. I think flexable lines have been proposed but not really sorting the problem if there is in fact a problem. I suspect the oil regulator needs replacing if it isn't part of the overhaul kit it may not have been changed. I will check the oil injection, good call.

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    Re: Grasso M-1 oil pressure

    Unfortunately oil pressure regulator not part of overhaul kit to my knowledge.
    Also need "0" rings for unloader block to replace pressure regulator, as underneath block.
    Although unlikely, but is possible to put it in wrong way causing overpressure.
    A strainer upstream of it as well, sort of like Danfoss EVRA3 ones inline.

  8. #8
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    Re: Grasso M-1 oil pressure

    Hi Superfridge and ranger,
    ckeck your Email

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    Re: Grasso M-1 oil pressure

    Hey thanks cricri,
    Some handy information.

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    Re: Grasso M-1 oil pressure

    Quote Originally Posted by Superfridge View Post
    Cheers for your help RANGER1

    Normal pumped oil pressure on the screws we look after is 2-3bar not 6bar or even 4.5bar. I don't know why 6bar is the norm for this machine but thats what the manual states.
    The 6 bar pressure is not the lubricating oil pressure, but the oil pressure to control the compressor capacity. The oil lubrication pressure is the discharge pressure minus the suction pressure

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    Re: Grasso M-1 oil pressure

    Hi, dear Podik

    Quote Originally Posted by podik View Post
    The 6 bar pressure is not the lubricating oil pressure, but the oil pressure to control the compressor capacity. The oil lubrication pressure is the discharge pressure minus the suction pressure
    I'm a little bit confused ... can you explain your post,please?

    I can agree with you about oil pressure for capacity control ....

    (I believe internally within that compressor are smaller channels to reduce oil pressure appropriate for lubrication of bearings - if the oil quantity i.e. oil pressure is too high we would have overheating and vibration of bearings) for this I am not sure - have not experience with that machine ...



    Dear Podik as I understood your post ... for example:

    at suction of 2bar (-10*C) and and condensation pressure of 13bar (36,3*C) - usual high stage of ammonia plant - oil pressure will be 11bar ... seems too much for me


    N.B.
    Cricri, can you please share your post ... thanks a lot


    Best regards, Josip

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  12. #12
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    Re: Grasso M-1 oil pressure

    Josip,
    This machine is differential oil pressure feed & pump driven by compressor that supplies 6 bar oil pressure for capacity control only.
    Excess oil pressure from pump returns into differential oil pressure circuit.
    Cricri simply replied to my statement that strainer behind unload block not used anymore.
    This machine has roller bearings no doubt with orifice in oil channels.
    Maldonado spring to unload if machine stops loaded.
    Last edited by RANGER1; 13-02-2018 at 08:27 PM.

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    Re: Grasso M-1 oil pressure

    Hi, RANGER1,

    Quote Originally Posted by RANGER1 View Post
    Josip,
    This machine is differential oil pressure feed & pump driven by compressor that supplies 6 bar oil pressure for capacity control only.
    Excess oil pressure from pump returns into differential oil pressure circuit.
    Cricri simply replied to my statement that strainer behind unload block not used anymore.
    This machine has roller bearings no doubt with orifice in oil channels.
    Maldonado spring to unload if machine stops loaded.
    all clear, Cricri sent me the same document where is complete oil circuit visible .... good solution forcapacity control ...

    but still remain question to Podik ... he wrote "The oil lubrication pressure is the discharge pressure minus the suction pressure" ... I'm not sure about that, but I can be wrong - maybe Podik can put some light on that ...

    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
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  14. #14
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    Re: Grasso M-1 oil pressure

    QUOTE=Josip;324149]Hi, RANGER1,



    all clear, Cricri sent me the same document where is complete oil circuit visible .... good solution forcapacity control ...

    but still remain question to Podik ... he wrote "The oil lubrication pressure is the discharge pressure minus the suction pressure" ... I'm not sure about that, but I can be wrong - maybe Podik can put some light on that ...

    Best regards, Josip[/QUOTE]

    Josip, to me it is but with a few pressure losses on pipework, valves & oil filter etc
    A booster may require full lube pump.

  15. #15
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    Re: Grasso M-1 oil pressure

    Hi, RANGER1,

    Quote Originally Posted by RANGER1 View Post
    QUOTE=Josip;324149]Hi, RANGER1,

    all clear, Cricri sent me the same document where is complete oil circuit visible .... good solution forcapacity control ...

    but still remain question to Podik ... he wrote "The oil lubrication pressure is the discharge pressure minus the suction pressure" ... I'm not sure about that, but I can be wrong - maybe Podik can put some light on that ...

    Best regards, Josip
    Josip, to me it is but with a few pressure losses on pipework, valves & oil filter etc
    A booster may require full lube pump.[/QUOTE]


    agree with you ... it was colloquial question - for general discussion ... and you answer to it ....


    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
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  16. #16
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    Re: Grasso M-1 oil pressure

    Quote Originally Posted by Josip View Post
    Hi, RANGER1,



    Josip, to me it is but with a few pressure losses on pipework, valves & oil filter etc
    A booster may require full lube pump.

    agree with you ... it was colloquial question - for general discussion ... and you answer to it ....


    Best regards, Josip [/QUOTE]

    Sorry, should have let it go, not much to work on at the moment on forum.
    Tried to add information from GEA Docnav, but is a nightmare to find anything as it's like Encyclopedia Britannica with no index.
    They must get paid by the word

  17. #17
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    Re: Grasso M-1 oil pressure

    Docnav is also a nightmare from the other side...
    A new system should be coming soon. Docnav is no more updated.

  18. #18
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    Re: Grasso M-1 oil pressure

    Hello,
    sorry for the late reaction and my English. :-)
    Yes, internally within that compressor are smaller channels and a few pressure losses on pipework, valves & oil filter.
    The lubrication pressure in the GSC, GSC TP and now OMNI control system is given by Pdis - Psuc (hidden parameter) or oil filter pressure drop (Pdis - Poil oil filter output).

    The new design of the small range of GEA compressors does not have an oil pump to control capacity, and there are problems

  19. #19
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    Re: Grasso M-1 oil pressure

    I'm sorry, I'm stupid. :-)
    Lubricating pressure is Poil - Psuc. But as you can see, Poil is about - 1.5 bar Pdis (few pressure losses on pipework, valves & oil filter). It is similar.

    Here is compressor without pump driven by compressor


    Last edited by podik; 20-02-2018 at 01:32 PM.

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