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CrimsonK
17-02-2008, 06:49 PM
Hi ,
we made a unit with vmy 346 . it has shaft mounted oil pump and horizantal oil separator. while the oil temperature and differential temperature become higher. the oil pressure drops slowly. does anyone has similar problem and advise something.

RalfWeiser
18-02-2008, 04:31 PM
Hi Crimson K,

What you are descibing is considered to be a pretty normal phenomenon on a VMY type oil flooded screw compressor. Is this causing you any trouble?

CrimsonK
18-02-2008, 06:19 PM
Hi Ralfweiser,
The capacity slide valf requires 8 bar oil pressure ( P oil manifold -Pdischarge) . So we have a trouble to reduce the capacity when the oil pressure below 6 bars.

Josip
08-03-2008, 01:55 AM
Hi, CrimsonK :)


Hi Ralfweiser,
The capacity slide valf requires 8 bar oil pressure ( P oil manifold -Pdischarge) . So we have a trouble to reduce the capacity when the oil pressure below 6 bars.


sorry, somehow I miss this post....

:confused::confused: please can you upload a scheme of your oil distribution on that unit...and some explanation what is unit for...working conditions....

Best regards, Josip :)

CrimsonK
08-03-2008, 10:35 PM
Hi Josip,
The compressor is used as high stage compressor in ammonia refrigeration:
Working conditions:
Suction pressure : 2 bars
Discharge pressure : 12 bars

best regards,

Josip
09-03-2008, 02:49 AM
Hi, CrimsonK :)


The compressor is used as high stage compressor in ammonia refrigeration:
Working conditions:
Suction pressure : 2 bars
Discharge pressure : 12 bars

...seems normal operational points...is that cold store



........
The capacity slide valf requires 8 bar oil pressure ( P oil manifold -Pdischarge) . So we have a trouble to reduce the capacity when the oil pressure below 6 bars.

:confused::confused: are you sure you need 8 bar diff oil pressure..... how you obtain that... oil pump + oil presssure regulator or....

oil pressure 8 bar above discharge pressure is very high..., but I am not familiar with VMY 346 models...much more with VMY 347 /447...

....some normal diff of oil pressure for screw compressors is from 2,5 - 3,5 bar ...............(minimal is 1-1,5bar and can be maybe up to 6-8bar at start with cold oil)

... this is the first time (at least for me:confused:, to hear that you need 8 bar diff oil pressure to control capacity) ... please can you upload scheme of oil distribution....

Best regards, Josip :)

CrimsonK
09-03-2008, 12:27 PM
Hi josip ,
The oil pressure requirements of vmy compressors is attached .i think the problem is the oil cooler and filter are at the pump(shaft mounted oil pump) suction line. and the pump is above the oil level of the separator. i can send the flow diagram to your e-mail.

Grizzly
09-03-2008, 08:08 PM
Hi Ralfweiser,
The capacity slide valf requires 8 bar oil pressure ( P oil manifold -Pdischarge) . So we have a trouble to reduce the capacity when the oil pressure below 6 bars.
CrimsonK
Hi I am reading your post and have looked at the data you have kindly posted.

It might be me but is it not possible that you are misreading the data.

It makes more sence if you read 8 bar discharge.
Which is not uncommon for Discharge pressurised Oil lubrication systems on a lot of screws.



So given that you have oil pressure problems.
May I ask when you last changed the Oil and Oil Filter.......?

Also when did you last have the Oil Analised.


Just a thought!
Grizzly