Grasso twin screw paks

[RANGER1]

Can anybody tell me under what circumstances do you use Grasso twin pak ie low stage pumps directly
into suction of high side screw .
Mycom would only suggest to do it for ultra low temp application .
It appears popular in Europe .

Thanks

[Andy]

Can anybody tell me under what circumstances do you use Grasso twin pak ie low stage pumps directly
into suction of high side screw .
Mycom would only suggest to do it for ultra low temp application .
It appears popular in Europe .

Thanks

Hi Ranger
for freezers and blast freezers instead of booster or economiser screw plant. Where a higher COP is required.

Kind Regards Andy D

[aawood1]

Hi RANGER1, We have two systems now on site with Grasso two stage packs. The 1st one has two units and is working at -32oC on Ammonia to rum a Freezer. The one that I'm involved with at this time is is two packs rated at 1.2 maga watts working at -42 oC again on Ammonia. From what Grasso say the main compressor and gas cooling in between the stages is done by the oil as its cooled by an ammonia fed oil cooler and the interstage ammonia injection is only used for start up, but from temp. readings on the pipe work there is still some ammonia injection
Regards
Arthur.

[RANGER1]

So on these plants they don't have any subcooling of liquid line at all ?

What about interstage , does it have any side loads or anything ?

This style of system was used years ago in Australia but havn't seen any for years .

The ones here were set up so second stage machine could run single stage if you wanted it to with check valve arrangement on suction so it could change over mechanically without touching anything .

[Andy]

So on these plants they don't have any subcooling of liquid line at all ?

What about interstage , does it have any side loads or anything ?

This style of system was used years ago in Australia but havn't seen any for years .

The ones here were set up so second stage machine could run single stage if you wanted it to with check valve arrangement on suction so it could change over mechanically without touching anything .

Hi Ranger

No they usually have a sub cooler, with the flash gas going into the LT discharge/HT suction.

The check valves and change over suctions I have seen added onto the basic screw packs to allow cold stores to run off the HT suction should the need arise.

The HT can be sized for addtional cooling load, but more usually a number of piggyback screws are arranged on the same header, with only the HT running on the one that is taking care of the HT side load. This compressor is rotated to allowthe LT compressor to have some hours on it.

Kind Regards Andy D

[RANGER1]

Thanks Andy