"SPECIAL" screw compressor

[RANGER1]

Have a process application which would run under following conditions .

NH3 Economized VSD -33 C SST
+ 48 C SDT

Apart from possible higher pressure rated casting would anything else have to be "SPECIAL" about it ?

Anyone have experience ?

[NoNickName]

Why not a normal cascade system with NH3 on the low stage, and some other natural refrigerant on the high stage?

[josef]

http://www.th-witt.de/witt/useranhaenge/komponenten/eco/witt_eco_3530_6.01_de_en_.pdf

[sterl]

Air cooled on R-717 is comparable to these conditions; considerable data on that in the IIAR technical sessions. Also more recently on using R-717 in central heat pump arrangements. Check the Vilter web site; they did nice work on a "small channel" single rotor screw for such purposes; high side to 85-deg C condensing.

http://www.emersonclimate.com/Documents/Vilter/Product%20Brochures/Heat%20Pump%20Brochure%20US%20Version.pdf

[MCR717]

Limits on Vilter standard Single Screws are MAWP above 33 bar and pressure ratio 20:1.
This application is within the limits, no need for their special high pressure compressors (MAWP 75 bar).