Hiya Lana, i work in a large Refrigerated depot with 3 seperate R22 overfeed systems doing +7c, +3c and -20c running on stal open drive recips. I've got some technical specs for design and sizing for surge drums from the 1970's which are really indepth. All run on a saturated design temp of +35c with single stage compression. Each compressor has an individual oil seperator plus an oil seperator in common discharge. If you need an info send me a post