Quote Originally Posted by NoNickName
no customer will pay for such a plus (4 inches suction pipe check valve costs an arm and a leg). And it would add pressure drop to the suction line.
The suction check valve should not be considered an optional item. The disc type check valves have low pressure drops.

You could also use a high performance butterfly valve with a motorized actuator. On start-up the valve opens. On shutdown the valve closes. Very low pressure loss during operation.

no oil cooler, because it is not required, according to the compressor manufacturer literature. If I had an oil cooler, refrigeration dilution would be even worse.
I have seen some applications like this. The low specific heat ratio of some refrigerants require additional suction superheat to prevent condensing close to the compression cycle.. R-114 was similar to this also.

In some cases you have to add a heat exchanger in the suction line to specifically superheat the suction gas.