Parallel Compressor Setup With Uneven Capacities

[amophy]

Hello,

Has anyone come across a reciprocating compressor setup with non-symmetrical redundancy, something like 20%, 30%, and 50% capacity units in parallel?

Curious how the flow distribution and control were handled. Was one unit used as a trim? Any issues with load sharing, suction pressure imbalance, or control logic?

Would appreciate any real-world examples or lessons learned.

Thanks!

 

[georgeverghese]

If machines are auto start / stop on discharge pressure control, you'd need a buffer vessel on the discharge side to minimise hunting.

 

[LittleInch]

Depends what your flow range is and pressure range you want / need.

Also assumes each compressor is rated the same for pressure and have common inlet and discharge piping.

Common control is by VFD or recycle if it doesn't exactly match your 50,30,20 jumps so you would get 20 or 30 or 50 or 70 or 80 or 100 asc combination options.

Is that what you need? Then fixed speed is OK, but as George says when turning one on or off you will get a pressure surge or drop as each one on kicks in.

I've seen multiple air compressors on a system feeding a receiver when the flow is variable which then operate between two pressures to reduce any cycling.