Revamping of THOMASON Reciprocating Compressor

The capacity cannot be controlled, for it is whatever the equipment designer has provided; only the output can be controlled and provided the output is less than or equal to the capacity, there will be an applicable method.

• Please describe the circumstances using recognisable dimensioned numbers?
• Please describe the various techniques that <...THOMASON...> and <...THOMASSON...> have both suggested in response to telephone enquiry?

A single sentence with no numbers is insufficient to render valuable guidance from this forum!

Multi-stage air compressors have a low-pressure section, an intercooler passage, and a high-pressure section that is capable of being step-controlled in increments identified by dividing the number of stages into the total output rating of the compressor. (Example: 3 Stage compressor capable of outputting 3,000SCFM = 1500 SCFM per step. Step 0 = 0 SCFM, Step 2 = 50% at 1500 SCFM, and Step 3 = 100% at 3,000 SCFM)

The amount of air admitted into the air compressor cylinder(s) is controlled by paired sets of inlet and outlet valves which control the output air flow capacity of each stage.

The total output capacity of the compressor is determined by the piston and cylinder bore size and length of crankshaft stroke.

The total capacity of the compressor is the sum of all stages operating at 100% throughput.

Which method of control to use is determined by the Original Equipment Manufacturer design specifications and any deviation from the original method of control does not usually work well.

If operated outside original design parameters the compressor will not perform well and may suffer irreversible damage.

Applying reverse flow regulation to a reciprocating compressor could easily result in excessive crankcase pressure and/or piston or crankshaft mechanical damage.

Bypass control could cause excessive heating in the compressor due to inadequate air flow throughput and if experienced, compressor damage will occur.

If the step change in compressor output is too large for providing the required process demand air flow in an efficient manner it might be possible depending on number of compressor inlet and outlet valves, to add additional loading steps by splitting up the valves or combining them is different groups/combinations.

I suggest you review the compressor OEM operations specifications and adhere to all design requirements recommended for controlling the compressor.

Their service department should be able to guide you to the best control method possible.

These people will have all your answers for you. They are just waiting to help you.

Howden Thomassen Compressors