A speed controller can help extend the operating range and efficiency of the compressor. As the flow rate increases, the compressor speed can be increased to handle the additional gas. Compressor speed will stabilize when the actual flow rate to be compressed equals the required flow rate for the cylinder at the preset suction pressure. As the flow rate decreases, the compressor slows until the preset suction pressure is maintained.
A speed controller does not eh’minate the need for a recycle valve, flare valve, or suction throttling valve, but it will minimize their use. The recycle valve and suction throttling valve add arbitrary loads to the compressor and thus increase fuel usage. The flare valve leads to a direct waste of reservoir fluids and thus loss of income. For this reason, engine speed control is recommended for most medium to large size (>500 hp) reciprocating compressors where a constant flow rate cannot be ensured by the process.
