Multi-compressor string with multiple variable speed fluid drives

Abstract

Starter arrangement for high power rotating equipment strings with multiple compressors driven by a single turbine or motor includes multiple variable fluid drive torque converters (CSTCs) to start the compressors in a pressurized start. The string can use a single CSTC for each compressor or a single CSTC for more than one compressor with at least two CSTCs for a given string. The starting procedure is sequential. After the turbine or motor is started and brought up to speed, successive CSTCs are operated from zero to lock-up speed sequentially to start each compressor or group of compressors in turn. In order to cool the working fluid of the CSTCs, a single heat exchanger is provided and the working fluid of each CSTC in turn is circulated through the heat exchanger as they are sequentially started. At lock-up speed, the CSTC is locked up, the working fluid is drained, and the working fluid of the active CSTC is isolated from the heat exchanger and the next succeeding CSTC in the start sequence is in turn, filled with the working fluid and connected to the heat exchanger. At full start, with all compressors operating at full speed, no working fluid is present in the CSTCs, and no working fluid is circulated through the heat exchangers from the locked-up CSTCs. A single heat exchanger may also be used for multiple strings, each having multiple CSTCs for multiple compressors. The starter arrangement is useful in high compressor load strings for LNG refrigeration service.