Method and device for controlling a hot restart of a centrifugal compressor
Methods, devices and systems capable of performing a hot restart of a compressor driven by a turbine are provided. The turbine has a high speed shaft and a low speed shaft connected to the compressor. A base slow roll speed at which a speed of the low speed shaft is in a slow roll range is maintained at the high speed shaft for a predetermined time. Then, when a vibration amplitude of the compressor is larger than a vibration limit, the maintaining is repeated. Otherwise, a set speed of the high speed shaft is increased, until a current speed of the low speed shaft reaches a minimum operating speed. If, while increasing the set speed, the vibration amplitude becomes larger than the vibration limit, the maintaining is repeated.
1. A gas processing system, comprising: a compressor; a turbine having a high speed shaft and a low speed shaft, the low speed shaft being configured to drive the compressor; and a controller connected to the compressor and the turbine, and configured to control a speed of the high speed shaft, and to receive information about a current speed of the low speed shaft, and a vibration amplitude of the compressor, wherein whenever the controller determines that the vibration amplitude is lower than the predetermined vibration limit, the controller is configured to maintain for a predetermined time the speed of the high speed shaft at a value at which the current speed of the low speed shaft is in a slow roll speed range and then increase the speed of the high speed shaft until the current speed of the low speed shaft exceeds a minimum operating speed.
2. The gas processing system of claim 1 , further comprising:
an operator interface connected to the controller and configured to allow an operator to set any one of slow roll parameters, the slow roll parameters including the slow roll speed range, the predetermined time and the vibration limit.
3. The gas processing system of claim 1 , further comprising:
an emergency shutdown unit connected to the controller and configured to perform a shutdown procedure when the controller indicates that the value of the speed of the high speed shaft is not within a predetermined speed range.
4. The gas processing system of claim 1 , further comprising:
a slow roll counter connected to the controller and configured to count a number of times the controller performs maintaining the speed of the high speed shaft at the value for the predetermined time,
wherein the controller repeats performing the maintaining of the speed of the high speed shaft at the value for the predetermined time, when the vibration amplitude exceeds the vibration limit.
5. The gas processing system of claim 1 , further comprising at least one of:
a gearbox located between the turbine low speed shaft and the compressor;
a speed sensor configured to measure a current speed of the low speed shaft;
a vibration sensor configured to measure a vibration amplitude of vibrations of the compressor; and
a timer configured to measure a time while the controller maintains the speed of the high speed shaft at the value at which the slow roll speed of the low speed shaft is in the slow roll speed range,
wherein the at least one of the speed sensor, the vibration sensor and the timer are connected to the controller.