| 摘要 |
After the pumping station set points for a desired pipeline operation are calculated, they are used by process controllers at the individual pumping stations to control operations at the station. Measured values of the station's performance are compared with the set points. If these values differ enough as to require a change in the speed of the compressors, the speed of the compressors then operating is then slowly changed (or ramped) so as to bring the pipeline into operation at the set points that were calculated. Ramping is performed so that the operating efficiency of the compressors is always maintained at approximately a predetermined level. If it is found that a change is required in the number of compressors being used, this is brought to the attention of the operator of the pipeline who must then decide to let the controller effect the change. At frequent intervals, each compressor is checked for surge and stonewall conditions. In the event a surge condition is detected, the compressor's bypass valve is opened and the compressor is idled. After a suitable time delay, a test is made to determine if there is any speed at which the compressor can be operated for existing flow and compression ratios which will be on the compressor efficiency curve then being used. If so, the compressor is then loaded back on-line and ramped to the correct speed. If not, the operator is requested to permit operation of the compressor at a different efficiency level. If stonewall is present, it is necessary to put additional compressor units on line.
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