Method for operating a multistage compressor

Abstract

A method for operating a multistage compressor is provided. The method includes monitoring the pump limit, wherein at least a first measurement parameter measured during operation is compared to a reference parameter. The reference parameter is characteristic of reaching the surge limit or a specific distance of the operating point from the surge limit. A multistage compressor is also provided. In order to enlarge the operating range without risking safety, it is proposed that each stage to be monitored individually for the onset of the surge.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of application Ser. No. 13 / 130,619 filed on May 23, 2011 which is the US National Stage of International Application No. PCT / EP2009 / 065613, filed Nov. 23, 2009 and claims the benefit thereof. The International Application claims the benefits of German application No. 10 2008 058 799.0 DE filed Nov. 24, 2008. All of the applications are incorporated by reference herein in their entirety.FIELD OF INVENTION[0002]The invention relates to a method for operating a multistage compressor with a monitoring means for the surge limit, in which method at least one first measured variable which is measured during operation is compared with a reference variable, which reference variable is characteristic of the reaching of the surge limit or a defined gap from the operating point from the surge limit. In addition, the invention relates to a multistage compressor having an evaluation module for monitoring the reaching ...

AI Technical Summary

Benefits of technology

[0008]The invention has therefore made it its object to improve a method of the type mentioned in the introduction, in such a way that the operating range of the turbocompressor is enlarged, without the safety against surging being impaired.

[0017]The invention avoids effects of this type by the individual consideration of each individual stage with respect to the reaching of the surge limit, and accordingly optimizes the utilization of the actually possible operating range without increasing the risk of surging. It is even shown that the stage-specific monitoring according to the invention affords greater safety against surging.

[0018]The pressure in front of the respective stage is expediently measured as first measured variable. The temperature in front of the stage can be determined as second measured variable, which increases the accuracy of the localization of the surge limit. One particularly favorable embodiment of the invention provides for the volumetric flow, mass throughput or mass flow of the process fluid to be measured only once along the flow path, preferably at the inlet of the turbocompressor. Greater accuracy and improved utilization of the operating range can be achieved if this measurement, which regularly takes place as a pressure differential measurement across a restrictor, is provided at the inlet or outlet of each stage.

Problems solved by technology

Considerable backflows occur with the start of the surging in a compressor, which backflows cause pressure fluctuations and temperature increases which already lead to damage after a comparatively short operating duration in this state.

The reaching of the surge limit can be discerned clearly, even for an inexperienced operator, since the pressure fluctuations cause considerable oscillations, the noise of which exceeds the level of usual operation.

Experience shows, however, that determinations of this type are imprecise and these conventional monitoring methods require a comparatively great safety gap from the surge limit, which safety gap unfavorably restricts the available operating range of the turbocompressor.

If this safety range is reduced, high loadings of the turbocompressor as a consequence of surging occur in certain operating states, with the result that the mechanical integrity is endangered.

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