Validating anti surge control systems
A dynamic compressor, also known as a "turbo-compressor", is generally provided with an anti-surge valve (Fig- ure 1) in order to keep the compres- sor in a stable operating range.
This is achieved by assuring a suction flow that is higher than the corresponding flow at the surge.
Meaningful gains can be made by a better understanding of the interactions between the compres- sor, the anti-surge valve(s) and the facility piping and layout (including coolers, scrubbers, check valves, vent valves and more).
Key parameters for anti-surge valve selection and sizing include the following: fast response, optimum size, high integrity, accuracy and noise abatement.
Testing is performed with experiments using suction and discharge side disturbances, which are created by rapid valve closures.
For comparison the same tests are repeated with conventional control approaches.
An anti-surge valve with a relatively large capacity (com- pared to the compressor's volumetric flowrate), but with the same opening time (compared to relatively small anti-surge valves), will allow the shutdown surge to be avoided (or the shutdown surge will occur at a lower head condition).
On the other hand, a relatively small anti-surge valve could cause a more energetic and more po- tentially damaging shutdown.
The ability to quantify these ef- fects and select a proper valve size by dynamic modeling can be very useful.
The anti-surge valve The size of an anti-surge valve influ- ences the amount of fluid that can be moved from the discharge side of the compressor to the suction side. The speed with which an anti-surge valve opens CHEMICAL ENGINEERING WWW. COM NOVEMBER 2012 4 3 Engineering Practice is also important in rapidly reducing the discharge pressure (the head and stored energy at the compressor dis- charge).
One important trade-off in relation to anti-surge valves is that larger valves exhibit slower opening rates. The faster the valve can be opened, the more flow can pass through it and the more effective it is in surge prevention.
Search for validating anti surge control systems:
For the purpose of testing and validating the proposed control algorithm, an experimental compressor test rig is presented, which is designed to mimic a typical centrifugal compressor application in the oil and gas industry.