INTRODUCTION
An anti-surge valve is a valve that was designed and installed to protect the compressor from reaching its surge point. The valve is in the system, in a by-pass that connects the inlet and the outlet of the compressor. In normal operation, this valve remains closed, however, if the surge is detected, it will quickly open to maintain a minimum flow and directs the backflow to the outlet of the compressor to avoid damage. The valve must be completed with controllers that use the suction and discharge pressure and temperatures to determine the flow at which the condition of surge will occur. It is crucial for such valves to be operated by actuators that can achieve extremely fast stroking times, high frequency of operation, minimal dead time, and minimal overshoot.
Design of anti surge valve
The anti-surge control valve typically comprises a valve, actuator, positioner, and other accessories, like a volume booster, solenoid, and position transmitter. Depending upon actuator type, volume tank, and related accessories may be required.
How does an anti surge valve work?
The anti-surge valve is a failed open solenoid valve, so because of this it needs a high signal to close the valve, so 20mA is needed, and to open the valve a low signal will be used which will be 4ma. So in case of any surge, the valve will receive a low signal and it will open the valve. Initially, the compressor will be with the valve at 100% open and after that, the valve characteristics of 100% open must be removed from the compressor operational region, while the startup of the compressor. The valve must be sized almost 2 times the maximum surge point flow rate and an oversized valve won’t operate properly.
Advantages of anti surge valve
Reduce process upsets.
Surge can be prevented from virtually any disturbance.
Assist the compressor process control strategy.
