Problems with the compressor anti-surge valve?

The surge line under normal operating conditions of the compressor is determined from the performance charts and data sheets provided by the manufacturer, and the absolute condition curve is converted into an actual condition curve using the gas equation of state. P1 V1/T1 = P2 V2/T2. From the relationship between flow rate and pressure difference: Q2 = CΔh/ρ, where ρ = PsM/ZRTi. The surge line equation for this unit is: Pd/Ps = a + b*Δh/Ps. Here, Pd represents the outlet pressure in Kpa ； Ps——Inlet pressure, Kpa ； C — constant (determined by the orifice plate size), m2 ； △h — differential pressure across the orifice plate (the relationship with flow rate is Q2 = h), Kpa; Ti — inlet temperature ； Z is the compression factor, R is the gas constant, and M is the molecular weight ； ρ——density ； a and b are surge line coefficients, determined by the unit’s characteristics. The values of a and b are determined using the expected performance charts and data sheets provided by the manufacturer to obtain the compressor surge curve; thereafter, shifting this curve by 10% to the right yields the compressor anti-surge setting curve, which forms the PID-based anti-surge control loop for the compressor. During actual commissioning in our factory, a margin of 5% was set as the emergency shutdown line; thereafter, through three adjustments of 1% each, gradual approximation was made to ultimately obtain an approximate actual surge line. The main purpose of this surge control system is to effectively regulate the compressor flow rate in order to meet the operational requirements of various process operations ； Secondly, it is also very important to protect the compressor under various normal and abnormal process conditions.

Choke valve: The pressure measurement signals provided to us by SHENGU are: inlet flow rate, outlet pressure, and inlet temperature signals

The SP value of the given signal is calculated using the anti-surge line. Generally, during the mechanical testing of a compressor, performance tests are conducted to determine its surge line; subsequently, the anti-surge line of the compressor is determined based on a certain safety margin. During actual production operations, to ensure the safe operation of the unit, once the operating condition of the unit reaches or exceeds the anti-surge line (that is, when the measured PV value exceeds the specified SP value), the anti-surge valve should open automatically.

It is the inlet flow rate of the compressor.:lol If the inlet flow rate is lower than the set value for the compressor, the compressor will surge, which can cause serious damage to it

Currently, the common approach is to make adjustments based on inlet flow rate. There are also compressors with large fluctuations in inlet pressure, for which adjustments are made using the inlet flow rate, inlet temperature, and inlet/outlet pressures, in order to ensure that the flow rate remains above the surge flow rate at the corresponding speed, and that the inlet and outlet temperatures and pressures meet the specified requirements. Of course, this approach is rather complicated, but it is done to ensure the safe operation of the equipment

In my opinion, this is not the cause of surge. Under nitrogen operation conditions, the flow rate is much lower than that under normal operating conditions, and surge should not occur in such cases. The cause of surge is likely a sudden drop in inlet pressure or a sudden increase in outlet pressure. It is also caused by fluctuations in import pressure. I think the question raised by the original poster pertains to both imports and exports.

Adjust based on inlet flow rate, inlet temperature, and inlet and outlet pressures

Issues with compressor anti-surge valves – very useful, thank you!