PID interlock settings
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I need help. Dear experts, when working with PID control and interlock systems, are there any standards regarding the settings that need to be made? ! ! !
1’ Systematics * Instruments and Automation Course 2. Experience values: Control objects – Characteristics kp Ti (m) Td (m) Flow: Small value; noisy signals 1-2.5 0.1-1 Temperature: Large lag in multi-volume systems 1.6-5 3-10 0.5-3 Pressure: Small lag in volume systems 1.4-3.5 0.4-3 Level: Integration is not necessary if a static error is acceptable 1.25-5 Parameter tuning should be done by trying values from smallest to largest; start with proportionality, then integration, and finally add differentiation. If the curve oscillates frequently, increase the proportionality setting. If the curve wanders around in large loops, decrease the proportionality setting. If the curve takes time to return to its normal state, reduce the integration time. If the curve has long fluctuation cycles, further increase the integration time. If the curve oscillates rapidly, first reduce the differentiation setting. Large dynamic errors result in slow fluctuations. The differential time should be increased. For the ideal curve, there are two waves – the first one is higher and the second one is lower, in a 4-to-1 ratio. Observe carefully, make adjustments as needed, and conduct thorough analysis; this way, the quality of the adjustments will not be poor
HAZOP analysis – handle it yourself
PID is a method for stabilizing control loops; in the context of control, interlocks are primarily used in ESD systems. The logic of the interlock circuits is determined based on HAZOP analyses or the SIL level required by the process package. These two concepts are not the same, and the standards applicable to each are also separate. Interlock design follows IEC61508, while standards for instruments follow IEC61511.