First, temperature control instrument system fault analysis steps

When analyzing the fault of temperature control instrument system, we should pay attention to two points: the instrument is used to measure, indicate and control the instrument.

1, the temperature indicator system suddenly changed to the maximum or minimum, generally for the instrument system failure. Because the temperature measurement system is lagging behind, it will not change suddenly. At this point, the main reason for the failure is the thermocouple, thermal resistance, compensation wire disconnection or transmitter amplifier failure.

2, the temperature control instrument system showed rapid oscillation phenomenon, mostly for the control parameters PID improper adjustment caused.

3, temperature control instrument system indication of a very slow fluctuations, is likely to be due to changes in the operation of the process, if the process is not changed, it is likely to be the fault of the instrumentation control system itself.

The analysis steps of failure 4, the temperature control system itself: check valve whether the input signal changes, the input signal does not change, regulating valve, valve head leak check diaphragm membrane; adjusting valve positioner input signal is changed, the input signal does not change, the change of the output signal, a fault locator locator; check the input signal changes then, check the regulator output with no change, if the regulator input does not change, the output changes, this is the fault regulator itself.

Next, the pressure control system fault analysis steps

1, the pressure control system instrument instructions appear rapid oscillation fluctuation, first check whether the change of the process operation, this change is mostly process operation and regulator PID parameter adjustment is not good.

2, the pressure control system of the meter indicates deadlines, process operation changes the pressure indication or not change, the general faults in a pressure measurement system, first check whether there is pressure measuring catheter system blocking phenomenon, no blocking, check the pressure transmitter output system has no change, change, fault indication system in measuring controller.

Flow control instrument system fault analysis steps

1, the flow control instrument system to achieve the maximum value of the indicator, first check the field test instrument, if normal, then the fault in the display instrument. When the field detection instrument is also the smallest, then check the control valve opening, if the valve opening is zero, it is often the fault between the regulator to regulator. When the field detection instrument is the smallest, the valve opening is normal, the cause of the failure is likely to be the system pressure is not enough, the system pipeline blockage, the pump is not on the amount of crystallization, improper operation and other reasons. If there is a fault in the instrument, the reasons are as follows: the orifice plate differential pressure flowmeter may be a positive pressure guide pipe blockage; the differential pressure transmitter is leaking in the positive pressure chamber.

2, flow control instrument system indication value reaches the maximum, then the meter will often indicate the maximum. At this point, the remote control valve can be manually opened or closed small, if the flow rate can be reduced to the general reason for the operation of the process. If the flow value does not drop down, it is the cause of the instrument system, check the control flow meter system regulating valve action; check pressure measuring system is normal; check the signal transmission system is normal.

3, flow control and instrumentation indication frequent fluctuations, can be changed to manual control, if the fluctuation is reduced, cause the instrument or meter control parameter PID is not appropriate, if the volatility is still frequent, is caused by the process operation reasons.

The last is the level control instrument system fault analysis steps

1, liquid level control instrument system indication value change to the maximum or the minimum, you can check whether the test instrument is normal, such as the normal indication, the liquid level control to manual remote control level, see the change in the level of. If the liquid level can be stable in a certain range, the fault in the liquid level control system, such as the stability of the liquid level, generally caused by the failure of the process system, to find reasons from the process.

2, differential pressure type liquid level control instrument and field emission type indicating instrument instructions on site, first check the direct reading instrument is normal, if normal check indicator, negative pressure differential pressure level meter tube sealing whether there is leakage; if there is leakage, re filling sealing liquid, zero leakage; may be the wrong amount, negative transfer instrument, re adjust the amount of migration makes the instrument indication.

3, the liquid level control instrument system indication value change frequently, first of all, to analyze the level of the size of the object, to analyze the cause of the fault, the capacity is generally caused by instrument failure. Small capacity of the first analysis of the operation of the process is changed, if the change is likely to be caused by frequent fluctuations in the process. If there is no change may be caused by instrument failure.