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technical article
Control instrument failure analysis
2011-9-6 16:20:18

     流量 压力 液位。 In the current market, people generally think that there are four major control instruments, such as: temperature , flow , pressure , and liquid level. In the use of various instrument products, no matter how good the product is, there are failures for many reasons. The following is an analysis of several situations:

1. Temperature control instrument

分析温度控制仪表系统故障 注意系统仪表多采用电动仪表测量、指示 控制;系统仪表的测量往往滞后较大。 When analyzing the temperature control instrument system failure , it should be noted that the system instruments are mostly measured, indicated and controlled by electric instruments ; the measurement of the system instruments often has a large lag.
最小 的时候 ,一般为 温度 仪表系统 故障。 (1) When the indicated value of the system suddenly changes to the maximum or minimum value , it is generally a failure of the temperature instrument system . 往往 系统测量滞后较大,不会发生突然变化。 Because the system measurement lag is often large, no sudden change will occur. 此时的故障原因 大部分 是热电偶、热电阻、补偿导线断线或 变送器放大器失灵 的; At this time, most of the faults are caused by broken thermocouples, thermal resistors, compensating wires, or failure of the transmitter amplifier ;
大部分是 为控制参数PID调整不当 造成 (2) When the system indicates a rapid oscillation , most of it is caused by improper adjustment of the control parameter PID ;   

系统指示出现大幅缓慢的波动 ,可能是工艺操作变化引起的, 但如果 当时 工艺操作没有变化, 那么 很可能是仪表控制系统本身的故障 (3) When the system indicates a large and slow fluctuation , it may be caused by process operation changes, but if the process operation does not change at that time , then it is likely that the instrument control system itself is faulty ;
有没有 变化, 如果 输入信号 没有 变化, 那么 调节阀膜头膜片漏了;检查调节阀定位器输入信号 有没有 变化, 如果 输入信号 没有 变化,输出信号变化, 那么 定位器有故障;检查定位器输入信号 有没有 变化,再查调节器输出 有没有 变化,如果调节器输入 没有 变化,输出变化, 那么 此时 是调节器本身的故障 (4) Failure analysis steps of the system: Check whether the input signal of the regulating valve has changed. If the input signal does not change, then the diaphragm of the regulating valve is leaking. Check whether the input signal of the regulating valve positioner has changed. Change, the output signal changes, then the positioner is faulty; check whether the input signal of the positioner is changed, and then check whether the output of the regulator is changed. If the input of the regulator is not changed, and the output is changed, then the regulator itself is faulty. Already .

2 . Flow control instrument

     ,首先 检查现场检测仪表,如果正常, 那么 故障在显示仪表。 (1) When the system indication value reaches the minimum , the on-site testing instruments must be checked first . If normal, the fault is displayed on the instrument. 那么 检查调节阀开度, 如果 调节阀开度为零, 一般 为调节阀到调节器之间故障 当现场检测仪表指示最小 ,调节阀开度正常,故障原因可能是系统压力不够、系统管路堵塞、泵不上量、介质结晶 操作不当等原因造成。 When the on-site testing instrument indicates the smallest , then check the opening degree of the regulating valve . If the opening degree of the regulating valve is zero, it is usually a failure between the regulating valve and the regulator. It may be caused by insufficient system pressure, blocked system pipelines, improper pump capacity, medium crystallization or improper operation. 是仪表方面的故障 孔板差压流量计是正压引压导管堵;差压变送器正压室漏;机械式流量计是齿轮卡死或过滤网堵等。 If it is a malfunction of the instrument : the orifice plate differential pressure flow meter is a positive pressure induced pressure pipe plug; the differential pressure transmitter positive pressure chamber is leaking; the mechanical flow meter is the gear is stuck or the filter is blocked.
,检测仪表也常常会指示最大。 (2) When the system indicates the maximum value , the detection instrument will often indicate the maximum. 关小,如果流量能降下来则一般为工艺操作原因造成。 At this time, the remote control valve can be manually opened or closed. If the flow can be reduced, it is usually caused by process operation. 流量值降不下来, 那么就 是仪表系统的原因造成,检查系统的调节阀 是不是工作 ;检查仪表测量引压系统 是不是 正常;检查仪表信号传送系统 是不是 正常。 However, if the flow value cannot be lowered, then it is the cause of the instrument system. Check whether the regulating valve of the system is working . Check whether the instrument measurement pressure system is normal. Check whether the instrument signal transmission system is normal.
,可将控制改 手动,如果波动减小, 那么 是仪表方面的原因或 仪表控制参数PID不合适,如果波动仍频繁,则 是工艺操作方面原因 造成。 (3) When the system's indication value fluctuates more frequently , the control can be changed to manual. If the fluctuation is reduced, it is caused by the instrument or the PID of the instrument control parameter is not suitable. If the fluctuation is still frequent, it is caused by the process operation. Caused by.
3 Pressure control instrument

    1) 系统仪表指示出现快速振荡波动 ,首先 检查工艺操作 有没有 变化,这种变化多半是工艺操作和调节器PID参数整定不好 造成 ( 1) When the system instrument indicates a rapid oscillation , first check whether there is a change in the process operation. Most of this change is caused by the poor operation of the process operation and the regulator PID parameters .
的时候 ,工艺操作变化了压力指示还是 没有 变化,一般故障出现在压力测量系统中, 所以 首先检查测量引压导管系统 是不是 有堵的现象, 如果 不堵,检查压力变送器输出系统 有没有 变化, 如果 有变化, 那么 故障出在控制器测量指示系统。 (2) When the system instrument indicates a dead line , the process operation has changed the pressure indication or there is no change. The general fault occurs in the pressure measurement system, so first check whether the measurement impulse catheter system is blocked. If it is not blocked, Check the pressure transmitter output system for changes. If there is a change, then the fault is in the controller measurement and indication system.
4. Level control instrument

最小时,先检查检测仪表 是不是 正常,如 指示正常,将液位控制改为手动遥控液位,看液位变化情况。 (1) When the indication value of the liquid level control instrument system changes to the maximum or minimum, first check whether the detection instrument is normal. If the indication is normal, change the liquid level control to the manual remote liquid level to see the change of the liquid level. 液位可以稳定在一定的范围 那么 故障 出现 在液位控制系统 ;如 稳不住液位,一般为工艺系统造成的故障,要从工艺方面查找原因。 If the liquid level can be stabilized within a certain range , then the fault occurs in the liquid level control system ; if the liquid level cannot be stabilized , it is generally a fault caused by the process system, and the cause must be found from the process side.
指示和现场直读式指示仪表指示对不上时,首先检查现场直读式指示仪表 是不是 正常,如 指示正常,检查差压式液位仪表的负压导压管封液是 不是 有渗漏; 如果 有渗漏,重新灌封液,调零点; 没有 渗漏,可能是仪表的负迁移量不对了,重新调整迁移量使仪表指示正常。 (2) When the indication of the differential pressure level control instrument and the on-site direct-reading indicator are not compatible, first check whether the on-site direct-reading indicator is normal. If the indication is normal, check the differential pressure level instrument. Is there any leakage in the sealing fluid of the negative pressure impulse tube ? If there is leakage, refill the sealing fluid and adjust the zero point; if there is no leakage, the negative migration of the meter may be wrong. Readjust the migration to make the meter indication normal.
,首先要分析液面控制对象的容量大小, 由此 来分析故障的原因,容量大一般是仪表故障造成 容量小的首先要分析工艺操作情况是 不是 有变化,如有变化很可能是工艺造成的波动频繁。 (3) When the indication value of the liquid level control instrument system changes frequently , the capacity of the liquid level control object must be analyzed first to analyze the cause of the failure. The large capacity is generally caused by the failure of the instrument ; the small capacity must be analyzed first. Are there any changes in process operating conditions? If there are changes, they are likely to be frequent fluctuations caused by the process. 没有变化可能是仪表故障造成。 If there is no change, it may be caused by a malfunction of the instrument.
There are some complicated control loops on the actual site. The analysis of these faults is more complicated.