Every instrument manufacturer, including our Noncon instrument, cannot guarantee that every instrument sold can achieve zero failure, which is related to the structure of the instrument and the operating habits of the on-site operators. Therefore, the maintenance of the instrument is also essential, it is a tedious and patient thing.
When analyzing the causes of on-site instrument failure, special attention should be paid to the changes in the characteristics of the measured control object and control valve, which may be the cause of on-site instrument system failure. Therefore, we need to comprehensively consider and carefully analyze from the two aspects of the field instrument system and the process operating system, and check the reason, the measurement parameters of the field instrument are generally divided into four parameters: temperature, pressure, flow rate, and liquid level.
First of all, before analyzing and inspecting the fault of the on-site instrument system, it is necessary to understand the production load and the parameter changes of raw materials from the on-site operators, check the record curve of the faulty instrument, and conduct comprehensive analysis to determine the cause of the instrument failure.
Secondly, before analyzing the on-site instrument failure, it is necessary to have a thorough understanding of the design scheme and design intention of the instrument system, the structure, characteristics, performance and parameter requirements of the instrument system, and the production process, production process and conditions of the relevant instrument system.
1. Fault analysis of flow control instrument system
The flow control instrument system indicates that the minimum value reaches the minimum, first check the on-site detection instrument, if it is normal, the fault is in the display instrument. When the on-site detection instrument indication is also minimal, check the opening of the control valve, if the opening of the control valve is zero, it is often a fault between the control valve and the regulator. When the on-site testing instrument indicates the minimum and the control valve is normally opened, the cause of the failure is likely to be caused by insufficient system pressure, blockage of the digital display controller system, pump failure, medium crystallization, improper operation and other reasons. If it is a failure in the instrument, the reasons are: the orifice differential pressure flowmeter may be a positive pressure pressure duct blockage; Differential pressure transmitter positive pressure chamber leakage; Mechanical flow meters are gear jams or filter blockages.
When the indication value of the flow control instrument system reaches the maximum, the detection instrument often indicates the maximum. At this time, the control valve can be manually controlled to open or close small, and if the flow rate can be reduced, it is generally caused by process operation. If the flow value cannot be reduced, it is caused by the instrument system, check whether the control valve of the flow control instrument system is working; Check whether the instrument measurement pressure system is normal; Check whether the instrument signal transmission system is normal.
If the fluctuation is reduced, it is due to the instrument or the instrument control parameter PID is not suitable, if the fluctuation is still frequent, it is caused by the process operation.
2. Fault analysis of the liquid level control instrument system
If the indication value of the liquid level control instrument system changes to the maximum or minimum, you can first check the detection instrument to see if it is normal, if the indication is normal, change the liquid level control to manual remote control the liquid level to see the change of liquid level. If the liquid level can be stabilized within a certain range, the fault is in the liquid level control system; If the liquid level cannot be stabilized, it is generally a failure caused by the process system, and the cause should be found from the process side.
When the differential pressure level control instrument indicates that the on-site direct reading indicator instrument does not match, first check whether the on-site direct reading indicator instrument is normal, if the indication is normal, check whether there is any leakage in the negative pressure guide pipe sealing liquid of the differential pressure level instrument; If there is leakage, repot the liquid and adjust the zero point; There is no leakage, it may be that the negative migration amount of the meter is wrong, and the migration amount is readjusted to make the meter indicate normal.
When the indication value of the liquid level control instrument system changes frequently, the capacity of the liquid level control object should first be analyzed to analyze the cause of the failure. If the capacity is small, first analyze whether there is a change in the process operation, and if there is a change, it is likely that the fluctuation is frequent caused by the process. If there is no change, it may be caused by instrument failure.
If users encounter problems with abnormal meter display during use, it will definitely be a troublesome thing, but careful investigation can always find the root cause of the problem. Noncon Instrument is the on-site use inspection of the majority of users, and will do its best to serve you.
