A common fault of wear-resistant thermocouple1

What are wear-resistant thermocouple common failures? All the instruments in the process of use will appear a certain fault, wear-resistant thermocouple is no exception. If we know some common fault of wear-resistant thermocouple can effectively avoid or solve these faults in time, so wear resistance thermocouple what are the common faults, the project is to introduce specific.

1, wear-resistant thermocouple compensating lead wires. Mainly infrastructure problems, responsible for connection of a moment of carelessness, artificial factor. When a thermocouple compensating lead wires connect the situations, the operator control site shows usually small or large than the actual value ( According to the channel measurement circuit and decide) 。

2, wear-resistant thermocouple compensation wire insulation layer is worn out, causing signal circuit grounding. This is mainly because compensation conductor should be hard, but also in terminal box was not placed flat again, deal with failure many times met compensating lead screw terminal box cover and it is worn out. Such failures are reflected in the operator controls the temperature on the general value for small.

3, terminal box poor contact terminals. Because compensation conductor and thermocouple wires are hard, so it is difficult to on-site maintenance when fastening connection, sometimes come to the conductor and tightened the but over time as the deformation of the wire is loose. Such failures are reflected in the operator to control the temperature of the site for the value for no show or display value range.

4, compensation fault resistance. Such failures of thermocouple to temperature display value after slow rise or fall.

5, the tail of the boiler flue measuring thermocouple failure rate is higher. Down thermocouple will be removed when found thermocouple head including protective casing by flue gas flushing after serious wear and tear, will protect casing under wear resistant steel, to eliminate such problems.

6, the temperature of the input signal after the isolator failure, reflect on the operator control site temperature signal abnormalities. After replacement of isolator is normal. Above is often encountered when the maintenance problems, but in finding these failure, suggest to use multimeter in DCS on the ark of the IO terminal measurement input voltage value, so that we can quickly judge the in situ measurement issues or DCS part of the problem, for more input can also be compared with several other thermocouple signal. Such as judgment is not the solution of any line measuring the resistance value, usually wear resistance value is about 100 Ω thermocouple.

7, signal shielding system in DCS cabinet earthing. Such failures is extremely easy to cause electric charge accumulation on the line, cause the signal drift or shaking. Because the problem is more difficult to find out the fault point, the usual treatment method is to solve signal lines, to the discharge process.

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key words: thermal resistance, thermocouple, thermal resistance, platinum resistance, PT100, PT1000, pressure sensor and digital temperature sensor