How is the calibration of on-site instruments carried out during the operation of the plant
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During the operation of the unit, it is necessary to determine how instruments such as temperature and pressure transmitters should be calibrated (as interlock instruments require verification of their accuracy); whether these instruments should be sent for testing or simply undergo a routine zero-point check on-site. How do you all do it? If the instrument is taken back for calibration on a test bench, it involves too much work, and there are no temperature or calibration devices available; what is the method for calibration?
It depends on the intensity of inspections by the local safety authorities and the requirements set by the enterprises. In private companies, it was common to submit a single batch of products in order to obtain a certificate and thus meet the requirements of the safety authorities, as the inspections weren’t strict. Chain instruments generally should not be altered casually during operation; self-calibration can be carried out during shutdown. Moreover, cascade instruments usually operate on a three-out-of-two or two-out-of-two principle, so there is no need to conduct tests during operating hours; also, the probability of them failing is relatively low.
Instruments should be calibrated regularly, usually in conjunction with maintenance cycles. Pressure transmitters are calibrated using standard instruments, while thermal resistors and thermocouples are calibrated in a similar manner. If a company does not have its own calibration equipment, it should send the instruments to a metrology testing facility. Among the instruments designated for mandatory calibration this year are pressure transmitters that are used for safety purposes
Well, in that case, the workload will increase a lot
That’s the method you mentioned; but for self-inspection, standards need to be established.
If the company is large, it’s possible to set up a calibration laboratory and carry out the calibrations oneself. Taking into account factors such as temperature and pressure on site, there’s quite a bit of work to be done. After all, mandatory inspections don’t cost anything these days, but the inspection process is too slow, which is unacceptable. It’s better to handle the calibrations oneself, as this allows one to arrange the work according to one’s own schedule.
Small companies cannot afford to do this, and even large enterprises and state-owned companies may not be able to handle it; every instrument needs to be calibrated regularly – this is something that’s impossible to achieve.