Challenges Faced in Field Instrumentation
Published on : Tuesday 31-12-2019
Dr VP Raman elaborates upon the challenges faced in field instrumentation. There are many challenges faced related to Field Instrumentation, as listed below:
Instrument failure and the lack of spares
Let us face the fact that Field Instruments do fail. Some field instruments are more reliable than others, but none are immune. Unexpected failure can shut down the production causing severe knock-on consequences like compromising the safety of plant and personnel, affects the quality of products, bring down the profit margins, etc.
To overcome this, undertaking regular technical system audits of all the field instruments, like mission critical elements to be identified and steps taken to minimise the risk of failure and ensure rapid repair, should the worst happen. This also implies holding stock of vital spares to meet the contingency. The cost of maintaining an audited system can pay real dividends when compared to the cost of a process system failure.
Incorrect use of equipment
This is a common problem faced during design stage, as many times the process requirements are not clearly spelled out. Thorough understanding of the process and its variations must be clearly understood during the design stage, which leads to wrong selection of field instrument. The selection of correct field instrument must be assessed by an experienced engineer, once all the process data is finalised and equipment’s are finalised, must be part of checklist during Quality Control.
Operator training
Typically in a small or medium scale industry, an operator sometimes does not understand the readings an instrument is giving or its implications on the production. Also many times some of the crucial alarms are missed, during the bust of alarms. Hence, it is important that personnel operating the plant and machinery/equipment are trained correctly, to interpreting various readings and criticality of various alarms and what actions must be done during emergency situations.
Incorrect diagnosis of system failures
Misdiagnosis of a system failure will lead to delay in repair, it can make the problem worse. Accurately diagnosing exactly what went wrong with a system is a valuable skill. Determining the problem quickly and correctly will help with a move towards fixing the issue.
Having a process in which a system failure can be identified and swiftly repaired and/or replaced is key. If this process is in place, downtime and consequent loss can be minimised.
Incorrectly installed instrumentation
Even correctly specified instrumentation will not perform to its best if it is incorrectly installed. Incorrect installation will lead to wrong readings, delay in signal transmission, leakages from process tapping points, flanges, etc. Hence reviewing a planned installation is valuable, so the most effective approach to installation will ensure proper instrumentation performance and reading.
Earthing
Though importance is given during the design stage, the successful implementation of creating various types of earthing system is during the construction stage, and it plays a vital role in the operation. Many times, it has been observed that the readings are not consistent and vary widely with the reference limits. This is all due to earth faults/spikes being transmitted to the system from field. Typically the earthing is classified as clean earth and dirty earth. Proper care must be taken during installation to ensure that the clean earth resistivity is less than the acceptable value. Adequate separation of electrical earth with instrumentation earth must be ensured.
Dr VP Raman is VP-Operations, TECTON Engineering & Construction LLC. He has 38 years of experience in the field of Design and Detailed Engineering, Operations and Business Development related to EPC, EPCM, FEED, Basic/Detailed Engineering, Procurement, Commissioning in process industries.
