Avoid Instrument Issues During Revamps

Reusing existing devices can save money but requires a thorough assessment.

By Girish Sathyanarayana, KBR Hydrocarbons

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The main intent of revamp and debottlenecking projects is to safely use the existing facility, equipment and installation as much as possible -- to reduce capital expenditures on material, installation, commissioning and spares. The same objective holds for in-place control and safety valves and instruments.

So, assessing whether you can retain existing devices is a critical activity. Adequacy checks include verifying plant and component safety, e.g., via Process Hazard Analysis (PHA) and Safety Integrity Level (SIL) assessment, and confirming suitability for the new process conditions.

THE STARTING POINT
Once the process diagrams and the new design conditions for the revamp are available, the immediate task is to identify the existing valves and instruments that must undergo adequacy checks. You must assess all units subject to new process conditions. These include control valves, flow instruments, safety relief valves, thermowells, pressure and temperature transmitters and gauges, analytical instruments and equipment-mounted instruments like level gauges and transmitters.

After you've pinpointed all units requiring adequacy checks, then you must gather as-built details (like datasheets, make, model, serial number, calculation sheets, catalog cut sheets, and inspection and test records) for each. The quality of documents gathered will directly bear on the quality of adequacy checks and, eventually, the success or failure of the revamp project.

Each plant handles documentation in its own way; more often than not, it's hard to get the latest information for instruments. Although use of data management packages is improving the quality of documentation and data archiving, some old plants may lack the procedures to manage the day-to-day changes and, so, documents may not be up-to-date.

Gathering details on existing instruments commonly poses a number of challenges:
• lack of instrument datasheets;
• mismatches between instrument datasheets and instruments in the field;
• missing name and tag plates (serial number information) on field devices;
• lack of instrument make or series details;
• obsolete instrument make or series;
• incomplete process data in existing datasheet or calculation sheet; and
• unavailability of functionality and operation-related issues for the existing instruments.

You thoroughly must check information gathered from the plant for correctness and update it to as-built status (if it isn't already) before using it to carry out the adequacy checks. This activity requires close interaction with plant operation and maintenance personnel so that all "known" changes are captured efficiently.

THE NEXT STEP
Once the as-built information is available, you should conduct the tough process of performing adequacy checks.