Instrument Installation and Calibration

Process instruments measure pressure, flow, level, temperature, and quality in water, wastewater, and industrial plants.
Installation involves working in process areas with chemical, biological, and mechanical hazards from operating equipment.
Instruments may be installed on pipework under pressure, in tanks, at height on structures, and in confined spaces.
Calibration requires applying known values using test equipment — incorrect calibration causes process failures.
Some instruments are installed in hazardous areas (ATEX zones) requiring intrinsically safe equipment and practices.
Cable routing for instrumentation must maintain the separation from power cables specified in the design.
Tapping points and instrument connections on pressurised systems must be isolated before installation.
The Electricity at Work Regulations 1989 and PUWER 1998 apply to all instrumentation installation work.
Commissioning involves loop testing from sensor through wiring to the PLC or SCADA system.
Instrument air supply systems operate at pressure and must be treated as pressurised systems during connection.

Prevent process failure	Incorrectly calibrated instruments give false readings that can cause chemical overdosing or system failure.
Pressurised system hazards	Installing instruments on live or pressurised systems without isolation risks uncontrolled release of process fluids.
Electrical safety	Instrumentation circuits in ATEX zones must be intrinsically safe to prevent ignition of explosive atmospheres.

Do

Don't

Isolate process connections and confirm zero pressure before installing any instrument
Use calibrated test equipment traceable to national standards for all calibration work
Follow the instrument data sheet and manufacturer instructions for installation and setup
Maintain cable separation between instrument and power circuits as specified in the design
Complete loop testing from sensor through to PLC/SCADA before declaring the instrument live
Wear appropriate PPE for the process area including chemical-resistant gloves and eye protection
Check ATEX zone classification and use only intrinsically safe instruments and barriers
Record all calibration values, as-found and as-left readings, and certificate references
Brief all workers on the process hazards present in the installation area before starting
Label every instrument and cable clearly with the tag number from the instrument schedule

DON'T install instruments on pressurised pipework without confirmed isolation and venting
DON'T calibrate instruments with uncertified test equipment — results will be unreliable
DON'T install non-IS equipment in ATEX-classified hazardous areas without IS barriers
DON'T route instrument cables alongside power cables without the specified separation distance
DON'T commission instruments without completing a full loop test from sensor to control system
DON'T enter confined spaces or process tanks for instrument work without a valid permit
DON'T force threaded connections on pressure tappings — cross-threading causes dangerous leaks
DON'T leave instrument covers off or cable glands unsealed exposing electronics to moisture
DON'T modify instrument ranges or alarm settings without the control engineer's authorisation
DON'T work in operating process areas without assessing chemical and biological exposure risks

See also: MEICA Safety Awareness | Commissioning Safety

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