Compliance hub / Sector guide

Calibration — UKAS, ISO 17025 and traceability

If your work depends on a measurement — torque settings on critical bolts, pressure readings on a vessel, weighing for trade — the measurement is only as good as its calibration. UKAS-accredited certificates carry the legal and contractual weight; an in-house sticker doesn't.

What the law says

There's no single 'Calibration Act', but the duty arises through PUWER 1998 (suitable, maintained equipment), the Weights and Measures Act 1985 (trade), HSE inspection guidance, customer contracts and ISO 9001 quality management. The accepted technical standard for calibration laboratories is ISO/IEC 17025; in the UK, conformity is assessed by UKAS. Traceability ends at the National Physical Laboratory (NPL).

Recommended starter spec

Asset register of every measuring instrument with serial number and last/next calibration date.
Calibration intervals matched to use — typically 12 months, shorter for critical or heavily used kit.
UKAS-accredited certificates for instruments used for compliance, trade or customer evidence.
On-tool labels showing calibration status and next-due date.
Pre-use checks and out-of-tolerance / drop procedure.
Storage that protects instruments from shock, dust and temperature extremes.

Common gaps we find

In-house 'calibration' done by comparison to another uncalibrated tool.
Certificates from non-accredited labs accepted where the contract specifies UKAS.
No record of impact events that should trigger early recalibration.
Torque wrenches stored under load (springs left compressed).
Pressure gauges that have drifted out of tolerance but stayed in service.

This guide is for general information. A site-specific risk assessment by a competent person is required under the relevant regulations.