HSE – Offshore isolation failures pose a serious major accident risk

January 14, 2026

Failures in process isolation remain one of the leading causes of hydrocarbon releases on offshore installations. These incidents are not minor events; many have the potential to escalate into serious injuries, fatalities, or major accidents if ignition occurs. The Health & Safety Executive (HSE) has repeatedly identified significant shortcomings during inspections, leading to enforcement action across the offshore sector.

To drive improvement, the regulator is sharing lessons from inspections and investigations to help dutyholders strengthen isolation practices and prevent avoidable incidents.

HSE expectations and regulatory focus

According to Scott Templeton, Principal Specialist Inspector in HSE’s Offshore Energy Division, the issue is rarely a lack of written procedures.

“The problem is not what is written down, but the failure to follow procedures in practice. Most UK operators already have isolation procedures broadly aligned with HSG 253,” he said.

He stressed that meaningful and sustained improvement requires commitment at all levels of an organisation — from senior leadership to those carrying out work on the plant — to consistently apply isolation procedures to the required standard.

HSE will soon publish updated inspection guidance to clarify how operators will be assessed. Safe isolation will remain a regulatory priority.

Key inspection and investigation findings

HSE inspections have identified several recurring weaknesses in offshore isolation arrangements:

Inadequate standards and planning

Company isolation standards below HSG 253
Some dutyholders use internal selection tools that allow isolation standards lower than those set out in HSG 253.
Poor isolation planning
Complex isolations involving multiple passing valves or extended boundaries are being undertaken instead of waiting for planned shutdowns, resulting in risks that are not reduced to ALARP.

Weak hazard identification and documentation

Incomplete hazard identification
Risk assessments frequently fail to identify trapped fluids, pressure sources, or non-return valves. Electronic systems often promote generic “copy-and-paste” assessments that do not reflect actual task hazards.
Inaccurate P&IDs
Plant drawings do not always reflect real conditions, leading to incorrect isolation design and implementation.
Insufficient method statements
Step-by-step instructions for applying, testing, and removing isolations are often missing or lack sufficient detail, increasing the likelihood of human error.

Any deviation from established isolation standards must be formally risk-assessed and approved by a technically competent, operationally independent person, typically based onshore. Identified control measures must always be implemented.

Questions for organisations to consider

Procedures

Do your isolation procedures fully align with HSG 253?
Do they provide clear guidance on safe venting and depressurisation?
Are detailed, task-specific method statements required?

Risk management

When are single block and bleed isolations permitted on hazardous systems, and how is ALARP demonstrated?
Is there a defined acceptable leakage rate for isolation valves?
How are systems with difficult-to-prove valve integrity (e.g. flare headers) managed?
What criteria must be met before breaking containment?

People

How is human error minimised during isolation activities?
Are training and competency assessments suitable for everyone involved?
How are high-risk situations managed when multiple activities occur simultaneously?

Assurance

Are monitoring and auditing systems robust enough to detect non-compliance?
How are deviations from isolation procedures controlled and reviewed?
Are plant modification opportunities considered to reduce isolation risk?
Are problematic valves systematically identified and rectified?

Preventing isolation failures

Isolation risks exist throughout the lifecycle of a task — from planning through execution to reinstatement. Well-written procedures alone are not enough. Preventing incidents requires consistent adherence and genuine commitment at every level of the organisation.

HSE continues to engage with industry to raise standards and share learning, with updated guidance due to be issued shortly. The regulator states these failures are entirely preventable — the key question is whether organisations act before an incident occurs.

HSE