Loss of Containment (LOC) Data

The UK’s Health and Safety Executive (HSE) and the onshore chemical and major hazard industries collaborated in the collection of causation information and lessons learnt from Loss of Containment incidents.  This was a voluntary scheme aimed at collecting information on the underlying causes of loss of containment events. The aim being to identify common failure mechanisms that feature in chemical incidents.  There are two sets of data, one for the chemicals sector (excluding refineries) and one for the refineries sector.  The data obtained is quite telling…

NOTE: This report is a MUST READ for all process safety professionals.

Overview

• 69 % of incidents can be categorised as either being as the result of an incorrect action by an operator (37%), or the equipment or plant failure (32%). The remaining 31% of incidents are spread across the other primary cause categories.
• Operator Error:
  • 34% – inadequate operating procedures
  • 18% – inadequate plant design
  • 14% – inadequate supervision
  • 12% – management of change
• Equipment Failure:
  • 30% – inadequate maintenance
  • 28% – inadequate design
• Across all incidents the three most common Risk Control Systems to fail, which may warrant further attention are:45% of incidents occurred from the use of flammable substances (including extremely flammable, highly flammable, flammable and flammable liquids)27% of incidents involved non-COMAH (PSM/RMP) substances.
  • 37% – Operating Procedures
  • 32% – Plant Design, and
  • 26% – Hazard Analysis
• 14% of incidents involved the release of a toxic or very toxic substance.
• 56% of incidents occurred during normal operating mode. It has always been presumed that the majority of incidents occur outside of normal operations.

Site of Release

• Flexible hoses – 18%
• Storage Vessels – 14%
• Pipework – 12%

Costs (in pounds)

• Damage to property & plant in the establishment – £252,545
• Business Interruption – £645,280
• Clean up costs – £259,109
• Total Cost – £1,156,934

Dispersion/Off Site Emergency Plans

• Only 11% of incidents spread offsite, with 8% of incidents involving the activation of the offsite emergency plan.

Mitigating Defenses

• 42% of incidents involved either no mitagatory action or the mitigating measure was unknown.
• For 19% of incidents the mitigation was that the process was stopped.
• For 19% of incidents the loss of containment was contained within the bund (e.g. dike) or effluent system.

Primary Cause of Incident

• The two main causes of Operator Error and Equipment Failure comprise of the following categories:
  • Operator Error:
    • human error,
    • impact/dropped object,
    • procedural violation,
    • inadequate isolation,
    • incorrect installation
  • Equipment Failure:
    • corrosion,
    • defective equipment,
    • overpressure,
    • stress/fatigue/vibration, and
    • unsuitable equipment

Risk Control Systems
The risk control systems found to have weaknesses/failures where:

• Operating Procedures – 37%
• Plant and Process Design – 32%
• Hazard and Risk Assessment – 26%

Operating Procedures
A failure of the operating procedure risk control system can occur for a number of reasons:

• a work activity is deficient,
• procedure is documented adequately but not followed or an error is still made by an operator/contractor,
• procedure is not documented, or inadequately documented causing operator/contractor error.

Plant and Process Design

There were no particular problems highlighted in any aspects of design. The incidents were due to many different design faults:

• non return valves not fitted,
• restricted views or
• shut off valves not accessible,
• drums/barrels falling off FLTs (e.g. forklifts) and shelving systems,
• pressure vessel bursting discs set too high,
• bungs/valves being able to be manually opened closed,
• flexi hose used instead of hard piping

Hazard and Risk Assessment
Upon further analysis there are four main areas of failure:

• Choosing unsuitable equipment,
• not knowing/obtaining information on intrinsic hazards of substances in the context of their use,
• over-reliance on prevention rather than linking hazard assessments to mitigation and management of change – not assessing risks attached to changing a process,
• not complying with a HAZOP action.

Health and Safety Management System

• 37% incidents were caused by a failure of the planning and implementation aspect of the Safety Management System
• 16% by organising – control
• 16% by monitoring

Click Here to see the full report.