L122: Pressure Systems Safety Regulations 2000

What is L122?

L122 is the HSE's Approved Code of Practice (ACOP) and guidance for the Pressure Systems Safety Regulations 2000 (PSSR). It provides detailed guidance on how to comply with the legal requirements for the safe design, manufacture, installation, operation, maintenance, and examination of pressure systems.

Pressure systems store significant amounts of energy. When they fail, the results can be catastrophic - explosions causing deaths, serious injuries, and major property damage. The PSSR and L122 exist to prevent such disasters through proper design, maintenance, and periodic examination.

L122 covers all pressure systems including steam boilers, autoclaves, compressed air systems, hydraulic systems, gas storage vessels, and any equipment containing fluids under pressure that could cause injury if released.

Who Needs This Document?

L122 is essential for:

• Manufacturers and suppliers of pressure equipment
• Owners and operators of pressure systems in any industry
• Facilities managers responsible for building services
• Maintenance engineers working on pressure equipment
• Competent persons who examine pressure systems
• Installation contractors fitting pressure equipment
• Food and beverage manufacturers with steam and pressure processes
• Hospitals and laboratories with autoclaves and sterilisers
• Laundries and dry cleaners with steam boilers
• Any business with compressed air systems, steam, or pressure vessels

Key Topics Covered

What is a Pressure System?

L122 defines pressure systems as:

• A system containing relevant fluid under pressure
• Including pipework, protective devices, and vessels
• Where stored energy could cause injury from release

Relevant fluids include:

• Steam at any pressure
• Any fluid at pressure greater than 0.5 bar above atmospheric
• A gas dissolved under pressure in a solvent in a container
• Gases that are liquefied under pressure

Common examples:

• Steam boilers and heating systems
• Compressed air systems and receivers
• Autoclaves and sterilisers
• Pressure cookers (industrial)
• Hydraulic systems
• Refrigeration systems with relevant pressure
• Pressure fryers
• LPG storage systems

Written Scheme of Examination

The cornerstone of PSSR is the written scheme of examination:

Purpose:

• Defines what needs to be examined
• Sets examination intervals
• Specifies the nature of examinations
• Identifies protective devices to be examined

Requirements:

• Must be drawn up or certified by a competent person
• Must cover all parts of the system that could cause danger
• Must specify safe operating limits
• Must be reviewed and modified when necessary

The scheme must include:

• Parts to be examined and nature of each examination
• Preparatory work needed before examination
• Intervals between examinations
• Critical aspects and measures to prevent danger
• Any additional requirements from competent person

Competent Person

L122 explains the role of the competent person:

Definition:

• A person (individual or organisation) with sufficient practical and theoretical knowledge
• Experience of the type of system to be examined
• Ability to detect defects and assess significance

Typical competent persons:

• Insurance company engineering surveyors
• Independent inspection bodies
• In-house engineers meeting competence criteria

The competent person must:

• Be sufficiently independent and impartial
• Draw up or certify written schemes
• Carry out examinations under the scheme
• Make reports of examinations
• Advise on any repairs or modifications needed

Periodic Examination

Examinations must be carried out:

• In accordance with the written scheme
• By a competent person
• At intervals not exceeding those in the scheme
• After any significant repairs or modifications

The examination must identify:

• Defects affecting safety
• Whether safe operating limits are appropriate
• Whether repairs or modifications are needed
• The date by which any defects must be rectified

Examination reports must include:

• Date of examination
• Parts examined and nature of examination
• Any defects and repairs needed
• Date by which repairs must be done
• Date of next examination required
• Safe operating limits

Safe Operating Limits

L122 requires safe operating limits to be set:

Limits typically include:

• Maximum working pressure
• Minimum and maximum temperatures
• Any other limits necessary for safety

These limits must:

• Be established before operation
• Be included in the written scheme
• Be marked on the equipment where appropriate
• Not be exceeded during normal operation

Maintenance and Operation

The ACOP covers ongoing requirements:

Maintenance:

• Pressure systems must be properly maintained
• Maintenance must ensure they remain safe
• Records should be kept of maintenance work
• Protective devices must be maintained in good condition

Operation:

• Systems must only be operated within safe operating limits
• Operating instructions must be provided
• Operators must be trained and competent
• Emergency procedures must be established

Protective Devices

L122 addresses safety devices:

Types of protective devices:

• Safety valves
• Pressure relief valves
• Bursting discs
• Pressure gauges
• Level indicators
• Temperature controls
• High/low limit controls

Requirements:

• Must be suitable for the application
• Must be properly maintained
• Must be included in the examination scheme
• Must not be adjusted to increase pressure beyond safe limits

Installation and Modification

The ACOP covers design and installation:

Design requirements:

• Equipment must be designed to be safe
• Must be suitable for intended conditions
• Must comply with relevant standards

Installation:

• Must be carried out competently
• Must not compromise safety of equipment
• Pipework and connections must be adequate

Modifications:

• Must be properly designed
• May require revision of written scheme
• Must be examined before return to service

Legal Status

L122 is an Approved Code of Practice under the Health and Safety at Work etc Act 1974. Following its guidance provides the clearest route to compliance with the Pressure Systems Safety Regulations 2000. Failure to follow ACOP provisions can be cited as evidence of non-compliance, and you must demonstrate an equivalent level of safety if using alternative approaches.

Why It Matters

Pressure system failures can be catastrophic:

The Risks

Explosive release of energy:

• Sudden release of stored pressure energy
• Similar effect to a bomb explosion
• Can destroy buildings and cause multiple fatalities

Steam and hot water releases:

• Severe burns and scalding
• Often fatal or causing life-changing injuries
• Invisible superheated steam particularly dangerous

Projectiles and fragmentation:

• Failed vessel fragments become high-velocity projectiles
• Can penetrate walls and cause distant injuries
• Pipework whip can cause severe injuries

Historical Incidents

Major pressure system disasters have shaped the regulations:

• Boiler explosions causing multiple deaths
• Compressed air receiver failures destroying premises
• Autoclave explosions in hospitals and laboratories
• Steam system failures in laundries and food factories

Consequences of Non-Compliance

For workers and the public:

• Death or serious injury
• Burns, scalding, trauma injuries
• Long-term disability

For employers:

• Criminal prosecution and imprisonment
• Unlimited fines
• Civil compensation claims
• Business closure
• Insurance invalidation

Benefits of Compliance

Following L122 provides:

• Prevention of catastrophic failures - examination detects developing problems
• Legal compliance - meeting statutory duties
• Insurance requirements - most insurers require PSSR compliance
• Business continuity - avoiding unplanned shutdowns
• Peace of mind - knowing systems are properly examined

Typical Examination Intervals

Note: Actual intervals are set by the competent person based on specific circumstances.

Key Compliance Steps

1. Identify all pressure systems - audit equipment and installations
2. Appoint a competent person - typically an insurance engineer or inspection body
3. Establish written schemes - for all systems requiring examination
4. Conduct examinations - according to the scheme
5. Act on reports - rectify defects within specified timescales
6. Maintain systems - ongoing maintenance programme
7. Keep records - examination reports, maintenance records
8. Train operators - on safe operation and emergency procedures

Further Resources

• Pressure Systems Safety Regulations 2000↗
• HSE Pressure systems web pages↗
• INDG261 - Pressure systems at work: a brief guide↗
• SAFed - Safety Assessment Federation↗

This page summarises the ACOP L122. For full legal compliance, obtain and read the complete document from HSE. This summary is not a substitute for professional advice or the full ACOP text.