What is PSSR

PSSR stands for the Pressure Systems Safety Regulations 2000 in the UK. These regulations are designed to protect workers and the public from the dangers of pressurised systems, such as boilers, compressed air systems, and gas storage vessels

• Purpose: The aim is to prevent serious injury caused by the sudden release of      stored energy if a pressure system fails.
• Scope: Applies to most workplace pressure systems, including:
  • Boilers and steam systems
  • Compressed air systems
  • Refrigeration plants
  • Pressure cookers and autoclaves
  • Gas storage vessels and pipelines
• Relevant Fluids: Covers steam at any pressure, compressed or liquefied gases,      and certain fluids kept under pressure

Definition of Relevant Fluid

A relevant fluid includes:

• Steam at any pressure.
• Any gas (compressed, liquefied, or dissolved) under pressure.
• Liquids that exert a vapour pressure greater than 0.5 bar above atmospheric pressure at 17.5°C (such as liquefied petroleum gas, ammonia, or certain refrigerants).

• The definition determines whether a pressure system is covered by PSSR.
• If your system contains a relevant fluid, you must have a Written Scheme of      Examination (WSE) and comply with inspection requirements.
• Systems with non‑relevant fluids (like water at low pressure) may not fall under PSSR.

Examples

• Covered (Relevant Fluid):
  • Steam boilers in factories.
  • Compressed air systems in workshops.
  • Refrigeration plants using ammonia.
  • LPG storage tanks.
• Not Covered (Non‑Relevant Fluid):
  • Domestic hot water systems at low pressure.
  • Closed systems with liquids that don’t meet the vapour pressure threshold.

• Written Scheme of Examination (WSE):
  • Before using qualifying pressure equipment, a WSE must be prepared by a competent person.
  • This sets out how and when the system must be examined.
• Safe Operating Limits:
  • Duty holders must establish and document the safe pressure and temperature limits of their systems

 Regular Examinations:

• Systems must be examined in line with the WSE before being operated and at      specified intervals thereafter.

 Maintenance & Instructions:

• Proper maintenance must be carried out, and clear operating instructions provided      to staff

A Written Scheme of Examination (WSE) is a formal, legally required document under the Pressure Systems Safety Regulations 2000 (PSSR). It sets out how a pressure system must be examined to ensure it remains safe to operate.

What a WSE Is

• A document prepared by a competent person (usually an independent inspection      body or engineer).
• It describes which parts of the system need examining, how often, and what      methods should be used.
• It must be in place before the system is first used.

What the WSE Must Include

• Identification of the system: details of the pressure vessel, pipework, protective      devices, etc.
• Safe operating limits: maximum pressure, temperature, and other operating conditions.
• Examination details:
  • Which parts of the system must be examined.
  • The nature of the examination (visual, non‑destructive testing, etc.).
  • The frequency of examinations.
• Preparation requirements: steps needed before examination (e.g., isolation, cleaning).
• Critical  protective devices: safety valves, pressure relief devices, alarms.

. Competent person’s signature: confirming the scheme is valid.

 How Frequency Is Set

• Written Scheme of Examination (WSE):
  • Must be in place before the vessel is first used.
  • Specifies which parts of the system must be examined, how often, and by what methods.
• Competent Person’s Role:
  • A qualified engineer or inspection body assesses the risks and sets the       examination interval.
  • They consider factors such as operating pressure, fluid type, age of       equipment, and history of use.

  Typical Intervals in Practice

• Annual (12 months): Common for many steam boilers and compressed air receivers.
• Every 24–36 months: Sometimes applied to lower‑risk vessels, depending on design and duty.
• Shorter intervals: If the vessel operates under severe conditions (e.g., high      pressure, corrosive fluids).
• After Exceptional Events: Any damage, modification, or unusual incident requires      re‑examination before reuse.

Legal Consequences

• Criminal Offence: Operating pressure equipment without a valid Written Scheme of      Examination (WSE) and inspections is a breach of UK law.
• Fines & Prosecution: The HSE (Health and Safety Executive) can issue enforcement notices, fines, or prosecute duty holders.
• Insurance Invalidity: Most insurers require proof of compliance. Without inspection      records, claims may be rejected after an incident.

Safety Risks

• Catastrophic Failure: Pressure vessels store huge amounts of energy. Without inspection, defects like corrosion, cracks, or faulty safety valves can go unnoticed.
• Explosions or Toxic Releases: Failures can cause devastating explosions, fires, or      release of hazardous gases.
• Injuries & Fatalities: Workers and the public could be seriously harmed or      killed.

Practical Impact

• Work Stoppages: Inspectors can shut down unsafe equipment immediately.
• Legal Liability: Employers and managers can be held personally responsible for negligence.
• Reputation Damage: A single incident can destroy trust with clients, regulators, and      the public.

Example

A factory operating a steam boiler without inspections risks:

• Boiler explosion due to undetected corrosion.
• Criminal prosecution of the company directors.
• Fines running into tens of thousands of pounds.
• Potential fatalities and long-term reputational damage.

In short: Failing to inspect PSSR equipment risks catastrophic accidents, criminal prosecution, heavy fines, and invalid insurance.

 A boiler explosion at the Wensleydale Creamery in Hawes (September 2024) highlighted the serious risks of pressure systems in food manufacturing. Two workers were injured, and the incident triggered investigations into compliance with the Pressure Systems Safety Regulations (PSSR). 

• Date & Location: 13 September 2024, Gayle Lane, Hawes, North Yorkshire
• Incident: A boiler explosion occurred at the Wensleydale Creamery, a major dairy and food production site.
• Casualties: Two people were taken to hospital with non-life-threatening injuries; later discharged.
• Emergency Response: Fire, ambulance, and police attended. The site was evacuated, and investigations began immediately.
• Business Impact: The creamery, which includes a visitor centre and supplies dairy products across Wensleydale, faced operational disruption and reputational damage.
•  Regulatory Context: Boilers and pressure vessels fall under the Pressure Systems Safety Regulations (PSSR 2000), requiring written schemes of examination and regular inspections by competent persons. 

 Key Compliance Failures 

• Potential lapses in inspection or maintenance: Investigations focused on whether the boiler had been examined under a valid Written Scheme of Examination (WSE).
• Risk of inadequate monitoring: Food factories often run boilers at high loads; failure to detect deterioration can lead to catastrophic rupture.
• Emergency planning gaps: The incident highlighted the need for robust evacuation and incident response procedures in food production facilities.

 Lessons Learned 

• PSSR compliance is critical: Boilers must be examined at prescribed intervals by a competent person under a WSE.
• Integration with other regs: PUWER (safe use of equipment) and COSHH (handling of chemicals/steam) also apply.
• Preventive maintenance: Routine monitoring of pressure, temperature, and safety valves prevents dangerous overpressure events.
• Training & awareness: Staff must understand the risks of pressure systems and emergency response protocols.

 Practical Takeaways for Safety Managers 

• Maintain a pressure systems register with inspection dates, examiner details, and WSE documentation.
• Schedule independent inspections well before deadlines to avoid overdue compliance.
• Audit boiler rooms for safety valve testing, pressure gauge calibration, and logbook accuracy.
• Include boiler explosion scenarios in risk assessments and emergency drills.
• Ensure contractors and maintenance staff are competent and certified under PSSR requirements.

 Summary:  A chemical plant suffered a dangerous pressure relief system failure, highlighting how inadequate design, maintenance, or inspection of relief valves can lead to catastrophic overpressure incidents. Such failures are among the most hazardous events in the chemical process industry, often resulting in explosions, toxic releases, or major fires  

 Case Study Context 

• Hazard: Closed systems in chemical plants can be subjected to pressures beyond design limits.
• Cause of Failure:
  
• Malfunctioning or incorrectly sized pressure relief valves (PRVs)
• Blocked or corroded discharge lines
• Poor inspection/testing regimes
• Damage to valve components (e.g., bellows, seals)

 Consequences: 

• Overpressure leading to vessel rupture or explosion
• Release of hazardous chemicals into the environment
• Worker injuries or fatalities
• Regulatory enforcement under COMAH (Control of Major Accident Hazards Regulations) and PSSR (Pressure Systems Safety Regulations)

 Lessons Learned 

• Design Integrity: Relief valves must be correctly sized, installed, and connected to safe discharge systems.
• Inspection & Testing: Regular examination under a Written Scheme of Examination (WSE) is mandatory under PSSR.
• Maintenance: Corrosion, fatigue, and bellows damage can silently degrade valve performance
•  Risk Assessment: Relief system failures should be included in HAZOP and FMEA studies to anticipate failure modes 
•  Emergency Planning: Plants must prepare for toxic releases or explosions if relief systems fail. 

 In November 2016, a major ammonia leak at the Carlsberg brewery in Northampton led to one fatality, one serious injury, and 20 others requiring medical treatment. The incident occurred in the brewery’s refrigeration plant and resulted in prosecution by the Health and Safety Executive (HSE) 

• Date: 9 November 2016
• Location: Carlsberg brewery, Northampton, UK
• Incident: Release of anhydrous ammonia gas from the refrigeration plant.
• Casualties:
  
• 1 worker killed
• 1 worker seriously injured
• 20 others required medical assistance
• Cause: Failures in safe planning of works involving ammonia-containing plant and equipment.
• Legal Outcome: Carlsberg Supply Company UK Ltd was prosecuted by HSE for breaches of health and safety law.

 Regulatory Context 

• COSHH (Control of Substances Hazardous to Health): Ammonia is a hazardous chemical requiring strict risk assessments and exposure controls.
• PSSR (Pressure Systems Safety Regulations): Refrigeration systems with pressure vessels must have a Written Scheme of Examination (WSE) and regular inspections by competent persons.
• Contractor Management: HSE highlighted failures in managing contractors and ensuring safe isolation procedures during maintenance.

 Lessons Learned 

• Isolation Procedures: Work on ammonia systems must include robust isolation and purging before maintenance.
• Contractor Oversight: Employers must ensure contractors are competent and supervised when handling hazardous substances.
• Emergency Preparedness: Adequate alarms, ventilation, and evacuation procedures are essential.
• Inspection & Maintenance: Regular checks under PSSR and COSHH prevent leaks caused by corrosion, fatigue, or poor design.

 Practical Takeaways for Safety Managers 

• Maintain a hazardous substances register for ammonia under COSHH.
• Audit refrigeration systems against PSSR requirements (inspection intervals, WSE documentation).
• Ensure fixed ammonia detectors and alarms are installed and tested regularly.
• Train staff and contractors in safe isolation, purging, and emergency response protocols.
• Include ammonia leak scenarios in risk assessments and evacuation drills.
• Liaise with local emergency services to ensure coordinated response plans.

 In short: The Carlsberg brewery case shows how failures in isolation, contractor management, and compliance with COSHH/PSSR can lead to fatal ammonia releases. For you, Lee, the lesson is to embed robust inspection, contractor control, and emergency planning into your compliance frameworks to prevent similar tragedies. 

 Here’s a structured case study on a Compressed Air Receiver Collapse — a classic example of why PSSR compliance is critical in industrial settings: 

• Incident: A compressed air receiver (pressure vessel) ruptured in a UK engineering works.
• Cause: Severe internal corrosion due to water accumulation and lack of drainage/maintenance.
• Failure Point: Vessel wall thinned until it could no longer withstand operating pressure.
• Consequences:
  
• Explosion-like collapse, sending fragments across the workshop.
• One worker killed instantly; several others injured.
• Significant structural damage to the building.
• Legal Outcome:
  
• Employer prosecuted under the Pressure Systems Safety Regulations (PSSR 2000).

• Failings included absence of a Written Scheme of Examination (WSE) and overdue statutory inspections.
• Heavy fines imposed, alongside reputational damage.

 Regulatory Context 

• PSSR 2000: Requires all pressure vessels (including compressed air receivers) to be:
  
• Covered by a Written Scheme of Examination.
• Inspected at prescribed intervals by a competent person.
• Health and Safety at Work Act 1974: Employers must ensure equipment is safe and maintained.
• Key Failings:
  
• No inspection records.
• No drainage routine to remove condensate.
• No safety valve testing.

  Lessons Learned 

• Corrosion is silent but deadly: Internal rusting can weaken vessel walls without obvious external signs.
• Inspection is non-negotiable: Receivers must be examined under a WSE at intervals set by a competent person.
• Maintenance routines matter: Regular draining, valve testing, and gauge calibration prevent hidden deterioration.
• Emergency planning: Collapse scenarios should be included in risk assessments and drills.

 Practical Takeaways for Safety Managers 

• Maintain a pressure vessel register with inspection dates, examiner details, and WSE documentation.
• Audit compressed air systems for:
  
• Drainage routines (daily/weekly).
• Safety valve testing (annual).
• Gauge calibration (regular intervals).
• Train staff to recognize early warning signs (unusual noises, leaks, pressure fluctuations).
• Integrate compressed air receivers into your compliance calendar alongside boilers, refrigeration systems, and lifting equipment.
• Liaise with competent inspectors to ensure statutory examinations are never overdue.

 In short: Compressed air receiver collapses are rare but catastrophic. This case shows how corrosion + missed inspections = fatal consequences. For you, Lee, the key is embedding PSSR-driven inspection frameworks and proactive maintenance into your safety systems.