Written Scheme of Examination For Air Compressors
Is Your Air Compressor System Legally Compliant? in the United Kingdom?
Your air compressor could be a ticking time bomb without proper inspection. If your system stores pressure exceeding a 250 bar-litre, PSSR 2000 – a set of UK regulations – requires a Written Scheme of Examination (WSE). This is not just paperwork – it protects your business, people, and all related plant or equipment.
Control Gear has made compressed air installation compliance simple since 1973. Our WSE service ensures your system meets all legal requirements while preventing costly breakdowns and dangerous failures.
Need a WSE urgently or unsure if you are compliant?
What Is a Written Scheme of Examination?
A Written Scheme of Examination is a legally required document under the Pressure Systems Safety Regulations 2000 (PSSR 2000). It is essentially a detailed inspection plan for your compressed air system that:
- Identifies all critical pressure equipment and safety-critical parts requiring examination
- Specifies how often each component must be inspected
- Details the type of safety inspection needed for each part based on complexity and size
- Must be prepared by a ‘competent person’ or inspector with appropriate qualifications
A WSE is a 'living document' that must be reviewed periodically. Any amendments are made by a competent person if your system is modified to ensure it remains up-to-date and accurate.
‘According to the Health and Safety Executive, 90% of pressure system accidents are preventable with proper maintenance and inspection regimes.’
Does My System Need a WSE? The 250 Bar-Litre Rule
A WSE is legally required for most compressed air systems. The primary test is the '250 bar-litre' rule.
The calculation is:
System Pressure (bar) × Vessel Volume (litres) = Product [bar · litres]
If the resulting number is 250 bar-litres or more, you must have a WSE. For example, a 150-litre air receiver (tank) operating at 10 bar has a product of 1,500 bar-litres, placing it well within the legal requirement.
Even if your largest vessel is below this threshold, the regulations may still apply to smaller components, like those containing steam, or if the system pressure is above 0.5 bar. It is always safest to have your system assessed by a professional.
Who is a 'Competent Person' under PSSR?
The PSSR regulations state that a 'Competent Person' must create, certify, and conduct your examinations. This term has a specific legal meaning.
A Competent Person is not just any engineer. They must have the necessary training, expertise, and practical experience to manage the risks associated with pressure systems. Crucially, they must be independent and impartial, ensuring their decisions are based purely on safety and compliance, without influence from operational or production pressures.
This individual is responsible for:
- Drawing up and certifying the initial Written Scheme of Examination.
- Conducting the examinations as specified in the scheme (e.g., thorough internal checks, ultrasonic thickness testing).
- Amending the scheme after any significant repairs or modifications.
Key Components Covered in a WSE
| Component | What is Examined | Why It Matters |
|---|---|---|
| System Pressure Vessels (air receivers, tanks) |
Internal/external condition, welds, corrosion | Prevents catastrophic ruptures |
| Safety Valves (& other protective devices) |
Calibration, operation, seals | Ensures pressure relief works when needed |
| Pressure Gauges | Accuracy, functionality | Prevents dangerous overpressurisation |
| Pipework | Connections, corrosion, supports | Prevents leaks and system failures |
| Control Systems | Function tests, safety interlocks | Maintains operational safety |
The Real Cost of Non-Compliance
Without a valid WSE, you are not just breaking the law you are risking:
- Fines up to £20,000 for non-compliance with PSSR 2000
- Insurance invalidation if accidents occur
- Production downtime from preventable failures
- Legal liability for injuries or damage
- Reputational damage to your business
‘Recent industry data shows that unplanned downtime from air compressor failures costs UK businesses an estimated £180 million annually. Many of these failures could have been prevented with proper examination regimes.’
– Control Gear
Our WSE Process: Simple, Thorough, Compliant
What is included in the WSE by Control Gear?
Typically, the inspection is undertaken by one of our qualified inspectors.
1. Initial Consultation
We start by understanding your compressed air system and operations. Our team will do the following:
- Review your current setup
- Identify system components and other safety-related equipment
- Discuss your operational needs
2. Comprehensive System Inspection
Our certified engineers conduct a thorough examination, including:
- Pressure vessel assessment (including non-destructive testing where required)
- Safety device testing
- Operational risk evaluation
- System efficiency analysis
3. WSE Documentation and Certification
We create your statutory and legally compliant WSE package, including:
- Detailed examination schedule
- Component-specific inspection requirements
- Clear, easy-to-follow documentation
- Digital and physical copies for your records
4. Ongoing Compliance Support
We do not just hand over paperwork and disappear. We also include:
- Regular re-examination reminders
- WSE updates when your system changes or amendments are made
- Digital record-keeping assistance
- Advice in accordance with the Written Scheme of Examination whenever you need it
WSE vs. Routine Maintenance: A Critical Difference
A common and dangerous misconception is that a regular air compressor service (like changing filters or oil) is the same as a Written Scheme of Examination. This is incorrect.
- Routine Maintenance focuses on performance, efficiency, and reliability.
- A Statutory WSE is a legal safety inspection focused on preventing catastrophic failure of pressure components.
While our engineers can conveniently perform both during the same visit to minimise downtime, a routine service alone does not make your system legally compliant.
Why Choose Control Gear for Your Air Compressor WSE?
Certified Expertise
- 50+ years of compressed air experience since 1973
- Fully qualified engineers with F-Gas certification
- ISO 9001, 14001, and 45001 accredited
- Specialists in air compressor regulations and all services required by the pressure systems
Worry-Free Service
Our service team handles everything, including:
- Notification when examinations are due
- Convenient scheduling to minimise downtime
- Comprehensive reports after every inspection
- Clear advisories on any required actions
No Hidden Costs
- Transparent pricing with no surprises
- Fixed budgeting solutions available
- Guardian Service plan option for 7–9 year coverage
- Coverage includes parts, labour, and callouts
Tailored to Your Needs
- Flexible service plans based on your system
- Options from full management to parts-only
- Customised examination schedules
- Solutions for any budget or operational requirement
Beyond Compliance: Benefits of Professional WSE Services
A proper Written Scheme of Examination delivers more than just legal compliance.
- Extended equipment life: regular examinations catch issues before they damage expensive components
- Improved energy efficiency: well-maintained systems use up to 30% less energy
- Reduced carbon footprint: efficient systems mean lower emissions
- Better air quality: regular inspection ensures cleaner compressed air
- Peace of mind: knowing your system is safe and you comply
Frequently Asked Questions
What is a Written Scheme of Examination for an air compressor?
A WSE is a legal document required by PSSR 2000. It is a detailed plan, created by a Competent Person, that specifies which parts of your air compressor system need to be inspected, how they should be inspected, and how often, to ensure they are safe to operate.
Do all air compressors need to be inspected in the UK?
Yes, virtually all industrial air compressors require some form of inspection. A WSE is legally mandatory if the system includes a pressure vessel where the pressure (in bar) multiplied by the volume (in litres) exceeds 250 bar-litres. All systems operating above 0.5 bar are subject to PSSR regulations and must be safe, well-maintained, and suitable for use.
What are the air compressor inspection requirements?
The primary requirement is to have a WSE in place for any system over 250 bar-litres. The scheme then dictates the specific inspection requirements, which typically include a thorough internal and external examination of pressure vessels, functional testing of safety valves and protective devices, and checks of gauges and pipework. The system must be examined by a competent person at the intervals specified in the WSE.
Can I write my own Written Scheme of Examination?
No, not unless you are a 'Competent Person' as defined by the HSE. The scheme must be drawn up or certified by a person with the necessary independence, training, and experience to assess the risks and determine the appropriate inspection intervals for your specific plant or equipment.
Ready to Ensure Your Air Compressor Compliance?
Do not risk operating without a proper Written Scheme of Examination. Contact Control Gear today to schedule your system assessment and get your WSE in place. We have been serving businesses throughout South Wales and the West, including the Cardiff, Newport, Swansea, Bristol, Stroud, and Swindon areas since 1973.
Control Gear – Your Complete Industrial Air Solution
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