Written Scheme of Examination (WSE) for Compressed Air Systems Over 250 Bar-Litres
Written Scheme of Examination (WSE) for Compressed Air Systems Over 250 Bar-Litres
If you operate a compressed air system in the UK, it’s crucial to understand your legal responsibilities under the Pressure Systems Safety Regulations 2000 (PSSR) — especially if your system stores more than 250 bar-litres of compressed air.
In this article, we explain what a Written Scheme of Examination (WSE) is, when it’s required, and how Airmass Limited can help you stay compliant, safe, and operational.
🔧
What is a Written Scheme of Examination (WSE)?
A Written Scheme of Examination is a legally required document that outlines:
Which parts of your pressure system must be examined.
The frequency and type of inspections required.
The scope of the examination.
Who is responsible for carrying out the inspection.
This scheme must be prepared or certified by a competent person, as defined in the regulations — someone with sufficient knowledge, training, and experience to assess the risks of a pressurised system.
⚠️
When is a WSE Legally Required?
A WSE is mandatory if your system exceeds 250 bar-litres of stored energy. This includes most compressed air systems with:
A pressure vessel (such as an air receiver).
Pressure and volume that, when multiplied, exceed 250.
📐 Example:
If your air receiver has a capacity of 50 litres and operates at 6 bar pressure:
50 litres x 6 bar = 300 bar-litres
→ A WSE is required.
Even if your system runs below 20 bar pressure, it’s the total stored energy (bar × litres) that triggers the requirement.
🛠️
What Does the WSE Inspection Involve?
A qualified inspector will:
Review the layout and pressure components.
Identify which items need examination (e.g. air receivers, safety valves).
Define how and when each item should be inspected.
Carry out the examination to identify wear, corrosion, or safety concerns.
Provide a report of findings, actions required, and compliance status.
✅
Why a WSE is Important
Legal compliance: Avoid fines, enforcement, or system shutdowns.
Insurance: Required by most commercial insurers.
Safety: Prevent equipment failure and serious injury.
Reliability: Detect issues before they cause downtime.
👷♂️
Airmass: Certified to Carry Out WSE Inspections
At Airmass Limited, we have an in-house certified competent pressure inspector qualified to carry out Written Scheme of Examination inspections in accordance with PSSR 2000.
We provide a complete service, including:
System assessments to determine if a WSE is needed.
Preparing or reviewing your WSE documentation.
Performing statutory inspections on air receivers and safety equipment.
Issuing reports and compliance certificates.
No need for third-party involvement — we handle it all, quickly and professionally.
📞
Contact Airmass Today
If you’re unsure whether your compressed air system requires a WSE, or you’re due for an inspection, get in touch today. Our team is ready to help you stay compliant and avoid unnecessary risk.
📞 0151-909-5573
📧 sales@airmass.co.uk
❓
FAQs
Q: What if I don’t have a WSE and my system exceeds 250 bar-litres?
You could be in breach of UK law and at risk of enforcement action by the HSE. Insurance claims could also be denied.
Q: Can Airmass inspect and certify my system?
Yes — we have a certified competent pressure inspector on staff and can carry out the full inspection process.
Q: How often is a WSE inspection required?
Typically once a year, but the exact interval will be defined in your WSE based on system type, usage, and risk.
🧾
Need Help? Let Airmass Take the Pressure Off
Whether you’re setting up a new compressed air system or maintaining an existing one, Airmass provides expert support to ensure you’re safe, legal, and running smoothly.
📞 0151-909-5573
📧 sales@airmass.co.uk