Cylinder Inspection, Testing and Oxygen Cleaning
Introduction to Scuba Cylinder Testing
Scuba Diving offers incredible opportunities to explore the underwater world, but every safe dive begins with reliable equipment. At the heart of this is the Cylinder — a high‑pressure vessel that must be maintained to strict standards. Regular testing is essential to ensure Cylinders remain safe, compliant, and ready for use. This guide explains why Cylinder testing matters, the legal requirements in the UK, the types of tests carried out, and how divers can keep their Cylinders in top condition.
Why Scuba Cylinder Testing Matters
Scuba Cylinders contain air at extremely high pressure, and any weakness in the Cylinder’s structure can lead to dangerous failures. Routine testing identifies issues such as corrosion, cracking, contamination, or mechanical damage before they become serious. Proper inspection and maintenance ensure Cylinders remain safe, reliable, and compliant with recognised safety standards.
UK Laws and Regulations
In the UK, scuba cylinder testing is governed by strict legislation designed to protect divers. The Health and Safety Executive (HSE) oversees these requirements, which align with European and international standards.
Key Regulations
Pressure Systems Safety Regulations 2000 (PSSR)
- All pressure systems, including Scuba Cylinders, must be kept in a safe condition.
- The regulations cover design, construction, use, inspection, and testing.
- Cylinders must be tested at defined intervals by competent, approved facilities.
Periodic Testing Requirements
- Visual Inspection (every 2.5 years):
Internal and external checks for corrosion, contamination, dents, bulges, and other damage. - Hydrostatic Test (every 5 years):
The cylinder is filled with water and pressurised to its Test Pressure to confirm structural integrity and acceptable expansion.
Approved Testing Centres
Testing must be carried out by Certified Centres following standards set by the British Standards Institution (BSI) and other recognised bodies. In the UK this is typically done by an IDEST Test Centre; ppO2 Dive Works is IDEST-approved Test Centre E6.
Marking and Documentation
- After testing, cylinders are stamped with the test date and the Testing Centre’s IDEST Stamp.
- Detailed records must be kept by the Testing Centre, and divers should retain their own certificates.
Relevant Standards and Best Practice
- BS EN ISO 18119 – Gas Cylinders. Seamless Steel and Seamless Aluminium-alloy Gas Cylinders and Tubes. Periodic Inspection and Testing
- BS EN ISO 11623 – Gas Cylinders. Composite Cylinders and Tubes. Periodic Inspection and Testing
- BS EN ISO 23434 – Gas Cylinders. Inspection and Maintenance of Valves
Enforcement and Compliance
The HSE enforces compliance with PSSR and related regulations. Diving operators and individual divers are responsible for ensuring their Cylinders are tested, maintained, and used in accordance with the law. Failure to comply can result in penalties and, more importantly, serious safety risks.
What Happens If a Cylinder Fails or Is Neglected?
A Cylinder that has not been tested, maintained, or stored correctly can become extremely dangerous. Failures can be catastrophic.
Types of Scuba Cylinder Testing
Visual Inspection
A detailed internal and external examination to identify corrosion, contamination, dents, bulges, or other deformities. This is the first and most frequent line of defence.
Hydrostatic Testing
Required every five years (depending on local regulations). The cylinder is filled with water, pressurised, and observed for leaks, etc..
Eddy Current Testing
Used mainly for aluminium cylinders, especially around the neck area, to detect cracks using electromagnetic fields. I do not currently offer this service.
Ultrasonic Testing
Uses sound waves to detect internal or external flaws, including corrosion and cracking that may not be visible during a visual inspection. I do not currently offer this service.
The Testing Process
- The Boot and any Decals on the Cylinder are removed
- The Cylinder is externally assessed for damage and corrosion
- The Valve is removed using a special jig to ensure that it is not damaged
- The Stem Threads (the part that is screwed into the Cylinder) and the Outlet Threads (where you screw your DIN Regulator into the Valve) are cleaned
- Once clean, all Threads are checked with a Go Gauge, and a No Go Gauge. If there is a fault with the Threads they are duly inspected
- In the case that the Valve passes the Go/No Go gauge test, it is then dismantled and put into an Ultrasonic Cleaner to clean all the parts
- The Cylinder is placed on a bench and inspected internally with a Drop Light and a Borescope, inspecting the base, walls and the inside of the shoulder for damage, corrosion, or anything abnormal
- If Hydrostatic Testing is required, the Cylinder is filled with Water to the Test Pressure (150% of the Working Pressure) to check for deformation, leaking etc.
- The Valve is washed in fresh water, dried and reassembled with new O-Rings and white Teflon Rings
- The Valve is then screwed into the cylinder and made “hand tight.” It is then torqued to the correct setting
- The Cylinder is stamped with the IDEST Centre’s unique stamp (E6), and is then Stickered to show when it is next due for Service, and which Service is due
If a Cylinder Fails
A Cylinder, or Valve, that fails any part of the testing process must be removed from service. Depending on the severity of the defect, it may be condemned and destroyed. Any Cylinder or Valve that is condemned will be destroyed and the Customer will not be allowed to leave with it. A suitable alternative will be offered for purchase, and the Diver may also provide their own replacement, but these will be subject to the usual Inspection and Testing regime prior to reassembly. Divers should never attempt to repair or use a failed Cylinder or Valve — doing so could result in serious injury or death.
Tips for Maintaining Your Cylinder
- Regular Checks: Look for visible signs of damage between official inspections
- Proper Storage: Keep cylinders pressurised above ambient, and in a cool, dry environment away from direct sunlight and corrosive conditions
- Valve Care: Keep Valves clean and capped when not in use
- Professional Servicing: Always use Certified Technicians for Servicing and Testing