Explain the maintenance and inspection that should be carried out on SCUBA cylinders.(10)
Maintenance and Inspection of SCUBA Cylinders (10 marks)
1. Visual inspection (annual or as per regulations)
- Each cylinder should be visually inspected internally and externally at least once a year (or as required by flag-state or manufacturer).
- The inspection checks for corrosion, dents, mechanical damage, bulging, heat damage, and internal rust or pitting.
- The valve should be removed, and the interior inspected with a light and mirror or a borescope.
2. Hydrostatic testing (every 5 years typically)
- Cylinders must be hydrostatically pressure-tested at intervals specified by the relevant authority (commonly every five years).
- This test confirms that the cylinder can safely withstand working pressure without excessive permanent deformation.
- The test pressure and date are permanently stamped or labelled on the cylinder shoulder after a successful test.
3. External cleaning and protection
- The outer surface should be cleaned of salt deposits, oil, or corrosion products.
- Paintwork should be maintained to prevent corrosion, and protective mesh or boot covers should be fitted to reduce abrasion.
4. Valve maintenance
- The cylinder valve should be periodically removed, cleaned, lubricated, and inspected for damage or corrosion.
- O-rings and sealing washers should be replaced regularly using oxygen-compatible lubricants and materials if used for enriched air.
5. Internal cleaning and drying
- Any signs of internal rust, oil, or moisture should be removed by washing with an approved cleaning agent and then thoroughly dried.
- The cylinder must be kept dry internally to prevent corrosion.
6. Checking cylinder markings and identification
- Ensure that the serial number, test dates, working pressure, and gas type markings are legible.
- Cylinders must not be used if markings are missing or unclear.
7. Leak and pressure checks
- After filling, the cylinder should be checked for leaks at the valve, neck threads, and burst disc using a leak-detection solution.
- Pressure gauges should confirm the correct fill pressure within safe limits.
8. Correct filling procedures
- Cylinders should be filled slowly to avoid overheating.
- Only clean, dry, and oil-free air should be used from a certified compressor system to prevent contamination.
9. Storage and handling
- Store cylinders upright, secured, and away from direct sunlight or heat sources.
- Avoid dropping or striking cylinders and ensure protective caps are fitted to the valve during transport.
10. Record keeping
- Maintain records of visual inspections, hydrostatic tests, and maintenance work in accordance with regulatory requirements.
- Cylinders that fail inspection or testing must be clearly marked and removed from service.
✅ Summary (for examiner marking guidance):
Marks are awarded for mentioning annual visual inspection, hydrostatic test, cleaning and corrosion control, valve and O-ring maintenance, pressure/leak checks, correct filling, storage precautions, and record keeping — all contributing to safe operation and compliance with standards such as BS EN 1968 / ISO 6406 or equivalent.