Pressure Vessel Testing

 

PJ Edwards cc is a Type A testing facility with ISO 17020 accreditation Through SANAS.


We have been testing seamless cylinders for the last 16 years without incident.


Cylinders we test are;

Oxygen cylinders, both medical, aviation and industrial.

Compressed gas cylinders for nitrogen, air, helium, &c.

Diving SCUBA and SCBA cylinders.

Carbon Dioxide fire extinguishers.

Carbon Fibre cylinders.


Amongst our vast capabilities are, ultrasonic thickness testing, Sustained Load Crack (SLC) detection, ultrasonic and chemical cleaning. meet the requirements of HM220 and the requirements of Luxfer Gas Cylinders for inspection of 6061 alloy cylinders

Understanding Scuba
Cylinder Inspections















The major reason for having your cylinders visually inspected, once a year or more, is for your safety in handling and breathing from them, as well as those individuals who fill them. Complete and thorough cylinder system inspections are serious business, not just a quick peek in a tank! If you believe your last one was, you need to find a competent repair facility and have it done properly with a documented checklist from a certified inspector.

Air quality pumped from a compressor should be odourless and colourless for breathing. My first dive shop was located in the Chicago suburbs in 1972, next to a Swedish bakery. It had an 18.5 cfm Worthington compressor which we filled AGA tanks to 5,000 psi. Our air smelled great the first few days and later went sour. Although breathable, we had to add a charcoal filter and run the compressor after baking hours.

Periodic compressed air testing is important to your health and welfare and is conducted by independent labs. This same air filled in your cylinder may contain contaminants, oil or oil vapour, moisture, carbon monoxide and odours. If you want blended nitrox mixes, the air needs to be of a higher quality, requiring additional filters and the removal of solid and gaseous hydrocarbons. Synthetic high grade food oil, such as CF-2000, conforms with the FDA for nitrox use.

A cylinder system inspection overview includes preparing it for an initial informal inspection, followed by a detailed formal check list evaluation. This list is used to identify flaws, errors, omissions and damage to the external and internal portions of the tank, including the valve. Depth of pitting and the amount of rust and corrosion can cause the cylinder to be condemned and removed from service. Neck cracks, damaged or missing threads to the cylinder can cause catastrophic failure at the time of filling.

Although aluminium cylinders made of 6351- T6 alloy (prior to 7/1988) need an eddy/Foucault current test for neck thread cracking at time of hydro (CFR requirement), it has been a standard of the diving community to eddy current test aluminium cylinders yearly.











Note: Steel cylinders never have neck cracks but still need to be visually inspected for corrosion, cross threading and missing threads. Eddy current tests only work on aluminium tanks.


Following are the basic steps involved with most cylinder system inspections:

•Fill out an inspection form including: cylinder serial numbers, manufacturer, material code, first hydrostatic test date. Remove tank boot and any other attachments.

•Ask questions about the customer’s tank, amount of use, last visual if not labelled and if there are any problems or if the tank was drained empty on a dive.

•Do a cursory evaluation of the outside of the cylinder and valve for any damage, whether the tank is empty, odour when opening the valve and anything rattling around inside.

•Look for fire damage, bulges, dents, dings and newly painted tanks.

•Heat treating aluminium tanks causes them to explode upon filling.

•Check the ease of opening the valve, removing the valve, inspecting the threads and changing the neck and face "o" rings.

•If you can have the test facility the valve for you and Look inside the cylinder for contaminates, rust, corrosion and pits. Smell it for odours when the valve is off.

•Valve safety assembly must be changed at time of hydro and the burst pressure should be checked for being compatible to the tanks rated working pressure.

•Final filling will be considered a leak test for the neck "o" ring and valve safety.

•The final disposition evaluation of the cylinder will state Condemn (scrap), Reject (repair before use) or Acceptable. If it passes the inspection, a completion (EOI) evidence of inspection sticker, showing the date inspection, will be placed on the cylinder for easy identification.

The industrial and medical gas industry has strict rules to follow for care, filling, handling and transporting high and low pressure cylinders, some of which are hazmat rated. Dive facilities need to understand that, although they deal with recreational and technical filling of cylinders, they are under the same scrutiny and safety standard as if they were a welding gas supplier. The DOT (Department of Transportation) approves the manufacturing of high pressure cylinders and how they are transported, while OSHA (Occupational Safety Health and Administration) is an agency of the United States Department of Labour which issues and enforces standards for work place safety and health.SANAS oversees, accredits, develops and promotes safety standards and safe practices in the industrial and medical gas industry.

Cylinder inspections require over 25 or more evaluation considerations. This is not a five or ten minute process. From the time a cylinder comes into a facility and is finally picked up after fill testing, it may take as long as 30 minutes, not including any cleaning, tumbling and valve repair.

Remember that once-a-year tank inspections were based on the average new diver doing around 10 to 15 dives a year. If you are diving more than that, or using nitrox mixes, you should consider having an inspection every six months. Facilities using their tanks daily should do them quarterly.