Inspecting Cylinders – Beyond the Hydro

by Don Kinney:
visual inspectionThe primary rule affecting the inspection of high pressure cylinders in the United States is the U.S. Code of Federal Regulations (CFR) 180.205. This section refers to the hydrostatic requalification of cylinders, but also mentions that during this requalification, a visual inspection must be performed. The hydrostatic requalification may vary amongst high pressure cylinders, but a common time frame is every five years. This infers that a cylinder gets a visual inspection every five years, even though cylinders may be exposed to safety concerns countless times within a five year cycle.

Scuba diving organizations, being aware of these hazards, encourage annual visual inspections of cylinders. The National Fire Protection Association (NFPA) 1852 ( requires an inspection of the cylinder at the beginning of each duty period. The Occupational and Safety Health Administration (OSHA) requires that each employer ensures that gas cylinders are safe, which can be determined by a visual inspection (1910.101(a)). None of these rules or regulations explain what to look for during these visual inspections. How can a person know what conditions are considered a safety risk?

A proper high pressure cylinder visual inspection course will show a user/inspector what conditions are acceptable and what conditions could be dangerous. The course also helps guide the user/inspector on what the next steps are to ensure safety. Each type of cylinder has unique characteristics which must be monitored to ensure its structural integrity.

steel cylinderSteel cylinders are common in most industries. They include storage, fire suppression, scuba diving and compressor systems. They are susceptible to moisture from their storage environment and need to be closely monitored for issues of corrosion. These cylinders are also commonly transported from location to location and have specific safety protocols; such as attaching caps during transportation and being properly secured during use.

Composite cylinders are light weight and handle greater pressures than their solid metal counterparts, but that does not mean that they can handle the same type of environment or abuses. Users/inspectors must pay close attention to cuts and gouges, as even a small cut can render the cylinder condemnable. They also respond differently to impact damage, which might not be easy to detect without proper training. These cylinders also are highly susceptible to chemical exposure and a minor incident involving a chemical might condemn a composite cylinder.

abrasionAluminum cylinders are common in the beverage, scuba diving and medical industries. Aluminum is softer than steel, but the walls on the aluminum cylinder are manufactured with a thicker dimension than steel or composite. Even with these thicker walls, aluminum cylinders are prone to cuts and gouges which may render them unsafe . Some aluminum cylinders also require specific testing during a hydrostatic requalification and a closer inspection of the threads before continued use.

Cylinders are exposed to extreme conditions on a regular basis, thus it is recommended that they are inspected more frequently than every five years. Some of these exposures may make a cylinder unsafe long before it is due for it’s next hydrostatic requalification. A cylinder inspection course will train the user/inspector on the unique characteristics of each type of cylinder and how to recognize potential dangers before they become dangerous hazards.

Don Kinney
High Pressure Cylinder Inspecting Instructor

Interested in International Training Visual Inspection Course? Get more info here >

11 replies
    • Don Kinney
      Don Kinney says:

      we do have an on-line component for people to review the material before the class if they desire. However this course requires hands on and class participation. It is also an interactive course giving the student the ability to speak with a trained instructor asking specific questions. We have a number of trained instructors in the states and internationally. I would be happy to refer you to the most convenient instructor in your area, or I am sure you can set up a class and possibly have them travel to you if you help sponsor a program.

  1. Barry A. Farley
    Barry A. Farley says:

    Glad to see something more in depth on the site about this class. Don has trained my entire aquatics staff in cylinder visual inspection / valve repair for several years now. I can recommend this class without hesitation for any facility that deals with high pressure cylinders on a regular basis. The safety edge you gain with this class cannot be substituted with guesswork. Barry Farley / Head of Aquatics / Cirque du Soleil “O” / Bellagio Hotel

  2. Chris wilkinson
    Chris wilkinson says:

    In Australia, other than general care and maintenance of the outside of your cylinder, I.E. fixing paint chips addressing external corrosion etc, any cylinder deemed to have been used for SCUBA purposes has to have a full hydro plus visual inspection every year. This shortens the life of the cylinder but has reduced the incidence of cylinders failing while in use, stored full in a hot garden shed, or the back of a Ute.
    The pressure cycling from this also saw the compulsory fitting of overpressure burst discs “Safety relief” to all of our cylinders. When they let go it frightens the poop out of you but won’t (easily) kill you like a rupturing cylinder might.
    These rules are mainly trying to protect the poor mug who has to fill your empty cylinder!!! Because if its going to cut loose thats when the most stress is on them as they heat up and expand as they are filling ( Advice:- Always get someone else to fill your cylinders).

    Emergency response, Fire and rescue SCBA cylinders, not used underwater have a five year inspection regime. Fibre wrapped cylinders also have a 15 year maximum life, (last time I checked).

    Part of the reason for these rules goes back in history when an air fill was an air fill for keen scuba divers and hydrocarbon contamination and a low dewpoint were not high on some suppliers agenda. This resulted in unacceptable internal corrosion and spectacular failures for some owners and and resulted in the surge in popularity of aluminum cylinders. Because despite the increased size, extra weight and buoyancy issues for the same quantity of gas they have a much greater resistance to corrosion.
    I think I’ve rabbited on long enough here hope you found this interesting, its about as useful as an ashtray on a motorbike if you don’t live in Australia but!!!
    Chris W

    • Alex
      Alex says:

      Many of us would like to know of a specific instance where a steel cylinder failed “spectacularly” causing people to switch to aluminum. Please post a link to a news article, post a photo, or give us a name of someone who was injured by a steel cylinder that ruptured.

      • Chris Wilkinson
        Chris Wilkinson says:

        Sorry I’m unable to show any pictures of the damage caused by cylinders failing. I only got to optic them myself, although there are a few cylinders I have condemned over the years that surprised me that they hadn’t already failed in service.
        The images I was shown were pre digital (35 mm) taken by Government ‘Work Safe’ Inspectors Who investigate incidents of this type. They were shown to me by the ‘QAS’ (‘Quality Assured Services’, formerly ‘Australian Standards’) examiner whilst I was being tested to become a licensed Hydro station manager and signatory (seamless steel, Aluminium and fibre wrapped cylinders). I think the photos were there to reiterate the dangers posed by storing that much energy in a small space if the containment failed.
        Of the failure photos I was shown standing out in my mind clearly are two. The cylinder that ruptured in the back room of a Karratha residential house (North West Australia, where the men are men and the sheep are nervous!), there was nobody home at the time and this particular brand of cylinder had no rupture disc either. When it let go it took the whole back wall of the house with it. The other was at a filling station in a dive shop; the cylinder had failed whilst filling to normal pressures in a water filled concrete tank used for cooling whilst filling. The tank was demolished and so was a significant part of the dive shop, stuff ripped of walls the ceiling had come down…; miraculously the operator filling the tank received only minor injuries but was left dressed in only the elastic waistband of his underpants as all his other clothes had been ripped of him. We were also shown photos of various cylinders after they had failed but none in situ.
        Sorry I can’t be more helpful.

        Chris W

  3. Vossie Vosloo
    Vossie Vosloo says:

    Hi Don,

    I would like to a full cylinder inspection course. Im in Mozambique where we don’t havenan authority to do inspections here and visual and hydro inspections are done from SA.


  4. Robert
    Robert says:

    i was part of the beta program for this class and it far exceeded my expectations and exceeded the training I received from a different inspection authority. Don does a great class and would recommend this to anyone.

  5. Philippe Yersin
    Philippe Yersin says:

    I took the instructor course with Don in December in Jensen Beach. I really enjoyed the program. I have been teaching a VIP class from a different training organization for a few year and really enjoy the format of the course Don has put together. In as little as 8 hours, you will learn Rules and regulations, Hydrostatic Testing, Cylinder Inspections, Steel, Aluminum and Composite cylinders, Cylinder Cleaning, Fill station and compressors, Safety and Records and Liabilities. The format of the class is great, made of classroom presentations and workshop. The course comes with a well written student manual and a handy knowledge quest workbook. I teach the class in Florida.


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