Home Podcasts THMG091 – Cylinders, Part III

THMG091 – Cylinders, Part III


In part three of this three-part series, we conclude our discussion of cylinders.

Complete Show Notes

2:45 High-Pressure Regulators

  • Most regulators are specific to certain Compressed Gas Association (CGA) valves in terms of classification
  • CGA takes gasses with similar characteristics and defines relationships between valves and the chemical-physical properties of a cylinder’s contents
  • Standard regulators have 4 parts: 2 gauges and 2 knobs
    • Gauge closest to the cylinder gives you the pressure inside the tank
    • Second gauge gives you the working pressure
    • Knob between the two gauges controls the amount of product going into the system
    • Other knob controls the pressure the product wants to reach once it’s flowing

4:45 Labels and Markings

  • These will be hard-stamped into the cylinder
  • If you’re dealing with a rusted cylinder, use a piece of paper and a pencil to make out the label
  • First line of information (similar to a VIN number):
    • Identifying information
    • Codes that tell you what the cylinder is made of – this is important because it helps you determine compatibilities and how the cylinder will react
      • There’s close to 100 different recipes out there for creating cylinders – check out the CGA or look it up on Google
    • Maximum allowable working pressure (MAWP) information is next to the material stamp
  • Keep an eye out for hydrogen – if you see an “H,” it means the cylinder’s metal is designed to hold hydrogen
    • Hydrogen embrittlement – when hydrogen is placed under pressure in the presence of carbon steel – the hydrogen actually goes into the metal and makes it crack
    • Because hydrogen is the smallest element, it can easily slip into different metals – it gets through atoms and shears the bonds between them, which contributes to embrittlement
    • You might see this in homes – people are trying to generate hydrogen and use it to live off the grid
  • Second line of information:
    • Serial number
      • Includes manufacturer abbreviations and symbols
    • Series of dates
      • These start off with the manufacturer’s inspection date and also include the hydrostatic test date – most cylinders are tested every 5 years
      • If you see a star, it only has to be tested every 10 years – some symbols allow the cylinder to be tested even more infrequently

14:30 On-Scene Evaluations and Questions to Ask

  • Questions to ask yourself and others:
    • What was the mechanism of injury?
    • Why were we called today?
    • Is it on fire? If so, what kind of heat is involved? How bad is it?
    • What’s in the cylinder? Are the contents attacking the cylinder?
    • What type of metal is on the inside of the tank?
    • Did the pressure relief device go off? Is it currently going off? Is it stuck because it’s going off?
    • What’s the general structural integrity of the tank? Are there any scratches, dents, gouges, scrapes, or rust (all referred to as “insults”)? Are there welding issues?
    • What are the manufacture and hydrostatic dates? If you don’t have the hydrostatic date, you don’t know the cylinder’s structural integrity – you can also assume the tank wasn’t well taken care of
    • Where is the cylinder leaking? If it’s leaking where the valve connects to the tank, there’s really nothing we can do – don’t try to tighten it down, because it’s leaking for a reason and we shouldn’t mess with it
    • Can we cap or plug the threading area to stop the leak? This may not be your best option if the tank has been illegally converted
    • Will opening and re-closing the valve solve the problem? In many cases, the valve isn’t working because something small is keeping the valve from closing the whole way – letting some air out can get rid of this obstruction
    • Is the packing nut snug? If it’s tight, you won’t be able to open or close the valve – it just needs to be leak-proof
  • If your department doesn’t have a temp gun, go buy a cheap one ASAP – doesn’t have to be top-of-the-line
  • Don’t run the cylinder down to zero – leave 10-20% of pressure inside the container to “save” it from damage since you may be keeping it
  • Cylinders can last for a long time (only a few have a 25-year life expectancy) – for the most part, cylinders can last almost indefinitely up to the 100-year mark

26:10 Containment with Cylinder Coffins

  • Giant cylinder that you put the problematic cylinder into
  • Designed specifically to hold a leaking cylinder
  • Some gasses can’t be used with a cylinder coffin
    • Acetylene is too unstable – there’s no packing in cylinder coffins, which is problematic and unsafe
  • Once the cylinder is in the cylinder coffin, you can evacuate it in a controlled manner – valving on cylinder coffin is specifically designed to offload the product
  • Several types of cylinder coffins out there – they’re all designed to hold specific chemicals that have their own specific chemical-physical properties
    • Types of cylinder coffins include stainless steel and carbon steel
  • Most industries have their own specific cylinder coffins set up for their own emergency use – identify where these are so you’re prepared

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