Home Podcasts THMG089 – Cylinders, Part I

THMG089 – Cylinders, Part I

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In this episode, we lay the groundwork for our exploration of the cylinder world.

Complete Show Notes

2:40 Liquefied Gasses

  • Liquefied gasses are gasses under normal circumstances, but become liquids during pressurization at normal room temperature
  • Once they’re removed from the container, they revert back to being gasses
  • Chemicals with a vapor pressure of over 760 mm of mercury – they really want to be gasses
  • To make a gas into a liquid, drop the temperature or pressurize it
  • Examples include anhydrous ammonia, chlorine, propane, and carbon dioxide
  • These gasses all have common features like boiling points, which are always between -130 and 30 degrees Fahrenheit
  • Pressure within the container is always directly related to the temperature of the product
  • We can’t determine how much product is in a tank based on the pressure alone – the pressure is the same whether the tank is full or empty
  • If the gas or liquid is released more quickly than the chemical can vaporize, you’ll reduce the pressure

7:50 Removing Liquid Faster Than the Rate of Vaporization

  • Warm it up with a hose line
  • Use padding, which is where you take an inert gas and inject it into the cylinder – this pressurizes the cylinder and adds gas to the headspace, which pushes the liquid out
  • It’s important to know that most of these tanks are low pressure in comparison to higher pressure gas cylinders
  • We need to know what the maximum allowable working pressure (MAWP) is for the cylinder we’re dealing with
  • We can easily figure out the MAWP for different tanks – it’s stamped directly on the cylinder and is the number at the end of the DOT ID number
  • We also need to know what the relief device is and what the activation pressure is – any time we leak product, it’s a bad thing
  • Don’t ever use air to liquefy the gas if the gas you’re working with is flammable – this can create an explosive mixture within the tank

12:25 Induction/Dip Tubes

  • Cylinders contain both phases of product (liquid and gas) with available space for both
  • Induction tube allows us to pull liquid out of a container
  • Goes from the valve (assuming it’s on top of the container) to the very bottom of the container (assuming it’s vertical)
  • Liquid line goes straight to the bottom and then hooks left – this is a gooseneck tube and ensures the tube is always in the liquid space
  • Some cylinders have both valves – one goes into the liquid space, and the other goes into the gas space –
    we call this a “Y” valve, which is essentially two gooseneck tubes going in opposite directions
  • On tube trailers, you can choose liquid or gas on either the front or the rear – liquid is usually in the front and gas is in the rear
  • We need to know what we’re dealing with before we attempt any kind of offload – take the wide and close 360s and examine the valving and MAWP information closely

15:30 Non-Liquefied Gasses

  • Also known as compressed or permanent gasses
  • These gasses don’t become liquid when they’re compressed at normal temperatures – they don’t even become liquids at high pressures
  • Examples include oxygen, helium, nitrogen, argon (i.e. welding gasses)
  • You’ll see 3,000-5,000 pounds of non-liquefied gasses in some cylinders, which is way more than we see in cylinders of liquefied gasses
  • Low-pressure cylinders have wide shoulders that taper down vertically and foot rings and welding towards the bottom
  • High-pressure cylinders are bullet-shaped and don’t have shoulders or welding lines – there’s also no protection for the valving

18:50 Dissolved Gasses

  • Very unstable gasses that are dissolved for a reason
  • One example is acetylene, which can explode when it’s close to atmospheric temperatures and pressures
  • Valving on these cylinders often indicates the danger level of the dissolved gasses inside

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Author: The HazMat Guys