Home Podcasts THMG033 – Propane II

THMG033 – Propane II

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In this episode, Bob and Mike conclude their discussion of propane by reviewing common mitigation techniques.

Complete Show Notes

00:35 Uses for LP Continued

  • Hardware or camping store – keep in mind that they sell tiny propane tanks
  • Stand-by generators – two types available: waiting to kick in or connected to a fuel source
  • Regardless of which type you’re dealing with, problems can occur when people go to use these since they’re not used that frequently

2:00 Propane Transportation and Use as Fuel

  • LP can be transported/delivered via trains, over-the-road trucks, and ships
  • While not nearly as popular as an LNG truck for transportation vehicles, there are some vehicles out there that run on or are augmented by propane
  • Tanks can vary in shapes and sizes to fit certain vehicles – common thread is the valving and the collar/protection devices that are around the tank
  • We should be able to identify these vehicles because, according to NFPA 58, these vehicles must have a diamond-shaped label
  • These tankers have shut-offs right on the tank and generally will vent out and away from the vehicle

4:20 Common Areas of Failure

  • Although these tanks are usually quite robust, there are some common areas and weaknesses where they can leak from
  • Large or bulk tanks are very thick and generally take decades to rust out, but it can happen
  • Don’t try to stop a tank leaking oil in a basement – do a proper size-up, realize the age, and let it drip into a pop-up pool
  • Threads
    • Everything that’s attached to the tank is done via threads, which are common leak points on all tanks – including LP tanks
    • Because these tanks are always outside and exposed to the elements, rain seeps into the threads and can cause rust
    • This slowly eats away the threads and creates a path for the pressurized gas to start to escape
    • There’s nothing we can do to fix this – we might be able to ice rag it if the flow is great enough, but small leaks are almost impossible to stop
  • Weld Points
    • These are areas where the sheets come together – they tend to oxidize and rust
    • These leaks generally start as pinholes and can really only be detected by something like a metal oxide indicator
    • While your PID will pick this up, there’s lag time because most PIDs have to pump air through the tubes
    • it’s also an issue because the contraction is so small in the areas that even at 1 or 2 PPM, it’s really difficult to locate a leak
    • One of the best methods for pinpointing the leak is to use soapy water
  • Valves
    • These are simple mechanisms, but they can leak every now and then
    • One way to mitigate this is to cap the valve – no fuss, no mess
    • This is a great reason to keep a set of reverse threaded caps of different sizes in your toolbox
    • Make sure to double-check around the stem of the valve for a bubble – sometimes the valve stem has gone bad and doesn’t show itself until the valve has been capped

14:55 LP Metering Options

  • We’re pretty limited in terms of metering devices that can pick up LP – you’ll mainly be working with your PID, LEL, and metal oxide
  • Metal oxide is great at picking up small changes in the amount of product that’s present – but if you take this sensor into an atmosphere with a lot of product, it would quickly become overwhelmed and rendered useless
  • PID has limited usefulness when searching for a tiny leak because of the lag time and limited amounts we get back – PID is good to quantify low levels in an atmosphere, but not great at searching
  • LEL is the weapon of choice when you’re dealing with large quantities of LP in the air – quantifying the buffer we have between us is must-have knowledge

17:00 Action Levels and Defensive Operations

  • When we’re inside, our action level is 10%
  • When you reach 20% action level, it’s time to get out of there
  • 20% is also the regular action level when we’re outside
  • Your defensive operation is controlling the product away from the release – don’t let anyone mingle with the product
  • If you need to get someone out of an area where there’s an LP leak, you have to act quickly
  • Technicians take care of offensive operations by going in and trying to mitigate and stop the problem
  • Life is always the priority here, so evacuation should be at the top of our list

19:55 Hazmat Drill Nugget from HazSim

  • Review and drill on your NIOSH handbook!
  • Review NIOSH definitions in the front of the book – study abbreviations and terms and quiz your coworkers
  • Use it as a NIOSH/resource drill – pick a chemical and provide information about chemical to coworkers; their job is to identify it and figure out how they’d respond

23:50 Dealing with Leaks

  • There’s really no major difference between small and large leaks – always be thinking about where the vapors are going and whether they’re dangerous to people
  • Always secure the scene and set up a hot zone – use your meter to determine if an area needs to be closed; if you don’t have a meter, use the distances in the ERG (Emergency Response Guidebook)
  • Determine if you can eliminate sources of ignition
  • Try to move the vapors from the area
  • A lot of these techniques require in-depth knowledge of propane – you should always be training and learning so you’re prepared
  • It’s essential to have a good working knowledge of the tank to be able to size up the damage and know your limits you’re working with

27:30 Mitigating LP Issues

  • Transfer
    • Pumping isn’t commonly handled by hazmat because we don’t have the lines and pumps to hold that pressure
  • Burn off
    • There are three kinds of vapors:
    • Pole burn off (most common)
    • Barrel burn
    • Cap and burn kit
  • Water injection
    • If you have a liquid leak at the bottom (or a low point) of the tank, you can put water into it – then, it leaks water
    • This option isn’t usually the best choice because you need specialized equipment
    • Includes things like pressure gauges and flow gauges
    • It’s important to be able to monitor pressure once you’ve mitigated the LP leak – you don’t want to overfill a tank and cause larger issues than you already have
    • Flow gauges help you determine how much water you’re putting into the tank – it’s important to create a situation where the water going in equals the water coming out
    • Better to underflow and adjust than to overflow and have a larger issue
    • Try using a fitting to adapt the water hose to the tank
  • Freeze plug
    • Based on the fact that a compressed gas (or liquefied compressed gas) will pull a tremendous amount of energy from its environment to change states
    • Take a wet rag and apply it to the vapor leak – as the temperature drops, an ice dam will form
    • This is a short-term technique – if you slow the leak down, there are no more evaporations (and therefore no more “cold”) being produced – this means your ice dam will melt, and the process will start again
    • This method doesn’t work well with liquid leaks because the power of the vapor at the leak creates the ice – if the liquid doesn’t evaporate until it’s out, the container does us no good
  • Additional mitigation methods
    • Fiberglass wraps – you can buy wraps that can stop vapors up to 200 psi
    • Plug a relief valve – this isn’t a great idea, because the relief valve is already doing its job – we just have to figure out why it went off
    • Over packing a drum – definitely don’t do this

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