A Common Misconception

“It’s hard to flare liquid propane in a tank that has been water injected.” 

    By: Ron Huffman, 06/05/2021

Whether you’re conducting a training evolution or on an actual incident, if the propane tank has water in it, you’ll need to remove the water prior to liquid flaring operations. If you don’t, you’ll most likely freeze your system up with ice and not be able to flare the tank.

Just like freon, ammonia and a few other products, as propane passes through an orifice to a lower pressure area it gets colder (flash or auto-refrigeration [i]). That orifice can be the opening in the tank or the valve in your flaring system. As the propane exits the tank and flows towards your flare and atmospheric pressure it’s auto-refrigerating. An easy way to identify where this begins is to look at your system and see where frost starts forming. In extremely low humidity climates, the use of a TIC (Thermal Imaging Camera) or infrared thermometer can help identify the point where auto-refrigeration starts.

NOTE: It’s not recommended to use a bare hand due to the extreme cold (as cold as -44F).

Auto-refrigerated propane mixed with water in your system means that your lines and/or flare will lock up and need to be thawed before you can continue, but there is an easy remedy. You must remove the water prior to flaring operations. During our class evolutions (Propane Response – 101 to Advanced Tactics[ii]) we must remove the water that was just pumped in. We’ve done this for years at every class with multiple evolutions. If you do it correctly you’ll never freeze a line or your flare.

So, then the question is how do we do it correctly?

The first issue is managing where the water starts to freeze. It’s really quite easy, first maintain full tank pressure to the release point. Next, have nothing beyond the release point that can trap the water and any created ice blocking the flow (I recommend the use of a ball valve). Also, it’s best to reduce the distance that the propane and water must travel together as much as possible. Depending on your location it may be necessary to utilize a handline to disperse propane vapors during this operation.

  1. Slowly release/vent the water in the tank to the atmosphere.
  2. When propane starts to escape with the water stop the release of water. Allow the water to gather and open the valve slowly again. When propane starts mixing with the water again, close the valve, allow the water to gather and open the valve slowly. Continue this process until all of the water has been removed and just propane is released when the valve is opened. 
  3. Open the valve fully and verify that all the water has been removed. There will still be moisture in the system, but if done correctly there will not be enough water to freeze the system closed. If you suspect that you may still have water in the system, install a valve at the base of your flare and close it enough to maintain tank (or back) pressure up to the flare. That way if you do have a freeze up it will be easy to identify and hopefully remedy.

Once all the water has been vented to atmosphere it will be safe to connect your flare lines and begin your liquid flaring operation. As I stated above, it’s really quite easy. But if you do lock up your system just thaw everything and start again.

And feel free to call me if you have any questions. Ron Huffman, Owner/Senior Instructor, Responder Training Enterprises, LLC. www.respondertraining.com

[i] https://en.wikipedia.org/wiki/Flash_evaporation

[ii] https://www.respondertraining.com/propane-response-101-to-advanced-tactics/