Vent valve issue
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We are currently working on an atmospheric pressure tank filled with ethanol. A breathing valve (PVSV) needs to be installed. When considering API 2000 standards, should we take into account only thermal expansion and contraction as well as the addition of chemicals, or do we also need to consider scenarios where the tank is exposed to fire? There is a significant difference between these two scenarios; we would appreciate some guidance from those with more experience. Additionally, what is the relationship between the liquid level (or pressure) in the overflow port (U-shaped liquid bag) of the tank and the set pressure of the breathing valve?
I have seen related posts on the storage and transportation forum regarding your question; you can go there to ask for further advice.
Thank you. In our company, it’s the people in charge of instruments who decide on the breathing valves; those in charge of containers don’t get involved until the tanks are already built. Fortunately, it’s at atmospheric pressure, so the pipe connections can be changed easily
In my opinion, nitrogen sealing and lightning protection measures are still necessary
At normal pressure, this isn’t a big deal; it’s just to balance the pressure inside the container. For media that are flammable and volatile, a breathing valve becomes very important; fire safety must definitely be taken into consideration.
“For a \"pressure/vacuum relief valve\" (breather valve), what needs to be taken into account is the amount of gas that must be released when there are changes in feed and discharge volumes as well as in temperature. In the event of a fire, if the relief capacity of the pressure/vacuum relief valve is insufficient, an additional relief outlet is required; this is what we call an \"emergency pressure/vacuum relief valve\". If a nitrogen sealing system is in place, then only \"pressure relief\" needs to be considered.
Fire protection is rarely considered; the nitrogen seal valve is filled with nitrogen, and the positive-pressure side of the breathing valve (single-exhale type) is connected to a pipe.