A few years ago I posted about Conrader air safety valves, and how they can safely vent air tank pressure should the pressure exceed the valve’s manufactured threshold.
That is, if a compressed air tank rises above say 100 PSI, a 100 PSI safety valve will open and release a sufficient amount of air so as to lower the tank pressure to ~100 PSI.
At the time of that post, I wrote that this was done to prevent an air tank from exceeding its recommended holding capacity.
What happens when you inflate a balloon past its holding capacity? It pops.
What happens when you pressurize an air tank beyond its rated pressure? It fails catastrophically and ruptures in a spectacular way that you wouldn’t want to witness firsthand.
Air tanks have safety air valves to prevent overpressure conditions.
But what does it do when installed to a portable air compressor? What could happen in a portable air compressor that doesn’t have one of these valves?
Why do you want to prevent overpressure conditions?
I hope you don’t mind, but I need to think aloud for a bit, meaning none of this is at 100% confidence and should be considered as my opinion and not safety advice or complete understanding of any kind.
Yes, a safety valve prevents tank pressure from building up past its recommended and tested pressures. If a portable air compressor is rated to say 125 PSI max, you don’t want that tank to build to 250 PSI holding pressure.
I don’t think it’s so much the risk of the air tank failing, as there should be a sufficient safety factor built into its specs, but perhaps other components could be more susceptible to damage?
That is, well before a holding tank bursts, what else could happen?
Let’s say that a portable compressor’s pressure sensor fails somehow, and it misses its cut-off pressure. So instead of turning off an air pump once the tank pressure reaches its max operating pressure, the pump continues to run.
Could this be a more likely danger to system failure?
Let’s say you have a inflatable device and a hand pump. The higher the pressure in the inflatable device, be it a ball, tire, or other object, the greater resistance you will feel when operating the manual air pump. The parallel would be an electric pump seeing an increased load during air compression.
If the air tank pressure isn’t accurately measured or reported by the pressure sensor responsible for turning the compressor pump on and off, then in a hypothetical situation the compressor might continue to pump and pump and pump until something else stops it. What could this lead to?
Every component of every tool has a purpose. The implementation of safety valves in air compressor tanks make sense – it reduces the tank pressure should the pressure exceed an established maximum. Navigating the WHY has been difficult. What if a portable air compressor does not have one?
How often do air compressor pressure sensors fail? It perhaps seems more likely that safety valves are mostly intended simply to help regulate the maximum holding pressure. Let’s say you operate an air compressor outdoors in winter, and it continues to fill up until it reaches temperature equilibrium. Then you take it inside. If the temperature increases several dozen degrees as the tank reaches a new equilibrium with indoor temperatures, the pressure will increase. Having a safety air valve ensures that the tank pressure, which will rise with the temperature, won’t exceed the system’s maximum rating.
There are fewer questions when it comes to standalone air tanks, where the safety valve is there to protect the tank from exceeding its maximum holding pressure rating. So am I overthinking things when it comes to portable air compressors that have an integrated air tank?
This seemed like an interesting and worthwhile topic to think about aloud. I also know some of you are experienced with industrial air compression systems, and others might have experienced product failures or even taken part in testing portable compressors to failure. I would even bet that maybe one or two readers will have surely designed or engineered one or more portable air compressors, or taken part in the development of such products.
Please share any insights or corrections you might have!
Beyond the obvious, to protect tank integrity, what other causes or reasons might there be to have a safety pressure valve installed into a compressed air tank?
Or, what could happen to the components of a portable air compressor if the tank pressure exceeds its rated holding pressure? What are all of the possible modes of failure? Might tank overpressure cause other components to fail or break much earlier and with greater likelihood than the tank bursting?
One thing that’s for certain is that I wouldn’t use a portable air compressor with built-in air tank or standalone air tank that didn’t have a safety valve.
Also, consult your user manuals and test your safety valves as recommended.
