I have a 7-gallon tank which has a maximum limit of 200 psi. I am running dual 400c compressors with a pressure switch that cuts off at 146 psi. The only safety valves I could find locally were 150 psi and 200 psi so I had to go with the 150 valve to avoid exceeding the tank max spec. I fully expected the 150 valve to blow when I got above 140 but surprisingly it has held all the way up to 146 psi and not popped off yet. I read somewhere that the valves have a tolerance of +/- 10% so that could make it popoff as low as 135 or as high as 165. Looks like in my case it must be set high unless it is set at 150 and just extremely accurate.
So my question: do I need to replace it with a slightly higher safety valve, maybe a 165 or 175? Do they even make safety valves in these odd increments? What is the typical accuracy tolerance for most air gauges and safety valves?
Yes they do make safety valves in 175 psi, I have never seen them in 165. As for their accuracy, I have never had a problem with mine and my tank is a 200 psi rated with a burst pressure of 450psi and has a 235psi safety valve. I have done some tests with my tank at a local machine shop before installing my tank and when pressure hits around 233psi the safety lets loose. So from my perspective, I can say they are accurate.
That’s considering i have stuff in place to help eliminate tank rusting, valve failures and wrong pressure readings. System checks are good. Dont wait for a problem to arise before dealing with it. Preventative maintenance is key.
Just dont go past the pressure rated for your compressor becasue it will damage it sooner or later.
Then on the tank itself there is a warning label which says never to exceed the pressure gauge limit of 140 psi, which is as high as the gauge will read. And then the same label goes on to say that you should only fill the tank with a low pressure system that has an upper limit of 90 to 120 psi. And then the safety valve which is built on to the tank is set to blow at anything above 110 psi. So it is not clear what the real limit is for the tank. I replaced the gauge with a unit that reads up to 160 and I replaced the safety valve with a 150 psi unit and filled the tank to 146 psi and it works fine. My compressors are dual Viair 400c units so they are rated to work up to 150 psi so I assume all is well, but I worry about the safety valve being too close to the pressure cutoff switch value. And I wonder if the aluminum tank is going to hold up. Another big warning sticker on the aluminum tank says “do not drop” which I assume means that it could burst or explode if hit or dropped. How to determine the true rating and safety of everything?
for starters, a single port tank isn’t the best thing to use in a horn system, second, a steel tank is more reliable, and third, the ratings on a tank are below its burst pressure.
to be safe, never pressurize a tank beyond its max rating.
I can understand why a multi-port tank may be better for a multi-horn setup but I don’t see the improvement on a single horn setup. When sounding the horn the air is only going one way: out of the tank and into the horn. The other taps on the line for compressors, pressure gauge, and safety valve are not stealing air from the main flow while the horn is sounding, and in fact the compressors are increasing the air flow when they kick in, so I don’t see any benefit to extra tank ports for a single horn. With multiple horns you should still be able to use a single port tank without losing performance as long as you have a large enough manifold and airlines to support double the airflow compared to the single horn install. Am I missing something here?
Also, can you elaborate on why a steel tank is “more reliable”? I can see it being more durable than aluminum, and maybe it would handle higher pressures, but both tanks should be equally reliable in that there isn’t much they can do to fail if kept within the stated ratings.
The extra ports are for a safety valve, drain, & guage. The only thing that seems to missing from your system is a tank drain because it will need to be drained occasionally.
I’ve heard a steel tank will hold up better over time and is less like to rupture from some form of impact and that’s all. There’s nothing wrong with using an aluminum tank.
I have the safety valve, drain, and gauge connected to a manifold on the tank output. They don’t consume or restrict airflow so they are not limiting the flow rate or volume which is available to the horns, thus the single port tank should not be a constraint in my setup. If I later install a second horn then I will just increase the diameter of the main air manifold and line to feed both horns as needed.
I know the tank drain is normally on the bottom of the tank but my tank is quick and easy to remove so I will just pull it out, tip it over, and open the drain on the manifold once every few months.
I was concerned about the aluminum tank bursting but if I am in a wreck that bad then I will have other things to worry about. I would actually expect the aluminum tank to hold up better in my scenario since it won’t rust internally like steel tanks do, and thus the air lines will not get the rusty moist air flow which you will find on steel tank setups over time.
The main reason I used an aluminum tank, though, was because I wanted it to be lightweight for when I remove it to blow up tires and work outside of the vehicle. It is a LOT lighter than comparable steel tanks and no worries about external rust either. I just need to strap it in with a bungee and it should be good for the road.
when and if a aluminum tank explodes it will explode creating shrapnel a steel tank will just burst not fly in to a bunch of pieces…
2 that tank has one specific use and thats transporting air ti fill 30-50 psi a tire… its not ment for constant use of filling in a air system… when i first did my air system i was cheap but i would never use a tank like that i bought a 18 wheeler air brake tank.
