Air Tank Mounting Question

[Yobyllib]

Hello,

I have just finished mounting my Firestone 9248 five gallon tank between my rear bumper and rear mounted fuel tank. I have it so that the four ports face up and the bottom 1/4" hole is facing directly towards the fuel tank where I was going to install a pressure release valve. Should I redo my mounts and clock the tank 45 degrees so that hole is pointing down and put a drain cock in it or just leave it? I will be using a Viair 444C dual compressors, will I have much water to drain?

Thanks,
Bill

[Yobyllib]

I have another question, the tank is rated to 150psi and I'm going past that. Anyone have any problems on their tanks doing This?

[BR3W CITY]

A tanks working pressure rating, and burst pressure rating are much much different. As long as you aren't planning on putting a very high pressure system through it, your usually ok. Just be wary of pressure ratings on other stuff in the system (i.e don't put 400psi through 100psi rated valves). Nitrous, C02 etc will tend to hold much higher tank/bottle pressures, but those tanks are rated waay higher. Also worth considering what the rating on a burst/relief valve is if you have one. How much pressure are you planning on running?

[Yobyllib]

I don't plan on going past 200psi in the tank itself with a 220psi pressure release valve. So just leave it as is I guess?

[Killer Bee]

not going to make any recommendations here but I'll tell you this, I wouldn't run it myself without knowing the test criteria or safety rating.. 125%, 2:1, ???

and it would seem you already have some doubt yourself based on this thread..

you have an FMVSS standard 121 air tank rated at 150psi max working and typical D2 governors are set to 135 max..

you're planning to run that system working at 135% of max rating and safety relief at 145% max rating..

things to consider; heat, condensation, cyclic duty, etc.. in other words, working it lightly or working it heavily?

my question would be, what does the compressor manufacturer recommend?

there are plenty of air tank manufacturers, anything else available with 200 psi rating that fits your application?

good luck!

[Overdriven]

Originally Posted by Killer Bee

not going to make any recommendations here but I'll tell you this, I wouldn't run it myself without knowing the test criteria or safety rating.. 125%, 2:1, ???

and it would seem you already have some doubt yourself based on this thread..

you have an FMVSS standard 121 air tank rated at 150psi max working and typical D2 governors are set to 135 max..

you're planning to run that system working at 135% of max rating and safety relief at 145% max rating..

things to consider; heat, condensation, cyclic duty, etc.. in other words, working it lightly or working it heavily?

my question would be, what does the compressor manufacturer recommend?

there are plenty of air tank manufacturers, anything else available with 200 psi rating that fits your application?

good luck!

S5.2.1.2 Each reservoir shall be capable of withstanding an internal hydrostatic pressure of 500 psi for 10 minutes.

That’s the test criteria for FMVSS tanks. What you (not you specifically but everyone in general) need to understand about tanks that hold pressure, every time it is pressurized the tank expands and contracts when pressure is released, stressing the metal. I always use the analogy of bending a paperclip, eventually the metal gets stressed enough it breaks. Not totally accurate since tanks are built to undergo these cycles many times over and are built with a safety margin.

I do hydrotesting for work and for giggles I took a 30 year old fire extinguisher cylinder that has a operating pressure of 195psi and a test pressure of 585psi and over pressurized it. The cylinder didn’t noticeably deform until just over 700psi and didn’t fail (this one split) until over 900psi. I mention this only to demonstrate the safety margin. The flip side is this same fire extinguisher cylinder needs to be hydrotested to 585psi every 12 years because every time a tank is pressurized the metal gets stressed.

My recommendation is to rotate the tank so you have a drain point. Compressing air naturally creates moisture in the system. I bought my truck with a cheap air ride system installed and a worn out compressor. The previous owner obviously used the compressor and never drained moisture out because there was no provision to do so as evidenced by the multiple sticky solenoids. I’m redoing the system currently, relocating the tank and installing a solenoid so I can drain any moisture with the push of a button. I’d rather have to replace that solenoid every so often than deal with a rusty air tank and/or sticky solenoids for my bags.

[Overdriven]

As far as the pressure goes, why do you want to run more pressure? Let’s say you’re aired out, tank at 200psi and you air up to ride height. Tank pressure will probably drop to about 150ish. If you started out at 125psi you’d probably end up around 80ish, which is basically what my current compressor switch is set to. So by running higher pressure you get maybe one more fill of the bags before the compressor kicks on.

But you’re running the compressor to a higher pressure which arguably has more downsides. Higher pressure heats the air and compressor more, creates more moisture, more stress on the compressor in general. So you run the compressor maybe half as much but each time the compressor is run it’s with more stress. The Viair 444C’s you want to run have 100% duty cycle at 100psi, duty cycle goes down to 50% at 200psi because running to the higher pressure is more stressful. Of course running 2 compressors means they won’t be running for as long but they’d still last longer at lower pressure and you wouldn’t have to worry about the tank at all.

[BR3W CITY]

Overdriven - from my experience guys usually run higher pressure for more "pop" during playtime. More pressure= faster lift if the valves can move the air.

[Yobyllib]

I have decided that I will cut off the tanks mounts I made and redesign them so the drain valve is pointing down. I will also get a different pressure switch so that it only goes to 150psi. This is what I should have done to begin with. I don't really need the extra speed or play time, probably at first once I'm done building it but when the excitement wears off I will be ok. I'm a old guy and just like to keep up with the kids these days.

[Killer Bee]

Originally Posted by Overdriven

S5.2.1.2 Each reservoir shall be capable of withstanding an internal hydrostatic pressure of 500 psi for 10 minutes.

That’s the test criteria for FMVSS tanks. What you (not you specifically but everyone in general) need to understand about tanks that hold pressure, every time it is pressurized the tank expands and contracts when pressure is released, stressing the metal. I always use the analogy of bending a paperclip, eventually the metal gets stressed enough it breaks. Not totally accurate since tanks are built to undergo these cycles many times over and are built with a safety margin.

I do hydrotesting for work and for giggles I took a 30 year old fire extinguisher cylinder that has a operating pressure of 195psi and a test pressure of 585psi and over pressurized it. The cylinder didn’t noticeably deform until just over 700psi and didn’t fail (this one split) until over 900psi. I mention this only to demonstrate the safety margin. The flip side is this same fire extinguisher cylinder needs to be hydrotested to 585psi every 12 years because every time a tank is pressurized the metal gets stressed.

My recommendation is to rotate the tank so you have a drain point. Compressing air naturally creates moisture in the system. I bought my truck with a cheap air ride system installed and a worn out compressor. The previous owner obviously used the compressor and never drained moisture out because there was no provision to do so as evidenced by the multiple sticky solenoids. I’m redoing the system currently, relocating the tank and installing a solenoid so I can drain any moisture with the push of a button. I’d rather have to replace that solenoid every so often than deal with a rusty air tank and/or sticky solenoids for my bags.

and there it is.. a spec to use for making a decision, thank you!

I consider these things because I'm in the biz of heavy junk maint and repair for about 30 years and I've seen a lot of premature failures along some things hold incredible amounts over ratings..

but as a rule, sticking to posted ratings, things tend to go a lot smoother over time.. I've worked on 7200 psi hydraulic systems that require much respect of their potential danger..

one of the hydraulic companies I worked for serviced an account in long beach that manufactured CNG cylinders..

they used hydraulic pumps to cycle the hydro testing equipment and I had a couple of opportunities to tour the facility and work on some of their machines..

destructive and non-destructive testing is what gives us a reasonable safety factor while using what otherwise could be potentially hazardous equipment, such as pressurized vessels we're talking about here..

thanks for the NDT/DT input and good luck to the OP!

[Overdriven]

Originally Posted by BR3W CITY

Overdriven - from my experience guys usually run higher pressure for more "pop" during playtime. More pressure= faster lift if the valves can move the air.

Originally Posted by Yobyllib

I have decided that I will cut off the tanks mounts I made and redesign them so the drain valve is pointing down. I will also get a different pressure switch so that it only goes to 150psi. This is what I should have done to begin with. I don't really need the extra speed or play time, probably at first once I'm done building it but when the excitement wears off I will be ok. I'm a old guy and just like to keep up with the kids these days.

I didn’t even think of playtime, probably because I want to install limiters so my truck raises and lowers more slowly and smoothly. Not into the bounce or cycling the suspension very much, but to each their own.

Originally Posted by Killer Bee

and there it is.. a spec to use for making a decision, thank you!

That was the goal with quoting the spec and my experience with tanks of similar construction. I had to resist the urge to give anything resembling a recommendation and just provide info. As you said they are potentially dangerous and you’re better off err’ing on the side of caution.