Should I use a propane tank on my vac truck?

Question:

I had an old 1-ton truck with a 500-gallon boiler on the back. For vacuum, I tapped into the vacuum source of the truck’s engine. Well, I didn’t do this, the previous owner of the business did.

The truck got so old it had to be replaced with the new 2-ton truck that I just bought. I have a new 1,000-galllon 1/4-inch-thick steel propane tank to use for my new vacuum service truck. It’s 15 feet long and is one of the common propane tanks you see outside of small commercial businesses.

I have a fear that this tank might collapse under pressure. I will be hooking it to a Conde 70-cfm pump. Should I be bracing the sides of this tank with steel? On another note: The tank has dished ends not flat ends.

Answers:

If it’s 1/4-inch steel with rounded tank heads, the suction would most likely not make it collapse if the proper relief valves are installed.

Another issue to consider is that you will not have any internal tank baffles and your loads may abruptly shift during travel. A 1,000-gallon tank will carry 8,000 to 8,500 pounds, not including the weight of the tank itself. A 2-ton chassis would be capable of 4,000 plus or minus pounds on the rear axle. With the weight of the tank figured on top of that you’d be two to three times overweight. Not a very safe situation.

***

You would be wasting a lot of your truck’s hauling capacity by using the heavier propane tank. You would be much further ahead to buy a tank specific for the application. Then you could spec the necessary baffles and pressure/vacuum relief valves.

***

I did the very thing you’re talking about. I took a 500-gallon propane tank and shortened it up to install crossways on a truck. It was a big-time fire hazard while working on the tank. Propane tends to soak into the steel, even after a good washing. Just be careful.

***

I’m not fond of propane. It has always scared me. A friend (welding professional) put a 4-inch fitting/outlet on the end of the tank for me. The first thing we did was hook a hose onto the exhaust of my new International, and hooked the other end onto a pipe on the top of the new propane tank. We let it idle for about 20-30 minutes (until the tank felt warm to touch), and then he cut into it and welded it for me. I guess any of the propane pockets that were still inside were carried out by the exhaust. I had never heard of this before.

***

If you don’t install a baffle on the inside, you will look like a bobblehead doll at the red lights or stop signs, not to mention the dangers posed by liquid movement on curves, etc. You need to have someone in the manufacturing end of tanks give you some advice on this.