Pneumatic 101

When they say 10psi, I figure line pressure. And while it sounds backwards, yes, more line pressure and less tank pressure. By doing it this way, you are not forcing the product out of the tank, just pushing it through the line faster. If you try higher tank pressure, you are forcing more product out of the tank at a faster rate, only to be run into a 4 or 5 inch pipe that can only handle so much.

For unblocking, the worst one I've seen involved removing the pipes on the bottom and dumping them out. Messy job and one to avoid (thankfully it wasn't me). If I block up bad, and have to suck it back into the tank, here's what I do:

Leave blower running as normal
Close product valve.
Close aerator valve, sending all air to the line. Sometimes this alone will unblock it. If not, proceed as follows.

Open blow down valve. Drain tank pressure to near zero.

Go to rear hopper, or any empty hopper, and open and close product valve repeatedly until the blockage is removed. When you open it, the line pressure will drop. The trailer will bounce, this means you are now sucking material back into the trailer. Every time you close the valve, the line pressure will rise until the blockage is removed.

The whole process can take a few seconds to a few minutes.

Easisest way to avoid blocking is don't be in a hurry.

 

Yep I sit in the truck now and watch the hose and listen to my blower. Half of our trailers gauges don't even work.

 

In the winter when we haul nothing but lime, I usually fall asleep unloading. The trailer wakes me up when a hopper goes empty

 

I love blower work in the winter. The lines keep my hands warm

 

I miss tank'in sometimes. Blowin sand was fun

 

FYI most of these tanks are designed for 15psi mawp. The pop off valve is supposed to be set for 14.7psi. Be very careful, doesn't take much pressure to cause serious hurt or death

 

Cement is easy. I can usually hold 15psi in 1200cub and be done in about 35 minutes. Get to the more powdery stuff such as fly ash or lime kiln dust we can do it in under 30. Unloaded cement in Arkansas one time that I could do in under 30. Of course it was blown in to an elevator that emptied in to the silo rather than pushing all the way up the silo. Most of the small tanks I've ran in to don't have top air. We only have top air on our big tanks for packing down hydrated lime.

 

In regards to plugs. With cement its usually simple. I close my product valve and open my line air. It's fluffy enough you can usually push it through. If not close all your aerators and dump your tank pressure and then start opening and closing your back hopper valve in 3 second intervals in hopes you can pull the plug back in to the hopper. When line pressure hits zero with the product valve closed you're unplugged. You will learn your tank. Then it will be like second nature and you may even start talking to it. When it talks back is when you should get alarmed.