Can't keep pressure in pneumatic

I need some time today to ponder this problem.

Was the stuff wet? Raining maybe at all?

There are bolts up top for the hatch I think 7 of them. You didnt by chance loosen any of them a little bit to make trailer easier to seal shut?

My thoughts are reaching towards the three trailers recent shop history if any, check valve problems possibly and so on.

What about the two pumps, did you blow it off your truck engine blower or did you run off the Plant Blower?

Were you unloading with the rear pot first? Or trying to unload front pot first?

The last question is somewhat of a *Doh kind.. don't be offended...

Are you being too conservative in feeding the air to the discharge line? Assuming line pressure is lower than tank pressure, the tank will start draining PSI and your line does not have enough air pressure to flow until both are too low to move product.

You follow?

 

I'm assuming you're talking about pebble type limestone?

Literally the only thing I've ever found that worked with pebble lime is top air. I hauled it for two years, I'm by no means an expert though. Don't open all three hoppers with pebble. The air goes between the pebble and causes the pressure loss.

I used aerators to pressurize the tank initially, then maintain the pressure with top air. One hopper at a time, regulating the pressure with the line valve. Speaking of which, check where the line pressure gauge gets its air from.. follow the air line from the gauge to the pipe. If it's attached to the pipe before or above the line valve, it gives false readings. We have several trailers like that..

I'd only open one hopper at a time, usually because the places I unloaded at had some convoluted piping that could only make an engineer smile, and the Pope swear. It usually took me an hour to an hour and a half to unload 26 tons, depending on the silo and how it was piped.

The last thing I'll leave you with is this. While line and tank pressure is important, it's not always the best way to unload. High pressure is good for some things, and not good with other things. I look for constant flow at the discharge hose. A hose that's whipping around violently is not a good thing. It should move a bit, but if it's jumping around alot, it's on the verge of blocking up.

 

I have not met a silo pipe that was able to pull vacuum. You can almost lose a cigarette pack up there if it managed to catch it. To me thats a happy silo. Or rather a very HUNGRY one.

 

I accept your thoughts. Ive moved limestone in powder out of Bettenger PA off 30 three times. Otherwise it's Cement out of Limekiln or Blue Circle Baltimore. And later in Hope AR and fly ash out of Redfield.

The hose in my opinion as long it snakes and I can stand on it feeling the product move nicely Im happy, not necessarily violent. I should not have used that word.

Now that you are talking pebble as in rocks where you can leak tank air (Maybe you need that top air to get that rock out ....) Areoators for sure on those. Shake em out.

That is a product outside of my experience. If I had both gauges falling while trying to unload pot of rock, I probably would back off the line discharge and constantly feed tank air. But that also would be combined with constant trips to the hose to see if it's moving product by feel through the boots.

A plan B would be to allow the rock to move pull tank air from 16 down to 9 and wait a moment to get back to 16 then continue. It might be a little more than a hour.

 

Another thing with pebble, gravity does much of the work getting it out of the tank, assuming it's not a side discharge.

Take a funnel. Put some stones in it, and then try pushing the stones out. Chances are you can't. But just shake said funnel a bit, and they work their way out.

Same principle with your trailer.

 

So a plan c would touch the pot shakers now and then. Hopefully once it flows tank pressure should get back up.

 

Umm, any idea what size pebbles we're talking about? I've unloaded smaller pebble, up to 1/4 inch, and some miserable stuff that could be 1 1/2 inch.

Unloading the two required a different mindset. The bigger it was, the slower it went it seemed.