Decreasing Unload times for Pneumatics

I never ever EVER start a plastic load w/anything but the FIRST hopper.

Where the bottom line routes from the pressure control valve, the elbow is a big source of heat (every time air turns in those pipes it gets a bit hotter). Put 15,000lbs of plastic pellets on top of a metal valve (that is also getting hot as the air passes it) and one is asking for angle hair and it's also possible to get a large chunk of plastic to block the valve when you open it.

Not saying those are a given, but just more probable from starting w/the 2nd hopper on a plastic load.

On a plastic load, I go #1, #2, clean #1, #3, clean #2, #4 until it's empty, clean #3. Pressure control is wide open, top air is half-way, and the product valve is about 7/8ths open (about 5 o'clock if you think of it as a watch face).

 

Yea, right. 16 minutes of 27 tons of product

I'd like to see how you guys do that. It takes our best drivers 35 minutes to unload at the local cement plant. But the tallest silo is 100' tall . I need at least 10psi or I may plug up. So weather or not I have my 14' hose or a 7' hose isn't really going to matter much.

 

15 to 20 minutes is doable unloading into a pig or a railcar if they let you go crazy. 45 minutes to an hour is about right at a ready mix plant with cement. Class C flyash into the place I run to about 4 times a week is 1 hour 15 minutes.

It all depends on the place.

Have you ever pumped bottomash back up into a boiler? It takes freakin' forever. Hours. At this power plant we service, there's one boiler where the hose is around 100' and then a 90 degree turn to a pipe that goes straight up to the fifth story. 6.5 hour pump for 20 tons. Any little hiccup and everything clogs. Bottomash and bedash are also magnetic or something, and they clump up on the pod valves, blocking them. Every few minutes you have to go wiggle the pod valve and shake the stuff loose. At night, it's pretty neat because you can see the electrical arcs from the ash going through the metal joints of the hoses.

 

Yup! That's how I was taught and how I taught my students. Those lubed [Mobil b/4 Exxon merger] just flew, he vacuum loaded 48K in 35min. Since he did multiple trips every day he got away with the occasional 'christmas tree ornament' clumped in top of #1. He just brought it back to the yard and bought the railyard lunch to pay them for for getting it out. There were a few of them inside the trailer.

I used the hot unloading line as a seat while watching my trainees un-load in those cold NE winters.

 

Crystal Polystyrene was bad about fusing, 14-15 lbs pressure and you would get "clunkers" as we called them. I always unloaded front to back.

 

My average was 17.5 minutes (for cement), but everything went perfectly that day. I had 27 tons of Portland type I/II gray cement, courtesy of Cemex, and unloaded it into an empty pig (which was connected to the plant's dust collector) at the "pug mill" for Lone Star Infrastructure in Austin, TX. This was back when they were building TX 130 (the toll road).

I had a short hose, and it made one nice, gentle, constant bend from my discharge pipe to the inlet pipe on the pig, which was hooked up to the plant's dust collector system. My hose never touched the ground while connected.

I pressured up to 15 PSI, opened the jet line one notch, opened #3, and let 'er rip. I then opened #2 halfway, which is as much as I could do without plugging up.

Once #3 was below the aerators, I shut it off, opened #1 all the way, and left #2 halfway open. Once all three pods were empty, I pressured up to 15, left the jet line closed as I opened all three for cleanout, then I stopped the blower and let the residual pressure escape into the pig (customers loved me b/c I never kicked up dust by opening the blowdown valve when there was still pressure in the tank).

I just kept 15 PSI in the tank, and kept the jet line right on the verge of plugging up.

 

does your way work with sand too?

 

I don't know.

I've only hauled one load of sand, and it was back when I first started pulling a pneumatic. Back when I was scared to have more than 12 lbs of pressure in the tank...

 

Its my firm belief that if you ask five different people how to unload you will get 7 different answers. With Buesing the times differ depending on the product, the trailer and the restraints of where you are unloading. I've started keeping an excel spreadsheet for all the different loads, and using lbs per minute to compare to. Something as simple as the size of the load will either shorten or lenthen the unload time. Generally 90 to 120 minutes is a general average for me. At no time have I run over 12lbs basically for safety reasons. I've seen it at Long Lake where a tank pop-off valve was tested during regular service, and it didn't work. I like to give myself a little safety buffer.

 

Another thing that will add to unloading times is how far do you have to blow the product. I've unloaded plastic pellets right next to a short silo and unloaded 45000# in 20 minutes. That same 45000 would take up to an hour if you had to go through 100 ft of pipe and then to the top of a 2 story silo.