I’ve seen articles on unloading centreflow hoppers like Athearn make but never seen anything on Airslides. Can anyone help please? Pics please?
For the centreflows I understand that a pressure difference is created across the bottom of each bay that “sucks” the load out. Is that right? As far as I recall the siding needs the appropriate pipework and a pumphouse - and that’s about it.
Um… is it? What’s with “Pressureaid”?
So; anyway… I’m wondering whether Airslides need much more (and what it looks like). Do they get unloaded under cover or indoors? Does the air system have accumulators or run with straight air?
First off, my training is bulk Cement with a Heil or Butler trailers for semi trucks. We would pressurize these things to about 14 PSI and then open a pot to force the product which mixes with air to form a sort of fluff that flows to the silo. There is a balance act. Too much air, take too long to empty product. Too little air, you plug pipe up and force hours of beating on silo to clear it (If it happened to be raining, forget it because your product will harden putting the plant out of service for the day)
If a trailer pot is almost dry we hammer with a rubber mallet (Gently as the steel or aluminum is still under 14 PSI load) to get that last little bit out. At the end of the first pot and to the end of the middle to last pot, the trailer will start to “Sing” as it moves mainly air trying to get the last few hundred pounds out.
At the cement plant in Hope Arkansas, they run two bay covered hoppers under the silo. Under the hopper and rails are a chute that captures the cement and raises it up to the silo to dump to truck next to the track which is also a scale.
On that covered hopper is a giant man portable vibrator. On the bay hatch at the bottom of the covered hopper will vibrate the product down and out into the chute.
There is alot of shaking going on to get the product out.
At Grace in Baltimore at the seaport, they bring in Cement by ship. They pipe the powder straight to chute with a very large pipe and one hell of a air system. Eventually little trucks get the cement dumped out into their tanks or back up to a bag house to take away bagged product on pallets.
In other plants they will simply convey the cement to silo to ship out by truck or rail.
Airslides are special. You can put… I suppose a food product in it and force air in between the PRODUCT and the sides of the covered hopper to make it slide. Remember I spoke of tanker truck by MIXING air with the product inside the tank before forcing it all to flow out t
From what I understand, Airslides have a liner, and air is blown in between the liner and car body to agitate the load and get it to flow out.
A standard centerflow hopper has no special unloading requirements. CenterFlow was just ACF’s trade name for their center-discharge design that featured side sills instead of a central sill, like most other hoppers did at the time, with paired discharge outlets on either side, or outlets that joined back together to discharge below the main sill. These are used for just about any generic bulk commodity.
Pressuraid is ACF’s brand name for their pressure-unloading covered hoppers. These look like just like other centreflow hoppers, but with all the piping manifolds at the bottom. The load is moved out of the car using direct air pressure/flow. These are used for finely powdered commodities.
A third variation is a pneumatic unloading hopper like the type used for plastic pellets, where the outlets are basically hose attachments on the bottom of the hopper bay and the load is basically vacuumed out of the car. These are typically used for plastic & resin pellets.
Love the stuff on cement. I worked at a Lafarge site for a time weighing the trucks going out and another place I saw the tankers (road) unloading blowing their powder loads about 60’ up into the silos. I always dreaded a high wind tipping them over when they were rammed up to full tilt… I guess the drivers knew what was safe. [%-)] The times for unloading are especially interesting.
I wonder how many others never had a clue about the construction of airslides. That’s really interesting.
More please [:)] Especially any pics or links please [:)]
the airslide system uses a fabric liner in the bottom of the car through which air is blown to sort of liquify the commodity and make it flow better for unloading. this is used primarily with dry powder items like flour, starch, cement, etc.