A & J Mixing manufactures a variety of hoppers for feeding, intermediate storage, receivers, weigh hoppers and discharge hoppers. We have experience with a number of materials and know how in design. Hopper design has to fit the process requirements. All hoppers are modeled with the angle of repose to determine true volume. In places where height is tight, every dimension may have to be tweaked to get into the space. Sometimes we use larger valve sizes to reduce height and get enough space to install.
As a general rule, all hoppers over the mixer are funnel flow. After the mixer, some products need mass flow to prevent segregation. The shorter the drop the less elutrification segregation you will have and some additional remedies may have to be used.
There may be cleanout issues that need to be addressed. Polishing or coating with epoxy paint have a role. We have put split pipe in the corners to material will not compress in the corners and flow and clean easier. We use a UHMW milled slide over door ledges to material does not sit on the ledge.
Access is important to clean or service drop bottom mixers, and clean the hopper. We have a hinged and clamped door that does not leak, and on angles we can hinge it so the weight is supported.
We can recommend level sensors appropriate for your material. Maintenance valves are generally supplied over baggers when we have space. They are one of the items sacrificed when you have to jam into a restricted space.
Designing for the proper air exchange always is challenging. Some products leave the mixer like water, so a big surge of air has to go somewhere.
For support on load cells we like 3-point for ease of installation. Not all mixers will support on 3 points, so then we use 4. When there are load cells on the mixer, the hoppers needs a separate support. Our system is to support the mixer and hang the hopper. When there are no load cells, hoppers less than 5,000 lb. (2500 kg.) gross can hang from the bottom flange of the mixer. Heavier than that, we incorporate a separate assist.
Weigh hoppers need jacking points so you can change load cells. There has to be lifting lugs such that the hopper can be handled in the shop, loading and unloading without damage, and to hoist the hopper into place. The piece of metal in the middle keeps the hopper from tipping off short forks and getting damaged. It looks like a superfluous piece after the hopper is installed.
We have designed interfaces with various baggers. Most bagger suppliers with give us their drawings in Autocad so we can lay them in and create a proper interface. Customers who know us just give us their layout problems and say "Solve it". Know how to design hoppers is part of that.
"After talking with the mixer supplier's reps, I was impressed with how helpful and supportive they were. I also liked that they could supply both the mixer and ancillary equipment. With the new mixer, we can make two, sometimes 3 batches per hour. (in the same space). It's a huge productivity improvement."
Fred Gomez, Western Regional Manufacturing Director (Cement Products)
Most mixers are shipped on flatbeds or in containers where we pay for the truck or the container, and hoppers travel for free so freight cost is negligible.