By Kadir Yılmaz, founder of ZENES Makina Mühendislik (20+ years in the foundry industry)
What is the best way to convey sand in a foundry?
Green sand is almost always moved on belt conveyors and bucket elevators. Dry new sand and reclaimed resin sand travel better in dense-phase pneumatic lines, which are cleaner and easier to route. Hot, lumpy return sand from shake-out goes on vibrating conveyors. The right choice comes down to moisture, temperature, distance and hourly throughput.
Systems and typical figures
| System | Sand | Typical throughput | Notes |
|---|---|---|---|
| Belt conveyor | Green or dry | 10–200 t/h | Belt 500–1,000 mm, max incline 15–18° |
| Bucket elevator | Green or dry | 10–150 t/h | Vertical lift to mixers and silos |
| Vibrating conveyor | Hot return sand, lumps | 10–100 t/h | Under shake-out, before metal separation |
| Screw conveyor | Dry sand, fines | 2–30 t/h | Short runs, metering |
| Pneumatic, dense phase | Dry new or reclaimed sand | 2–40 t/h | Up to 200–300 m, low velocity, low wear |
| Pneumatic, dilute phase | Dust, small sand volumes | 1–10 t/h | High velocity, fast bend wear |
Typical ranges; actual figures vary by plant and supplier.
Belts and bucket elevators
In a green sand plant the sand loop runs on belts and elevators: shake-out, magnetic separator, screen, cooler, silo, mixer, moulding. Belts are simple and cheap, but watch sand temperature. Standard rubber belts break down above roughly 60–70 °C; for hot return sand use belts rated to 120–150 °C. Every transfer point loses sand and makes dust, so enclose the chutes and connect them to extraction.
For elevators, choose bucket material and chain or belt type for the abrasiveness of the sand. Green sand sticks in buckets, so discharge speed and bucket shape matter.
Pneumatic conveying
Sand is loaded into a pressure vessel and pushed down the pipe with compressed air. In dense phase it moves slowly, as plugs, so pipes and bends wear less and grains don't break. The pipe can run along walls and roof trusses, freeing the floor space a belt line would take.
The limit is moisture. Bentonite-bonded green sand will block the pipe, so pneumatic conveying is not used for it. Typical jobs: new sand from the delivery silo into the plant, reclaimed sand back to mixer silos, feeding the core shop.
Air demand sizes the compressor and rises with distance, lift and the number of bends. A dedicated compressor and dryer for conveying usually causes fewer problems than tapping the plant air line; wet air makes sand stick in the pipe.
Selection criteria
- Moisture and temperature: green sand on belts, dry sand by pneumatic or belt, hot sand on vibrating conveyors or heat-resistant belts.
- Throughput: peak hourly demand of the mixer and moulding line, plus 20–30%.
- Route: distance, lift, bends, free space in the building.
- Wear: silica is abrasive. Use ceramic- or basalt-lined bends on pneumatic lines and wear-resistant scrapers on belts.
- Dust: tie transfer points and silo vents into a filter.
- Maintenance access: belt tensioners, elevator boot cleaning, pneumatic vessel valves should be easy to reach.
From the field
Sand conveying is often the last thing anyone thinks about. The mixer and moulding machine get chosen, the conveying is left for later, and the line ends up needing 40 t/h from an elevator that moves 25. The same happens with used plants: the machines get moved, but the belts and elevators were sized for the old building and half of them don't fit the new one. Draw the new layout before you dismantle.
Used conveying equipment: checklist
- Belts: thickness, tears, splices; pulley lagging and idlers.
- Elevators: bucket and chain wear, pulleys, take-up at the end of its travel?
- Vibrating conveyors: springs, motor bearings, cracks in the trough.
- Pneumatic: vessel valves and seals, pressure vessel certificates, wall thickness of bends.
- Pipework and steel structure: will it fit the new building or need refabrication?
- Controls and sensors: level probes and speed monitors working?
FAQ
Can green sand be conveyed pneumatically?
In practice, no. Moisture and bentonite block the line. Use belts and elevators.
Does pneumatic conveying break sand grains?
Dilute phase does and creates fines. Dense phase runs slowly and breakage is low.
How steep can a sand belt run?
On a flat belt sand slides back above about 15–18°. Steeper routes need an elevator or a cleated or sidewall belt.
How much space does it need?
Belt systems need floor and structure. In a tight building a pneumatic line along the walls and roof saves space.
Related
- Listing: USED-1894 Omega Sinto USR reclamation with pneumatic conveying
- Listing: USED-1943 automatic sand preparation and distribution system
- Listing: USED-1955 shake-out and sand separation
- Guides: Continuous resin sand mixer, Foundry relocation, Choosing a sand mixer
How ZENES helps
We draw the whole sand loop on one layout, from shake-out to silo and from mixer to moulding. We calculate throughput and route, pick belt, elevator or pneumatic, and supply new or used equipment. When we relocate a used plant, we resize the conveying for the new building.
