In This Article
- 1.Knife Gate Valves - The Mining Standard
- 2.Pinch Valves - No Metal-Slurry Contact
- 3.Rubber-Lined Butterfly Valves for Tailings
- 4.Abrasion-Resistant Material Selection Guide
Mining slurry - a mixture of crushed ore, water, and chemical reagents - is one of the most demanding valve services in industry. Particle hardness (copper ore at Mohs 4-5, silica at Mohs 7, iron ore at Mohs 5-6, gold ore at Mohs 6-7), high solid content (30-70% by weight for dense media separation circuits), and abrasive particulate loading create valve wear rates that are measured in weeks rather than years for conventional valves.
Knife Gate Valves - The Mining Standard
Knife gate valves are the workhorse of mining slurry isolation. The design - a flat gate (knife) that slides vertically through the flow path - provides a full-bore opening when open (no obstruction) and a self-cleaning wiping action as the gate closes through the slurry. Key features: one-piece welded fabricated body (not cast) for full-bore opening equal to or greater than pipe bore; hardened gate (AR400 or AR500 abrasion-resistant steel, or SS 316L for corrosive slurry) with wear-resistant WC (tungsten carbide) edge overlay for knife edge durability; packing flush water connection (water seal above packing prevents slurry from entering the stem packing); DN100-DN2000 size range - much larger than any other valve type; AWWA C520 standard for slurry service knife gate valves.
Pinch Valves - No Metal-Slurry Contact
Pinch valves (sleeve valves) achieve throttling and isolation by externally pinching a flexible rubber sleeve (tube) - the slurry never contacts any metal valve body or mechanism. The rubber sleeve is the only part exposed to the slurry. This makes pinch valves ideal for highly abrasive, corrosive, or contamination-sensitive slurries. Natural rubber sleeves provide the highest abrasion resistance for coarse mineral slurry. Polyurethane sleeves provide better resistance to sharp particles and ozone. EPDM sleeves for alkaline slurry (pH 8-12). Pinch valve limitations: limited pressure rating (typically PN10-PN16 maximum for open-body pinch valves); temperature limited to sleeve material rating (natural rubber to 80°C); DN50-DN600 typical range; not suitable for very high-differential-pressure throttling (sleeve collapses asymmetrically and wears rapidly).
Rubber-Lined Butterfly Valves for Tailings
For larger bore tailings pipelines (DN400-DN1200) and distribution header isolation, rubber-lined butterfly valves (AWWA C504) provide an economical full-bore isolation option. Requirements for tailings service: ductile iron body with natural rubber or polyurethane lining (disc face, seat, and body bore); actuated with torque-override gearbox (tailings compact on the disc face during static periods, creating high breakaway torque); bidirectional seating for discharge manifold service; replaceable liner (full body liner and disc liner replaceable without removing valve from pipeline).
Abrasion-Resistant Material Selection Guide
| Slurry Type | Recommended Valve | Lining Material | Notes |
|---|---|---|---|
| Copper ore tailing (pH 7-9) | Knife gate or rubber BFV | Natural rubber NR | Coarse angular particles |
| Gold/silver cyanide leach | Knife gate or rubber BFV | EPDM or NR | Alkaline cyanide pH 10-11 |
| Iron ore concentrate (dense) | Knife gate or pinch valve | NR or polyurethane | >60% solids by weight |
| Coal slurry preparation | Knife gate or rubber ball | NR or polyurethane | Coal dust and water |
| Phosphate slurry | Rubber-lined BFV or pinch | NR with FRP body | May contain H3PO4 traces |
| Dense media (heavy liquids) | Knife gate full-bore | A350 LCC with WC edge | FeSi dense media at 3.0 SG |
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