How to select knife gate, metal-seated and rubber-lined valves for abrasive slurry, tailings and process water, with the wear materials, standards and test documentation mining projects specify.
Request a Quote →A mineral processing plant moves the same material through very different services. Run-of-mine ore arrives as coarse, fast-moving feed. Grinding circuits circulate a dense, fine slurry under pressure. Flotation and thickening stages handle chemically dosed pulp. Tailings lines carry the finest solids at the lowest concentration, often over long distances. Each duty punishes a valve differently, and a valve that performs well in one is frequently wrong for the next.
Valves appear at pump and mill discharges, sump and cyclone feed lines, equipment isolation points and the tailings delivery system. Isolation valves let a pump be worked on; control valves regulate a flow that varies with ore grade; check valves protect a pump from reverse flow when a line trips. A valve selected for tight isolation is rarely right for throttling solids.
The most useful thing a specifier can supply is the line data: particle size distribution, solids concentration, carrier liquid and pH, operating and shut-off pressure, temperature, velocity and cycle frequency. Failures usually trace back to one of those inputs being assumed rather than stated.
| Valve Type | Typical Duty in Mining & Slurry Service |
|---|---|
| Knife gate valve | Coarse ore, tailings and settled-solids isolation. The sharpened disc cuts through a bed of solids rather than compressing it. |
| Rubber-lined butterfly valve | Large-diameter fine slurry and low-cycle isolation. The elastomer deforms under particle impact instead of cracking. |
| Metal-seated butterfly valve | High-solids or high-temperature slurry where rubber would tear or soften. Hard-faced trim tolerates abrasion that destroys an elastomer seat. |
| Gate valve | Clean process water, reagent and utility lines where a full-bore passage is wanted. Not suited to solids settling in the seat pocket. |
| Control valve | Thickener underflow, cyclone feed and reagent dosing where flow must be modulated. Sizing must account for the slurry specific gravity. |
| Check valve | Pump discharge protection on sump, mill and tailings pumps, sized on how quickly the disc closes before reverse flow returns solids to the pump. |
Abrasion is a wear mechanism, not a corrosion mechanism, so the decision is about hardness, toughness and geometry. Hard materials resist scratching but can be brittle; tough materials absorb impact but wear faster against fine, sharp solids. Slurry valve problems usually come from optimising one at the expense of the other.
Ductile iron with an epoxy coating is a common economical body. Stainless grades such as CF8 and CF8M are chosen where pH, chlorides or reagents make corrosion the primary concern. Hard-facing and stellite-faced trim appear where a metal seat must survive both abrasion and repeated sealing. Natural rubber and EPDM suit fine, low-temperature slurry, while NBR is used where the carrier liquid is hydrocarbon-based.
Lining is a separate decision from body material. A fully lined body and disc protects the flow path from gradual wall loss on fine slurry, but a lining can be cut by coarse particles at high velocity. Where solids are coarse or velocity is high, a heavier unlined body with hardened trim is often more durable; where slurry is fine and the valve cycles often, lining earns its cost. Seat design then follows the same logic: a knife gate with a metal seat and a scraping action copes with settled solids that would jam a resilient seat, while a lined butterfly gives tight shut-off on fine slurry but should not be asked to close onto coarse rock.
Mining buyers usually inherit a valve specification from an engineering contractor, so the standard set mixes international and project documents. The following are requirements projects specify to suppliers, not claims about our own approvals.
| Standard | What It Covers in This Sector |
|---|---|
| API 609 | Butterfly valve design, face-to-face dimensions and pressure-temperature ratings, commonly invoked for large-diameter slurry butterfly valves. |
| API 6D | Pipeline valve specification, referenced where slurry or concentrate pipelines are designed to pipeline codes and full-bore isolation is required. |
| ASME B16.34 | Pressure-temperature ratings and wall thickness for steel valves, usually the baseline for any metallic body on a mining project. |
| API 598 | Shell and seat pressure testing, including test duration and permissible leakage. This is the test most often witnessed by a third-party inspector. |
| ISO 5211 | Actuator mounting flange dimensions, so a pneumatic or electric actuator can be fitted without an adapter plate. |
| EN 10204 3.1 | Inspection certificate format for the mill test certificate, traceable to the heat number of the body and trim materials. |
On a mining project the paperwork is reviewed as closely as the hardware, because a valve that cannot be traced cannot be accepted into the plant maintenance system. A typical package contains an inspection certificate to EN 10204 3.1 covering body, disc, stem and seat materials, each traceable to its heat number; shell and seat hydrostatic test reports to API 598; and dimensional inspection records confirming face-to-face, flange drilling and actuator mounting dimensions against the specified standard.
Where an elastomer seat or lining is fitted, the elastomer grade specification with its batch reference is normally requested, since rubber is often the first component to fail. If the valve is actuated, the actuator nameplate data, mounting interface and function test record are added. Third-party inspection at the works can be witnessed before packing.
Our quality system is certified to ISO 9001, and factory audit reports from SGS-CSTC are available. Product approvals that projects require — for example API 607 fire-safe testing, ATEX or PED documentation, or a SIL assessment — are project requirements and can be provided on request for qualified orders. We do not present those as standing certifications. See our certifications page for what we hold.
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A knife gate valve with a sharpened disc cuts through settled solids and is the usual choice for tailings and coarse ore lines. A rubber-lined butterfly valve handles fine slurry where the line is large and isolation infrequent. Metal-seated valves suit high-solids or high-temperature slurry where rubber would tear or soften.
Typically a mill test certificate to EN 10204 3.1 traceable to the heat number, shell and seat hydrostatic test reports to API 598, dimensional inspection records against the face-to-face standard, and the elastomer specification with a batch reference. Third-party inspection at the works can be arranged.
Not always. Lining is most valuable where the medium is fine, consistently abrasive and the valve cycles often, because it protects the body from gradual wall loss. On coarse ore or high-solids duty a lined body can be damaged by impact, and a heavier metal-bodied valve with hard-faced trim is more durable.
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