Replaceable underflow apex (spigot) for slurry hydrocyclones: wear-insert material, adjustable orifices, and reading spray versus rope discharge
The replaceable spigot at the bottom of a slurry hydrocyclone · elastomer, urethane or ceramic inserts, fixed or sleeve-adjusted orifices, the spray-versus-rope discharge that shows whether the apex is right, and sensors that report wear and roping
The apex is the narrow outlet at the bottom of a hydrocyclone's cone. Its bore sets how much water and fines leave with the coarse underflow, so wear of its lining changes the separation. Buyers therefore treat it as a replaceable insert: they choose a material for the slurry, decide between fixed spigots swapped by size and an adjustable orifice, and watch the discharge shape, a hollow spray when the cyclone is working and a solid rope when the apex is overloaded.
Replaceable apex (spigot) inserts and adjustable apex discharge ports for slurry hydrocyclones: insert materials (elastomer, urethane, ceramic), spigot ranges by cyclone size, sleeve-adjusted resilient apex bodies, the spray and rope discharge patterns, underflow water and roping, and wear and roping sensors at the apex. The geometry of the cone and apex in starch cyclones (cone angle, cone length, apex-to-chamber sizing and the cone-to-apex joint) is covered on the Hydrocyclone cone and apex page; multi-cyclone starch washing stations on the Continuous starch hydrocyclone separator page; their feed-pressure control valves on the Starch slurry pressure control valve page; drilling-mud cyclones on the Desanders and desilters page; gas cyclones on the Cyclone separator page; and slurry pump wear liners on the Slurry pump casing liners and wear parts page.
CNFX editorial research · Sources checked October 13, 2026 · 3 sources
Elastomer, urethane or ceramic spigots, and an apex whose orifice can be closed or opened in service
Weir's Cavex range shows how spigot choice follows cyclone size: the 100, 150, 250 and 400 models in fibre-reinforced plastic casings take elastomer, urethane or ceramic spigots with snap-fit replaceable liners, while the 500, 650, 700 and 800 models in fabricated steel or ductile-iron casings take elastomer or ceramic spigots with replaceable elastomer liners up to 45 mm thick. [1] Weir presents its range of spigot and vortex-finder sizes as giving operational flexibility on one cyclone body. [1]
Weir's capacity chart for the range runs from about 1 to 400 L/s across feed pressures of 40 to 300 kPa (5.8 to 43.5 psi), from the 2-inch 40CVX to the 33-inch 800CVX, and its air core booster option is said to allow a larger apex for a given water by-pass to the underflow and to reduce the likelihood of roping or blockage by tramp oversize. [1]
A fixed spigot can only be swapped for the next size. Metso's European patent application EP 3 181 233 describes the alternative: an abrasion-resistant resilient body, rubber or polyurethane, holding the apex orifice, enclosed by a sleeve with a tapered inner surface that is moved axially, or screwed, to squeeze the body and narrow or widen the orifice during operation while keeping it at roughly the same axial position relative to the head. [2] The application gives its reason: the apex lining wears in service, so a parameter that sets the separation drifts, and earlier adjustable designs changed the cone length when they changed the orifice; it adds that tensioning or twisting the body increases its wear life and evens out wear. [2]
Cavex models
Casing
Spigot options
Liner
100, 150, 250, 400 (4–15 inch)
Fibre-reinforced plastic; cast metal on request [1]
Replaceable elastomer up to 45 mm; ceramic available [1]
State the slurry, solids size and abrasiveness, the cyclone model and the spigot bore range wanted; ask whether inserts of different materials share one holder, and how a worn insert is changed.
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Spray wider than 20° or a rope of coarse solids: what the discharge says about the apex, and the sensors that watch it
FLSmidth's patent US 11,090,662 B2 describes the normal underflow as a conical spray with an included angle greater than about 20°, and roping as the condition in which solids reaching the underflow exceed what the apex can pass: coarse solids build up, the air core collapses, the discharge becomes a tight rope, and coarse material passes to the overflow; uncorrected, the underflow can block entirely and the cyclone sends all flow to the overflow. [3]
For closed-circuit grinding the same document explains that the apex is sized to limit the underflow to the solids plus no more than about 50 % water; too large an apex sends more water and entrained fines to the underflow and back to the mill, limiting classification efficiency and new-feed capacity. [3] That is the trade-off a worn, enlarged spigot drifts into, and the one an adjustable apex is meant to correct.
On sensing, the patent records that wear has been tracked with wired sensors embedded in or between liners in areas of anticipated wear, and describes wireless units with their own battery and radio, including a wafer-style wear sensor suited to the apex section where wear is expected to be asymmetric, and a roping sensor that distinguishes normal, transitional and roping discharge. [3]
Ask whether the supplier can fit wear or roping detection at the apex, what the underflow should look like at design duty, and what spigot size steps are available to correct a rope or a watery underflow.
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Data for hydrocyclone apex inserts
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Cyclone: [make, model and diameter; cone angle; current spigot bore]
Slurry: [solids type and top size; solids concentration; pH and temperature]
Insert: [elastomer, urethane or ceramic; holder or flange type]
Adjustment: [fixed sizes or adjustable apex; bore range]
Duty: [target underflow density or water split; roping history]
Monitoring: [wear sensor; roping sensor; wired or wireless]
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
What materials are hydrocyclone spigots made of?
Weir's Cavex range offers elastomer, urethane or ceramic spigots on its 4 to 15 inch models and elastomer or ceramic on its 20 to 33 inch models. [1]
Can the apex opening be changed without stopping the cyclone?
Metso's patent application EP 3 181 233 describes a rubber or polyurethane apex body squeezed by an axially moved or screwed tapered sleeve, which narrows or widens the orifice during operation while keeping its position relative to the head. [2]
How do you tell a hydrocyclone is roping?
FLSmidth describes the normal underflow as a conical spray wider than about 20°; in roping the air core collapses and the discharge becomes a tight rope of coarse solids, with coarse material passing to the overflow. [3]
How much water should leave with the underflow?
For closed-circuit grinding, FLSmidth's patent says the apex is sized to limit underflow to the solids plus no more than about 50 % water. [3]
Sources and what still needs a direct check
Sources checked 2026-10-13. Weir Minerals' Cavex hydrocyclone brochure, Metso's European patent application on an adjustable apex discharge port, and FLSmidth's US patent on wireless roping and wear detection.
