Cartridge Seals for Pumps, Mixers and Process Equipment

Fitting errors are a common cause of early mechanical seal failure: wrong installed length, dirt on faces, damaged elastomers or uneven gland tightening. A cartridge seal removes most of those steps by delivering the faces already compressed and aligned. The setting clips (or tabs) hold the position until the seal is bolted up, then are moved clear so the faces can float.

Cartridge designs are common on standardised process pumps, on equipment built to API 682 and on many mixers and agitators. They also help where maintenance teams change seals frequently or where fitters vary in experience. The trade-off is a higher unit price than loose components and a design that must fit the pump's chamber and gland envelope. Where only the wearing parts need to be replaced and the metalwork is reusable, Component Mechanical Seals may be an alternative. The wider category overview is on our Mechanical Seals page.

Single cartridge seals

One set of faces with the sleeve, gland and drive collar integrated. Suited to many clean or lightly contaminated services, often with a simple flush from the pump discharge.

Double cartridge seals

Two seal sets in one unit, used with a barrier or buffer liquid. These are typically considered where leakage to atmosphere must be controlled or the liquid is hazardous, abrasive or prone to solidifying. They require a supply system, covered under Seal Support and Supply Systems.

Back-to-back and tandem layouts

Back-to-back double seals pressurise the barrier above process pressure. Tandem layouts use an unpressurised buffer between seals. The arrangement you need depends on the duty and any plant or site standard.

Gas-lubricated cartridge seals

Dry gas versions use a gas barrier and grooved faces to run without liquid contact, and are used mainly on compressors and certain mixers. They need correct gas supply and technical review.

Mixer and agitator cartridges

Designed for vertical shafts, often with larger shaft diameters, lower speeds and top-entry or bottom-entry mounting, sometimes with dry-running capability.

Split cartridge seals

Split designs can be installed around a shaft without dismantling the driver, useful for large or hard-to-access equipment. Fit accuracy depends on careful assembly and the split mechanism.

Cartridge seals combine the same face and elastomer choices as other mechanical seals, with additional metal parts for the sleeve and gland. These are typical options, not rules. Always confirm against the manufacturer's data for your application.

• Faces: carbon against silicon carbide is a common pairing for general duty, silicon carbide against silicon carbide where abrasives are present, and tungsten carbide for tougher mechanical duty.
• Sleeves and glands: 316-type stainless steel is typical. Duplex or nickel alloys are chosen when chloride or acid corrosion is a concern.
• Secondary seals: EPDM for water-based service, FKM for many oils and hydrocarbons, perfluoroelastomer or PTFE-based for aggressive chemicals. See the elastomer comparison.
• Springs and drive parts: alloy choice matters when the liquid is corrosive, since springs can be exposed to the process.

The key difference from loose-component selection is that a cartridge has fixed dimensions, so the chamber must be measured carefully before ordering.

• Shaft diameter at the sleeve seat, and whether the pump has a shaft sleeve already.
• Seal chamber bore, depth and gland bolt pattern. A cartridge that does not fit the chamber cannot be adapted easily.
• Axial space: the distance from the chamber face to the nearest shaft obstruction.
• Flush and port positions: where the flush, quench, drain and vent ports sit on the gland.
• Arrangement: single or double, and any supply system already installed.
• Drive method: set screws, clamp collar or keyed drive.

Where the pump cannot be identified, ask for a technical review before ordering.

• Pump make, model and serial number, or the equipment drawing
• Existing cartridge seal part number or label
• Shaft or sleeve diameter, chamber bore, depth and gland bolt circle
• Port positions and sizes for flush, quench, drain and vent
• Fluid, temperature, pressure and speed
• Photos of the current seal installed and removed
• Quantity, and whether you also need a support system

Genuine cartridge seals come from the brand fitted to the equipment. Compatible cartridges are built to match the same shaft, chamber and gland dimensions, and some are designed as direct replacements for named OEM models. Check dimensional equivalence, face materials, elastomers and flush connections before relying on compatibility, because small port or bolt-pattern differences can prevent fitting.

You can enquire about genuine or compatible replacement parts for equipment from manufacturers such as Burgmann, John Crane, Chesterton, Flowserve, KSB and Sulzer. Supply route and lead times are confirmed when you enquire.

Because cartridge seals are dimension-specific, most orders benefit from a check before purchase.

• Buy online: where a product is listed in the online shop with a confirmed price, you can order directly. Products are being added to the shop progressively, so not every item will be listed yet.
• Request a quote: for custom, bulk, unpriced or repeat-order requirements, send us a quote request with your details.
• Technical review: if you cannot identify the part, or the application is demanding, use Find My Seal or upload a drawing and our team will review it with you.

You can also call head office in Johannesburg on 011 079 6033, or WhatsApp 079 508 0989, or email info@globseals.com.

These guides support specifying and fitting cartridge seals.

• How to identify a mechanical seal: identify the seal fitted to a pump before replacing it
• Pump and seal maintenance guide: installation, alignment and run-in checks
• Common causes of seal failure: how to interpret premature failure