Cartridge seals

A cartridge seal is often the optimal solution for your pump or mixer when the lifetime of the seal and the surrounding equipment is essential. And when leakage levels and the ability to control downtime are important to you. We can provide advice and guidance for your specific application.

Several factors influence which shaft seal is applicable and optimal for your particular application:

  • Pump/mixer type?
  • Liquid to be pumped and temperature?
  • Pressure/vacuum before and after pump and flow?
  • Where on the pump curve is the system - is it in balance?

We help you find the cartridge seal that works well for your pump or mixer. Our products are of high quality at an attractive price. Contact us on 76 12 33 66 or to discuss your options.


A cartridge seal is a pre-assembled closed shaft sealing system where the construction is delivered as a complete unit. The cartridge seal is ready to be bolted to the pump casing or mixer.

Areas of application for cartridge seals:

  • The power plant sector
  • Heat distribution
  • Biogas
  • Power-to-X
  • Food industry
  • Pharmaceutical industry
  • Waste water treatment plants
  • Chemical industry

Examples of industrial applications:

The power plant sector

The power plant sector has high requirements for lifetime and availability. Simple and efficient maintenance. Low emission and leakage levels and proper environmental measures.

  • Feed water pumps
  • Boiler circulation pumps
  • Flue gas desulfurisation
  • Condensate pumps
Pharmaceutical industry

The pharmaceutical industry has high hygiene, health, legal and regulatory requirements. Materials must be approved for food contact. Materials must be smooth and have durable surfaces that are easy to clean. Complete units that can be sterilised and SIP/CIP cleaned.

  • Eccentric screw pumps
  • Sterile pumps
  • Centrifugal pumps
  • Filter driers
  • Agglomerator
  • Feed pump
Food production

Production of food places high demands on durability and availability. Materials must be approved for food contact. Resistant to crystallisation and carbonisation. Complete units that are easy to clean.

  • Water pumps
  • Circulation pumps
  • Stirrers and mixers
  • Pumps for mash

Compressors are high-speed equipment with high requirements for lifetime and availability. Focus on the working medium, compression rate, flow, number of intermediate inputs and outputs.

  • Ammonia compressor
  • Gas compressor
  • Ethylene compressor
  • Flash turbine
  • Screw compressor

Cartridge seals are the optimal technical solution if you have the space for them in your pump or mixer system. Or if you can free up space for the seal by making some simple adaptations. With a Single Seal, you get a strong technical solution. With a Double Seal, you get additional safety when the first seal section fails, and you also improve your ability to decide when the pump/seal should be taken out of production for maintenance.

The cartridge seal is mounted directly on the shaft and bolted to the pump or mixer. The seal is delivered as a finished unit. This makes the cartridge seal easy to install. However, service life and performance depends on the shaft being aligned correctly, the pump running at an acceptable operating point, the bearings being suitable for the task (axial and radial movement), the pressure/vacuum in and out of the pump, etc.

Advantages of using cartridge seals:

  • Cartridge seals are easy to install (do not necessarily require a specialist)
  • Less assembly time and thus shorter downtime
  • The pre-assembled unit provides higher functional safety. Less risk of measurement errors
  • Less risk of axial misplacement
  • Reduces the risk of impurities entering the seal and damaging e.g. the sliding faces
  • Parts can be repaired and replaced, eliminating the need to invest in a complete new unit

Disadvantages of using cartridge seals:

  • Higher purchase price than e.g. component seals
  • Requires more space than e.g. component seals
  • Requires more information/analysis to find the right "ready-to-go" solution

We can help you analyse your system and advise on which cartridge seal or component seal will be a good alternative in your situation. The right choice depends on the requirements you place on your installation:

  • The operating conditions that the plant components must be able to withstand (heat, vibration and pressure)
  • Availability at the installation (quality and lifetime of the installation components)
  • Ability to plan your downtime
  • Maintenance philosophy
  • Standardisation of spare parts
  • Occurrence of leaks and emissions

It is important to understand that the right mechanical shaft seal for the task is not necessarily the most expensive or the cheapest. The business case should be based on a total assessment, recognising the operational benefits of a good solution and, conversely, avoiding having to pay for a technical solution that does not provide more value than a cheaper alternative. Elements such as installation costs, long-term operating costs, pump characteristics, heat impact, vibration and pressurisation conditions are important.

We offer cartridge seals for a wide range of standard pumps and mixers. We can also find a solution for customised pumps and mixers. No matter what type of pump you have, we have a cartridge seal that will fit your system, your needs and wishes.

Cartridge seals often have 2 sealing sections. The primary sealing section is the sliding faces, where one face is stationary (in a fixed position) and the other sliding face is dynamic (rotating). The secondary sealing section consists of e.g. O-rings. In the seal, springs are used. All held in place in a basic construction. The materials used for the different parts may be e.g.:

Sliding faces


  • Carbon graphite
  • Carbon graphite impregnated with resin
  • Graphite impregnated with antimony


  • Tungsten carbide
  • Silicon carbide, sintered


  • Metal oxides

The sliding faces shall be made of materials and in a way that optimises their sealing performance. The sliding faces must allow the fluid to form the film between the sliding faces that seals them during rotation. And they must be able to withstand the temperature of the fluid and the temperature fluctuations that occur. Finally, it is preferable if the sliding faces can withstand running dry (if only for a short time) when errors occur in the system.

Secondary seals (O-rings)


  • Ethylene-propylene rubber
  • Silicone rubber
  • Viton rubber
  • FKM + PTFE
  • FKM + FEP



  • AISI 316Ti stainless steel
  • Hastelloy C-4
  • Hastelloy C-276

The springs in our cartridge seals provide the necessary tension to keep it tight - even when the pump is not running. The springs are isolated from the fluids so that they are not contaminated.

Cartridge seals - basic construction


  • AISI 314, 316…
  • Hastelloy C-4
  • Monel
  • Inconel
  • Titanium

The compact and simple installation design reduces installation time when replacement becomes necessary. Cartridge seals are assembled and prepared for easy installation before being delivered to you, allowing you to replace your cartridge seal with minimal downtime.

The optimal composition depends entirely on what properties the mechanical shaft seal should have in relation to the specific application. The choice of materials ensures the optimum lifetime of your pump, your shaft seal, etc. as well as the safety of the people on site.

The cartridge seal is only as good as the operating conditions in which it has to function. The system must be balanced so that plant components are not forced into operating ranges for which they are not designed. If there is an imbalance in the system, the cartridge seal will also fail sooner than expected. We can help you with the necessary analysis and advice on the correct operating conditions; contact us on 76 12 33 66 or and together we can find the right solution for you.

Which Mechanical shaft seal fit your needs?

The benefits of choosing a solution from WestCoast can be realised in several ways:

  • High quality products at attractive prices
  • Savings on purchasing with at least the same product quality
  • A better product for the task with less downtime and increased availability
  • Reduced operating costs
  • Better ability to plan your own downtime
  • Help with system analysis and solution advice
  • And much more...

Initially, we need to know something about your system:

  • Which pump are you using?
  • What type of liquid are you pumping?
  • What is your fluid flow rate?
  • What is the pressure into the pump and out of the pump?
  • What is the temperature of the liquid to be pumped?
  • Do you know where on the pump curve your system is (Best Efficiency Point)?
  • Do you know the viscosity? Is the material acidic, sticky or otherwise challenging?
  • What challenges do you have with the existing solution?

Once we have an understanding of the framework, we can pinpoint where products and solutions from WestCoast can add value for you. Including whether a cartridge seal or a component seal is right for you. Contact us 76 12 33 66 or and together we can find the right solution for you.

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