Mechanical shaft seals

The proper mechanical shaft seal keeps your pump, mixer or other rotating equipment tight and increases its lifetime. We can provide advice and guidance for your specific application.

Vi udskifter OEM akseltætninger både cartridge seals and component seals med en tilsvarende eller bedre kvalitet, men til en væsentlig reduceret pris.

Vil du vide, hvor meget du kan spare på din akseltætning? Kontakt os på 76 12 33 66 or for et uforpligtende tilbud.

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The purpose of a mechanical shaft seal is to maintain the pressure or vacuum inside your pump or mixer. In a pump, it is the pressure (the pressure difference created by the pump) that drives the fluid through the system, and if the pressure disappears through a leaking shaft opening, the pump's performance is reduced/disappears. At the same time, a mechanical shaft seal also has the function of keeping your pump or mixer vessel tight so that liquid or gases do not escape at the rotating shaft of the pump/mixer.

The pump inlet and outlet are normally completely sealed with flanges and gaskets. The shaft, on the other hand, must be free to rotate to drive the impeller, and thus there is an opening between the interior of the pump casing and the environment/atmosphere outside the pump. The shaft and pump casing need to be sealed ensuring a minimum of leakage (dripping), emissions (gases) or none at all.

It is essential that you choose the right mechanical shaft seal. 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. WestCoast can help with these analyses and assessments.

Areas of application:

  • 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

Which mechanical shaft seal is suitable for 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?

Så snart vi har rammerne på plads, kan vi spore os ind på, hvor produkter og løsninger fra WestCoast kan give dig værdi. Herunder om det rigtige for dig er en patrontætning eller en komponenttætning. Kontakt os på 76 12 33 66 or for hjælp til den rigtige løsning.

Cartridge seal

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.

The advantages of cartridge seals are, among other things:

  • 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 surfaces
  • Parts can be repaired and replaced, eliminating the need to invest in a complete new unit

The disadvantages are, for example:

  • 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

Component seal

A component seal consists of separate parts that are assembled individually. Stationary parts, which must not be able to move. And dynamic parts that must be able to rotate together with the shaft.

The advantages of component seals are, among other things:

  • The cost of component seals is lower than that of cartridge seals
  • The individual parts of the seal can be stocked and replaced
  • Component seals do not require the same space as cartridge seals

The disadvantages are, for example:

  • Component seals are more easily damaged during assembly and operation
  • Requirements for correct and accurate installation are high to avoid seal failure
  • Installation time is often longer than for cartridge seals

We offer mechanical shaft 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 mechanical shaft seal that will fit your system, your needs and wishes.

Mechanical shaft 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

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 basic construction


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

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 mechanical shaft seal is no better than the operating conditions in which it must function. There must be balance in the system so that the components are not forced into operating ranges for which they were not designed. If there is an imbalance in the system, the mechanical shaft seal will also fail sooner than expected. WestCoast can help you with analysis and advice for the right operating conditions, contact us at 76 12 33 66 or

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