Primair Air Seals

The most reliable sealing system. AEGIR’s next generation stern tube sealing technology physically seals the stern tube oil from the sea via an air space.

AEGIR-Marine is a manufacturer and supplier of high-quality spare parts. AEGIR-Marine PRIME Parts® is their own make for stern tube seals, bearings, liners, O-rings and many more propulsion spares. The R&D department is responsible for all engineering and development.


Primair Air Seals

Over the years AEGIR-Marine has developed many different types of seal assemblies. Careful engineering by the R&D department has led to spare parts as well as complete seal assemblies suitable for renowned makes like Wärtsilä, B+V Industries and Kemel. By applying modern technology and consistently choosing the best materials the seal assemblies meet the highest degree of quality and reliability


PRIMAIR is a very advanced sealing system. ‘Air Seal’ technology physically separates the stern tube oil from the sea via an air space and has a drain line back to the engine room to drain leaked fluids and prevent cross contamination in event of a seal ring failure. 

Variable air pressure. The PRIMAIR system works based on ‘Constant Air Flow/Variable Pressure’- technology. This system is engineered to discharge air through the seal box. The air pressure varies while the air flow is stable. The air pressure will vary to keep in sync with the outside seawater pressure (seawater pressure will vary not only with vessel draft but also wave conditions, i.e. swells). 

Reducing wear on seal ring and liner. The variable pressure method maintains a perfect pressure balance inside the seal box. This perfect pressure balance prevents flexing of the seal ring thereby reducing stress on the seal ring material. It also reduces wear on the seal ring and chrome steel liner because the pressure on the seal rings is lower than within a conventional system. This combination greatly improves seal reliability. 

PRIMAIR meets the VGP law requirements even when using conventional lubricants.

PRIMAIR Key features 
  • Works on constant air flow/variable pressure technology 
  • Maintains a perfect balance inside the seal box, reducing stress on the seal ring material
  • Physically separates the stern tube oil from the seawater by means of an air space eliminating a seawater oil interface 
  • A monitored air space removes the risk of cross contamination 
  • Meets VGP requirements even when using conventional mineral oils 
  • Class approved by most major classification societies


AEGIR-Marine can supply spares suitable for existing systems or retrofit your existing system using Prime Standard or Prime Standard Secure.

By choosing to have all PRIME Parts in stock, you will never have to wait for weeks. Just call us and we will deliver them immediately. It’s as simple as that. 
In case of emergency we guarantee shipment within the hour.
PRIME Parts® distinguish themselves because of:

  • the high quality, equal or better (according to TNO & ERT-tests) than original spares
  • their fair price
  • their suitability for all major makes
  • the TüV-certificate, confirming that all our products have been produced in Europe
  • their class certification by all major class societies
  • the intensive quality controls
  • their careful packing in specially designed boxes
Spare Prime Seal Rings:
  • are high quality components manufactured based on a unique Viton-formula
  • have a high resistance against biodegradable lubricants
  • have a perfect fit, guaranteed by our carefully designed moulds
  • are subjected to several manual checks before shipment
  • are always in stock
  • PRIME seal rings can -upon request- be produced in size 1250
Spare Prime Spacer Rings
  • Spacer rings (also called spacers) are installed between the stern tube and the AFT seal housing. The ring improves the durability of the liner and ensures a new, clean running surface for the seal rings.
  • Spacers can be installed without removing the propeller.
  • Available for seal sizes: 240 up to and including 1180. We can provide other sizes upon request.
  • Split (two halves), for installation without pulling the shaft.
  • Material: Mild steel.
  • Included: Longer bolts for installation and locking wire for securing the bolts and 2 flange sheet packings.
Spare Prime Liners
  • Our liners fit every make and type of lip-type shaft seal. 
    They are made from high-quality, wear-resistant chrome steel. Liners are available in sizes from 155 to 1180.
  • As one of the few suppliers in the world, AEGIR keeps castings suitable for Kamewa type liners in stock. Therefore, can be delivered at short notice.
  • Available sizes standard: 155 up to and including 1180.
  • Available types: we can supply almost any make and type of liner.
  • Split liners can be supplied on request.
  • Kamewa liners: Sizes 300 up to and including 750 from stock.
  • We can produce other sizes on request.
  • Material: Special Chrome Steel, high resistance to corrosion and wear


I want to replace the seal rings on my Stern shaft without withdrawing the tail shaft, is this possible?

Yes, the seals can be split then hot bonded around the shaft with our specialist tooling and expert technicians.

Why is the Primair VGP compliant even when operating on mineral oil?

Because the Primair physically separates the stern tube oil from the seawater by means of an air space, eliminating a seawater oil interface entirely.

I would like to change my Sterntube oil for something else, will AEGIR-Marine seals be compatible?

Almost certainly. We have an extensive list of approved oil both mineral and biodegradable. If it’s not on our list, then we can easily get it tested for you

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Our team of technical experts offer industry-leading consultation services, equipment sales and support and with a wealth of project management and technical experience, we plan and deliver. We work with you to ensure a smooth project from design specification to onsite installation. Our impartial guidance and multi-supplier approach mean we are focused on finding you the best solution meaning you can be confident in both our services and products.

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