materials

Sealing Rings

Materials used by B+V in their compact seal arrangements are perbunan, Perbunan-S, Viton Blank, Viton Superlip, Pod and water seal.  The choice of material is dependent on the circumferential speed of the seal, the pressure on the seal rings and the material of the liner. Provided the correct material is selected the seals should last for five years under normal deep sea operating conditions.

Note: sealing ring materials are a special compound formulated after extensive trials on test beds and then in the field. The ring material is designed to give the optimum strength and flexibility required in order to minimise wear, prevent pumping and avoid overheating and hardening / cracking of the rings.  It is very important that the correct material is used in each application.

• All seal ring materials deteriorate over time.
•   It is important that the correct shelf life is not exceeded.  
• Long term storage is possible.  If this is required, please contact us and we can provide the necessary information, but in general terms we do not recommend the storage of sealing rings. 
• The rings are available ex stock, just order them a few weeks in advance and that way you can be sure that the rings are in optimum condition. (Normal delivery for SIMPLEX seals is one week ex works, but this can be improved on in emergencies)

Special designs for special applications

Special seal designs are available for particular applications, for example Pod propulsion systems, Tidal Energy Turbines, submarines or simply to absorb the sudden peak pressures which can be experienced on Icebreakers.  Sometimes the special designs incorporate a hybrid system using both face and lip type technology.  If you have a special application, let us know.

Liners

In general terms liners need to be resistant to wear and corrosion.  Unfortunately materials tend either to be corrosion resistant or wear resistant.  The more corrosion resistant they are,  the softer the material tends to be.  All materials are a compromise between corrosion resistance, wear resistance, and cost.  There are some materials which possess both high corrosion resistance and high wear resistance, but these are all very expensive and are not justified for normal applications.  Our normal liner material provides good corrosion resistance and a time between overhaul of five years under normal circumstances.  During overhaul of the seal the grooves under the seal rings need to be inspected.  Generally speaking we would recommend that each aft seal is fitted with a spacer ring when originally installed. During service this spacer ring can be removed so that the rings run on a “clean” section of the liner.  At the next service the liner needs to be inspected to see if it can be machined down within the required tolerances.  This is often possible, in which case the liner may serve for another five or even ten years.

If high wear is expected ceramic coated liners may be fitted.  Alternatively special liners can be supplied with higher wear resistance.  In every case it is important to discuss in detail the operating parameters of the seal in order to achieve the optimum result.

In some cases, especially where CP propellers are fitted it may make sense to fit a split liner.  These are expensive, and the extra cost can only be justified where the cost of removing the tailshaft is high. However care needs to be taken during servicing (installation of split liners is complex) and under no circumstances should such service work be undertaken by anyone other than a trained service engineer.