Cut friction, reduce energy

When it comes to seal specification, friction is almost always the enemy. But by investing in the right seal for the job, the competitive status of a customer's product can be significantly improved resulting in increased sales and improved customer satisfaction. So what are the options for low friction sealing? 

Blue Diamond can offer a range of low friction options including its SBBT enhanced surface treatment and an advanced technology whereby a PTFE disc is actually bonded to the lip of a seal. Seals with these treatments combine the low friction benefits of PTFE together with the memory, flexibility and resilience provided by the seals' base polymer. In addition, these seals will resist the movement and forces caused by eccentric shaft rotation and offer improved performance in the event of shaft to housing misalignment, poor surface finish, vibration, high pressures and inadequate lubrication. 

While PTFE has excellent low friction characteristics, its memory and resilience properties mean that if the seal was manufactured completely from PTFE, it could snap or deform resulting in poor performance. By combining PTFE with other standard base polymer materials, Blue Diamond has developed high performance, low friction seals that have the ability to move and at the same time, retain their original shape.  

SBBT provides low start up and running friction, with the added benefits of extending wear life, retarding the ageing of the rubber and improving the corrosion resistance of metal substrates. SBBT bonds an ultra-thin PTFE coating to the base rubber or plastic component. The coating thickness is typically between 5 and 15 microns, and can be up to 25 microns, reducing the coefficient of friction to about 0.05 to 0.07. This minimises energy loss in dynamic applications, and is particularly important for avoiding torque loss in low power drives. 

SBBT has a longer wear life than pure PTFE coatings and can be applied with a much more uniform thickness of material. The clean dry film protects substrates from oils, alcohol, fuels, some inorganic acids and dirt and contaminants, which might otherwise shorten the life of the product. SBBT-treated O-rings are easier to assemble, without the need for messy pre-greasing operations.     

So which technology is best? The application engineers at Blue Diamond have the knowledge and experience to design and manufacture seals to meet individual customers' requirements. For example, most items of rotating equipment feature seals which make contact with a rotating shaft. When the lip of the seal bears down on the shaft there is friction and stiction to be overcome. Friction and stiction are affected by factors such as lip design, lip force and material, operating environment, age and usage. 

With efficiency becoming increasingly im-portant, a modest improvement in seal design can reduce losses and extend operational life. For example, the geometry of the lip, radial load and materials all affect the performance of a seal and with so many different applications, materials and design options, designing the correct seal can be a daunting task. Using powerful software, CAD and parametrics packages, Blue Diamond's designers can build in a range of factors such as pressure and temperature to minimise cost and maximise performance.

Blue Diamond seals are available in a range of standard base polymer materials including Viton/FKM, Silicone, Nitrile, HNbr or ACM. By changing different elements of the design, the application engineer can achieve the optimum result. For example, the material, lip interference and spring loads can all be instantly varied and their effect on the performance of the seal observed. All this is possible without having to manufacture any prototype products, with their inherent implications of time and cost. 

When the engineers are satisfied with the performance of the seal using the computer simulation, samples can be manufactured and the seal characteristics confirmed using Blue Diamond's extensive in-house test and development facility. And because the product design and manufacturing programme takes place under the same roof, development times can be minimised.