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Sealing a march on the competition

01 February 2008

Defining the correct sealing technology specifications and requirements is demanding enough. Combine this with a lack of consistency in the UK's supply chain and you have a recipe for disaster. Rick Treharne offers some advice

The purchase of O-rings and seals is often based on price alone, resulting in inferior or inappropriate seal installations. The market has also been slow to react to changing environmental and Health & Safety regulations and the need for technical certifications and traceability documentation (the Water Regulations Advisory Scheme’s requirement for high purity elastomer seals in water fittings is a good example). Making correct choices in terms of seals can also prolong the life of equipment and reduce MTBF (mean time between failure), cutting maintenance costs considerably.

My company recently had to deal with an unusual case in which bearing sets, expected to last between two to three years, failed after just eight weeks. The application was particularly demanding, involving high speeds and high loads. A specialist team at our Sealing Technology Centre quickly established that the bearing seals were to blame and that the choice of seal material was at fault, leading to catastrophic seal failure and consequent contamination of the bearing races. A relatively non-standard, high-performance material was required to resolve the problem.

A search of the company’s nation-wide branches identified one set of suitable seals available from stock in Liverpool, and these were dispatched immediately. However, a second set of seals could not be found anywhere in the UK and with the customer’s production line effectively halted, the situation took on a degree of urgency. The company offered an appropriate response by calling on its in-house CNC seal cutting service, and within one hour was able to manufacture and despatch a suitable set of seals to get the line up and running.

This distribution service is supported by the company’s Warrington based Technology Centre, which has recently seen new investment in simulation software and dynamic seal testing and analysis equipment. The centre is an ISO TS 16949 accredited manufacturing site that is able to provide one-off seals for development projects or, indeed, emergencies such as the one described above. Seals from 5 to 4,000mm diameter can be CNC machined in virtually any profile from a range of specially developed materials, with finished products available for despatch on a next-day basis.

The Machined Seal Service offers fifteen specially developed materials and 170 standard seal profiles to meet the majority of customer requirements. There are also many specialist profiles on file that can be used to create a multitude of combinations and manufactured seals to suit every application. The key to the flexibility of the system is the bespoke CNC operating software, which generates the optimum seal geometry for each batch of seals. Customers can also supply their own profiles, if necessary, and the system will optimise the geometry, taking into account the size, performance criteria and material selected.

Material testing is a very useful development tool. By artificially ageing the seal material, engineers can see how it will perform in the field in a given application. Both tensile and compression seal strengths can be tested to the extreme, over a temperature range of -70 to +350ºC. In addition, compound analysis equipment, including thermogravimetric analysis and Fourier transform infra red spectroscopy, allows seal compounds supplied by customers to be ‘fingerprinted’ and the individual elements of the compound to be defined.

All of this equipment is networked, allowing documentation (material performance test reports, certifications, initial sample inspection reports and statistical process controls) to be produced for goods inwards records, or held in-house for product assurance between batches and traceability purposes.

Rick Treharne is technology director of ERIKS Sealing Technology UK

ERIKS Sealing Technology UK includes Wyko’s UK seals business, which includes the seals division based in Halesowen, and Pioneer Weston in Warrington.

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