Non-asbestos gasket developed
By By Bill Searle
For over 50 years, the fluid sealing industry has been attempting, with limited success, to find an ideal solution to replace asbestos-based gaskets. However, a new product has now come on to the market that meets the needs of users and avoids...
April 1, 2014
By By Bill Searle
For over 50 years, the fluid sealing industry has been attempting, with limited success, to find an ideal solution to replace asbestos-based gaskets. However, a new product has now come on to the market that meets the needs of users and avoids all the hazards of using asbestos-containing products. This new material is NA 1122 premium sheet, available from Teadit North America of Houston, TX.
On June 30, 2013, the last Canadian manufacturer of asbestos sheet product, from which asbestos-based gaskets are made, announced that it would no longer be supplying asbestos sheet. This has left a number of large users of asbestos-based gaskets looking for suitable alternatives to service their needs.
Despite the known hazards, asbestos-based gaskets do have some appealing performance characteristics. Asbestos-based gaskets have very high temperature and pressure limitations, and the material is resistant to a wide variety of aggressive chemicals used within industry. Despite these performance advantages, many well-known firms such as Suncor, Exxon, Shell, Ontario Power Generation (OPG) and ArcelorMittal have banned its use within their operations due to the toxicity of the material.
Asbestos-based gaskets have been linked to asbestosis, an occupational lung disease caused by the ingestion or inhalation of asbestos fibres. Such fibres can be given off by an asbestos-based gasket as it deteriorates and degrades. Asbestosis is a chronic inflammatory and fibrotic disease of the lung caused by the presence of asbestos fibres within the lung. The disease can result in significantly impaired lung function, respiratory infection, tumours (mesothelioma), and even death due to heart failure or lung cancer.
Given the toxicity of asbestos, materials and gasket manufacturers alike have been committed to finding safer alternative materials that avoid the problems associated with using asbestos in the workplace.
A major challenge in the development of alternative materials has been to not only achieve the same performance characteristics as asbestos sheet, but to also develop a cost-effective solution. Cost is a particularly important consideration as many applications require large gaskets: if the sheet cost is high, large gaskets cut from the sheet would be prohibitively expensive.
The problem of developing a suitable substitute for asbestos-based gaskets was taken on by Teadit, a manufacturer of CNA (Compressed Non-Asbestos) sheet. Teadit’s challenge was to develop a non-asbestos sheet that would support the cost-effective provision of gaskets as large as 96 in. in diameter, and which would be soft, flexible, and easy to handle and install. Critically, the new material would have to be resistant to a wide range of chemicals and support a high range of temperatures and pressures, including thermal cycling. The result of Teadit’s development effort was the NA 1122 premium sheet.
NA 1122 sheet is a compressed non-asbestos sheet gasket material produced from a combination of inorganic fibres and special fillers, bonded with nitrile rubber (NBR). It is manufactured through the hot calendar process under rigorous quality control standards, including ISO 9001.
NA 1122 sheet was specifically developed to have superior thermal stability in order to replace compressed asbestos gasket sheets in thermal cycling applications. It is specifically recommended for saturated and superheated steam applications. It is also suitable for sealing petroleum derivates, ethanol, chemical products and general services.
Field tests as well as laboratory tests have confirmed that, even under severe application conditions, NA 1122 sheet has exceptional performance without leakage. Laboratory tests have confirmed that NA 1122 sheet reached its target of work above 800°F and 1,480 psi without leakage. The maximum temperature limits of the Teadit NA 1122 product is 1022°F, and the maximum pressure limit is 2,177 psi.
Field performance is no less impressive. For example, CRGI is currently field-testing NA 1122 sheet in a mining application where the maximum recorded temperature is 780°F, and where the most critical chemical concern was SO2 gas at 5%-15% as off-gas system moisture.
In this test, a 73-in. NA 1122 test gasket was installed directly across from the original asbestos gasket application. All the same service conditions were present for both gaskets side by side, with no variance in either case. Both gaskets have been in service since January 8, 2014. The NA 1122 gasket is being monitored and inspected very closely, and it is performing as expected.
In this particular application, the NA 1122 gasket has met all of the customer’s requirements to-date. Probably the most impressive of all the requirements satisfied to date is the safe, reliable performance of the gasket, combined with the gasket cost. In this case, the finished fabricated cut gaskets were supplied to the customer at 2.6 times the price of the previous asbestos gaskets.
Gaskets cut from the NA 1122 sheet can meet most, if not all, applications that traditionally have been serviced by asbestos-based gaskets. Gaskets produced from NA 1122 sheets are now a preferred choice for severe-service applications.
Bill Searle is a technical sales specialist with Canada Rubber Group Inc. (CRGI), Bowmanville, ON. CRGI is a provider of fluid sealing products and services.