Achieving a successful seal means considering and accounting for gasket swell. Instances where there is a mismatch between the gasket material chosen and the media being sealed can cause the gasket to expand and thicken. The resulting swell can require increased bolt loads and may cause the gasket material to expand out of the joint. The net result can be a poor seal.

Most gaskets are not immune from swell. Depending upon the material used in its manufacture, there can be a number of fluids that can trigger swelling in a gasket. For example, gaskets made from NBR (nitrile rubber, or Buna-N) material can undergo significant swelling when they come into contact with acetone or certain ketones, but the same gaskets may exhibit little or no swelling in the presence of other fluids. Knowing combinations of materials and media that can cause swelling is a key factor in choosing gaskets that will seal successfully.

However, not all gasket swelling is bad! In difficult-to-seal applications, some swelling may, in fact, be desirable. In these types of applications, regulating the swell through the use of a controlled swell sheet gasket can result in a predictable swell with a superior seal.

What is a controlled swell sheet?

A controlled swell sheet is an especially formulated material that will produce a gasket having a predictable degree of swell when it comes into contact with certain media. Because the degree of swell is controlled and predictable, gaskets made from this type of material are a good choice in difficult-to seal applications where inadequate bolt loading or poor flange surfaces exist.

CRG uses Teadit Style NA1088 sheet to fabricate controlled swell sheet gaskets. Teadit NA1088 is a high-density, controlled swell sheet gasket material with a proprietary binder and reinforced with a synthetic/inorganic fiber blend. It is designed for demanding applications requiring excellent sealablity, torque retention, recovery, and conformability to uneven flange surfaces.

What types of media do controlled swell sheet gaskets service?

Gaskets made from Teadit Style NA1088 sheet provide a controlled swell in the presence of oils, fuels, lubricants, and water/coolant. When exposed to these media, controlled swell gaskets from Teadit NA1088 will undergo a controlled and predictable swell, resulting in a known increase in the thickness and weight of the gasket.

Specific media that controlled swell sheet gaskets made from Teadit NA088 will support include: petroleum and derivatives; synthetic oils; aliphatic solvents; mild organic acids; water and coolants; refrigerants, vegetable oils; and animal oils. In applications where a gasket will contact these media, a gasket made from Teadit NA1088 sheet will undergo controlled and predictable swelling, leading to superior sealing performance.

What types of applications do controlled swell sheet gaskets service?

Controlled swell sheet gaskets will service demanding applications where uncontrolled gasket swelling due to contact with the media highlighted above makes it difficult to achieve a good seal. In these applications, poor sealing performance can be further exacerbated by uneven flange surfaces and difficulty in achieving an adequate bolt load. These types of conditions often exist in a variety of industrial and heavy duty applications, including diesel engine oil pans and front covers, compressors, generators, pumps, valves, gear boxes and housings, transformers, forklifts/tow motors, sight glass, and man/hand-hole covers.

Controlled swell sheet gaskets made from Teadit NA1088 sheet will support applications with a maximum service temperature limit of 650°F (343°C), and continuous service temperature of 400°F (205°C).  These gaskets will also service application maximum service pressures of 1000 psi (69 bar) and continuous service pressures of 500 psi (34.5 bar).

How can I find out more about controlled swell sheet gaskets?

If you have a difficult-to-seal application, CRG will be pleased to review your needs and discuss the detailed properties and service limits of controlled swell gaskets made from Teadit NA1088 sheet. To find out more, please contact our sales department at crg@canadarubbergroup.com.

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