GASKETS

Engineering Data/FAQs

Selecting the Right Gasket

Selecting gasketing materials for particular applications is not an easy task. The variables present in a flanged connection seem endless and yet all of them must be taken into consideration to assure a proper seal. In the past, the acronym "TAMP" (Temperature, Application, Media and Pressure) seemed to give sufficient information to make a gasketing recommendation. Today, items such as: the flange metallurgy, the amount of bolt thread embedment, the amount of flange rotation, the amount of bolt stretch, the additives to the media and the flange surface finish (in addition to other variables) determine how well a gasket will perform. In general, the definition of what a seal is has changed drastically over the years. Leakage measurements have gone from drips a minute to parts per million.

This information is designed to help guide you through the various gasketing products and narrow your choices. All industry standard tests are included in order to allow an enduser a means of comparison between different materials. Many of the test procedures require that the tests be conducted in 1/32" (0.8mm) material. As a rule of thumb, gasket performance decreases as material thickness increases. In addition, compressive loads must be increased with thicker materials. Proper bolting sequences are necessary to ensure those compressive loads are uniform. The temperature, pressure and P x T ratings are all based on optimum conditions. When approaching those extremes, it is suggested that you consult with the Garlock Applications Engineering Department or possibly upgrade to a material that has higher ratings.

As industry standards change and new products are introduced, this information will be updated. In the meantime, we urge you to take advantage of our experienced personnel for assistance. In-plant training, instructional video tapes, additional technical information and gasketing recommendations all are available to help in your selection process. Please feel free to call, FAX, e-mail or write us if you have any questions or concerns. Garlock is here to help.

Temperature
In most selection processes, the temperature of the fluid at the gasketed joint should be considered first. This will reduce the number of product candidates quickly, especially as temperatures go from 200ºF (95ºC) to 1000ºF (540ºC). When system operating temperatures are approaching a particular gasket material's maximum continuous operating temperature limit, an upgrade to a superior material is suggested. In some situations cryogenic temperatures must also be considered.

Application
The most important information under Application is the type of flange and bolts used. The number, size, and grade of bolts used in the application determines the load available. The surface area being compressed is calculated from the gasket contact dimensions. The load from the bolts and the contact area of the gasket result in the compressive load available to seal the gasket. We have calculated and tabulated this information on standard ANSI raised face flanges. Compressive stress on non-standard flanges must be calculated on an individual basis and is available upon request. Without this information, we can not choose between various types of materials such as elastomeric (rubber) gaskets, compressed sheet, GRAPh-LOCK® and GYLON® styles.

Media
There are thousands of different fluids. We cannot make recommendations for all fluids. Fortunately, however, a relatively limited number of fluids make up the vast majority of the media encountered in industry. A general overview of fluid compatibility is provided for our most popular styles. System clean out and flushes should also be considered. Additional information on products versus fluids is available upon request.

Pressure
Next to be considered is the internal pressure of the fluid at the gasketed joint. We list the maximum pressure limits for each style. If severe and frequent pressure changes are involved, we should be given the details, since an alternative product may be needed.

Pressure: psi (bar) x
Temperature: ºF (ºC) Values
We strongly recommend that pressure and temperature be considered simultaneously by using the following procedure:

1. Select the Garlock style(s) being considered for your application/service
2. List the maximum pressure, temperature and P x T value for the style(s),
3. Make sure the actual service conditions do not exceed the style limitations in any of the three criteria. If the service conditions don't exceed the style limitations, the style(s) can be used, assuming all other requirements are met. If they do exceed any one limit, another style or styles should be considered. Rarely can a style be recommended when the service conditions of pressure and temperature are both at the maximum limits for that style.

1. Pressure Limit: 1,000 psig (70 bar)
2. Maximum Temperature Limit: +700ºF (+370ºC); Continuous Operating Temp.: +400ºF (+205ºC)
3. P x T Limit: 350,000* (12,000)
   At 1,000 psig (70 bar), maximum temperature is +350ºF (+180ºC).

Important: All pressure and P x T limits are based on laboratory tests utilizing ideal gasketing conditions. Field conditions will undoubtedly affect the gasket performance.

We hasten to point out that this method for gasket selection is merely a general guide and should not be the sole means for selecting or rejecting a product.

*P x T based on 1/16" (1.6mm) sheet thickness unless otherwise stated.
GRAPH-LOCK, GYLON and BLUE-GARD are registered trademarks of Garlock Inc.

WARNING:
Properties applications shown here are typical. Your specific application should not be undertaken without independent study and evaluation for suitability. For specific application recommendations consult Garlock. Failure to select the proper sealing products could result in property damage and/or serious personal injury.

This performance data has been developed from field testing, customer field reports and/or in-house testing. While the utmost care has been used in compiling this information, we assume no responsibility for errors. Specifications subject to change without notice. This edition cancels all previous issues. Subject to change without notice.