STAMP - Remember this for Gasket Selection Criteria

When you're specifying a gasket for even the simplest application, it is important that the gasket supplier know all the operating parameters.

There are five major pieces of information needed to select the appropriate gasket, known by the acronym S.T.A.M.P.:

Size:

While gaskets are most often used in standard ANSI flange connections, non-standard flanges can also be found throughout a plant.  In dealing with non-standard flanges, it is VERY important to obtain as much detail as possible about the contact dimensions (the portion of the gasket actually being compressed) and the fasteners or bolts being used (size, grade, quantity). This information is used to calculate the contact area and available assembly stress - a key factor in the selection process, as an improperly loaded gasket could result in premature equipment failure.

Temperature:

While many systems operate at a continuous temperature, or within a standard range, it is important to call-out any system temperature spikes, as well as thermal cycling, if they exist.  When a system temperature fluctuates or cycles, the gasket must react to movements in the application related to expansion, contraction, and change in internal pressure.

Application:

Application is similar to size, in that it relates to the equipment where the gasket is being used, but unlike size, application data may contain additional details that would not be covered by basic dimensional information.  Such as the end-use and equipment where the gasket is being installed.  Application-related questions must be answered to aid in the selection of the material.

Media:

The fluid or gas the gasket is sealing in, or out, of an assembly.  When choosing a product to seal a particular media, it is important to consider not only chemical compatibility but also emissions compliance.  For example, a gasket may work very well for sealing liquids, but may not provide the necessary level of permeation resistance for certain gases.

Pressure:

Most systems operate at a "constant" pressure, however, if system upsets occur, it is important to factor that into the selection process.  Some examples are:
Surging - When system pressures are drastically increased over a short period of time.
Hammering - Commonly created when valves are shut too quickly.  Media flowing through a pipe has inertia, and when valves shut too quickly, the system must absorb the inertia of the media.  The weakest point in the assemble is usually the gasket.
Thermal Expansion - When a liquid is heated in an enclosed space, with no air space for expansion, the internal pressure that is generated can be catastrophic to the system, equipment, or sealing device (gasket) in the system.

Side Note: Sometimes the acronym S.T.A.M.P.S. is used, with the second "S" being for "Speed".  Speed is not normally specified when it comes to gasketing, since most gasket applications are static, but it is worth mentioning for those who may need to specify a dynamic seal.

Speed:

Speed is required for rotating or reciprocating equipment. In the case of rotating equipment, speed must be expressed in feet per minute (FPM).  This is because large-diameter shafts rotating at a given number of revolution per minute (RPM) will have a higher FPM surface speed than a small-diameter shaft rotating at the same RPM.  In reciprocating applications, it is important to know the length of the stroke and cycles per minute.  This information will then be used to calculate the speed of the shaft or piston.