In flanged joints, gaskets are used as a sealing element between the flange faces. When a gasket is seated between flange surfaces it "flows," filling the imperfections between the flange faces and providing the necessary seal. Economic sealing requires that gaskets perform as intended once installed. Reducing the incidence of gasket failures is a key part of improving a facility’s sealing economics.
Gaskets fail for the following reasons:
Application temperature range incompatible with the gasket material.
Application pressure incompatible with the gasket material.
Degradation from chemical attack.
Thermal cycling incompatible with the gasket material.
Incorrect measurement and sizing of the gasket.
The surface finish of the flanges is incompatible with the gasket.
Flange material incompatible with the gasket.
Special characteristics of the equipment not addressed by the gasket.
Inadequate or improper gasket assembly/installation.
When considering how to reduce the incidence of gasket failures, it is important to consider the forces that affect a gasket once installed. In flanged joints, four major forces can be identified:
Blowout force. This force is a result of the internal pressure within the joint. This is the force which attempts to blow out the gasket.
Separation force. This hydrostatic force arises from internal pressure within the joint. It is the force that tries to separate the flanges.
Bolt force. This is the total load placed upon a gasket from when the flange bolts are tightened.
Sealing force. This is the force that presses the flange faces upon the gasket.
Quality gaskets are designed to accommodate these forces. Effective sealing requires addressing the following factors:
Gasket seating stress. Adequate pressure must be applied to seat a gasket correctly so it will be able to “flow” and fill the flange imperfections. This seating stress must be limited in order to prevent crushing of the gasket by excessive compression.
Sealing force. Sufficient residual pressure must be placed on the gasket in order to keep it in sufficient contact with the flange surfaces, thus avoiding leakage.
Media compatibility. The gasket material must be able to withstand the chemical properties of the media with which it is in contact, as well as the internal pressures of the application.
Surface finish. It is not widely appreciated that gaskets have different surface finishes. For example, there are smooth finishes and textured finishes. These different finishes can accommodate imperfections in flange surface finishes. Choosing a surface finish which is not compatible with the flange surface being sealed can result in leaks.
CRG can help you to avoid gasket failures. Our sales team can bring our 30-years of experience to bear and help you select the right materials, properties and finishes for your application. We can provide training and support for gasket installation and inventorying, helping you to achieve economical sealing without trading off performance.
To find out more about how CRG can help, please contact our sales team at crg@canadarubbergroup.com.