How Do You Calculate Sealing Pressure

To calculate the required sealing pressure for a gasket or seal, engineers rely on a straightforward formula that takes into account the key parameters influencing seal performance. The sealing pressure formula is expressed as:

Sealing Pressure = (Gasket Stress) x (Gasket Factor)

where:

• Sealing Pressure is the minimum pressure required to achieve a leak-tight seal, typically measured in psi (pounds per square inch) or MPa (megapascals)
• Gasket Stress is the compressive stress applied to the gasket material, determined by dividing the bolt load by the gasket area
• Gasket Factor is a unitless coefficient specific to the gasket material and operating conditions

To use this formula, one first needs to determine the appropriate Gasket Stress for the application. This value depends on the gasket material, thickness, and compression characteristics. Manufacturers typically provide recommended Gasket Stress values for their products based on testing and experience.

The Gasket Factor is a multiplication factor that accounts for real-world operating conditions like temperature, pressure, flange stiffness, and fluid compatibility. This factor essentially modifies the theoretical Gasket Stress to arrive at a Sealing Pressure suitable for the actual service environment. Gasket Factors usually range from 0.5 to 5 and are empirically derived for different gasket types and service conditions.

As an example calculation, consider a compressed fiber gasket with a recommended Gasket Stress of 4,000 psi being used in a moderate temperature, low pressure water application. An appropriate Gasket Factor might be 1.5. Plugging these values into the formula:

Sealing Pressure = 4,000 psi x 1.5 = 6,000 psi

So in this case, a minimum sealing pressure of 6,000 psi should be targeted to achieve a reliable, leak-free joint. Flange bolts would then be sized and torqued to develop this pressure on the gasket.