When tightened, bolts act like springs, pulling the flanges together. These bolts need to be preloaded enough to keep the minimum operating load on the gasket as the system is pressurized (during startup) and pressure and temperature is cycled (during normal operation).
Temperature fluctuations impact several components in a bolted joint. Lowering the temperature causes metal to contract, while elevating the temperature causes metal to expand. In the case of a flanged connection this means that the bolts, the gasket, and the flanges will contract and expand when the temperature fluctuates. Ultimately this means that the compressive force upon a gasket will change during operation. The summation in most cases will lead to a lesser compressive force upon the gasket in operation compared to the seating force during installation.
How effective the gasket is in this situation depends on how well the gasket is equipped to handle loss of compressive force upon it. The recommended torque values provided by your gasket supplier are precisely calculated to take the temperature fluctuations into account. But even so, most gaskets lose some of their tightness when they lose compressive force in operation. The DeltaV-Seal has shown an excellent ability to absorb loss of compressive force without sacrificing much of its sealing capabilities.
To validate the DeltaV-Seal's capability during thermal cycling, a test has been performed in accordance with Shell MESC 85/300 3.3.5.
Follow the link below to see the test results for the DeltaV-Seal.