It can also be the act of re-tightening a connection while the bolted joint assembly (flange/heat exchanger) is in operation. It might seem like common sense to not tighten bolts containing hot fluids or gases.
It is potentially hazardous and the utmost caution needs to be exercised when planning and carrying out this procedure. As a best practice, it is not recommended by Pipeotech, although this is widely carried out for other gasket materials. Any potential benefits arising from hot bolting should be carefully weighed against the risks encountered.
The Engineering Equipment Materials and Users Association (EEMUA) publish an information sheet named "Guidance Procedures for the Removal and Replacement of Flanged Joint Bolting on Live Piping and Equipment". It is essential to read this before carrying out any bolt work on a live plant.
During Hot Bolting there will be some loss of seating force, but most likely this will cause no leakage on the flanged joint with the DeltaV-Seal. The EN 13555 leakage test shows that the DeltaV-Seal remains tight even with a lower seating force than competing gaskets. One essential thing that differ DeltaV-Seal from many other gaskets: there is no need for re-torque after initial installation has been preformed. Thus there is no need for re-torque and Hot Bolting due to gasket compression set.