When you reduce the pressure of gas it has a cooling effect upon it called the Joule Thompson effect; this means that the gas could freeze in the pressure control valves or regulators, causing the whole system to stop working.
The way around this is to heat the gas prior to pressure reduction and there are several ways of doing this:
WATERBATH A waterbath passes the gas through a coiled pipe in a heated vessel similar to a boiler, this warms the gas enough to go through the pressure reduction without freezing.
HEATPACK Heatpacks use a closed loop boiler system in conjunction with in-line heat exchangers to transfer the heat to the gas.
FT Pipeline Systems believes that indirect heating via heat exchangers is by far the best way of getting heat into the gas as direct heating can cause temperature spikes in the gas flow which can cause the elastomers within the control system to fail.
Both waterbaths and heatpacks are called indirect fired water heaters, and are typically used to raise the temperature of fluids such as natural gas.
If the gas is not pre-heated, gas freezing (because of Joule-Thomson effect) can occur, while it is passing through the pressure reduction installation, damaging valves and instrumentation, or even causing the gas supply to be interrupted. That´s why these are called ‘indirect heaters’, and the process gas is heated with safety while passing through the coil.
FTPS has its own closed loop heatpack system called HEATPAK. These are compact systems and when installed with the vertical heat exchangers allow for a small system footprint. The Heatpak system keeps a reserve of heat at maximum and minimum set points and this heat, held in the water, is recirculated meaning the gas temperature is correct whatever the flow demand.
FT Pipeline Systems Ltd
6B Eastern Park
Tel: 01543 416024
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