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Effect Compensation - What is the J-T effect? Typically, it is
taken to mean the drop in temperature that occurs when gas pressure is
reduced. The magnitude of the temperature drop depends on the starting
pressure, the pressure change and the composition of the gas. The J-T
coefficient, or the change in temperature per unit change in pressure is
not a constant and is highly variable for any particular gas mixture
depending on the starting and ending conditions. Why is compensation
required? Under large pressure changes, the temperature of the gas or gas
mixture can fall to a point were the gas or a component of the mixture
starts to condense into a liquid, or in extreme cases to solidify (such as
ice formation where traces of moisture exist).The carry over of liquid
droplets or ice particles into valves and other machinery components can
cause equipment malfunction with catastrophic consequences.The way to
prevent this is to preheat the gas before the pressure reduction so that
the temperature after expansion is above the saturation temperature of
components of the gas mixture. From
When is a Heated Vessel a Pressure Vessel? - Many industries require electric heating of various fluids, either liquids or gases as a normal part of their processes.What are often not fully understood are the regulatory implications for suppliers, owners and operators of this heating equipment. This is especially so when it relates to the potential dangers of heated fluids within closed vessels, and when they become “Pressure Vessels”. This article seeks to provide some guidance for owners and operators of heated vessels so they are in a position to ask the right questions of their suppliers to protect themselves, their employees and their employer.