Dew point control is the practice of keeping natural gas dry enough - of both water and heavy hydrocarbons - that it will not condense liquids as it travels through a pipeline. Meeting dew point specifications is a core requirement for selling and transporting gas. This guide explains the two kinds of dew point, why they matter, and how they are controlled and monitored.
Dew Point Control in one line: Dew point control is conditioning natural gas so its water dew point and hydrocarbon dew point stay below the pipeline's specified limits. The dew point is the temperature at which the gas would start to condense liquid; keeping it low ensures the gas stays a dry gas throughout the pipeline's pressure and temperature range.
Gas has two separate dew points and both must be managed. The water dew point is the temperature at which water vapor in the gas would begin to condense; it is controlled by drying the gas, typically in a glycol dehydration unit. Pipelines set a water content limit (often around 7 pounds per million standard cubic feet in the US) to prevent hydrates and corrosion. The hydrocarbon dew point is the temperature at which the heavier hydrocarbons in the gas (propane, butane, and heavier) would begin to condense; it is controlled by cooling the gas to drop those components out, typically in a JT skid or a refrigeration or turboexpander plant.
The two are physically different problems. Water dew point is about removing H2O; hydrocarbon dew point is about removing the heavy ends. A gas can meet its water spec and still fail its hydrocarbon dew point, or vice versa, so a facility often runs both a dehydration process and a dew point control (liquids-dropout) process.
If gas is delivered above its dew point limits, liquids will condense somewhere in the pipeline as the gas cools or its pressure changes. Free water can freeze into hydrates that plug the line and combine with acid gases to corrode steel. Condensed hydrocarbons collect as liquid slugs that overwhelm downstream separators, damage compressors and burner tips, and can create safety hazards. Pipeline tariffs therefore impose dew point (or equivalent water-content and hydrocarbon) specifications as a condition of accepting the gas.
The most rigorous measure of hydrocarbon dew point is the cricondentherm - the maximum temperature at which any liquid can exist for that gas composition. Controlling to keep the gas below the pipeline's dew point across its whole operating envelope is what dew point control ultimately guarantees.
Control is achieved by the conditioning equipment: dehydration for water dew point, and cooling processes for hydrocarbon dew point. Operators verify the result with measurement - chilled-mirror dew point analyzers, moisture (water content) analyzers, or gas chromatographs that let the hydrocarbon dew point be calculated from composition. These instruments watch the outlet gas to confirm it is on spec.
Those analyzers and the process instruments on the dehy and dew point equipment feed a PLC or DCS. A cloud SCADA like Merobix reads the digitized readings over Modbus, DNP3, or OPC UA and trends water dew point, moisture content, and the health of the dehydration and JT processes across a facility or fleet, alarming when the gas trends toward its spec limit - so operators tighten the conditioning before off-spec gas is delivered and a pipeline imposes a penalty or rejects the gas.
Water dew point is the temperature at which water vapor in the gas starts to condense, controlled by dehydration. Hydrocarbon dew point is the temperature at which the heavier hydrocarbons start to condense, controlled by cooling the gas to drop those liquids out. They are separate specifications, and a gas can meet one while failing the other.
To keep the gas as a dry gas throughout the pipeline. If gas is above its dew point limits, water or hydrocarbons condense in the line - water forms corrosive, plugging hydrates, and hydrocarbons form liquid slugs that damage separators and compressors. Dew point specs protect the pipeline and downstream equipment from these liquids.
Water dew point is measured with chilled-mirror analyzers or moisture (water content) analyzers on the outlet gas. Hydrocarbon dew point is either measured with a chilled-mirror instrument or calculated from a gas chromatograph's composition analysis. These readings feed the control system so operators can confirm the gas is on spec and trend it toward the limit.
This page references the protocol specifications published by the organizations below. Editions, product capabilities, and documentation change over time - confirm current requirements and specifications directly with the source.
Last reviewed: July 27, 2026. Merobix is not affiliated with, endorsed by, or sponsored by these organizations; their names are used only to identify the standards and products discussed.
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