What is the dew point in natural gas systems, and why is its control important for pipeline integrity?

• A. The temperature at which water or heavier hydrocarbons condense from gas, and controlling it prevents condensation that could cause corrosion, hydrate formation, and liquid entrainment.
• B. The pressure at which gas becomes completely dry.
• C. The temperature at which gas reaches its maximum density.
• D. The temperature at which gas becomes flammable.

Answer: (A)

Dew point in natural gas systems is the temperature at which water vapor and heavier hydrocarbons begin to condense into liquids at the pipeline’s operating pressure. Controlling this dew point is crucial for pipeline integrity because condensation introduces liquids into the gas stream, which can cause corrosion, hydrate formation, and liquid entrainment. Corrosion can be accelerated when water is present with acidic gases like CO2 or H2S; hydrates can form in high-pressure, low-temperature sections and block flow; and liquid entrainment leads to slugging and damage to compressors, meters, and separators. To protect the system, gas is treated to keep its dew point below the temperatures encountered along the pipeline, ensuring the gas remains dry and free of condensates. The other descriptions describe different ideas (a pressure at which the gas becomes dry, a maximum density temperature, or flammability temperature) and do not describe dew point.