Liquid accumulation over the long term in pipelines due to low velocities can also lead to intermittent slug flow in pipelines. Additionally, the gas transport could see high-pressure drops and reduction in flow, putting excessive loads on gas compressors. The same problem of corrosion can occur as discussed for the flow of liquids. Liquid accumulation will occur at low points and direction changes in the pipe over a long period of time. The gas travels at the top part of the pipe and the liquid travels at the bottom part of the pipe, clearly parting the fluid in two parts. When the flowing velocity is low, the flow may be stratified in the horizontal run of pipe. Single Phase Gas Flow (with entrained liquids)Īn example of such systems will be natural gas with entrained liquid water droplets and heavier hydrocarbons. Such corrosion can lead to the failure of carbon steel piping/pipeline over the long term. The mechanism of corrosion in simplistic terms is that carbon dioxide and/or hydrogen sulfide will react with the accumulated water in the pipeline leading to acid corrosion by the formation of Carbonic Acid (H2CO3) and/or Sulfuric Acid (H2SO4).
If the hydrocarbon liquid has even trace amounts of dissolved carbon dioxide or hydrogen sulfide, pipe/pipeline corrosion can occur. Water accumulation will occur in low points of the piping over the long term. At low flowing velocities, the entrained discontinuous phase water will drop out from the continuous phase hydrocarbon liquid to the bottom of the pipe.
Flow of Liquids through pipelinesĪ typical example would be a hydrocarbon liquid with entrained water, where the hydrocarbon liquid is the continuous phase while the water is the discontinuous phase. the operating point of the pump moves towards shut-off leading to reduced pump efficiency and accelerated mechanical wear and tear of the pump and pump sealing system.