Arrangement of piping designed to catch a slug of liquid in the gas pipeline to separate it from the gas, or equipment for the purification of water.

In a natural gas pipeline, the liquids flow along the bottom of the pipleines (except in steeply inclined and vertical lines) with the gas flowing over the top “sweeping” the liquid along the pipelines. At lower gas flowrates, the amount of liquid held up in the flowlines tends to build up as the gas velocity is insufficient to “sweep” the liquids up the inclines and out of the flowlines. In addition, steep rises and falls in hold up rate can be caused by the undulations in the pipeline. In order to properly estimate all of the above, accurate bathymetric information needs to be available.

At very low flow rates, the amount of liquid held up in the low parts of the flowlines can build up to the point that a liquid “blockage” occurs. This liquid blockage is often referred to as a slug. The formation of slugs can result in instabilities in flowline operation leading to unsteady flows to the inlet of the receiving facility at the end of the flowline. Unsteady flow of gas and liquid to the terminal facility can result in poor operation of the facility. In order to help smooth the flow of fluids into the facility, a “Slug Catcher” may be installed, which provides a storage volume for liquids produced from the pipeline system. This volume allows the flow to the downstream plant to be smoothed out, helping a steady flow to be maintained.

Another reason for provision of a slug catcher is to manage liquids produced as the flowrate through the pipeline system varies. In general, an increase in gas rate is generally accompanied by an increase in liquid rate at the terminal both due to the increased liquid volumes associated with the additional gas, but also due to the production of the difference in liquid holdup between the lower and higher gas rate.