Pipeline Column Separation / Slack Line

Pipeline Column Separation

Column separation is the occurrence of two-phase flows in a liquid pipeline system. In liquid pipelines, this is considered a detriment to pipe integrity and operations if the system has not been designed to control and manage its occurrence. Generally pipeline operators detect the occurrence of column separation by inference. It may be inferred from dedicated pressure measurements at high elevation points, or through calculations made by a Computation Pipeline Monitoring system (CPM).

Vanmok LD™ Studio has built in a module for Column Separation or Slack line prediction.
More details can be found at: Columnfinder

Pipeline Column Separation Management – A Controller’s Perspective

Columnfinder™ can be a valuable tool for Controllers facing column separation in the following ways:  recognizing, interpreting, prioritizing, deciding on and implementing remedial action, and monitoring for column re-integration. Below are detailed descriptions of these key actions required to effectively deal with column separation.


Recognizing column separation requires Controllers to actively monitor pipeline operations, which will include monitoring column separation alarms that are received from Coulmnfinder ™.


Generally speaking, the pressure and flow on a pipeline will rise and fall in direct relation to energy available for moving the commodity in the pipeline during the course of operations. Controllers can determine the cause and effect of their actions,  such as start / stop of pumps or changes in set point control, and assess the impact on upstream and downstream sections of a hydraulic event, such as column separation. In the absence of Controller input, a sudden or steady decrease in pressure and flow may result in a column separation. Controllers are trained to react to this type of scenario by using a “Think Leak” mentality and disproving the loss of energy conservation. Controllers must be well-versed in using their observation of the hydraulic state of the pipeline and tools that they have available, such as Coulmnfinder™, to rule out a leak scenario, because column separation may mask a leak. It is difficult to assess the dynamic change in energy state due to column separation vs. a leak scenario.

Decide & Implement

Vanmok LD™ Studio can help a Controller to decide if the scenario represents a leak condition or a column separation. Once this decision has been made, then the Controller can respond, based on previously approved procedures, and take steps to minimize the potential leak condition. Alternatively in the case of a decision that determines a column separation is the more likely event, the Controller can perform actions that manage the pressure profile on the pipeline to ensure the whole pipeline is maintained in a liquid state. Recommended procedures instruct Controllers on specific actions and time required to re-integrate a column.


Once the Recognition, Interpret, Decide & Implement elements of a planned response have been initiated, continued monitoring through Vanmok LD™ Studio is required. It has the capability to distinguish between a column separation and a leak