The Importance and Uses of Outflow Analysis

Henry Lin, Integrity Engineer-In-Training at Dynamic Risk, shares his insights on the importance of outflow analysis and its diverse applications in liquid pipelines.


What is outflow analysis?

Outflow analysis is a process used to predict the volume of product loss in liquid pipelines in the event of a failure. By evaluating operational parameters and hydraulic considerations, a release can be modeled at points along a pipeline centerline. The volume of product released is dependent upon the local hydraulic profile pressure at the release site, the duration of the shutdown procedure, and the geometry of the pipeline.

Four (4) distinct phases are considered during outflow analysis:

Phase 1 – Full Operation

In the event of a loss of containment, there is opportunity for some time to pass before the shutdown of the pipeline begins. During this phase, the pumps are in full operation and the release flows at a constant rate for the full duration.

Phase 2 – Pump Shutdown

This phase estimates the amount of potential product loss after detecting a release and initiating the shutdown of the pipeline.

Phase 3 – Valve Closure

In this phase, the pumps have been shut off and the product flow is solely gravity fed. As the valves close during this phase, the flow rate is proportionally reduced.

Phase 4 – Gravity Drainage

After all valves are closed, the bulk flow of the product is stopped. However, an isolated section between the closed valves can be drained by gravity through the release opening.


Outflow Analysis Methodology


Figure 1. Outflow Analysis Methodology



Why is outflow analysis important?

The potential impact of loss of containment is a major factor in the overall risk associated with the operation of liquid pipelines. Performing outflow analysis helps estimate the environmental impact of potential product releases and allows operators to implement preventative measures to reduce the consequence in the event of a pipeline failure. This reduces the overall risk of the pipeline and enhances public safety and environmental protection.


What instances would pipeline operators consider conducting outflow analysis?

Pipeline operators could consider conducting outflow analysis whenever there are changes in pipeline operational conditions, such as product change and flow reversals, changes in shutdown procedures, such as troubleshooting time and pump shutdown time, or whenever there are changes in pipeline configuration, such as pipeline reroutes, valve additions/removals etc. In addition, outflow analysis could be considered during emergency response planning and pipeline maintenance.


What are some additional applications/uses of outflow analysis?

Additional applications/uses of outflow analysis include:

  • Baseline Outflow Volume Analysis for Risk Assessment – The calculation of worst-case discharge (WCD) baseline outflow volume analysis to evaluate the environmental impact (consequence) for risk assessments and emergency response planning.
  • Overland Spill Modeling – The calculation of product volume discharged at spill points along the pipeline centerline resulting from a pipeline rupture, and the modeling of overland and downstream pathways of the predicted spill volume.
  • Valve Placement/Optimization Study – The placement of new valves to optimize outflow volume and environmental consequence reductions.
  • Automation of Existing Valves – The automation of existing manual valves to optimize outflow volume reductions.
  • HCA Mileage Impact – A combination of outflow and overland spill modeling can be used to determine HCA affected segments.
  • CSA Z662-23 Annex B – Outflow analysis can support consequence analysis for environmental risk.
  • CSA Z662-23 Clause 4.4.9 Conformance – A combination of baseline outflow volume analysis and valve placement study can be used to assist with the determination of valve placements to minimize environmental impacts from pipeline failures.
  • 49 CFR 195.452(i)(4) Conformance – A combination of baseline outflow volume analysis and valve optimization can be used to determine the location of an emergency flow restricting device (EFRD) that would enhance environmental protection.


Dynamic Risk offers all of the above services to assist clients with performing outflow analysis, utilizing an internal proprietary outflow calculator to achieve optimal results.


hydrogen pipeline


Figure 2. Outflow Profile with Elevation Profile



Solution Brochure: Industry Leading Engineering Expertise for Outflow Analysis, Overland Spill Modelling and Valve Optimization Analysis

We invite you to download our Solution Brochure to learn more about our industry-leading engineering expertise for Outflow Analysis, Overland Spill Modelling and Valve Optimization Analysis, as well as their benefits for effective pipeline integrity management.

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Contact us for more information about how our team can help operators better manage their pipeline infrastructure for increased pipeline safety and reliability. 

About the Author:

Henry Lin, Integrity Engineer-In-Training

Henry Lin is an Engineer-In-Training registered with the Association of Professional Engineers and Geoscientists of Alberta (APEGA). He holds a Bachelor of Science (B.Sc.) degree in Civil Engineering from the University of Calgary and has over 6 years of experience in pipeline integrity. As an Integrity Engineer-In-Training at Dynamic Risk, Henry supports a variety of pipeline integrity related projects, including outflow assessment projects, ILI assessment projects and pipeline threat assessment projects.