BY G2 INTEGRATED SOLUTIONS
An operator’s worst fear is a leak or rupture in their pipeline. Excavation damage (mechanical damage, dents, gouges, etc.) are one of the leading causes of pipeline incidents; however, external and internal corrosion can result in significant consequences as well.
Myth: All pipelines corrode.
Fact: With proper maintenance and monitoring, a pipeline can be safely operated for many decades.
Before delving into the methods for prevention, you need to have a good understanding of what pipeline corrosion entails.
WHAT IS PIPELINE CORROSION?
Pipeline corrosion is a natural deterioration and destruction of pipe material and essential properties due to electrochemical and other ingredient reactions of pipeline materials with their environment – on the inside as well as outside surfaces. Like any other naturally occurring hazard, a pipeline corrosion can result in a life-threatening failure and expensive damage to the pipeline and related system. These incidents can also cause more scrutiny by regulators and delays in future pipeline projects.
EXTERNAL V. INTERNAL
A component that can have a significant effect on your cross bore program budget is the efficiency of the sewer inspection execution. Sewers are fundamentally complex, reliable maps are hard to track down, and there are often times access limitations such as offsets, collapses, or buried cleanouts. Since locating the inspection can become area difficult, field crews run into inadvertent challenges such as:
• External: Occurs in response to environmental conditions on the outside of the pipeline. When an unprotected pipe is buried in moist soil, an electric current naturally flows from the pipe metal into the soil. The current flow causes the metal to dissolve in the surrounding moisture, resulting in corrosion.
• Internal: The type of product carried inside the pipe can sometimes create corrosion, such as the type of gas (wet or dry) or oil being transferred. The gradual reduction of wall thickness of the pipe occurs resulting in loss of pipe strength. It can be spread relatively evenly over an area of the pipe surface or in isolated spots on the pipe.
Risk Management techniques, such as HAZOP and LOPA, can be implemented to point out areas of concern.
The intention of performing a HAZOP is to review the design to pick up design and engineering issues that may otherwise not have been found. The technique is based on breaking the overall complex design of the process into several simpler sections called ‘nodes’ which are then individually reviewed.
Layer of protection analysis (LOPA) is a recently developed, simplified method of risk assessment that provides the much-needed middle ground between a qualitative process hazard analysis and a traditional, expensive quantitative risk analysis. Beginning with an identified accident scenario, LOPA uses simplifying rules to evaluate initiating event frequency, independent layers of protection, and consequences to provide an order-of-magnitude estimate of risk.
External coatings are designed to prevent steel from coming in contact with the surrounding environment. These are formed from an electrically insulating material to prevent electric current from flowing between the pipeline and the surrounding environment. External coatings can be applied both at the manufacturing plant or in the field before installation, providing effective electrical insulation, moisture barriers, and a good adhesion to the pipe surface. Common coating types include:
• Bituminous Enamels (Coal-tar/ Asphalt enamels)
• Asphalt Mastic (mixture of sand, crushed limestone, fiber and air blown asphalt)
• Liquid epoxies and phenolics
• Extruded plastic coatings
• Fusion-bonded epoxy (FBE)
• Three-layer Polyolefin
• Wax coatings
Since corrosion is an electrochemical reaction, the objective of cathodic protection is to prevent the pipe metal from acting as an anode so while currents are flowing the metal does not lose surface. The two types of protection, sacrificial anode and impressed current, ensure that the current will flow from the soil into the metal and not vice versa. A low voltage DC current flow is induced within the pipeline in a direction opposite to naturally existing current, allowing the pipeline to serve as a cathode in the electrochemical circuit..
Controlling the composition of the product being transported can help eliminate, or limit, corrosion-causing contaminants. These contaminants include water, CO2, H2S, and more. Corrosion inhibitors can be introduced into the pipeline to form a protective film on the internal surface of the pipeline. These will reduce corrosive interaction between the pipeline material and the product being transported. Cleaning pigs can also be used to remove accumulations or water or other elements.
The more knowledge you have, the better for prevention. However, a lot of times operators don’t know what they have. Implementing an Integrity Management Program that entails monitoring the process and product will help reduce pipeline corrosion. Asset integrity experts will look at all documents, inspection records, pipeline history, CP records, types of coatings being used, and all the effects of external corrosion. They will also inspect processes you are running, such as dry gas, wet gas, anything containing chlorides, crude oil, etc.
Based on risk assessment data and records, experts will advise on specialized protection techniques via engineering analysis and MAOP. Corrective action procedures can be implemented case by case after analyzing mitigative measure for internal and external corrosion during the risk assessments.
Through records search, field inspections, and other pipeline integrity data, including the grade and wall thickness, G2 can provide engineering analysis and support for various pipelines. Contact us today to see how our experts can optimize your business and extend the life of your pipeline.