Sponsored Content: Helping to prevent CUI In Hydrocarbon Processing – An Engineer’s Perspective
Insulation systems in hydrocarbon processing facilities are integral to the effective thermal performance of process pipes and vessels. While insulation plays an important role in process control, energy efficiency, noise reduction and passive fire production, it is important to consider how an insulating system stands up to a persistent threat in hydrocarbon processing facilities – corrosion under insulation (CUI).
Below, Alec Cusick, Technical Services Engineer at Owens Corning discusses the conditions that lead to CUI, shares strategies for defending against CUI, and describes how the selection of insulating system materials can help protect hydrocarbon piping and storage infrastructure against CUI.
What is CUI and how does it occur?
Corrosion can be described as the deterioration of a material that occurs from a chemical or electrochemical reaction within its environment. Typically, that material is a metal. Over time, corrosion can slowly degrade the integrity of piping, equipment and structural steel. Because pipes are covered by insulation, the degradation may remain undetected until damage is extensive.
In the case of carbon steel, corrosion occurs as oxygen reacts with iron to form iron oxide. This process requires the presence of oxygen along with liquid moisture to act as an electrolyte for the reaction. If these conditions are met, elevated temperatures can further increase the rate at which corrosion occurs, as electrochemical processes typically occur more rapidly at higher temperatures. Other conditions in hydrocarbon facilities – such as the presence of chloride ions from dissolved salts – can accelerate the rate of corrosion. In the case of stainless-steel, dissolved chloride ions are capable of stripping away the protective surface layer of chromium oxide which provides stainless steel its corrosion resistance.
What are common approaches for protecting hydrocarbon processing pipes and vessels from CUI?
There are three methodologies that are commonly employed in today’s industry for mitigation of CUI. All three approaches address the presence of water, albeit in different ways. One approach is to change the chemistry of any water present in the system in some manner to make it less corrosive. A second option is to allow gravity to channel away any moisture that gets into the system. This approach is typically limited to above ambient processes, as a physical path must exist for water to exit the system. The third approach involves fully sealing off a system to prevent water from coming into contact with steel surfaces. This approach is often utilized for systems within hydrocarbon processing facilities, as insulation systems on below-ambient processes are commonly designed to be sealed against water vapor ingress to begin with. The use of a low or zero permeability insulating material can assist in preventing water from getting into the insulating system and reaching the substrate.
How does permeability factor into keeping water out of an insulating system?
In below ambient piping systems, there will be a natural tendency for water vapor in the air to drive towards the cooler surface of the substrate under the insulation. Selecting a low or zero-permeability insulation will resist the vapor drive and prevent it from passing through the insulating material to the substrate below.
Owens Corning FOAMGLAS® cellular glass insulation is used in hydrocarbon processing facilities around the world for its impermeable qualities. It has a permeability rating of 0 and does not allow for the passage of water vapor through the material. The non-absorbent nature of FOAMGLAS® means it will not retain any condensation from nearby cold surfaces. Additionally, FOAMGLAS® cellular glass will not absorb or retain any liquid hydrocarbons that it might come into contact with if installed around an area such as a valve or flange.
What are some other material performance considerations when defending against CUI in hydrocarbon processing facilities?
Combustibility, compressive strength, dimensional stability, and durability should also be considered when selecting insulation materials. Processing hydrocarbons typically involves a wide range of temperatures. The span of process temperatures – from extreme cold to extreme heat – as well as the presence of hazardous materials should be considered. As flammable materials are usually present in hydrocarbon processes, an insulating material should ideally be non-combustible. The compressive strength and dimensional stability of materials in the insulating system should also be considered given the extreme conditions in industrial facilities.
All of these factors have helped inform the specification of Owens Corning FOAMGLAS® cellular glass insulation in petrochemical plants around the globe. FOAMGLAS® cellular glass insulation is non-combustible, and ideal for environments processing volatile materials. It also boasts a high compressive strength. It also has a coefficient of thermal expansion similar to that of steel and stainless-steel, meaning it can closely match the expansion and contraction of steel substrates over a wide range of process temperatures. FOAMGLAS® is made of 100% glass and is chemically resistant to many hazardous materials and chemicals found in industrial processing facilities.
What are 3 best-practice takeaways for defending against CUI?
The first consideration to make for mitigation of CUI must be avoiding the corrosive effects of moisture. As noted earlier, there are three common strategies for managing this challenge: Change the chemistry of the liquid moisture, provide a way for moisture to exit, or prevent liquid moisture from ever entering the system. In hydrocarbon processing facilities, keeping liquid from ever entering the system is often the method of choice.
Second, taking a system approach helps ensure that all of the parts work together. A system approach considers how the insulating materials, accessories, vapor barrier and installation techniques work together to make sure the entire system remains protected from water infiltration.
Finally, the integrity of the installation process cannot be overlooked. At the end of the day, an insulating system is only as effective as the practices used in installing the system. For that reason, Owens Corning conducts education sessions at our global training centers, offers on-site support working alongside installers in the field and provides documentation to support specifiers and installers.
Learn more about defending against CUI in Hydrocarbon Processing's podcast or visit www.FOAMGLAS.COM.
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