Insulation system failure prevention on below-ambient piping
An ounce of prevention is worth a pound of cure when it comes to a properly designed, installed, and maintained pipe insulation system. Mechanical insulation failures occur for a variety of reasons, including improper design for the application conditions, faulty materials, poor installation techniques, or damage to the insulation. Many of these failures can be prevented through careful preparation and planning.
Appropriate design, quality materials, and proper installation can drastically reduce the possibility of a compromised insulation system. Damage should be minimal or nonexistent with the proper selection of materials. A proper design anticipates the stress and abuse an insulation system will face, and specifies an appropriate insulation and jacket. There are a variety of insulation and jacketing choices. But, often the lowest cost product is selected rather than the one that best meets the job criteria, which may result in system failure down the road.
All insulation systems require a degree of maintenance, and some materials may require considerably more than others. Insulation systems should always be properly maintained. But, if resources for maintenance will be minimal, then that should be factored into the material selection and insulation system design. Proper installation of the insulation system, including planning for the other parts of the construction process and the scheduling of other trades, will result in a system that is less vulnerable to damage. Frequently, buildings are not enclosed before insulation is installed, and the insulation may be exposed to the environment. Similarly, other aspects of building construction may affect insulation. Thus, engineers and general contractors should consider types of insulation or jacketing that can withstand the environment stressors, such as higher humidity. Appropriate storage is another important consideration, as materials can become wet or damaged if left exposed at the job site. Again, careful planning and the anticipation of potential issues are keys to reducing damage to the insulation.
The consequences of a damaged insulation system vary greatly, based on whether it is a hot or cold (below ambient) system. Damage to a hot system will result in energy loss and possibly pipe corrosion, depending on the conditions. Damage will likely be fairly localized and manageable, if repaired in a timely fashion. Damage to a cold system can, and often does, result in a catastrophic failure of the whole system, especially if it is not repaired immediately. Damage to a cold system will usually result in moisture penetration, which can cause a number of issues, including:
• Loss of thermal resistivity
• Saturated insulation
• Mold growth
• Corrosion under insulation (CUI)
• Surface condensation
• Formation of ice on or in the insulation system
• Complete system failure
If damage to the insulation system is not repaired immediately, the failure will spread as moisture penetrates to other areas of the insulation. Potential solutions for limiting the extent of an insulation failure on a cold system include:
• Select low permeability. Closed cell insulation materials that resist moisture absorption/wicking.
• Choose insulation and jacketing materials that are mold resistant. If a problem with mold growth is anticipated, materials that meet certain performance requirements, such as ASTM C1338—08 Standard Test Method for Determining Fungi Resistance of Insulation Materials and Facings, or others can be helpful in this area.
• Select the best type of vapor retarder jacket for the type of application—e.g., indoor, outdoor, or buried applications. ASTM standards can be an excellent resource. For example, ASTM C 1423 addresses criteria for choosing jacketing materials for application over thermal insulation covering piping, ducts, and equipment. ASTM C 1136 lists several jacket options for indoor applications. Furthermore, a specification for outdoor applications is in the works at ASTM Subcommittee C16.40: Insulation System under the Laminate Protective Jacket and Tape for Use on Thermal Insulation task group. These examples are by no means all inclusive; vapor retarder jacket selection based on the specifics of a given application will yield the best results.
• Choose materials and accessories that meet the performance criteria for the specific job, and make sure they are properly installed—which includes ensuring that workers are trained in how to protect the integrity of the system during installation. Foot traffic and other physical abuse can damage many insulation systems and should be considered when selecting materials. It is also important to consider whether the environment is conditioned, as well as the humidity level of the space, as different options will perform better under different conditions.
• Use moisture vapor stops on cold systems to isolate insulation sections and limit the failure caused by a damaged section.
• Be sure all seams, joints, and termination points are secure and moisture tight on the vapor retarder and/or the insulation. Do not leave any seams or termination points unsecured or any insulation exposed when leaving a job location at the end of the day. Only install in a day what can also be covered by vapor retarder and jacketing that same day.
• Perform an inspection of each insulated area before moving on to another section, specifically checking for any open seams, discontinuities in the vapor retarder, or problems areas. Immediately repair any areas that need attention.
• Install an outer protective jacket (e.g. aluminum outdoors or PVC indoors) if needed to protect the insulation system and the vapor retarder from physical abuse.
While the frequency of problems is probably equal for hot and cold systems, the failures most often publicized are those on cold systems—e.g. chilled water—due to their severity. For example, cold systems where the ambient space is unconditioned can have a particular concern for the issue of surface mold, which can result in major problems sometimes culminating in lawsuits and replacement of entire insulation systems. Project types where this could occur include condominiums, office buildings, dormitories, hotels, sports arenas, or convention centers. Lawsuits occurring from system failures can become very difficult situations where blame is exchanged between multiple parties—the designer blames the installer, while the installer blames the designer, manufacturer, or other trades that may have damaged the insulation while they were on the job. Regardless of who is at fault, the failure may have been prevented if proper materials were selected in the design stage, better installation scheduling and techniques were used, and proper maintenance was followed.
Unfortunately, when failures do occur, it is typical for those involved to look for a guilty party rather than consider how the problem may have been prevented. Proper preparation is often all it takes to prevent insulation damage that can cause a system failure. It is time to approach hot and cold systems differently by specifying materials that are designed for below ambient conditions on cold systems. This is particularly critical when the insulated pipe is located in an unconditioned space.
When looking at materials, designers must examine the physical properties of the material—specifically, the properties of the material as installed. The design should consider the building envelope, building use, maintenance that will be available after the job is completed, as well as the desired energy savings when the building is actually operating. Insulation should be viewed as a way to lower operating costs and save energy, rather than just a building expense.
All contractors should work together, allowing each trade to do its job while keeping in mind how their actions will affect the entire project. The insulation contractor should use the best installation techniques available—those that not only save time, but also ensure performance and reliability. If they do follow these protocols, they should be able to produce cold insulation systems that operate effectively and without errors.
Steve Fisher is a Product Development and Installation Field Support Manager for K-FLEX USA. Fisher is experienced in installation best practices for mechanical insulation, as well as insulation product development and quality assessment. He is a NIA Certified Insulation Energy Appraiser with a B.S. in Textiles Engineering and an MBA from North Carolina State University.