Preventing Mechanical Insulation Systems Nightmares
Before starting a discussion of the issues associated with mechanical pipe insulation system failures (nightmares), it is important to note that the vast majority of insulation applications function as designed, meaning they provide 1 or more of the following: energy savings, process control, personnel protection, emission reductions, noise reduction, condensation control, and plant operating efficiencies for the life of the application. In addition, in many cases where the insulation system does not meet expected performance criteria, the situation would not merit being classified as a “nightmare.” With that said, it is important to learn from history and modify actions when less than expected performance does occur in order to prevent future issues.
Additionally, it is important to note that this discussion is inclusive of the entire insulation system, not just the insulation material used on the system. The insulation is only 1 component of the system, and while it is an important component, any component of the system or installation can cause a failure, as will be discussed in this article. The insulation system performance issues that have been brought to my attention over the years can be divided into 2 groups: those that could have been prevented through better design, installation techniques, maintenance, or common sense, and those incredibly rare circumstances, that were not anticipated and could not have reasonably or cost effectively prevented. This article will concentrate on issues that could have been prevented.
Major issues can generally be classified into 3 broad categories:
- Mechanical damage;
- Corrosion under insulation (CUI); and
- Condensation (potentially resulting in mold growth). It should be noted that on cold operating systems in unconditioned spaces, when condensation occurs for a short duration as a result of the environmental conditions exceeding the design during brief extreme conditions (i.e., casual condensation), this should not be considered a failure but rather part of the design. In unconditioned spaces, condensation cannot be prevented all the time.
Mechanical damage and CUI can occur on both hot- and cold-temperature systems. Issues relating to condensation only occur on below-ambient systems and are usually the failures that receive the most attention because they are extremely noticeable, creating immediate concern and requiring immediate action. Thus, many of the examples given in the article refer to systems operating at below-ambient temperatures.
An insulation system is designed to operate under a given set of operating and environmental conditions. If the design team does not exercise due diligence to gather the information necessary to develop the correct design conditions for the specific application, there is a good chance that at some time during the operation of the system, it will not perform as desired. Obtaining a local engineer’s or insulation contractor’s insight (prior to the RFQ going out) into the material selection and installation process is invaluable. A design engineer should not overestimate a product’s/material’s performance properties and should stay well within the scope of the insulation material’s performance parameters. This will help create a “fail safe” system where the failure of 1 aspect of the system will not jeopardize the entire system. An example would be to specify a sealed low permeability (.02 perm or less) vapor barrier system and a sealed low permeability closed cell foam insulation on a cold system for added insurance against moisture intrusion, rather than depending only on the vapor barrier system or the closed cell foam insulation. “Value engineering” a system—a phrase often associated with cost cutting—may sometimes result in taking value out of the system rather than putting value into it. All too often, value engineering results in saving pennies up front and costing dollars later down the road.
A system should be designed for the worst conditions that might be expected to occur, and contingencies should be in place for when extreme conditions occur. Typical examples of this type of situation would be: convention centers, warehouses, and back room storage areas—they all may be conditioned spaces part of the time, under normal conditions, but when the loading dock doors are open for long periods of time, some of the space becomes unconditioned, particularly if the area has high ceilings and the cold pipes are located in the elevated areas where hot, moisture laden air or high humidity would collect. If the designer does not want to account for these times in his design conditions, he should consider a contingency plan such as drip pans under the piping or fans that increase the air flow in the area to reduce the chance of condensation when the temperature or humidity goes up, such as in the aforementioned scenario. Preparing for a situation in which the HVAC system cannot maintain the area within the design conditions can eliminate a problem situation.
While some systems operate continuously, many are shut down at certain times of the year for changeovers or maintenance. Some buildings are designed to have the HVAC system shut off during the evening hours or on weekends to conserve energy (i.e., idle building syndrome). This type of condition can create unexpected issues if not designed for, especially in high-humidity geographical areas such as Houston, Texas.
Consider the following example of a shutdown situation on a hot operating system and the issues it could create. Picture an outdoor high-temperature system that operates at 300°F, so the designer does not expect there to be any moisture/corrosion issues due to the high operating temperatures. Then, during the summer, the system is shut down for repair. During this shut down period, moisture has a chance to ingress into the insulation, creating a potential long-term corrosion issue if the insulation is not protected 100% from moisture ingress. A similar example would be on an indoor system that is not operating, the insulation system may cool down enough during the evening that during a hot humid day, condensation can occur on the surface of the insulation system. If the system was jacketed with a stapled all service jacket (ASJ), moisture will penetrate the system through the holes that the staples create, creating a potential CUI situation.
Another example of an unexpected condition causing issues is an underground parking garage in a coastal area that periodically floods during the rainy season, creating unusually high humidity for extended periods of time. High humidity may have been anticipated, but not to the extent and prolonged time period this situation creates, thus causing the insulated piping to be exposed to out-of-design conditions for extended periods of time, creating a potential for condensation and mold growth on the insulation and corrosion of the exposed piping—there is also risk of CUI developing under the insulation if the system is not designed correctly or if a critical component of the system such as the vapor stops or vapor barrier fails. A contingency plan for increased drains, pumps, and high velocity fans for increased air movement during this rainy period would prevent this situation from occurring.
In commercial, industrial, and even multifamily residential buildings, it is possible for “non-conditioned” spaces to occur that are sometimes overlooked. Buildings under construction that have not been closed in (doors, windows, or even roofs not yet in place) are non-conditioned spaces and subject to moisture-related issues if a chilled water system is turned on prior to the building being enclosed. In these cases, hot and humid outdoor conditions can become the indoor conditions, resulting in excessive condensation formation on the chilled water piping. For this reason, insulation should not be installed until the building is fully enclosed. Even if the chilled water system is not on, rain can often get into the building, soaking any insulation if it is not enclosed. Another example is a mechanical room with no air movement where operating equipment can add significant heat to the room and exceed the design conditions.
If a robust insulation system is required (such as a roof top application) and there is the opportunity for mechanical damage, it is important to specify a robust jacketing system. Outdoor applications susceptible to wide swings in environmental conditions (temperature/wind) or indoor applications where the operating system temperature cycles from hot to cold place greater demand on the compatibility of the insulation and the jacketing system. The jacket has to allow for any differential expansion and contraction of the insulation, often requiring mechanical fasteners.
If the insulation is being installed outdoors in an area where there is a high concentration of chemical plants or close to a salt body of water (e.g., Houston and the nearby gulf coast) the jacketing system must withstand the potential of air or water that may have a high concentration of corrosive chemicals not found in other areas. Again, the knowledge of an experienced local contractor can be very valuable in this circumstance. When determining the insulation thickness required for an operating system, the engineer will use the design conditions (operating and environmental conditions) in conjunction with the thermal conductivity of the insulation. However, a common mistake is made when jacketing is involved, in that the designer may overlook the effect that the emittance (ability of a material to absorb or reflect heat) of the jacket being specified may have on the thickness of the insulation required to prevent condensation, particularly if the emittance of the jacket and the insulation vary, which is often the case. If this difference is not considered, it could likely create an unexpected condensation issue.
When installing any jacketing, the overlap seam should be positioned down to act as a water shed. On a cold operating system, there can be no breaks or holes in the vapor barrier system—jacketing installed using staples or ASJ paper clad should not be used as it creates a wicking seam when casual condensation occurs on the surface of the jacket during those times when the design conditions for temperature or humidity are exceeded. These type of oversights in specifying materials or installation techniques can turn what would have been a minor issue into a major problem. Also, maintenance that involves cutting into the system or destructive testing will compromise and ruin the system it is checking.
An insulation system design is only as good as its weakest link. If the designer accounts for 95% of the stretch-out plan but leaves the last 5% open to interpretation, he or she is probably going to have problems, particularly if it is a below-ambient system where condensation is a key concern. A design for a cold operating system will always call out the areas to be insulated, type of insulation, and thickness of insulation, but if it does not address the longitudinal seams, butt joints, pipe supports, termination points, and fittings, it is not addressing the most common areas of failure in an insulation system. On a cold operating system, the designer would want to ensure that these areas meet the same requirements for thermal conductivity, water vapor transmission, etc. as the rest of the system. Otherwise, this becomes the weakest link and will be a potential failure point in the system. On cold operating systems, taped seams/joints are not acceptable. Adhesive or glued seams are more secure and generally offer better water vapor permeability properties and better longevity. When insulation absorbs and retains water from condensation, its thermal conductivity increases, leading to greater surface condensation and further problems associated with that phenomenon. Using materials or practices that minimize the risk of the insulation becoming wet will assist in maintaining the performance of the system. Chapter 23, Insulation for Mechanical Systems, in the ASHRAE Handbook—Fundamentals is a good design guide reference.
Best Practice Installations
The installation of the system is as important, if not more important, than the specification of the individual pipe insulation and accessory materials. Be familiar with the manufacturer’s installation instructions and never deviate from them unless the engineer or manufacturer is consulted first. If the application is unique or there are unique installation conditions, consult the engineer or manufacturer before going forward. Open seams, butt joints, or poorly fabricated fittings are the primary causes of cold system failures in the field. Using a contractor who is experienced in using the materials specified is very important. Each insulation type has its own set of “best installation practices” that are learned over time. Just because someone has years of experience in installing insulation, this does not automatically mean that he or she has experience with the specific type of insulation being used or for the specific type of system being insulated. Good timing and cooperation between the building trades is important to keep the insulation from being damaged after it has been installed. When sheet rock is being installed or other stages of the building process are completed, the indoor building environment (humidity) can be affected and must be accounted for. Storage of the insulation in a clean, dry area is mandatory so it does not get damaged or wet prior to being installed.
Minimizing seams or joints is always a good way to minimize potential failure points. On cold operating systems, using pre-fabricated fittings that are produced in controlled conditions help to ensure tight seams—as opposed to using fittings that are fabricated in the field under potentially challenging conditions.
Real nightmares can occur when a poor design or poor workmanship is covered up or enclosed. In this situation, a failure may go undetected until the situation is catastrophic, taking a potential minor issue to major status. Any part of the insulation system—particularly any below-ambient piping that is going to be enclosed—should be thoroughly inspected prior to it being hidden. This is also relevant to any insulation that is going to be jacketed.
ASTM has published several Installation Guides for various insulation materials, including ASTM C1696 Standard Guide for Industrial Insulation and ASTM C1710 Standard Guide for Installation of Flexible Closed Cell Preformed Insulation in Tube and Sheet Form. The National Insulation Association (NIA) has several videos on the installation of various types of insulation systems, and the February 2013 Insulation Outlook article, “Insulation Installation Checklist,” can also helpful. NIAMA also offers a Guide to Insulating Chilled Water Piping Systems with Mineral Fiber Insulation.
Best Practice Maintenance
All mechanical piping insulation systems require periodic inspection and possible repair. When problems are found, such as water condensation or CUI, they should be addressed immediately; these are issues that will only worsen if ignored. Failures on cold operating systems compound themselves the longer the failure point goes unchecked. Wet insulation has a higher (worse) K-value, resulting in higher heat flow that creates a situation for condensation to form more easily, allowing for the insulation to get wetter. Moisture forms around the inner diameter of the pipe and will travel/migrate to the lowest point in the system (often in fitting areas) creating potential for mold and corrosion depending on what type of piping is used. Repair often requires that the facility, or at least the operating system, be shut down. Since the repairs are usually not anticipated, they are usually not budgeted, causing delays in the repair. If the building manager is looking for a system that requires minimal maintenance, this should be considered in the design process, and a more robust system should be specified (i.e., insulation and a vapor barrier jacketing system).
One of the biggest maintenance issues results not from the failure of the insulation system, but when insulation is removed for various reasons, such as cutting into a line or getting to a valve, and it is not replaced, leaving uninsulated exposed piping that is at risk for damage. If you want to prevent your system from turning into a “nightmare,” it is important to remember that (1) good design means good performance; (2) design should follow best practice installation techniques; and (3) plan for periodic maintenance and follow up.
To design a high-performing insulation system, you need to have as much information on the actual application and the local environmental conditions as possible. One specification will not fit every application. Accounting for local environmental conditions is critical. Think of the worst case operating conditions and design for them. Be cautious of “value engineering” and last minute changes at the job site. It is vital to remember that insulation materials do not fail per se, but that entire systems fail. All aspects of the system are important. Failure in any component of the system will cause the system to perform at less than desired levels, but more importantly, it has the potential for a lost customer or even worse, a lawsuit, which is a real nightmare. If a good design is based on the best information available, along with the best practices, installation techniques and maintenance programs, the insulation system will perform as expected and “nightmares” can be avoided.
This article was published in the October 2016 issue of Insulation Outlook magazine. Copyright © 2016 National Insulation Association. All rights reserved. The contents of this website and Insulation Outlook magazine may not be reproduced in any means, in whole or in part, without the prior written permission of the publisher and NIA. Any unauthorized duplication is strictly prohibited and would violate NIA’s copyright and may violate other copyright agreements that NIA has with authors and partners. Contact firstname.lastname@example.org to reprint or reproduce this content.