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Those who regularly work with thermal insulation know that given the high cost of energy today and the high cost of dealing with corrosion under insulation (CUI), properly installing and maintaining insulation is of utmost importance. However, at any industrial facility—whether it is a power plant, an oil refinery, a pulp and paper mill, a chemical plant, or a food-processing plant—facility management faces many challenges every day, and insulation maintenance gets mixed in with all the rest. As a result, insulation problems often fall to the bottom of the list. This is because, for management, the primary objective is to keep the facility operating and producing whatever it produces (electricity, heating oil, gasoline, ethylene, paper, food, etc.), and the link between insulation maintenance and production may be hard to see.
How can management be made to understand the importance of properly maintaining insulation so that it functions the way it was originally engineered? What can be done to get management to budget the money needed to maintain the insulation properly?
Start With the Basics
It is critical to go back to basics and answer the question, “What is the purpose of the insulation on the pipes and/or equipment?” As emphasized in the National Insulation Association’s (NIA’s) National Insulation Training Program (NITP), that purpose could be one or more of the following:
Condensation control (for below-ambient service temperatures)
Process control and efficiency
Sometimes overriding all of those is the need to mitigate CUI, a costly problem that can lead to plant shutdown if not addressed. Once the purpose of insulation at your plant is understood, it is a lot easier to understand the link between insulation maintenance and plant productivity.
Wasted Energy From Missing or Damaged Thermal Insulation
In the May 2005 issue of Insulation Outlook, an article titled “How Many Barrels of Oil Can Mechanical Insulation Save?” estimated that if all damaged or missing insulation at U.S. oil refineries was repaired, replaced, or reinsulated, the equivalent of 585,000 barrels of oil per year could be saved. (See www.insulation.org/articles/article.cfm?id=IO050505 for more details.) This savings equates to two-thirds the estimated average output of the Alaska National Wildlife Refuge, if it was opened up to development and was operating at full production. Although these figures are only estimates, the conclusion is certain: The energy waste that results from missing or damaged insulation on an industrial facility can be huge when considered collectively for all of North America—or for the entire world.
An Insulation Survey
Management often thinks insulation lasts forever. If metal jacketing does not look damaged or degraded, people often assume that the insulation is performing well. If the metal jacketing and the insulation beneath it are damaged on only 5 percent of the pipes, management is often willing to overlook it. The reasoning behind this is that if 5 percent of the insulation needs replacement, the heat loss is just 5 percent higher than it would be otherwise. They assume 5 percent is not worth worrying about.
Most people tend to think linearly. Unfortunately, heat loss is not linear. Thermal insulation can last a long time, but it does not last forever.
With an insulation survey, one can take an inventory of the condition of the insulation and those areas that need replacement. Clearly, there needs to be a systematic way of taking this inventory. (See www.insulation.org/training/ieap for information on NIA’s Insulation Energy Appraisal Program, which teaches a standardized approach to conducting insulation energy appraisals.) Further, if either energy efficiency or process control is a role for the insulation, then the appraisal gives a method of quantifying the results in British thermal units (Btus) of energy saved per year and thereby calculating dollars of energy saved per year. By taking each scope separately (such as a pipe of a certain size and temperature), one can quantify the amount of any energy loss and the dollar value of that energy loss.
Brian Niemi of Dupont Engineering Services (DES) conducts insulation appraisals for various clients. At one chemical plant, DES identified approximately 11,000 details (places requiring insulation replacement or repair), with a total area of 45,000 square
feet. This included many valves and flanges that had been left uninsulated, resulting in enormous unnecessary heat loss and safety hazards (due to the high temperatures, which can cause burns). The total estimate to replace this insulation was about $2.2 million, or $200 per detail, including costs for removal and disposal of old insulation, new insulation materials, labor to install, scaffolding where necessary, and other ancillary costs.
Since this facility normally spends only $300,000 to $400,000 annually for insulation maintenance, the $2.2-million estimate was more than the facility owners were prepared to spend at one time. Consequently, DES prioritized the details in terms of heat loss (a function of the process temperature, the area of the detail, and the condition of any existing insulation). Facility management was then able to focus on the work that would save the greatest amount of energy before moving on to the details, which would give slightly less bang for the buck. While it would have been ideal for all 11,000 details to be addressed immediately, the reality is that the facility owners did not have sufficient resources, such as an on-site maintenance crew, and they did not have access to all areas at the same time. By prioritizing the work, facility management got all of the work done over time.
In one chicken-processing facility, DES surveyed the insulation on pipes that handled liquid fat, which would clog the pipes if it solidified due to low temperatures. Clogged pipes had posed a problem at the facility in the past. In this case, DES recommended that a heat-trace system be added to the pipes, with sufficient insulation thickness to limit heat loss and maintain the chicken fat in a liquid state. The economics were straightforward: Replace the insulation with new insulation, and keep the plant operating without interruption. The consequences of insulation failure were simply too great to allow it to happen.
Niemi notes that in some facilities with extensively degraded insulation, DES may recommend a high compressive strength insulation as a replacement for lower compressive strength material. For example, where horizontal pipes are frequently stepped on, resulting in damage to a softer insulation with thin aluminum jacketing, DES may recommend the use of either calcium silicate or expanded perlite insulation with thicker steel jacketing. DES’ energy analysis details the energy savings that result from this insulation system upgrade.
CUI vs. Energy Savings
Many industrial facilities—particularly oil refineries and petrochemical plants located near the ocean or a sea, or in areas where it rains a lot—suffer from both CUI and energy waste when insulation becomes damaged. When insulation systems age or become damaged, the caulk sealant cracks and the metal jacketing can open up gaps where rainwater—which may contain salt—intrudes. If the insulation is an absorbent type and the service temperature is relatively low (below 300°F), then CUI can result. The heat loss from wet insulation may be as much as 10 times that for dry insulation. This can be a constant battle at older facilities because the caulk used to seal metal jacketing embrittles with time, and the metal jacketing itself may get dented, opening gaps and admitting water.
To prioritize maintenance work at refineries, petrochemical plants, and chemical plants, owners typically perform a risk assessment of the piping and equipment. These assessments help prioritize the most important items from the perspective of plant operation and/or plant safety. This risk assessment can be used to identify those areas where insulation needs to be repaired or replaced sooner rather than later since problems, such as CUI, can result in a partial facility shutdown or, worse, in a pipe or equipment leak.
To mitigate CUI, many refinery owners apply immersion-grade coatings to all piping and equipment that operate continuously at temperatures below 300°F. Some owners also require the use of non-absorbing insulation materials for all service temperatures. While the practice of using non-absorbing insulation is not prevalent everywhere, it is becoming increasingly common at facilities located along the Gulf Coast.
With today’s high energy costs, which make up approximately half the operations and maintenance costs at a typical refinery, maintaining insulation is a matter of economics. However, damaged insulation does not usually stop a facility from running. Operators simply increase the heat input to maintain process temperatures as required. Many Gulf Coast refineries have had to increase the heat input during and immediately after heavy rains to compensate for water absorbed into the insulation at their facilities. One oil company engineer notes that it can take at least 3 days to dry out absorbent insulation following heavy rains at the company’s Gulf Coast refineries. So even for pipes and equipment operating at temperatures above 300°F, where CUI is less likely to occur, energy waste from wet insulation is always a concern with water-absorbing insulation.
Using non-absorbing insulation materials is one approach to preventing wet insulation and CUI. Another approach is to add a chemical inhibitor to the absorbent insulation during manufacturing. Such chemical inhibitors reduce the probability of corrosion by inhibiting the corrosive effects of chlorides from saltwater and other sources. Insulation with chemical corrosion inhibitors is available in the marketplace.
A new technology that helps avoid CUI when using absorbing insulation materials is self-adhering laminate jacketing—thick tape that comes in 36-inch widths to match the pipe insulation width. The jacketing can be effectively sealed to itself with overlaps along the lap joints and with a minimum of 4-inch-wide, self-adhering tape—of the same material as the jacketing—applied at butt joints, junctions, and penetrations. Self-adhering laminate jacketing requires minimal caulk sealants and is available in weather-resistant, chemical-resistant forms. Since it uses only a thin-coated aluminum foil as opposed to aluminum sheet, laminate jacketing also uses much less aluminum, which has skyrocketed in price over the past few years. The laminate jacketing is flexible and dent-resistant. Since the adhesion of the material to itself is so tight, this new technology promises to be an effective way of keeping water from intruding into absorbent insulation materials on above-ambient applications.
How Do Power Plants Handle Insulation?
Electric power plants’ number one priority is to produce electrical power at full capacity. More than half of U.S. power plants are fueled with coal, a relatively inexpensive fuel compared to heating oil or natural gas. It is almost always pulverized first; these plants are therefore called pulverized coal (PC) plants. Approximately 20 percent of U.S. electrical power comes from nuclear plants, which also use a relatively inexpensive fuel—usually enriched uranium. The role of insulation in these nuclear plants is to keep the operation running in a cost-effective, clean, and safe way.
Replacement or addition of insulation at power plants is usually part of a larger project, not part of an ongoing maintenance program. For example, when a plant adds certain air-quality control systems (AQCSs)—either scrubbers or selective catalytic reducers (SCRs)—boilers must be converted from operating at positive pressure to operating at negative pressure. This is done by using large suction fans to blow the polluted flue gases through the AQCS. First, the lagging and insulation must be removed. (The insulation is generally discarded, but the lagging may be reused.) After the structural retrofit, new insulation is installed onto the boiler sidewalls. This is typically a mineral fiberboard like the original insulating material. However, in some cases, the fiberboard is replaced by a pneumatically applied mineral fiber with a wet, uncured binder that can be more quickly blown and adhered to the irregular surfaces of the sidewalls before the lagging is reinstalled. In either case, the insulation is new.
PC power plants will continue to be retrofitted with new scrubbers and SCRs until all are compliant with the Clean Air Act. In the process, the boilers typically require structural reinforcement and insulation retrofit. This leads electric utilities to reinsulate boilers with insulation that will endure in the expected environment of high temperatures, vibration, and fly ash. It behooves utilities to assure that boiler insulation performs over time.
While there is some evidence of deteriorated mineral fiber insulation on boiler sidewalls, power plant owners can avoid many future problems by specifying the systems correctly in the first place. For example, fly ash gets all over everything at a PC power plant. Over time, it can get into the mineral fiberboards from the back side and saturate the boards. The weight of the fly ash, combined with boiler vibration, can accelerate insulation degradation. An effective way to avoid this problem at PC power plants is to add aluminum foil laminate on the hot side of the mineral fiberboard. Adding the foil increases the material costs, but extends the life and performance of the insulation boards.
Pipe insulation at PC power plants is usually indoors and so does not have water to soak up except when insulation jacketing is hosed down to remove the buildup of fly ash on the lagging and jacketing. In those cases, utilities try to prevent problems by ensuring that the jacketing lap joints are facing down and the seams are caulked.
Maintenance of Below-Ambient Applications
There are a variety of different types of ducts, pipes, and equipment that operate below ambient temperature. The primary purpose of the insulation in these cases is to prevent surface condensation and reduce energy use. The cost penalties of surface condensation vary from application to application, but having condensation within the insulation can be severe. For example, in typical indoor commercial heating, ventilating, and air-conditioning (HVAC) applications, condensation can get into electrical equipment, run onto floors creating a safety hazard, or damage building materials. Wet insulation, in turn, performs poorly, possibly leading to condensation on the surface of the jacketing and energy waste. It can also increase the load on mechanical cooling equipment, possibly resulting in a compressor getting overloaded and burning out. In industrial applications, condensation may corrode the carbon steel onto which it drips, increasing maintenance costs. Overall, water condensation will create all sorts of costly operational headaches that the facility owner should make an effort to avoid.
Porous insulations, such as mineral fiber insulation, can be used on below ambient applications as long as they are covered with a low-vapor-permeance jacketing, referred to as a vapor retarder. It is prudent to use these systems on air-handling ductwork down to a moderate temperature of about 50°F. A drawback to this type of insulation system is that, over time, holes or other imperfections may develop in the jacketing and could allow water vapor intrusion that then condenses on the cold surface, resulting in wet insulation. Since such holes can easily be patched with self-adhering tape, periodic inspections should be conducted to identify and repair these spots before condensation problems develop.
For chilled temperatures below 50°F, such as chilled water pipes, and/or for a relative humidity (RH) above 90 percent, a more robust system—either from an overall low water vapor permeance perspective or a wicking capability—is required. A lower permeance jacketing should ideally be a zero-vapor-permeance material (called a vapor barrier) that is extremely well sealed to itself to prevent any water intrusion. These zero-permeance jacketing materials include both sheet plastic and a self-adhering laminate. For wicking capability, the wicking type of fibrous pipe insulation can provide performance free of vapor condensation problems on chilled water lines down to about 40°F in less than extreme humidity conditions. Both types of systems, however, must be well maintained to avoid water condensation problems.
When well maintained, closed cell foams, which have low vapor permeability values, are well suited for below-ambient systems with minimum maintenance problems. The thicker the insulation, the lower the vapor permeance (vapor permeance equals vapor permeability and thickness). In general, these closed cell foams perform well with chilled water systems and high relative humidity. However, all seams and butt joints must be well sealed. Breaks in the seals and gaps in the closed cell foam insulation material will allow water vapor to intrude; this water vapor, in turn, will condense. This condensation may take more time to develop than with a porous, fibrous insulation material, but with a constant high vapor pressure, it will eventually result in water accumulation in the insulation. This will compromise its thermal performance and lead to the types of condensation problems already mentioned.
For outdoor applications where weather protection is required and/or for very high vapor pressure differential indoor conditions, these closed cell insulation materials perform best when combined with a zero-permeance vapor barrier (as opposed to a vapor retarder). In an actual application, if such a vapor barrier jacket is used, it must be sealed completely to prevent water intrusion or water vapor condensation within the insulation. Certain sheet plastic materials and the new self-adhering, laminate jacketing materials—mentioned earlier for high-temperature systems—can simultaneously provide both weather and vapor barrier protection for below-ambient systems.
For extremely high humidity conditions combined with low operating temperature systems, located either indoors or outdoors, a zero-vapor-permeance system with redundancy will perform best. This can be achieved with at least 2 inches of inorganic cellular insulation covered with the appropriate vapor barrier jacketing. The jacketing should have zero vapor permeance, and the 2 inches of inorganic cellular insulation will have near zero vapor permeance. Further, this type of cellular insulation will not absorb water, should it somehow condense against the insulation. Such an insulation system, however, still requires maintenance to prevent moisture condensation over time. The jacketing must be periodically inspected for holes, and the inorganic cellular insulation must be periodically inspected for any physical damage that might reduce its thickness, leading to surface condensation.
Regardless of the insulation type or low-vapor-permeance jacketing, the insulation system for below-ambient applications should be well designed and well maintained. In most cases, if the insulation system is ignored and/or abused, eventually water condensation problems can occur. The penalty to the owner can be water damage to stored materials, building materials, and equipment, as well as mold growth, energy waste, and cooling system overloads.
The Bottom Line
Well-maintained thermal insulation reduces heat loss and saves money. Damaged insulation saves less money, and missing insulation saves no money at all. With crude oil at about $65 per barrel, delivered heating oil at $2.50 per gallon, and delivered natural gas at more than $10 per million Btus, every day spent ignoring damaged or missing insulation is another day of paying the high cost of wasted energy.
Two years ago, crude oil was trading at about $50 per barrel. Since then, crude oil has sold for as much as $77 per barrel, and now gasoline is selling for a record average price of $3.20 per gallon. People keep waiting for energy prices to drop, but even when prices drop for a few months, they jump up again to an even higher level than they were previously. This is no time to waste energy. Thermal insulation maintenance is easy and inexpensive when compared to energy prices. Those in the insulation industry need to help the managers of industrial facilities understand the economics of insulation.
Whether the motivation is to reduce energy use, to prevent CUI, or to maintain boiler temperatures, when it comes to thermal insulation and its maintenance the old saying, “Pay now or pay later,” is appropriate. The cost of not maintaining insulation correctly is too great for facility owners to ignore.
This article appeared in the July 2007
issue of Insulation Outlook.
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Gordon H. Hart P.E.
Gordon H. Hart is a consulting engineer for Artek Engineering, LLC, having spent over 35 years in the thermal insulation industry. Mr. Hart is an active member of ASTM committees C16 on Thermal Insulation and F25 on Marine Technology, ASHRAE's Technical Committee on Insulation for Mechanical Systems, and the National Insulation Association's Technical Information Committee. Mr. Hart has engineering degrees from Princeton University and Purdue University and is a Registered Professional Engineer. He can be reached at: firstname.lastname@example.org.