November 2024
Maintenance, Reliability and Inspection
Use advanced thermal insulative coatings to improve safety, maintain access and protect against corrosion
Throughout refineries, petrochemical plants and offshore oil and gas platforms, personnel are often required to work near equipment that operates at high temperatures. Protecting those workers from skin-contact burns has typically involved two approaches: implementing physical barriers and covering the hot assets with insulation and cladding. This article details how thermal insulative coatings can be used to improve safety and guard against corrosion.
Throughout refineries, petrochemical plants and offshore oil and gas platforms, personnel are often required to work near equipment that operates at high temperatures. Protecting those workers from skin-contact burns—and maintaining compliance with U.S. Occupational Safety and Health Administration (OSHA) guidelines—has typically involved two approaches: implementing physical barriers and covering the hot assets with insulation and cladding.
Safety caging, fencing and similar physical barriers are certainly effective in helping prevent personnel injuries, since they inhibit accidental contact with hot surfaces. However, they can also take up valuable production space, carry high fabrication and installation costs, and make it more difficult to inspect and maintain assets.
Insulation systems also offer excellent protection against skin contact burns. The systems usually involve affixing a material (e.g., mineral wool) to an asset surface, and then protecting it with steel or aluminum cladding to prevent damage and keep moisture out. Cladded insulation is also excellent at retaining heat and delivering energy savings in high-temperature processes, particularly indoors and in consistently dry conditions. However, insulation systems can also be expensive to install and maintain, since they require regular inspections that include removing the cladding and insulation to examine the asset surface and measure its thickness. There are valid reasons for these checks. In addition to losing much of their insulating R-value when wet, these systems can be susceptible to corrosion under insulation (CUI)—a hidden threat that can compromise the asset itself.
Thermal insulative coatings (TICs) offer an alternative to physical barriers and cladded insulation. With as little as a single coat, a properly-formulated TIC can make an asset operating at up to 350°F (177°C) safe to the touch, meeting OSHA guidelines for providing sufficient skin contact burn protection (FIG. 1). While TICs are engineered primarily for personnel safety, they also eliminate the risk of CUI, as they bond directly to an asset and leave no room for the corrosion zone associated with insulation.
FIG. 1. When used on assets such as process vessels, spray-applied TICs can eliminate the need for physical barriers or cladded insulation systems.
TICs are also capable of maintaining a reasonable level of process heat within coated assets, offering sufficient insulating R-value even at one coat of 50 mils dry film thickness (DFT)─75 mils DFT, pairing safety with energy savings (FIG. 2).
FIG. 2. Spray-applied TICs can help maintain internal process temperatures—such as on this boiler room pipe—while minimizing burn hazards to personnel.
Preventing burn injuries. It does not take much more than a moment of contact with a hot pipe or surface to cause a skin contact burn in a high-temperature processing environment. OSHA references the American Society for Testing and Materials (ASTM) C1055 standard guide for heated system surface conditions that produce contact burn injuries, establishing a 5-sec maximum exposure time to avoid skin contact burns, and suggesting that simulated skin temperatures remain at or below 140°F (60°C) to minimize injury potential. Using a distance that approximates the extended reach of a 6-ft-tall worker, compliance with this standard requires any hot asset within about 8 ft. of a worker to be protected by a physical barrier, an insulated system or an insulative coating. This last option enables facilities to meet OSHA burn protection requirements without the fabrication, installation and other costs associated with physical barriers or insulation systems.
It may seem counterintuitive that a relatively thin, spray-applied coating can provide enough thermal protection to replace a layer of mineral wool insulation or a safety cage—especially considering that 50 mils DFT─75 mils DFT of coatings equals just 1.3 mm─1.9 mm of dried material on an asset’s surface. However, the composition of the authors’ company’s TICa makes this possible.
The company’s TICa is a water-based, acrylic TIC containing silica-based microspheres and low thermal conductivity aerogel particles. When the coating is applied, these small gas-filled spheres and aerogel particles spread out across the coating film, creating a surface with a high content of small, closed-cell air pockets. Because air has very low thermal conductivity, these enclosed air pockets function as additional insulation that effectively blocks the transfer of heat energy through the coating. As a result, coated surfaces of assets that contain fluids and gases that are stored or flowing at up to 350°F (177°C) inside can remain safe to touch—if they deliver simulated skin temperatures of ≤ 140°F (60°C)—for at least the OSHA-mandated 5-sec threshold (FIG. 3). Physical barriers or insulation may still be necessary to protect systems with operating temperatures exceeding 350°F.
FIGS. 3a and 3b. Forward-looking infrared (FLIR) imaging inspections of this ground storage tank reveal a cladded insulation system that is providing uneven thermal protection. The red spots indicate areas that may not be safe to touch, likely due to saturated insulation material conducting excessive heat.
Once a TIC is applied and cured, inspectors can use a thermesthesiometer to check its skin-contact protection capabilities. A thermesthesiometer measures temperature through an encapsulated material simulating the thermal properties of human tissue and skin. It is required because typical surface temperature probes do not provide an accurate reading of skin temperature. When placed in contact with a coated asset, this device can confirm that the surface temperature falls within OSHA requirements.
Moisture exposure and safe-touch properties. Traditional insulation and cladding systems are highly effective at maintaining safe-to-touch temperatures when they are first installed and completely free of moisture. However, their insulating R-values can diminish quickly if these materials are exposed to and penetrated by moisture from rainfall, humidity, condensation or safety systems like sprinklers (FIG. 4). Cracks, joints and irregularities in a cladding system can also provide a means for moisture infiltration.
FIG. 4. A spray-applied TIC provides a safe-to-touch surface on this asphalt tank—which operates at to up to 220°F (104°C)—while helping to conserve process heat.
No matter the source, when water or water vapor gets inside mineral or glass wool insulation, they displace the air held within the material, reducing the air content that is critical to maintaining the insulation’s rated R-value. Tests show that typical mineral wool insulation material, for instance, will lose up to 85% of its R-value if it is infiltrated by just 10% water by volume (FIG. 5).
FIG. 5. As water infiltrates the system and humidity rises, the R-value of an insulation system drops rapidly.
Additionally, water infiltration is often spread unequally across the surfaces of an asset (e.g., flat roofs vs. vertical tank walls). This means the amount of R-value reduction for a cladded insulation system can vary widely, creating the potential for hot spots that exceed OSHA requirements. The exterior cladding on the underside of an insulated process pipe may become too hot to touch following water infiltration as the moisture concentrates in the area and the water-logged insulation enables greater heat transfer.
TICsa effectively resist moisture penetration and quickly shed any temporarily absorbed moisture, making them subject to minimal, if any, thermal conductivity changes. So, although the R-value of a TIC application does not equal the R-value of a “dry” insulation system, the TIC’s air-filled microspheres, low thermal conductivity aerogel particles and closed-cell film are better able to provide consistent safe-touch compliance than a moisture-laden cladded insulation system.
A single solution with multiple benefits. Because TICs can replace bulky safety caging and physical insulation systems in various oil and gas, refinery and petrochemical plant applications, they can play a significant role in enhancing workplace safety and preventing avoidable accidental injuries. The right coating offers OSHA-required burn protection while eliminating the risk of CUI and still maintaining sufficient process heat inside coated assets. The insulating characteristics of spray-on TICs also help reduce ambient temperatures around high-temperature-operating assets. Because these coatings can be used in almost any situation in which traditional insulation or isolation systems would be effective, they are an ideal means of helping to shape a safer, more economical oil and gas production or refining operation.
NOTE
a Sherwin-Williams Protective & Marine’s Heat-Flex® 7000
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