Considerations for the application of high-temperature coatings – Part 2

Managers of petrochemical, refining, power, offshore, pulp and paper and other facilities with extensive hot processes and piping systems are frequently challenged with performing all the necessary coatings maintenance work only during periods of outages. When coatings work has to be performed on areas where elevated temperatures are involved, many think that the facility has to be shut down. This may not be the case. A question frequently posed by facility managers is, “Can I do maintenance painting work while the plant is operating?” As described below, the answer is, “Yes you can, but there are safety and health issues that must be considered”.

Worker welfare

Application of coatings on high-temperature surfaces increases the potential for heat-related illnesses, especially where chemical- or flame-resistant clothing is worn for personnel safety. Four environmental factors affect the amount of stress a worker faces in hot work areas: temperature, humidity, radiant heat (such as from the sun) and air velocity. Personal characteristics such as acclimatization to the heat, age, weight, fitness and medical condition also impact a given individual’s potential to experience a heat-related illness.

Specific disorders resulting from heat stress include the following:

Fainting or heat syncope can occur when an un-acclimatized worker stands in the heat. Victims usually recover quickly after lying down. Moving around, rather than standing still, will usually reduce the possibility of developing heat syncope.

Heat rash or prickly heat may occur in hot environments where sweat is not easily removed from the surface of the skin by evaporation. Heat cramps are painful spasms of the muscles, which are caused when workers drink large quantities of water but fail to replace their bodies’ electrolyte loss. Tired muscles, those used for performing work, are usually the ones most susceptible to cramps. In heat exhaustion, fluid and electrolyte loss through sweating is not replaced. Though the worker will still sweat, they experience extreme weakness or fatigue, giddiness, nausea, or headache.

Heat stroke is the most serious heat disorder and is caused by the failure of the body’s internal mechanism to regulate its core temperature. Sweating stops and the body can no longer rid itself of excessive heat.

Preventing heat stress

Heat-stress related health problems can be prevented or the risk minimized by implementing some basic precautions. Control measures that should be considered include the use of cooling fans to reduce heat in hot locations. Ventilation equipment should be approved for locations where flammable vapours are present.

Workers and their supervisors should be trained to recognize and treat heat-stress related disorders as well as control measures, such as the importance of fluid replacement. Employees should also be encouraged to maintain a healthy lifestyle including proper diet and body weight.

Inhalation hazards

Workers may also be exposed to solvent vapours during coatings application. This is especially true when solvent-borne coatings are applied to hot surfaces or in hot environments as the heat will likely increase the rate of solvent evaporation and increase the short term concentration in the air. The solvent vapours will be driven out of the coating quickly, but the vapours will also dissipate over a shorter duration as the solvents in the coating are quickly exhausted. Like all industrial coatings operations, employers should evaluate high-temperature coating tasks to determine whether steps should be taken to control respiratory hazards. The hazard determination will vary depending upon what materials may become airborne, their concentration, and their physical state.

Control methods

In general, control measures should be instituted for inhalation hazards when the occupational exposure limits for airborne hazards are likely to be exceeded during coating application. Information on occupational exposure limits can typically be found on Safety Data Sheets or Material Safety Data Sheets and applicable regulatory standards.

Engineering controls such as mechanical ventilation should be used to reduce airborne concentrations of inhalation hazards to as low as feasible before relying on respiratory protection. General considerations for implementation of mechanical ventilation were addressed in the section on fire hazards. Engineering controls may not be feasible or may not be enough to reduce concentrations of airborne hazards to below occupational exposure limits when applying coatings. In this case, respiratory protection will be necessary to control worker exposures.

Burn hazards

Workers applying high-temperature coatings may come into contact with hot surfaces in the work area. Engineering controls, such as placement of insulating materials on hot surfaces, or work practices, such as lock out/tag out of hot equipment or scheduling work when hot equipment is not operational, should be considered.

Where engineering or work practice controls are not feasible, the use of protective clothing will be necessary. All areas of exposed skin that may come in contact with hot surfaces or vaporized water should be protected with properly selected work clothing. Clothing made of artificial materials, such as polyester, which are not flame-resistant should not be worn.

Surface preparation

Coatings professionals agree that the better the surface preparation the better the lifecycle of the applied coatings. Many typical surface preparation methods are practical on hot steel. These include hand- and power tool cleaning, abrasive blast cleaning, as well as high pressure water cleaning, or a combination of methods. As indicated previously, several of these methods may require a hot-work permit in hazardous areas as they may create sparks that are not acceptable in some work environments.

Use of high-pressure water may not require a hot-work permit and may be appropriate for working on hot steel. As discussed earlier, the water may turn to steam and, therefore, proper personal protective equipment will be required.

If the surface temperature of the steel is over 100°C (212°F), then the water should evaporate from the steel before there is a chance for flash rust, thus mitigating the need for any rust inhibitors that might require additional safety precautions.

Conclusions

The case can be made that coatings specifically designed for application to hot surfaces can be safely applied in hot environments, but unique safety and health issues must be considered. These include the surface temperature of the equipment being painted must be below the AIT of the coating system.

Specific hazards and control measures are in addition to those typical to any industrial maintenance painting project, any special hazards like work in confined spaces, and any standard protective measures (such as hotwork permits) used at the facility. Naturally, none of the above control practices will be effective without proper worker training and supervision.

All parties involved with the application of specialty high-temperature coatings to hot surfaces should be medically qualified, trained in necessary work practices and controls, and monitored to verify consistent implementation of all control practices.

Coatings technologies allow for coating application on hot-steel surfaces but applying coatings to hot steel requires a review of safety practices and must be thoroughly planned to minimize the risk of accidents or injuries. Properly addressing the safety and health issues described above may increase application-related costs.

However, the fact that coatings work may be performed during normal operations and without the need for equipment shut-down can result in significant overall savings to the facility owner, especially when the facility normally operates 24/7 throughout the year. As such, proper application of specialty coatings to hot surfaces can be considered as a potential cost-savings tool for facility maintenance and repair.

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