The pressure to keep equipment running continuously is greater than ever. As demand for output continues to grow, a facility’s maintenance engineers, who wear many hats in their day-to-day duties, must walk a fine line when it comes to scheduled maintenance. Taking a section of a plant down, even for a few hours, can have major financial implications. At the same time, this cost has to be balanced with the what-if scenarios of unscheduled maintenance.
In a perfect world
Ideally, a program of scheduled maintenance exists; in some cases, such maintenance might have to wait until a mechanical shutdown, for any reason, occurs.
When it comes to coatings maintenance procedures, there are no hard and fast rules for maintenance decision-makers to follow. Depending on the facility and its requirements, coatings maintenance might fall far down the list. But without careful monitoring of facility assets, the full value of equipment investment might not be realized, and maintenance costs could rise dramatically as unplanned shutdowns occur.
There are several factors to consider when putting together a coatings maintenance checklist and timetable. Obviously, the assets essential to daily operation must receive priority attention. Likewise, the funds invested in a particular asset might determine where it falls on a coatings maintenance schedule. In other cases, such as with lower-cost, commodity equipment, it might be more economical to simply schedule asset replacement, say, every five years, than to include it on a coatings maintenance schedule.
Part of the equation regarding scheduled maintenance might involve the facility’s location. If a plant is located in a salt-air, damp environment, for example, facility assets will require more frequent monitoring because of the atmosphere’s corrosive nature. The facility’s age and level of depreciation also might be factors; an older, nearly fully depreciated facility might not receive the maintenance attention that a newer, more efficient plant receives.
Much farther down the list but still relevant are overall aesthetics. If a plant has high visibility — for example, if it’s easily seen by passers-by on a highway or an interstate — the areas most visible will most likely receive more regular, scheduled attention.
More often than not, coating maintenance is done during mechanical shutdowns. It’s at that point, when a section of the refinery is taken off line, that a maintenance team has the opportunity to perform several tasks. So a fast return to service and the ability to withstand high temperatures are two critical components of most coatings under consideration.
In new construction, appropriate coating specifications are crucial to maintaining equipment’s useful life. In existing plants, proper selection can add years to the life of coatings, especially in areas where they are covered by insulation.
A high percentage of the coatings in a refinery are concealed under piping insulation. If these pipes move extremely hot product only sporadically, it generates a cyclical wet/dry condition. This combination of heat and severe chemicals with, in many cases, a harsh overall environment because of weather and salt air, provides the potential for corrosion if the proper coatings haven’t been specified. One of the most common refinery coatings challenges occurs when corrosion develops behind insulation. This condition is sometimes not obvious until the insulation is stripped away, and, at that point, the pipe might already be corroded beyond use.
Problems like this can be prevented by selecting the proper coating:
- Non-insulated structures (piping, vessels, tanks and furnaces), temperature between 200°F and 400°F: inorganic zincs, silicone acrylics, epoxies, urethanes
- Non-insulated, high-temperature equipment (piping, stacks, mufflers), temperature between 400°F and 1,000°F: inorganic zincs, silicones
- Insulated, fireproofing or cementitious, heat limits to 250°F: epoxy phenolics
- Insulated piping, vessels, towers, storage tanks, exchangers, furnaces, stainless steel surfaces, temperature between 400°F and 1,000°F: high-temperature coatings
- Non-insulated stainless steel equipment, temperature between 400°F and 1,000°F: Chloride-free, high-temperature coatings
- Galvanized structural appurtenances, temperature less than 200°F: epoxy/urethanes
- Chemical-resistant linings and containment, heat limits vary with commodity and use: epoxies, epoxy phenolics, epoxy phenolic novolac, vinyl esters
Specifying the proper coatings, however, is only one part of the equation. Making certain that the coatings are properly applied is just as important for long-term success.
Experience in refinery and petrochemical projects ranks high on the short list of requirements for selecting an applicator. The contractor should certainly have a résumé, a documented safety plan and a list of references that prove he knows his way around a facility. If the applicator is being selected using a bid process, each bidder should demonstrate that it can perform in a refinery and petrochemical environment.
Beyond insisting on a demonstration of the knowledge and technical expertise to do the job, a maintenance engineering staff should consider a short list of qualifications when reviewing potential applicators:
- Overall capabilities and record-keeping procedures.
- Experienced and properly trained personnel who have worked in a petrochemical environment.
- Compliance with state and federal health and safety requirements.
- Willingness to work with an independent inspection company.
The final point listed — that of working with an independent company that will provide final inspection — is the key to ensuring that a coatings project has been completed properly. The inspector, the applicator and the coatings supplier must be willing to work together, along with the maintenance engineering staff, throughout the project to ensure success.
Perhaps the best resource for guidelines in selecting the proper applicator and inspection company is the Society for Protective Coatings (SSPC) in Pittsburgh (www.sspc.org). SSPC’s Qualification Procedure No. 1 is the Standard Procedure for Evaluating Painting Contractors (Field Application to Complex Industrial Structures). Qualification Procedure No. 5 is the Standard Procedure for Evaluating the Qualifications of Coating and Lining Inspection Companies.
Products that extend lining lives
In any industry, once a tank is returned to service, the last thing an owner wants is to have to take it back offline before the next scheduled maintenance period because of incomplete coating or improper film thickness. Proper application and inspection are musts, and the product itself can help. Coatings technologies, at least in tank linings, have advanced to the point where they can help applicators and inspectors assure proper film thickness.
For example, optically activated pigments (OAP) in chemical-resistant glass flake-filled epoxy novolac lining, were originally developed for use in marine ballast tanks. Coating inspection requires LED illumination. The pigment itself fluoresces and glows. Pinholes and holidays appear black in contrast to the fluorescing lining in a one-coat system, and blue in a two-coat application. Improper film thickness appears less bright than the properly applied fluorescing lining. This allows corrections to be made while the coating is still wet. Inspection even can be done during application, saving time while identifying areas in need of attention.
Like x-ray vision
Having a coatings maintenance schedule in place and adhering to it is always the best policy. However, given today’s environment, such maintenance often is done when other factors force a mechanical shutdown. In either case, a maintenance engineering staff can guarantee coating success by remembering and embracing to three basic tenets:
- Proper coatings specifications.
- Experienced industrial plant applicators.
- Final inspection before return to service.
Thomas W. Burker is strategic account manager, petrochemical, at Sherwin-Williams Protective and Marine Division in Cleveland. Contact him at [email protected] and (216) 566-2000.