Transmission Tower and Pole Painting
- 5 February 2018
- Posted by: Stm Coatech
- Category: Educational Articles
Transmission Tower and Pole Painting
The North American electric transmission grid, considered by many to be one of the greatest engineering feats ever to be implemented, is in rough shape. The American Society of Civil Engineers (ASCE) assigns a grade of “D+” to the grid infrastructure and ranked its aging and condition the Number One challenge to reliability, both in likelihood of occurrence and potential severity.1 An unreliable electric grid will have significant negative impact both from an economic and security aspect. The direct cost to the grid from corrosion alone is some $700 million annually with indirect costs much higher.
Fig. 1: Mitt application of high-build (10-to-12 mils WFT/9-to-11 mils DFT) zinc-dust oil alkyd tower paint to an energized 500 kV weathered galvanized steel lattice electric transmission tower.
The majority of the North American transmission system was constructed from the 1960s through the 1990s. Commonly referred to as second-generation structures, these lines may significantly increase the amount of maintenance work required to keep the grid safe and reliable, as many structures will require attention all at once. Unfortunately, most utility companies are not performing proactive maintenance, but rather take a reactive approach and are only dealing with corrosion-related problems as they occur. A recent Associated Press study2 found that electric companies are spending 43 percent more than they did in 2002 to build and maintain the grid, and while the number of power outages remains infrequent, it is taking longer to restore service, indicating that the system is not being maintained or upgraded to improve reliability.
Although there is no question the North American electric transmission system has serious corrosion issues, it is not all doom and gloom. Line failures can be prevented by a proactive approach that includes timely inspection and effective maintenance practices. There are proven, cost-effective methods of preserving and extending the service life of transmission structures and minimizing grid failures due to corrosion. A comprehensive corrosion-mitigation program comprising structure inspections and assessments followed by a well-executed corrosion-control program can and will eliminate corrosion-caused power outages.
The first step in the process is to perform an assessment of the system. A utility company must understand the condition of its structures before it can determine what needs to be done and how much it will cost to do. The assessment should include a visual inspection of the system components, a condition rating (per industry guidelines), prioritization based on the utility’s requirements (i.e. component criticality, condition, logistics and outage limitations), surface preparation and coating system requirements, and cost estimates. Simple testing such as for lead in the existing coatings and coating film thickness and adhesion should be performed as part of the assessment. NACE and the Institute of Electrical and Electronics Engineers (IEEE) joint task groups are currently writing and publishing standards referencing corrosion control in the transmission and distribution (T&D) industry that include details on performing coating assessments on transmission and distribution structures.
Fig. 2: The individual components of a transmission tower.
A defined program can then be developed using data collected during the assessment that conforms to the utility’s long-range plans. Once funding is secured, a project scope can easily be assembled using the assessment as its basis, followed by job award to a qualified contractor. It is critical that only contractors and workers with specific training and experience working on electric transmission structures, especially while energized, be permitted to bid on and perform this work. Aside from demonstrated capabilities in preparing and coating these complex structures, the contractors must have an excellent documented safety record with a health-and-safety program specific to transmission structures. Each crew member must have proven relevant experience and comprehensive training. The project specification must be tailored to the scope and not generic. A coating schedule detailing surface preparation and coating system requirements is an integral part of the specification, as is a listing of all applicable safety rules and regulations.
Often the painting of electrical transmission structures involves the application of a protective coating over weathered and/or previously painted galvanized steel. Although many transmission structures — mainly tubular poles — are painted carbon steel, most structures, especially lattice type towers, are galvanized and are either unpainted and weathered or previously painted.
Galvanizing and paint perform the same function: the protection of the carbon steel substrate from corrosion attack. Each works as a barrier to separate the components of the electrolytic cell that causes corrosion. When properly specified and applied, this barrier of paint or zinc-iron alloy (galvanizing) will keep the moisture (electrolyte) from contacting the anode and cathode (steel and its corroding surface). When this is successfully accomplished, corrosion cannot occur and the substrate will not be detrimentally affected.
Over time, both galvanizing and paint will degrade to a point where they will not provide adequate protection to the steel substrate. The rates of degradation will vary widely. Exposure conditions have the greatest effect on the longevity of protection, but the quality of product and its application are other critical factors.
When it is determined that the galvanizing or paint film can no longer adequately protect the substrate, a new barrier must be applied to fend off the costly ramifications associated with corrosion. The most practical and cost effective method of “re-protecting” the structure is the application of a paint or coating specifically intended for this use. When properly formulated, specified and applied, coatings can protect a transmission structure for 25 years or more.
High-voltage electric transmission structures are complex, elevated industrial structures, and to further complicate the situation, most coatings on previously painted transmission structures contain lead (Pb). Therefore, the contractor must have the required worker and environmental plans to work on these structures and be in full compliance with all regulations, including those required by OSHA and the EPA at federal, state and local levels. Contractors that have the SSPC QP 1 and QP 2 certifications have demonstrated programs in place that are audited by an independent organization to verify compliance.
Specific, relative experience and training on both the contractor’s corporate and individual worker levels plays a critical role in the safe and successful completion of a transmission structure painting project. As most transmission towers are painted while energized, workers must be trained in electrical safety and the contractor must have a written health-and-safety program specific to this type of work. Climbing, fall protection and rescue certifications should all be required as well. Proven performance should be mandated by the utility company.
Based upon the existing condition of the structure, the level of surface preparation can vary. Levels can range from SSPC-SP 1, “Solvent Cleaning” to SSPC-SP 14/NACE No. 8, “Industrial Blast Cleaning” and various levels in between. The surface preparation methods recommended for weathered, previously painted or galvanized structures normally require hand tool cleaning (wire brush, scraping or sanding) in accordance with SSPC-SP 2. Especially as lead coatings are often involved, minimizing the amount and degree of surface preparation is important. Costly enclosures and containments are logistically very difficult or impossible to use due to the configuration of transmission structures, operating considerations and structure access. As most transmission structures are painted while energized, it is also important to eliminate or minimize the use of cables, hoses or other equipment that could possibly encroach on the OSHA established Minimum Approach Distance3 of the energized circuits. The Minimum Approach Distance (MAD) is the safe distance specified by OSHA or the utility company that a worker must stay away from the energized conductor. It varies depending on circuit voltage. Coatings designed for application to minimally prepared steel are generally the best choice for transmission structures.
The application of paint to a transmission structure is more complicated than one might think. This type of painting involves climbing complicated lattice-type towers or tubular poles that vary in size and configuration (depending on voltage) when appropriate phase-to-structure distance or the OSHA MAD can be satisfied.
Painting an electric transmission structure requires a team effort. For example, a crew of three or four painters will paint a standard 100-foot lattice tower in approximately three-to-four hours. For the most part, coating application is accomplished using a paint mitt. Brushes or rollers may be used on certain structure components. No spray application is used. Experience is an important factor in using either method of application as it is very important that the specified film dimension is achieved and a smooth consistent film is obtained. The coating type typically used in this work is a high-solids, high-build, zinc-dust alkyd and its service life is a direct function of its applied film thickness.
Given the complexities of a transmission structure’s configuration, the large numbers of bolted connections, the sheer number and varied sizes of the structural steel members and the difficulties associated with accessing all structure surfaces, as well as the height and electrical issues, a unique skill set and training is required of the painter.
Most often, a high-build, rust-inhibiting, surface-tolerant coating system is utilized for transmission structures. The long oil-alkyd formulation incorporates metallic zinc dust, aluminum or stainless steel flake, micaceous iron oxide and other pigments to provide a sacrificial barrier to protect the weathered galvanized or previously painted carbon steel structure surface. Depending on the condition and type of substrate, a 100-percent-volume-solids epoxy penetrating sealer may be applied first. These coatings are intended for use over hand-tool-cleaned (SSPC-SP 2) surfaces and do not normally require power tool or abrasive blast-cleaning.
During surface preparation, airborne particulates and debris from the removal of paint (particularly paints containing lead, cadmium and chromate pigments) can contaminate the air, soil and water surrounding the work sites. The potential environmental hazards are reduced by minimizing or eliminating the airborne particulate and by containing and collecting the debris. Controlling airborne particulate and other emissions may be necessary to comply with federal, state and local regulations. Based upon the level of surface preparation that is selected, the degree of environmental controls can vary as well from the most stringent — a full containment enclosure — to the much lesser of non-mesh tarps on the ground covering the exposed area. Appropriate collection methods such as the use of HEPA-filtered vacuums are then implemented and followed by appropriate and approved handling and disposal procedures in compliance with applicable regulations.
Painting electric transmission structures poses many significant hazards with the two most important being fall hazards and high-voltage electrical exposure. Others include hazardous material handling, access difficulties and general industrial work-site hazards. Fall-protection training, tower-climbing training, and safety and rescue training are all necessary and should be mandated by the utility company. OSHA states that any worker on a walking or working surface that has any unprotected side or edge which is six feet or more from a lower level requires fall-protection training. A substantial portion of safety training should cover OSHA certification topics such as OSHA safety requirements, the physics of falls, personal protective equipment (PPE), fall-protection concepts and safety equipment, treatment of frequently encountered tower injuries, documentation, along with solo and small group rescue deployment options.
High-voltage safety training is necessary to certify personnel as “qualified electrical workers” and covers the key aspect of the OSHA Generation, Transmission and Distribution Standard, 29 CFR 1910.2695. This standard applies to organizations that either generate electricity or transmit energy to others. It also applies to organizations that have their own substations or electrical distribution systems. Proper electrical safety training will emphasize the correct minimum approach distances applicable to circuit voltages, as well as the use of proper voltage rated tools and the use of proper PPE. Other electrical safety issues, such as step potential, over-voltages and static discharge should also be included in worker training. By educating workers on the high-voltage safety issues central to the safe performance of their everyday jobs, loss of life or serious injuries can be reduced and eliminated.
Additional training relative to this type of work that should be performed includes the 10-Hour OSHA Construction Safety Training Course, first-aid, CPR, lead awareness and others.
ON-SITE TRAINING AND DOCUMENTATION
Qualified contracting companies require crews to conduct daily tailboard meetings prior to the start of work to discuss and document the daily work plan, assess and address the job hazards, identify and inspect the necessary PPE, and review the emergency response plan. Additional meetings are scheduled if conditions change during the day. Most utilities require these meetings and are often present or request documentation of the daily tailboard meeting form.
Weekly safety toolbox meetings with field employees should also be performed at the site. The meeting should be led by the safety representative/competent person assigned to the project. Safety topics vary but may include the following.
- Equipment, vehicle and tool safety.
- Material handling hazards (silica, cement, asbestos).
- General health topics (heart disease, stroke, flu prevention).
- Stretching and physical fitness.
- General environmental hazards (heat/cold exposure, blood-borne illness).
QA/QC DISCUSSION AND TYPICAL DOCUMENTATION
It has been estimated that 80 percent of coating failures are due to mistakes during the surface preparation, application and curing process. It has also been said that “a painter covers his or her mistakes.” Unfortunately, after the surface has been coated, it is exceedingly difficult to verify the adequacy of surface preparation, coating thickness or the number of coats applied. It must be recognized that any level of inspection has a cost associated with it. Formal inspection is more costly up front, but proper inspection by certified personnel is an investment which returns its original cost many times during the lifetime of the coating.
Properly trained and experienced third-party inspectors can eliminate many common causes of coating failures. It is an industry standard to require inspection personnel to have certification from an accredited organization that would establish a certain minimum requirement for the inspection staff. Keeping proper documentation is an important factor that must be performed and issued to the owner to confirm that the specification requirements were met to the satisfaction of the contract and the owner. Without proper and complete documentation, the potential failures cannot be diagnosed without forensic testing, which is a costly and time-consuming expense.
As mentioned previously, another major component for painting projects is the environmental oversight during a project of this size and scope. This is not limited to just environmental compliance requirements established in the contract documents, but also the health and safety oversight and compliance during the contract work. If handled correctly, the contractor will know and understand that the contract requirements will not only be reviewed for compliance but will also be enforced. Understanding the federal, state and local rules and regulations is a very important aspect of a smooth-running project.
The contract documents should include the minimum certifications and work experience requirements of the third-party inspection staff. Being familiar with similar painting projects is critical to a project’s success. This will reaffirm that the quality of work is witnessed, inspected and documented on a daily basis and according to the written contract documents.
In most cases, the utility company’s engineering department in conjunction with the purchasing department supervises the entire operation by specifying and/or procuring the coating material, contracting with a qualified applicator and providing full-time inspection or part-time surveillance of the coating work. In order to attain maximum results, the program must be managed properly and include the following.
- Specification of the proper surface preparation.
- Specification of proper coating materials.
- Specification of proper dry-film thickness.
- Use of proper application methods.
- Allowing only qualified applicators to bid work.
- Use of qualified inspectors.
- Implementation of proper safety and environmental requirements.
DOCUMENTS THAT WILL ASSIST THE BIDDER
Information that will assist the contractor during the bidding process for transmission structure painting projects include but are not limited to the following.
- Reference drawings of the tower structures with structure dimensions.
- Tower locations with longitude and latitude coordinates as well as satellite view.
- Surface condition of the existing structure.
- Pictorial reference of surface condition levels.
- Lead test results (if applicable).
THE END RESULT
That our electrical transmission system is ageing and degrading from corrosion is a given. It’s a natural process of time. The good news is this process can be controlled, costly line failures due to corrosion can be minimized and the system’s reliability can be improved by taking a proactive approach to structure maintenance. The cornerstone of this approach includes the use of a properly executed maintenance program that requires an acceptable technical specification, a qualified contractor and professional quality control. This type of program has repeatedly proven to ensure the long-term, cost-effective protection of transmission structures.
STM Coatech, SSPC PCI (International Coating Enspektörlüg), and Corroder (MPA Group England), Turkey, Romania, Ukraine, Georgia, Russia, Azerbaijan, Turkmenistan, Kazakhstan, Iraq, Qatar, Kuwait, Oman, the Sudan and Algeria official licensors.
It is also authorized examination center of the country we have already mentioned above, especially Turkey. Corrodere Training Courses are listed below.
1.Icorr Level 1
2.Icorr Level 2
3.Icorr Level 3
5.Corrodere Hot Galvanizing
6.Corrodere Insulation Inspector
7.Practical Workshop Icorr 1,2,3
8.Corrodere Marine & Offshore Inspector
9.Transition to Icorr
Paint Square, Transmission Tower and Pole Painting, data of access: 1 February 2018, http://www.paintsquare.com/archive/?fuseaction=view&articleid=6100
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