Quality Control Specialist (514.03)
Application Equipment (514.15)
In order to protect structural steel from corroding, it is necessary to apply a protective coating system. The coating system normally consists of three coats. On existing steel all three coats are applied in the field. On new steel, normally the primer is applied in the fabrication shop and the remaining two coats are applied in the field.
When applying coating systems it is very important for the Contractor to constantly monitor the quality of the work. Due to his many duties and responsibilities, the foreman is not able to properly monitor the quality of the work. Therefore, the Contractor is required to assign one person the duties of a quality control specialist. If there is no quality control specialist on the project, the Contractor is not allowed to proceed with any production work.
This person must be formally trained as a quality control specialist. Prior to allowing the quality control specialist begin working, the Contractor must provide documentation to the Engineer verifying that the quality control specialist has been trained by one of the sources listed in the contract documents.
The quality control specialist is only to be involved in quality control work while production work is going on. He is not to be a foreman or a member of the Contractor’s production staff. He is not allowed to abrasive blast, apply coating, recover spent abrasive, mix paint, run errands, set up or maintain the traffic control, run or work on the equipment, etc. If the quality control specialist is involved in any work other than quality control while production work is proceeding, all production work should be halted until corrections are made.
The quality control specialist must be properly equipped with all the necessary testing equipment, and able to climb to all parts of the structural steel. He is to have the authority to stop the Contractor’s work if necessary, and to inform the foreman of all work that does not meet the requirement of the specifications.
One of the most important items of work is surface preparation. It is also the most labor intensive and expensive phase of the work.
Prior to abrasive blasting, areas that contain asphalt cement, oil, grease, or diesel fuel deposits must be solvent cleaned. It is not necessary for the Contractor to solvent clean the entire surface of the steel to be coated, but only those areas that contain asphalt cement, oil, grease, or diesel fuel deposits.
All solvent cleaning should be completed prior to the start of the abrasive blasting operation. If this is not accomplished, the abrasive blasting operation will not remove the asphalt cement, oil, grease, or diesel fuel deposits but drive them into the steel.
In order to remove all residual solvent, asphalt cement, oil, grease, or diesel fuel deposits after the solvent cleaning, all solvent-cleaned areas are to be washed with water at a pressure of at least 1,000 PSI (7 Mpa). In order to be effective, the nozzle must be held no further then 12 inches (300 mm) from the surface being washed.
The prime coat contains zinc that protects the steel by reacting chemically with the surface of the steel. Therefore, it is important to remove all foreign material from the surface of the steel to allow the zinc particles to come in contact with the bare steel. It is also important to roughen up or produce a profile on the surface of the steel. The profile aids the coating in adhering to the surface of the steel.
Steel surfaces to be painted are to be abrasively blasted to a near white metal, SSPC-SP10. During inspection, pay special attention to areas that are more difficult to blast or areas that might be difficult to inspect. These areas include under cross frames, around bolt heads and nuts, end dams, cross frames next to or close to back walls, and any areas where the Contractor suspects that the inspector will not go. After the steel is blasted, it must be maintained in that condition until it is painted. The backside of cross frame assemblies that are 3 inches (75 mm) or closer to backwalls may be commercial blast cleaned according to SSPC-SP6.
The abrasive must be steel grit. The abrasive must be recycled to minimize the volume of waste material placed into landfills. The size or gradation of the grit is not specified, but must provide a profile of between 40 μm to 90 μm (1.5 mils to 3.5 mils). The profile should be continuously monitored during the blasting operation since the size of the abrasive can be reduced due to being recycled, which can in turn reduce the size of the profile. The size of the profile can also be reduced if the air pressure at the blasting nozzle is reduced or the Contractor changes the type of grit.
Some abrasives, when received by the Contractor, can be contaminated with oil. Therefore the abrasives should be checked to insure that they are free of oil. This check should be made by placing a small amount of abrasives in a jar with tap water. The abrasives and water should then be stirred or shook up. The top of the water should then be checked for signs of oil. If oil is detected, the abrasives should not be used.
Due to the possibility of condensation, any abrasive blasting done when the steel temperature is less then 5° F (3° C) above the dew point must be reblasted when the temperature of the steel exceeds 5° F (3° C) above the dew point.
All steel surfaces must be painted the same day they are blast cleaned. If the steel surfaces are not painted the same day they are blasted, they can begin to rust and become contaminated. Any steel surface that is not painted the same day it is cleaned must be reblasted.
After abrasive blasting is completed, all abrasive and dust must be removed from the surface to be painted. Dust and abrasive must also to be removed from any adjacent painted surface that also includes any adjacent structure. Dust and abrasive should be removed as soon as possible to prevent rust staining of adjacent surfaces. Rust stains can be very difficult to remove.
Occasionally the compressed air used to propel the abrasive can become contaminated with oil or water from the compressor. This oil or water, if deposited on the surface of the steel to be painted, can be detrimental to the coating system. To prevent this problem, the quality control specialist must blow air from a nozzle for 30 seconds onto a white cloth or blotter held in a rigid frame. This testing must be done at the start of each shift, and at 4-hour intervals. If any oil, water, or other contaminates are present on the cloth or blotter, the blasting operation must be suspended until the problem is corrected. After the operation is corrected, and before the blasting operation is permitted to proceed, another test should be made to insure that the problem has been corrected.
Due to the possibility of the existing coating containing lead, which is considered a toxic substance, the Contractor is required to erect an enclosure to completely surround the area where the existing coating will be removed. Not only should the enclosure be placed vertically around the sides of the blasting operation, it should also be placed on the ground under the blasting operation. In addition to containing lead, the enclosure also prevents fugitive dust from escaping into the environment.
The enclosure must be constructed of materials that are free of tears, cuts, or holes to prevent dust and lead from escaping into the environment. Holes, cuts, or tears that do occur should be repaired immediately. If flexible materials such as tarpaulins or containment screens are used, they should be weaved to contain a maximum of 15 percent holes and a minimum of 85 percent material. The perimeter of the enclosure should also extend up between the beams to the bottom of the concrete deck. All seams should be fastened or lapped in a manner that insures a seal and does not allow any openings between the screens or materials of the enclosure. The area where workers enter and exit the enclosure should also be sealed.
In addition to placing an enclosure around the blasting operations, the Contractor must also place ground covers under all equipment. This ground cover must be placed under the equipment for its entire length, not just a portion of its length. If the ground is not properly covered, there is the possibility that it could become contaminated with toxic waste.
Abrasive blasting debris picked up at the end of the day must be stored in steel containers that have the lids locked. Normally the Contractor will store the debris in 55-gallon drums with lids. The lids have a ring around them that are capable of being locked. Normally, the Contractor will lock the lids by means of a bolt. This method is acceptable as long as there is a nut placed on the bolt and tightened by the use of a wrench. Many times all of the lids are not properly locked at the end of the day. They should be checked at the end of the day or the first thing in the morning to insure that the Contractor is locking the lids at the end of the day.
If the debris is toxic, the Contractor must dispose of it within 60 days after it is generated. The 60 days starts as soon as the Contractor generates the debris, not after the completion of the abrasive blasting operation. If the debris remains on the project site over 90 days, the State and the Contractor could be cited by the Environmental Protection Agency. On smaller structures the debris can be removed in one operation. However, on larger structures where the abrasive blasting operation extends over a period of several months, it will be necessary to make several trips in order to comply with the 60-day limit. If after the 60 days, the Contractor has not properly disposed of the toxic debris, all abrasive blasting and painting of the structural steel on the project must immediately cease until the toxic waste is properly disposed. At this time, the Department must cease processing all pay estimates and send notification to the Contractor’s surety that he has breached the contract.
Paint must not be applied when the temperature of the air within the enclosure, steel surface, or paint is below 50° F (10° C) or is expected to be below 50° F (10° C). At lower temperatures the paint will not cure and in some cases the paint may not resume curing when the temperatures warm up. It becomes important to pay closer attention to the temperature in the early spring and the late fall. During the early spring and the late fall, the temperatures will be above 50° F (10° C) during the day, but the temperature will drop during the early evening hours before the paint has had enough time to properly cure.
Paint must not be applied until the temperature of the steel is at least 5° F (3° C) above dew point. Applying paint to steel at temperatures below 5° F (3° C) could result in condensation on the surface of the steel.
Heated enclosures may be used to maintain the temperatures above the minimum specified temperatures. If combustion type heating units are used, the exhaust fumes must nut be permitted in the enclosure but should be vented away from the enclosure. If exhaust fumes are not properly vented, they can leave a deposit on the surface that could affect the ability of remaining coats of paint to properly bond to the steel. These exhaust deposits could also contaminate the freshly applied paint.
If a heated enclosure is used, a recorder thermometer should be used to insure that the minimum temperature is maintained until the coating has cured. The thermometer should be placed close to the perimeter of the enclosure since this is the area subject to cooler temperatures.
Prior to applying paint it is necessary to thoroughly mix all the ingredients together. This is to be accomplished with a high shear mixer. Paddle mixers are not allowed due to the fact that they will not do an adequate job of mixing the different ingredients together. Using compressed air to cause a stream of bubbles in the paint and paint shakers also is not allowed since it will not properly mix the ingredients.
During the application of the primer, it is important that it be continuously mixed. If it is not continuously mixed, the zinc particles in the primer will settle to the bottom of the container and will not be applied to the structural steel. To insure that the mixing process is not interrupted, it is also important that the mixer be an automated mixer, and not a hand held mixer.
Normally thinning of the paint is not required. However if the Contractor elects to thin the paint, it is important that it be thinned with the correct type and volume of thinner. In order to insure that the Contractor is using the proper type of thinner, only use thinner recommended and supplied by the manufacture of the paint. The maximum rate of thinner is to be as per the manufactures printed instructions.
In an effort to insure that the thinner the Contractor is using is the thinner recommended and supplied by the manufacture, only use thinner that has been supplied to the project in unopened containers with the labels intact. The amount of thinner used from each container should be monitored to prevent the Contractor from refilling container with other types of thinner.
The above restrictions do not apply to the thinners that the Contractor uses to clean his equipment.
Paint is only to be applied by the use of brush or spray equipment. Rollers can cause bubbling and other irregularities in the coating and are not permitted except in certain detailed locations.
Certain areas are difficult to properly coat with spray equipment, therefore it is permissible to use daubers, small diameter rollers, or sheepskins for these areas. Daubers, small diameter rollers, or sheepskins are required to be used where cross frame angles are located within 2 inches (50 mm) of the bottom flanges, where end cross frames are within 6 inches (150 mm) of the backwall and the bottom of the bottom flanges around bearings that are less than 6 inches (150 mm) in height.
The prime coat must be applied the same day the surface is blast cleaned. Any surface not painted the same day it is blasted is to be reblasted.
The maximum elapsed time allowed between the application of any portion of the prime coat and the application of the intermediate coat is 30 days. The maximum elapsed time allowed between the application of any portion of the intermediate coat and the application of the finish coat is 13 days. The maximum recoat times shall also not exceed the maximum recommended by the manufacture. Extending the time beyond that mentioned above could adversely affect the bond of the coating. No additional time is allowed due to weather related delays. Any coat that has been allowed to cure more then the above allotted time is to be removed and the steel reblasted to SP10.
During spray application of the paint the operation is to be totally enclosed. The enclosure must be identical to the enclosure used during the abrasive blasting operation. Failure to properly utilize the enclosure could result in overspray damage to private property including automobiles, the ground, public property, vegetation, streams, lakes, etc. The enclosure is not required if the paint is being applied by brush or other means.
Each coat of paint is to be applied as a continuous film of uniform thickness. It is to be free of all defects such as holidays, runs, sags, etc.
Many time holidays in the form of pinholes are difficult to detect. The best way to view pinholes is with the aid of a flashlight after the finish coat has been applied. The flashlight should be placed to shine a beam of light parallel to the painted surface. If pinholes are present, they will appear as small white specs about the size of the end of a needle.
Repairing pinholes can be very difficult. Applying another coat of paint over the pinholes will only result in the pinhole reflecting through the additional coat of paint. It is the Contractor’s responsibility to repair the pinholes. The best way to correct pinholes is by removing the coating at least down to the prime coat of paint. If the prime coat is not removed, measurements should be taken to insure that the required minimum thickness of prime paint is still present. If the Contractor elects to attempt to leave the prime coat, he will probably remove the topcoats with sand paper. If a large area needs to be repaired, it will probably be more prudent for the Contractor to abrasively blast the coating down to bare metal and reapply it.
A small number of runs can be expected and are acceptable around bolts and areas where the cross frames attach to the beams. Runs, sags, etc. in other parts of the steel are not acceptable and must be removed.
If it is necessary to make repairs, the intent of the specifications is that the repair be made in a manner that the repaired areas will blend in with the surrounding area so that it is not evident that a repair was made.
If the area to be repaired does not cover a large area, abrasively blasting the surface may not be advisable due to the fact that it will damage the surrounding coating that does not need to be removed. In lieu of using abrasives, it is acceptable to use machine tools such as grinders. However, whatever method is used, it is still necessary to prepare the surface in a manner that will give a surface profile of between 1.5 to 3.5 mils (40 to 90 μm).
In order to produce a smooth transition, it is necessary to feather the adjacent coatings. This cannot be accomplished through the use of abrasives. The new coat of paint should only applied to the same coat as was feathered, i.e. the prime coat should only be applied to the feathered prime coat, the intermediate coat should only be applied to the feathered intermediate coat, and the finish coat should only be applied to the feathered finish coat. Applying the finish coat to existing finish coat that has not been feathered or in any other way abraded will result in finish with a dull, frosty appearance in lieu of a bright glossy finish.
Prior to measuring coating thickness it is necessary to determine the effect of the blasted surface of the steel on the paint gage. Due to the fact that the steel has received a profile of between 1.5 to 3.5 mils (40 to 90 μm), this profile will cause the paint gage to read high. To compensate for this additional height it will first be necessary to take a reading on the blasted surface immediately prior to applying the prime coat. Preferably three or more readings should be taken and averaged out. This average reading should then be subtracted from all paint film thickness readings. As an alternate to subtracting the thickness attributed to the surface profile from the paint film thickness, recalibrating the paint gage to read 0 mils (0 μm) on the blasted steel is also acceptable.
It is very important to determine the coating thickness by taking the average thickness in the manner specified in the specifications. This involves taking 5 spot readings over an area of one hundred square feet. A spot reading is comprised of the average of three closely-spaced individual readings. The average reading for this one hundred square feet is to represent one thousand square feet. The number of one hundred square feet areas to be measured is determined by the area of steel painted. Form CA-S1 should be used to tabulate the results.
Measurements must be taken on flanges, webs, cross bracing, stiffeners, etc. It is acceptable to use readings from one type of member to comprise an area, i.e. all cross bracing, or all stiffeners, or all flange edges, etc. as this will more accurately determine the thickness of the coating applied to that type of member. However it is still important to take coating thickness measurements on all members.
Normally caulking is used to seal a void greater than 1/8 inch around the perimeter of adjacent steel plates. This void is normally caused by rust forming between the plates and forcing the plates apart to the extent that it is not possible to seal the void with paint. Caulking is not needed to be placed around the perimeter of adjacent plates that are in intimate contact with each other.
Caulking materials are not on an approved list. Materials that meet the generic requirements and will bridge the required gap without sagging or separating are acceptable for use.
Proper inspection cannot be accomplished unless the inspector has access to every surface to be painted. To accomplish this, the Contractor is required to provide, erect, and move scaffolding and all other equipment necessary to provide the inspector access to closely inspect the work. On bridges with tall girders, placing scaffolding only under the girders is not adequate to provide proper access to the work. The inspector should not climb around on the structural steel to inspect the work. If the Contractor fails to provide proper access to inspect the work, he should not be allowed to continue since proper inspection cannot be performed.
All scaffolding of any width, whether it is supported by a wire rope, mounted on the back of a truck, or supported by any other means, that is at least 21 inches (533 mm) or more below the surface to be painted must have guard rail placed on all sides. It is not necessary for scaffolding that is less then 21 inches (533 mm) below the surface to be painted to have guardrail, but in this case the scaffolding must be at least 28 inches (711 mm) wide.
One row of guardrail is required to be placed around the scaffolding when it is at least 21 inches (533 mm) but less then 43 inches (1092 mm) below the surface to be painted. Two rows of guardrail are required when the scaffolding is placed 43 inches (1092 mm) or more below the surface to be painted.
Abrasive blasting and painting is to be done between April 1, and October 31. However, if the Contractor only needs a few more days to finish painting a structure after October 31, he should be allowed to continue as long as the weather permits. The Contractor should not plan on starting work on a structure around the end of October with the intent of completing work on the structure well after October 31.