PAINTING AND CLEANING ROUTE FOR A CONTRACT
The requirements of this article on painting and cleaning schedules of a contract should be interpreted in accordance with the requirements and recommendations of standard BS 5493 and CP 231, CP 3012 and the paint manufacturer’s special instructions where applicable. Color selection should be in accordance with BS 1710 and BS 4800 or equivalent material standards.
The Paint Supplier Selection
Immediately following the award of a Contract, the Service provider should submit the names of the proposed paint supplier and applicator together with a quality assurance program for approval. All paints for a contract should be provided by one manufacturer and preferably should be manufactured in one country to ensure compatibility
Schedule and Service Life for Painting Work
The painting of the plant should be carried out in accordance with the appropriate schedule. The work is generally covered by the schedules but where particular items are not referred to specifically, they should be treated in a manner similar to other comparable items as agreed with the Engineer.
The schedule indicate standards of surface preparation and painting which is intended to give a minimum service life of 10 years in a coastal industrial environment, with need for minor remedial work only during the intervening period.
How Ensure Painting Standard
Steel sections and plate should be free from surface flaws and laminations prior to blast cleaning and should not be in worse condition than Pictorial Standard B, Swedish Standard SIS 05 5900.
The Engineer is prepared to consider alternative paint schemes to meet the requirements of fabrication using modern automated materials handling systems, provided they offer the same standards of surface protection and service life as those intended by the schedules.
All coating proposed for the internal protection of domestic water storage tanks and Employer sanitation plants should be certified by an approved independent Authority as suitable for use in potable water installations and should meet the non-painting requirements of BS 3416.
The Painting and Cleaning Procedure
All paints should be applied by brush or spray in accordance with the schedule, except for priming coats for steel floors, galleries and stairways where dipping is permitted.
Where paint is to be applied by spray, the applicator should demonstrate that the spray technique employed does not produce paint films containing vacuoles.
Where paint coatings are proposed for the protection of surfaces of equipment exposed to corrosive conditions, such as plant items exposed to brines or sea water immersion in liquid, or wet gases, the coatings should be formulated to the suitably corrosion resistant and should be high voltage spark tested at works and/or at site prior to commissioning.
High Voltage Direct Current Test Procedure for Painting
The test procedure should be based on the use of a high voltage direct current. The voltage used should be 75% of the breakdown voltage of the coating. This breakdown voltage should first be separately determined using test plates coated with the specified coating formulation and thickness. The coating on the test plate should also be micro-sectioned by the applicator to show that it is free from vacuoles and other defects likely to invalidate the test procedure.
If the defects revealed by the above test procedure do not exceed one per 5m2 of coating surface, the coating need not be re-tested after the defects have been repaired. If the defects exceed one per 5 m2 of coating surface, the repairs should be resettled after any curing is completed, and this procedure should be repeated until the defects are less than one per 5 m2 of coating surface. After repair of these defects, the equipment can be placed in service without further testing.
Especial Consideration for Painting and Cleaning
Weather Condition: Painting should not be carried out under adverse weather conditions, such as low temperature (below 40oC) or above 90% relative humidity or during rain or fog, or when the surfaces are less than 30oC above dew point, except to the approval of the Engineer or his duly appointed representative.
Dew Linger Point: On sheltered or unventilated horizontal surfaces on which dew may linger more protection is needed and to achieve this additional top coat of paint should be applied.
Damp & Condensation: Paint should not be applied to surfaces which are superficially or structurally damp and condensation must be absent before the application of each coat.
Sheet & Bright Parts: All plain sheet and bright parts should be coated with grease, oil or other approved rust preventive before dispatch and during erection and this coating should be cleaned off and the parts polished before being handed over.
Joint Part: Where lapped or butted joints form part of an assembly which is assembled or part assembled prior to final painting, the jointed surfaces should be cleaned free from all scales, loose rust, dirt and grease and given one brush applied coat of zinc phosphate primer before assembly.
Paint Film Thickness: All paint film thickness quoted are minimum and refer to the dry film condition. All thickness should be determined by the correct use of approved commercial paint film thickness measuring meters.
Bolt & Timber Painting: Structural bolts should be galvanized, sherardized or cadmium plated and painted as for adjacent steelwork.
All structural timber like timber joists, flooring, etc. not require to be painted and should be treated with two coats exterior grade approved timber preservative.
Adequate Permission for Painting and Cleaning
Priming coats of paint should not be applied until the surfaces have been inspected and preparatory work has been approved by the Engineer or his duly appointed representative.
No consecutive coats of paint, except in the case of white, should be of the same shade. Thinners should not be used except with the written agreement of the Engineer.
The schedules differentiate between Treatment at Maker’s Works and Treatment at Site after Completion of Erection but the locations at which different stages of the treatments are carried out may be modified always providing that each change is specifically agreed to by the Engineer and the painting is finished at Site to the Engineer’s satisfaction.