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The purpose of SCA Paint Specification & Maintenance to existing & new telecommunication towers is to detail the materials, surface preparation, and application for the corrosion protection, and paint to steel towers.
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Formalising a uniform instruction for the corrosion protecting and maintenance painting of in-service and new telecommunication steel towers.
This applies to the camouflage refurbished, maintained, repaired and completely repainted steel towers.
REQUIREMENTS: Coating Material Composition
A signed copy of the coating manufactures’s data sheet(s) shall be submitted with the tender. This is to ensure that the Contractor is aware of this specification, the conditions under which it will be applied and to allow for technical back-up where required. All paint systems shall allow for protection in very high marine environments as classified by ISO. The paint system shall have high durability and only allow for maintenance after more than 15years in a C5-M enviroment (coastal regions). All coats on a given system shall come from the same coating manufacturer. In the case of steel members being painted overseas, compatible alternatives locally available, shall be provided. Where the substrate had received a primer coat in the factory, the Contractor shall check the compatibility of the coatings, which he proposes with the primer coat. NOTE: All coatings for SA Towers shall be solvent based, water based coatings shall only be allowed with special consideration and approval shall be made in writing.
PREPARATION OF METAL SURFACES: Degreasing/HP Cleaning
All harmful deposits of oil or grease spots and all other matter, which is detrimental to the adhesion of coatings to the surface, shall be removed. Bonding of the first coat/ primer to the prepared metal surface is extremely important and special care shall be taken to ensure that the surface is properly degreased. High–pressure washing with water to remove all traces of residues shall follow the degreasing operation. Once dried the coating will commence. Only Municipal grade water shall be used for washing surfaces. Water with high mineral content shall not be used for degreasing or washing of steel structure surfaces.
Abrasive Blast Cleaning
Prior to blast cleaning, all welds shall be free of sla, slag inclusions and pinholes. Adjacent areas shall be free of weld spatter. Which shall be removed by grinding or scraping. All oil and grease deposits shall be removed prior to blast cleaning. In this regard special attention shall be paid to drillings, bolt holes and etc. Blast cleaning shall be carried out on dry surfaces using dry air, free from impurities (in particular grease or oils). All surfaces that are blast cleaned shall be coated with a primer coat within 4 hours. Alternatively, provided the surface cleanliness requirements of ISO 8501-1 or SIS 055900 are maintained, the primer coat may be applied within the same working shift. Under no circumstances shall blast cleaned surfaces be left uncoated overnight.
Blast cleaning may be carried out using grit or slag that shall comply with strict quality requirements - details available upon tender.
Irrespective of the material used for blast cleaning, it shall in all cases be free of foreign matter such as clay, humus, chlorides and bitumen. In all cases, after blast cleaning, all traces of blasting media and dust shall be removed from the steel surface by compressed air or vacuum cleaning. Cleaned surfaces shall not be contaminated with oil, grease, rust or other deposits before coating. After completion of blasting all used and unused blast media shall be removed from site and disposed off at approved disposal facility. Where blasting is performed on towers with exposed cables, tele-communcation antennae equipment, nameplates, and all other equipment that can be damaged by the effects of blasting shall be protected.
Mechanical Wire-Brushing or Grinding
Surface preparation by mechanical wire brushing or grinding may only be used for coating repairs and maintenance on already painted units. All oil and grease deposits shall be removed prior to wire brushing. Special attention shall be paid to bolt and other holes. In all cases, after wire brushing or grinding , all traces of loose material shall be removed from the surface. Bushing tower shaft, base & top flanges ,hot dipped galvanised parts and protective devices shall not be prepared for painting. Where tower is completely repainted, old paint residue shall be removed by sanding of the entire surface area. Cleaned surfaces shall not be contaminated with oil, grease, rust or other deposits before coating.
APPLICATIONS OF COATINGS: General Conditions of Workmanship
All work shall be carried out under the supervision of an experienced supervisor.
All coatings shall be evenly applied to form a smooth, continuous, unbroken coating free from sags, runs and other defects. Care shall be taken to ensure adequate coating of all bolt holes, kidney ports, edges and other areas normally prone to corrosion attack.
Where appropriate these areas shall be stripe coated.
Steel surfaces, which are to rest on concrete or other floors, and any other surfaces inaccessible after erection shall receive the full specified coating system prior to erection. Additional stripe coating of final coat paint shall be applied to the base edges that rest on the concrete plinth before lowering the unit into final position. SCA shall touch-up paintwork damaged during transport or erection.
When site repainting is necessary, labels and all other areas not to be painted shall be carefully masked. SCA shall remove any over spray, which occurs despite this masking. Spot repairs shall be carried out such that the patch painting extends at least 25 mm beyond the damaged areas.
Spot repairs shall reinstate each of the previous coats and shall commence directly after surface preparation. No cleaning or coating applications shall take place when site conditions are likely to adversely affect these operations.SCA shall be responsible for providing all protective equipment necessary to prevent contamination of the coatings and to minimize delays due to such site conditions.
All newly primed steelwork, prior to erection, shall be stored clear of the ground on trestles or other suitable structures. The steelwork shall be placed in such a manner as to ensure adequate drainage of rainwater and condensation. The storage of galvanized components shall comply with SABS ISO 1461.
COATING APPLICATION & THICKNESS: Maintenance of Towers
Coating and application thickness for the maintenance of Towers have the following processes with specific thicknesses for each. Creating a consistent final application thickness:
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Surface preparation
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First coat / Primer
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Stripe coating
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2nd coat / Intermediate
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Final coat/ Top coat
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Total dry film thickness : Typical 310 microns (Tolerance 270 - 350 microns)
COATING APPLICATION & THICKNESS: New Towers
Coating and application thickness for the New Towers have the following processes with specific thicknesses for each. Creating a consistent final application thickness:
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Surface preparation
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1 st coat I Primer
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Stripe coating
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2nd coat intermediate
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Final coat /Top coat
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Total dry film thickness: Typical 3 10 microns (Tolerance 270 - 350 microns).
Coating Colour
The colour of each coat shall be different from the previous coat. The type of paint used for stripe coating shall be the same as the f irst coat but of different colour. The colour of the Polyurethane topcoat shall be International orange and white for all new, refurbished and completely repainted towers.
QUALITY CONTROL: Quality Requirements
During blast cleaning, the relative humidity, the ambient temperature, The standard of finish for wire brushed and blast cleaned surfaces shall all be strictly controlled and monitored.
Where surfaces are blast cleaned, the roughness of the blast profile shall be measured in accordance with SASS 772 and shall be as specified by the material manufacturer's technical note. The blast profile (Sa 2,5) shall not exceed the specified thickness of the primer or first coat. Blast cleaning of severely corroded surfaces may result in high roughness profiles (i.e. > than 40 microns). In these cases, an additional first I primer coat will be required. However, agreement should be reached between the Contractor and Coating Manufacturer as to the most suitable profile range for a specific coating application/system.
QUALITY CONTROL: Coating Applications
The application, method of application and drying times shall be as specified in the product data sheet submitted with the tender and approved by SCA thickness on metal substrates shall be measured in accordance with ASTM E376 or SASS ISO 2080. These measurements shall be made on surfaces free of all contaminants. Calibrated electronic instruments shall be used for determination of film thicknesses. In cases of dispute,SCA appointed inspector’s dry film thickness testers shall be re-calibrated and the percentage variation between the two testers shall be applied as being the standard deviation for each reading. The thicknesses of each coat shall be as defined in Sections 6.2, 6.3, 6.4 & 6.6. No individual reading shall be less than the minimum or exceed the maximum specified values. All deficient film thickness shall be rectified to approval at the Contractor’s expense. Where excessive film thickness can be detrimental to the integrity of the coating, the Manufacturer's recommended maximum shall apply.
Defects during the Guarantee Period
Paintwork will be considered defective if, during the guarantee period, latent defects appear which could lead to a general breakdown of the coating system.
Technical Evaluation and Final Approval
This specification serves as a minimum requirement for Contractors that perform complete paint refurbishment or do tower paint repairs and maintenance. Any deviation from this specification has to be approved by SCA in writing. Alternatives will be considered and final written approval shall be provided once a technical evaluation has been completed and the paint application system found in compliance with this specification and SCA requirements.
TOWER PAINTS: Inland Paint Supply
The colour of each coat shall be different from the previous coat. The type of paint used for stripe coating shall be the same as the f irst coat but of different colour. The colour of the Polyurethane topcoat shall be International orange and white for all new, refurbished and completely repainted towers.
TOWER PAINTS: Coastal Paint Supply
The colour of each coat shall be different from the previous coat. The type of paint used for stripe coating shall be the same as the f irst coat but of different colour. The colour of the Polyurethane topcoat shall be International orange and white for all new, refurbished and completely repainted towers.
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