Methods Used for quality Maintenance

SURFACE TREATMENT – METAL FINISHING

SURFACE TREATMENT – METAL FINISHING
  • All welding spatters, slags, exposed sharp edges and irregularities shall be ground off by grinding wheels, pneumatic chisels or other suitable devices.
  • Inspection for sign of grease, oil or solids on surface and remove oil, grease by solvent cleaning and cleaned down by a non-toxic detergent in water. Solids and Deposits of rust to be removed by hand tools.
SURFACE TREATMENT ABRASSIVE BLASTING
  • All fabricated steelworks will normally be abrasive inside enclosed Grit – Chamber built and equipped with sufficient lighting, dust exhaust and ventilation system.
  • Air control – Operating air pressure at blast nozzles will be at minimum of 621 Kpa supplied by electronically driven air compressors, air receiver through filters and dryer.
  • Abrasive control – Only dry and clean steel grits of gauge 40 to be used for blasting and broken down grits are automatically sieved and extracted.
  • Standard control – unless otherwise specified all steel – work surfaces to be painted shall be abrasive blast clean to class 2.1/2 and profile measured by comparator.
  • General – Abrasive blast cleaning and painting shall not be carried out together in the same are nor shall abrasive cleaning be carried out in proximity of recently applied paint.

In performance, particular attention shall be paid to joints, angles, pits and weld areas to ensure that their surfaces are brought to the required standard. After blasting, all dust and grits shall be removed from pockets and corners using clean and dry compressed air. Between cleaning and priming, the steel shall not allow to be contaminated. All surfaces shall be prime coated before discoloration occurs and all cases within four of blast cleaning.

SURFACE TREATMENT ABRASSIVE BLASTING

SURFACE TREATMENT ABRASSIVE BLASTING
  • All fabricated steelworks will normally be abrasive inside enclosed Grit – Chamber built and equipped with sufficient lighting, dust exhaust and ventilation systb) em.
  • Air control – Operating air pressure at blast nozzles will be at minimum of 621 Kpa supplied by electronically driven air compressors, air receiver throughc)  filters and dryer.
  • Abrasive control – Only dry and clean steel grits of gauge 40 to be used for blasting and broken down grits are autom atically sieved and extracted.
  • Standard control – unless otherwise specified all steel – work surfaces to be painted shall be abrasive blast clean to class 2.1/2 and profile measured by comparator.
  • General – Abrasive blast cleaning and painting shall not be carried out together in the same are nor shall abrasive cleaning be carried out in proximity of recently applied paint.In performance, particular attention shall be paid to joints, angles, pits and weld areas to ensure that their surfaces are brought to the required standard. After blasting, all dust and grits shall be removed from pockets and corners using clean and dry compressed air. Between cleaning and priming, the steel shall not allow to be contaminated. All surfaces shall be prime coated before discoloration occurs and all cases within four of blast cleaning.Surfaces not prime coated within prescribed time after blast cleaning for any reason shall be cleaned again with care before primer is applied.
  • Other methods of blast cleaning – these shall be carried out as and when become necessary and meet requirement of the relevant standard, but shall in all cases include the metal surface preparation procedure.

APPLICATIONS OF COATING

APPLICATIONS OF COATING
  • Paint shall be applied by means and to the film thickness indicated in the approved painting system schedules and data sheets.
  • The method of application shall be specified in the painting system schedules and data sheets.
  • Paint shall be applied so that an even film of uniform thickness, tint and consistency covers the entire surface, and is free of pin holes, runs, sags or excessive brush marks. If the paint film finish equal to that to first class brushwork.
  • Margins adjacent to field welds shall be taped off and left unpainted. After welding this unpainted section shall be painted as specified or approved method.
  • All painting materials shall be stored in accordance with the manufacturer’s written recommendations or procedure for protection against temperature extremes, and shall be brought to the point of application in original sealed cans, supplied and delivered in labeled containers.
  • The labels shall be legible at the time of application and if possible shall include: Brand Name/Name of Manufacturer Formula or Specification Number Colour Manufacturer’s Application Instruction Validity date.
  • Method of application – Conventional or Airless.

BRUSING APPLICATONS

BRUSING APPLICATONS

The pressure on the material in the pot and of air at the spray gun shall be adjusted for optimum spraying effectiveness. The pressure on the material in the pot shall be adjusted when necessary for changes in elevation of the gun above pot. The atomizing air pressure at the gun shall be high enough to properly atomize the paint but not too high as to cause excessive fogging of paint, excessive evaporation of solvent or loss of paint by over – spraying.

Where applied by brush the paint shall evenly over the entire area with the minimum practical amount of brushing. The method of application and the type of brush used shall be suitable for the paint specified and surface being painted. Brushes shall be maintained in good order and condition.

Conditions of application – No application shall be made if one or more of the following conditions is likely to exist at the time application or during curing period:-

  • Rain or wind borne dust, including dust from blast cleaning operations.
  • Relative humidity above 85% or the surface temperature of the steel surface is less than 3 Celsius above the dew point.
  • Ambient temperature of the metal surface is outside the range of 10 Celsius – 50 Celsius.

Thickness of Coatings – The minimum coating thickness shall be in accordance with each painting system adopted and the maximum thickness in any one application will not exceed that recommended by the paint manufacturer or as specified.

Wet film thickness – The wet film thickness of each coat and the amount of thinners used in application shall be in accordance to manufacturer’s specification and recommendation.

Painters to be issued with proper wet film thickness gauges and shall be use for frequent checks on applied wet film.

Multiple coat application – Generally where more than one coating is specified each coating shall be tinted differently from the others so that MISSED areas will be visually apparent.

Preparation of surfaces between coats – Immediately before each coating after the first (except those prescribed by the manufacturer as wet on wet) the surface shall be examined to determine its need for cleaning to accept subsequent coats. If grease or oil is present, it shall be removed by a suitable of non – ionic detergent and then pressure – hosed. The same treatment shall be given to areas from which grease or oil has been removed.

Timing of coatings – Except for coatings designated by the manufacturers as wet on wet, coatings shall be applied only under the following conditions:- The surface has been cleaned and dried The manufacturer’s specified minimum time for recoat has elapsed The manufacturer’s specified maximum time for recoat has not elapsed Damaged areas in the proceeding coat have been made good or repaire