BLASTING & PAINTING

PROCEDURE FOR SURFACE PREPARATION & PAINTING

1.   SCOPE

·        This procedure covers the method for below specifications that covers the minimum requirements for the supply of paint and the paint work.

1.1.       Standards and Tech. Specification

SSPC Steel Structure Painting Council Specification.

SSPC - PA1 - Shop, Field and Maintenance Painting

SSPC - PA2 - Measurement of Dry Paint Thickness with Magnetic Gauges

SSPC - SP1 - Solvent Cleaning

SSPC - SP2 - Hand Tool Cleaning

SSPC - SP3 - Power Tool Cleaning

SSPC - SP4 - Flame Cleaning

SSPC - SP5 - White Metal Blast Cleaning

SSPC - SP6 - Commercial Blast Cleaning

SSPC - SP7 - Brush-Off Blast Cleaning

SSPC - SP8 - Pickling

SSPC - SP9 -Weathering

SSPC - SP10 - Near-White Blast Cleaning 

2.   REFERENCE DOCUMENTS

·        Technical Specification & Approved Drawing

3.   PROCEDURE / METHOD

·        Steel Surface of Equipment shall be thoroughly blast cleaned with shot or grit in accordance with below mentioned preparation grades and standard.

·        SA 2.5 (as per customer requirements) to Make the surface free from visible oil, grease & dirt, mill scale, rust, paint during blasting to prevent damage.

 

SALT CONTAMINATION TEST KIT

·        The Compressed air that is used for blasting should be preferably blast cleaned prior to fabrication and paint these with one coat of pre fabrication primer prior to fabrication. After adequate blast cleaning of each large surface where blasting time is more than three hours, an overall blast cleaning is to be done on the entire surface once more so that entire surface area is exposed as fresh for first coat of primer paint.

·        The First coat of primer paint should be applied not later than 3-4 hours after preparation of surface to avoid oxidation.

·        Painting shall be carried out in a closed and dust free area. The Paint selected shall be stable in outdoor condition such as rain, sunlight, pollution etc.

·        If Paint used for primer, intermediate coat and top/finish coat are not from the same manufacturer then compatibility test of the paint from different source shall be carried out. Painting shall be applied as per the recommendation of the paint manufacturer. The number of coats shall be such that the minimum dry film thickness (DFT) specified is achieved. The DFT of painted surface shall be checked with a measuring gauge (Digital Coat Meter) to ensure specified DFT.

 

                              

4.   SURFACE PREPARATION GRADES. BLAST 

·        It is assumed that prior to treatment the steel surface has been cleaned of dirt and grease, and that the heavier layers of rust have been removed by chipping.

·        Sa 1 Light blast cleaning: Loose mill scale, rust and foreign matter shell be removed. The appearance shall correspond to the prints designated Sa 1.

·    Sa 2 Thorough blast cleaning: Almost all mill scale, rust and foreign matter shall be removed. Finally, the surface is cleaned with a vacuum cleaner, clean dry compressed air or a clean brush. It shall be greyish in colour and correspond in appearance to the prints designated Sa 2.

·       Sa 2½ Very thorough blast cleaning: Mill scale, rust and foreign matter shall be removed to the extent that the only traces remaining are slight stains in the forms of spots or stripes. Finally, the surface is cleaned with a vacuum cleaner, clean dry compressed air or a clean brush. It shall correspond in appearance to the prints designated Sa 2½.

·      Sa 3 Blast cleaning to pure metal: Mill scale, rust and foreign matter shall be removed completely. Finally, the surface is cleaned with a vacuum cleaner, clean dry compressed air or a clean brush. It shall then have a uniform metallic colour and correspond in appearance to the prints designated in Sa 3.

5.   ACCEPTANCE CRITERIA

·        The preparation of steelwork obviously has a bearing on the success or failure of any surface coating, and therefore the following information is relevant to steelwork prepared to Swedish Standard SIS 05 59 00 – Sa 2.5. British Standard.

·        BS 7079: Part A1: 1989 (ISO 8501 – 1:1988) – Surface Finish of Blast Cleaned Steel for Painting and Steel Structures Painting Council of America also set out standards for cleanliness.