Thursday, 5 November 2020
Tuesday, 3 November 2020
Monday, 2 November 2020
Monday, 22 June 2020
Tuesday, 19 May 2020
Paint Inspection of Steel Box Girder and Cross Beam
mixing of shall be complied with instructions prepared by the manufacture’s in the mixing
procedure, mixing ratio and recommended use by time.
The expired paints from the term of validity as specified in a manufacturer’s instruction
shall not be used. The paint containers shall be opened only at the time of use. Paints which
have liveried, gelled or otherwise deteriorated during storage shall not be used. After the
paint has been opened and mixed, the paint will be used within the pot life as recommended
by the paint manufacturer.
The labels on sealed containers of paint are maintained and are carried in the painting
yard for the work. Shipping certificate and test certificate including date of manufacture, lot
number, color and quantity, are recorded.
Temperature Control and Equipment
Painting work will be carried out in an air-conditioned painting shop to minimize effects
of inclement weather. The air-conditioned painting shop will maintain the following
atmospheric conditions
Paint shall be applied only on thoroughly dry surfaces, and shall not be permitted when
metal surfaces are less than 3℃ above the dew point. Metal surface which are hot enough to
cause the paint to blister, to produce a porous paint film, or to cause the vehicle to separate
from the pigment shall not be painted.
13.4 Surface Preparation
All surfaces of new structural steel shall be cleaned by the blast-cleaning method unless
otherwise specified in the Contract Documents. The methods used in the cleaning of metal
surfaces shall conform to the following sections.
(1) Blast Cleaning
Abrasives used for blast cleaning are steel grit (Profilium PRO45). Unwashed beach
sand containing salt or excessive amounts of silt will not be allowed.
All dirt, mill scale, rust, paint, and other foreign material shall be removed from
exposed steel surfaces in accordance with the requirements of ISO Sa2.5, “Near-White
Metal” Blast Cleaning. Blast cleaning shall leave all surfaces with a dense and uniform
anchor pattern of not less than 25.4 μm or more than 76.2 μm as measured with an
approved surface profile comparator.
When blast cleaning is being performed near machinery, all journals, bearings,
motors, and moving parts shall be sealed against entry of abrasive dust before blast
cleaning begins.
Blast-cleaning is carried out in interior paint shop with tent to prevent rain for
members and to avoid influence on environment by dust of blast cleaning.
Blast-cleaned surfaces shall be primed or treated the same day blast cleaning is
done.
The surface prepared by blast cleaning is inspected by the following method.
Degree of derusting : Degree of derusting of blasted surface is inspected by
comparison with Rust Grade Book including Swedish steel
blasting grades (Sa 2.5).
Anchor pattern : The anchor pattern of blasted surface is measured by
comparison with surface profile comparator.
Inspection record of Visual Inspection of Surface Preparation shall be recorded.
(2) Hand Cleaning
Wire brushes either hand or powered, hand scraping tools, power grinders, or
sandpaper shall be used to remove all dirt, loose rust and mill scale, or paint which is
not firmly bonded to the metal surfaces.
Application
Surfaces of high-tension bolts joint will be painted by zinc rich paint only and will be
masked before 2nd coat. The masking will be carried out so that 10mm outside the
perimeter of the splice will receive the prescribed coat of paint.
Paint will be applied by airless spray. The proper nozzle tip and nozzle pressure shall be
selected, in accordance with the Paint Technical Data provided Paint Manufacture.
Re-entrant corners, narrow areas and other areas difficult to access by spray will be
painted by brush. Brushes, when used, shall have sufficient body and length of bristle to
spread the paint in a uniform film. Round, oval-shaped brushes, or flat brushes not wider
than 115 mm shall be used. Paint shall be evenly spread and thoroughly brushed out.
Rollers, when used, shall be of types that do not leave a stippled texture in the paint
film. Rollers shall be used only on flat, even surfaces to produce a paint film of even
thickness with no skips, runs, sags, or thin area.
Paint will be applied evenly to prevent sagging, over-coating and under coating. On all
surfaces that are inaccessible for painting by regular means, the paint shall be applied by
sheepskin daubers, bottle brushes, or by any other means approved by the Engineer.
Mixing of paint will be performed in strict accordance with the paint manufacturer’s
recommendation. Mechanical mixers shall be used to mix paint. Prior to application, paint
shall be mixed a sufficient length of time to thoroughly mix the pigment and vehicle together,
and shall be kept thoroughly mixed during its application. Paints that are specified
“formulated ready for application” and “no thinning” shall be allowed unless otherwise
provided in the applicable materials specification for the paint being used.
Painting interval between the two coats will follow the specification in Section 13.2 of
this Method Statement and Quality Control Plan. The surface of the paint being covered
shall be free from moisture, dust, grease, or any other deleterious materials that would
prevent the bond of the succeeding applications. In spot painting, old paint which lifts after
the first application shall be removed by scraping and the area repainted before the next
application.
Repair of Painting Defect
We repair painting defect (cissing, sagging, bleeding, lifting etc.) when it occurs in painting process.
For repair of painting defect, the damaged coating layer is peeled off by sandpaper. Thereafter we
repaint from the layer again
.
If painting defect affect from 1st layer of coating, all painting layer is peeled off by power tool. In
that case, organic zinc rich primer is painted for 1st layer.
Saturday, 2 May 2020
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