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 What is Surface preparation?
What is the difference Between Sand Blasting/Shot
Blasting/Abrasive Blasting & what is SA 2˝? |
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Surface preparation
is the essential first stage treatment of a substrate before
the application of any coating, The performance of coating
is significantly influenced by its ability to adhere
properly to the substrate material. It is generally well
established that correct surface preparation is the most
importance factor affecting the total success of surface
treatment. The presence of even small amounts of surface
contaminants, oil, grease, oxides etc. can physically impair
and reduce coating adhesion to the substrate. Chemical
conformant that are not readily visible, such as chlorides
and sulphates, attract moisture through coating systems
resulting in premature failure The imporeance of a
chemically clean substrate to provide the impatience of a
chemically clean substrate to provide the bese possible
contact surface for the applied coating connote to
over-emphasized.
In the Sand Blasting process, a high velocity jet of fine
Silica Sand Particdes and carrier gas coming out from a
nozzle impinges on the target surface and erodes it. The
fine paticles are accelerated by the gas stream commonly
compressed air at a few times atmospheric pressure. Shot
blasting is a process in which Splerical Shape Abrasive with
compressed air impinges on the metal surface. In Abrasive
Blasting process the angular shape particles with compressed
air impinges on the metal surface.
SA 2 ˝ is a grade of surface preparation which means.
‘’Thorough Blast cleaning early to pure metal”- Millscale,
rust and foreign matter shall be removed to the extent that
the only traces remaining ane slight stains in the form of
spots or strip. Finally, the surface is cleaned with a
vacuum cleaner, clean dry compressed air or a clean brush. |
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Compressed Air requirements for
sand blasting? What is CFM & how it related with Nozzle
diameter? |
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Air consumption
depends mainly upon the orifice size and pressure. It also
depends whether it is flowing free through the nozzle or
carrying abrasive.
CFM means cubic feet per minute. The following table gives
the relation between consumptions of air, carrying
abrasives, through orifices of various sizes and at various
pressure.
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Nozzle Orifice mm |
Nozzle Pressure Kg/cm (psi) |
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4.22 (50) |
5.36 (80) |
7.03 (100) |
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AIR CONSUMPTION IN CUBIC
METERS/SEC (CFM) |
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4.0 |
0.012 (25) |
0.014 (30) |
0.17 (37) |
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5.0 |
0.014 (30) |
0.018 (38) |
0.021 (45) |
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6.0 |
0.025 (54) |
0.032 (68) |
0.038 (81) |
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8.0 |
0.041 (89) |
0.053 (113) |
0.064 (137) |
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How
to select the type of machine? |
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To know or select
the type of machine, we should know the following parameters
:
1. What is the surface roughness requirement?
2. What is the substrate material?
3. What is the production output requirement?
4. What type of surface finish is required? |
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What
is Abrasive and how to select? |
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Abrasive defined
as, which adrupts the substrate material. To select the type
of abrasive we should know the following parameter.
1. What type of substrate material?
2. What is the surface roughness requirement?
3. what type of surface finish required? |
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What
is Shot Penning? |
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Shot peening is a
method of cold working in which compressive stresses are
indeed in the exposed surface layers of metallic parts by
the impingement of a stream of shots directed at the metal
surface at high velocity under controlled conditions. |
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What
are application of abrasive blasting Equipment? |
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The applications of
blasting equipments are in Automotive industries, ship
manufacturing industries, medical and optical equipment, Air
craft, Electric utility, Mining, Agricultural Equipments,
Food & Daing industry, Glass manufacture, Jewelry, Oil &
Petroleum industry, Tyre & Rubber industry etc. |
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