Dear
Readers,
Sand
blasting is one of the surface cleaning process for structural steel.
Sandblasting is a general term used to describe the act of propelling very fine
bits of material at high-velocity to clean a surface. Sand used to be the most
commonly used material.
As per ISO and Swedish standard, Surface preparation by blast cleaning is designated by the letters "Sa". Swedish standards has been accepted worldwide. As per standards Sand blasting is classified under four category namely Sa1, Sa2, Sa 2 ½, & Sa3.
Brief descriptions are as follows.
Sa1
= Light Blast Cleaning
Sa2
= Through Blast Cleaning
Sa 2
½ = Very through blast cleaning
Sa3
= Blast cleaning to visually clean Steel
“Sa” means Swedish air blast similarly “St” means Swedish tool cleaning. Detailed description of each grade is as follows.
Blasting Grade Sa 1: It is a light blast cleaning. Loose mill scale, rust and foreign matter must be removed. When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter.
Blasting Grade Sa 2: It is a through blast cleaning. Almost all mill scale, rust and foreign matter must be removed. When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter. Any residual contamination shall be firmly adhering.
Blasting Grade Sa 2 ½: It is a very through blast cleaning. This grade is very often used in construction industry. Mill scale, rust and foreign matter must be removed to the extent that the only traces remaining are slight stains in the form of spots or stripes.
Blasting Grade Sa3: Blast cleaning to pure metal. Mill scale, rust and foreign matter must be removed completely and it shall have a uniform metallic colour.
“Sa” means Swedish air blast similarly “St” means Swedish tool cleaning. Detailed description of each grade is as follows.
Blasting Grade Sa 1: It is a light blast cleaning. Loose mill scale, rust and foreign matter must be removed. When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter.
Blasting Grade Sa 2: It is a through blast cleaning. Almost all mill scale, rust and foreign matter must be removed. When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter. Any residual contamination shall be firmly adhering.
Blasting Grade Sa 2 ½: It is a very through blast cleaning. This grade is very often used in construction industry. Mill scale, rust and foreign matter must be removed to the extent that the only traces remaining are slight stains in the form of spots or stripes.
Blasting Grade Sa3: Blast cleaning to pure metal. Mill scale, rust and foreign matter must be removed completely and it shall have a uniform metallic colour.
Notes.
1). Surface
cleaning should be mention along with rust grade. For example B Sa2, here first
letter "B" represents rust grade.
2). Prior to blast –cleaning, any heavy layers of rust shall be removed by chipping. Visible oil, grease and dirt shall also be removed.
3). Finally the surface is cleaned with a vacuum cleaner, clean dry compressed air, or a clean dry brush before painting.
2). Prior to blast –cleaning, any heavy layers of rust shall be removed by chipping. Visible oil, grease and dirt shall also be removed.
3). Finally the surface is cleaned with a vacuum cleaner, clean dry compressed air, or a clean dry brush before painting.
3 comments:
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