Glass Panels Inspection Procedure
Double Glazed Unit (or DGU) panels, Laminated Glass panels, and Toughened Glass panels are checked as per international standards.
Ref Standards:
- EN 572 – Float Glass standard
- EN 12150 – Thermally toughened safety glass
- EN 12543 -Laminated glass and laminated safety glass
- EN 1279 – Insulating Glass Panels
- EN 1863 – Heat Strengthened Glass panels
Glass inspection should be followed as per below said procedure.
The pane of coated glass being examined is viewed from a minimum distance of 3 m. The actual distance will be dependent on the defect being considered and which illumination source is being used. The examination of the coated glass in reflection (a) is performed by the observer looking at the side which will be the outside of the glazing. The examination of the coated glass in transmission (b) is performed by the observer looking at the side which will be the inside of the glazing. During the examination the angle between the normal to the surface of the coated glass and the light beam proceeding to the eyes of the observer after reflection or transmission by the coated glass shall not exceed 30°
For panes of coated glass in finished sizes ready to be installed both the main area and an edge area of the pane shall be examined. Each examination will take no more than 20 s.
Uniformity defects and stains
- Under the conditions of examination, note any coating variations either within one pane or between neighboring panes which are visually disturbing
- Under the conditions of examination, note any spots, pinholes and/or scratches that are visually disturbing.
- For spots/pinholes measure the size and note the number relative to the size of the pane. If there are any clusters found their position relative to the through vision area shall be determined.
- For scratches determine whether or not they are in the main or edge area. Measure the length of any scratches noted. For scratches > 75 mm long determine the distance between adjacent scratches. For scratches <75 mm long note any area where their density produces visual disturbance
Acceptance criteria for coated glass defects.
The acceptance criteria for defects in coated glass, examined according to the Standard is given below in the Column.
Assessment of fragmentation for Heat Strengthened Glass
Each fragment produced during the test shall be assessed as follows:
- At least one edge of the fragment shall reach the excluded area. The particle count and measuring of the dimensions of the largest particle shall be made between 3 to 5 min after fracture.
- Where no edge of the fragment reaches the excluded area, either an island or a particle is produced. Particles are fragments with area/mass equivalent less than 100 mm². Islands are fragments with area/mass equivalent greater than or equal to 100 mm².
- The number of island fragments shall be counted and each island shall be weighed.
- Area = mass / (thickness × density), for example, a fragment of 6 mm thick glass of mass 1.5 g has an area/mass equivalent of 100 mm²
- At least four out of five specimens shall meet the following requirements Each test specimen shall not have more than 2 island fragments
- Each test specimen shall not have any island fragments with area/mass equivalent exceeding 1000 mm2 and each test specimen shall not have the area/mass equivalent of all particles exceeding 5000 mm2
Assessment of Fragmentation for Toughened Safety Glass
The particle count and measuring of the dimensions of the largest particle shall be made between 3 min to 5 min after fracture. An area of radius 100 mm, centered on the impact point, and a border of 25 mm, around the edge of the test specimen, shall be excluded from the assessment.
The particle count shall be made in the region of coarsest fracture (the aim being to obtain the minimum value). The particle count shall be made inside a square frame of (50 ± 1) mm × (50 ± 1) mm on the test piece or by any other suitable means. The number of crack-free particles within the square shall be counted. A particle is ‘crack-free’ if it does not contain any cracks which run from one edge to another
The particle count determination of glass sheet shall be completed within 5 min of the fracture of that glass. No magnifying lens or other aid to vision (except spectacles if normally worn) shall be used when making the particle count as described below.
All particles wholly contained within the area of the square frame shall be counted as one particle each and all the particles which are partially within the square frame shall be counted as 1/2 particle each.
| Glass Type | Nominal Thickness in mm | Minimum Particles Count |
| Float | 4 to 12 | 40 |
TOLERANCE LIMITS FOR DIMENSION (As per EN 12150 -1)
Dimensional tolerance following as per below given tabular column.
| Dimensions |
Tolerance t |
||
| W/L/H | Thickness < 12 mm | Thickness > 12 mm | Diagonal |
| < 2000 | + 2.5 mm | + 3 mm | 4 mm |
| 2000 < L > 3000 | 3 mm | 4 mm | 6 mm |
| >3000 | 4 mm | 5 mm | 6 mm |
Measurement of Local Bow and over all Bow:
For the Overall Bow and Low bow Maximum level is following as per the given details.
| Type of Glass | Over all Bow | Local Bow/ 300 mm |
| Float uncoated glass | 0.003 mm/mm | 0.3 mm |
| Others | 0.005 mm/mm | 0.5 mm |
For Insulating Glass Panels the following test are carried out and confirm the Quality
- Desiccant Absorption test
- Butyl weight test
- Butterfly test
- Snap time test
- Peal addition test
- Shore A test
- Visibility test
For the Laminated Glass Panel the listed tested conducted and confirmed the Quality
- Dimensional test
- Visibility test
- Thickness test