Canning and Fish Packaging Technology

Unit3 - Unit operations in canning

3.2.4.4.Seam defects
1. False seam
False seam is formed without interlocking of body and cover hooks. This is a gross defect and cans definitely leak.

2. Backward extension of seam or cut over of cover
When cover is pressed and rolled part of the cover is push above the chuck, cut over happens. If cut over takes place it may be difficult to remove cans from the seamer. Due to this incomplete seam or the seam may get cut.

The reason for this are

• Wear and tear of chuck.
• Fixing of chuck at a lower level than required in the seamer.
• More solder on the side seam.
• More force exerted by the seaming rollers.
• Looseness between chuck and the lid/cover.

3. Lips in the seam
Part of the steel plate comes out of the completed double seam which appears like lips.

The reasons for this defect are,

• Second seaming roller is more lightly fixed.
• Pressure by base plate is more.
• Loosely fitted first operation roller.
• Completely worn out roller.

4. Wrinkle in the double seam
Wrinkled seam is due to worn out rollers.

5. Lines on the seam
In such seams have lines on the outer surface of the seam. This is due to worn out second operation roller or distortion.

6. Cut seam
Seam is cut from top to bottom. This is due to,

• Excessive base plate pressure.
• Tightly fixed second operation roller.
• Excessive solder on the side seam.
• Chuck is fixed at a lower level than the desired level.