Can seam evaluation is the responsibility of the company that is filling and closing the can package. Depending on the type of products being canned—food, beverages, pharmaceuticals, etc.—there are specific regulations on how and when can seam evaluations are to be conducted, as well as documentation and reporting guidelines. Your Quality Assurance program should, at a minimum, include hourly visual seam inspections and a complete seam tear-down every four hours. A physical report of the complete seam tear-down should also be completed and kept on file.
External examination of the can double seams should be made at least every 4 hours of operation (once in the morning and once in the afternoon) to check for proper seam adjustment. Examinations should be more frequent if changes in can size, shutdowns, or problems with a particular sealing machine have occurred.
In order to make an internal inspection of the seam, the body and end must be separated in a manner that exposes the body hook and cover hook so they can be accurately measured. This procedure is termed a “cut-down,” “stripping,” or “tear-down.”
Cutover is a situation where the seam is sharp enough to fracture the metal at the top inside portion of the seam. Possible causes are a worn seaming chuck flange or roll grooves, or the first or second seaming operations being set too tightly.
Droop is a situation in which there is a projection of the double seam below the bottom of the normal seam. Possible causes include excessive body hook, or the first operation being too loose.
False Seam is one where a portion of the seam is entirely unhooked and in which the folded cover is compressed against the folded body hook. Possible causes for this include a bent can flange, misassembly of the can and cover, or the can not being centered on the seaming chuck.
Proper seam formation cannot be judged by purely mechanical means or measurements. The evaluation of good double seams requires experience, skill, and above all, good judgment.
Manual Can Seam Tear-Down Video (Sanitary Can): The video is at the bottom of the page.
There are many companies that offer can seam saws and optical scopes with software to evaluate can seams and produce reports. https://doubleseam.com is another can seam information resource that provides in-depth information on all types of double seams.
Below are links to important rules and regulations for can seaming. Regardless of the product or further processing, you are responsible for making sure all of your products are packaged with an acceptable seam. Your QC program should become more comprehensive as more knowledge and experience are gained.
