The intention of this website is to help can seam inspectors navigate the ins and outs of double seam inspection.

Leaking seams compromise the integrity and quality of canned product, and can seams should be inspected on a regular basis to ensure that your canning equipment is creating air-tight seams.

OneVision Corporation is a seam inspection and weighing equipment manufacturer located in Westerville, Ohio. We empower our customers in ensuring the quality of product they package is the same quality that reaches the consumer.

Let’s start with the basics…What is a Double Seam?

A Double Seam may be defined as follows:
A hermetic seal is formed by interlocking the edges of both the end component and body of a can. It is commonly produced in two operations. The first operation forms the metal to provide the five thicknesses or folds, and the second operation flattens or irons these components to produce the required seal.

Forming the Double Seam…

First Operation Seam Formation
It is imperative to have a good first operation seam, as it is impossible to form a quality finished seam unless the first operation seam is correct. A correctly formed first operation is a major key to the control of the cover hook which in turn partially controls the body hook as well as the countersink depth and degree of wrinkle in the cover hook. A poorly formed first operation seam cannot be corrected by the second operation roll(s). It is recommended that first operation seams be checked weekly or when seam problems occur.

First operation seams will determine the length of the finished second operation seam. Typically as the first operation roll groove profile gets narrower, the seam height begins to shorten. Wide profiles will yield longer seam heights.

A useful rule of thumb is to closely observe the bottom portion of the first operation seam. It should have a smooth radius with minimal scuffing.

Second Operation Seam Formation
The Second Operation Formation is the final operation in double seaming. In this operation, the double seam components formed in the first operation are ironed or flattened, compressing the compound to fill the voids not occupied by metal.

The lower compound tunnel should be filled with compound as the tunnel provides the primary seal. The upper tunnel acts as a reservoir for excess compound and may not always be filled with compound.

The tightness of the double seam is determined by evaluation of the degree of wrinkle in the cover hook section.
**A double seam must be evaluated in its entirety and not by dimensions alone.

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Seam Inspection 101
Double Seam Defects
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