A Complete Guide on Double Seaming - Levapack

A Complete Guide of Double Seaming

Can seaming is an old packaging technique that goes a long way back to the industrialization era. Once the demand for processed foods started to go up, the need to create reliable storage and packaging solutions led to the invention of canning line assembly. Since then, the process has undergone a lot of transformation and improvements to become what it is today. At the center of this revolution, the one seating technique that has left the biggest impact would be double seaming.

We are going to explore double seaming, find out how it works, the benefits it can bring to the manufacturing and packaging space, the defects that are associated with the process as well as the factors one has to pay attention to when choosing double seaming. If you are looking to get into the packaging space, then this is for you.

Table of Contents

What is a Double Seam?

Canned Tuna
Source: Pixabay

A double seam is the use of two layers to seal a can; one being the lid and the other being part of the can. It is a process that uses two seaming rollers to create a double layer of seal that ensures the contents of the can remain fresh and tight enough to stop any outside contaminant from getting in. The process is the most widely used in the can packaging industry and is perfect for food and beverage packaging as well as the packaging and storage of toxic chemicals. 

Double seaming is as old as the canning process itself, and to understand its origins; you have to know the history of canning. The process of canning food owes its origin to the French, who during the Napoleonic wars sought to find a lasting solution for providing food for the soldiers on the battlefield. The government even offered 12000 Francs to anyone who would come up with a lasting solution to the food problem. Eventually, a man called Niclas Francois Apeert discovered that cooked food that was placed inside a jar did not spoil easily unless the seal was opened or was leaking. This gave him the idea of the first food packaging, but it wasn’t until 50 years later that the presence of microbes was confirmed by Louis Pasteur. The confirmation of dangerous microbes further pushed the importance of double sealing a notch higher.

This led to the creation of branded tin packages for food which improved over the years to become what they are today. Since then, more variations of the packaging technique of using cans have found their way in all the major packaging industries around the world. They are now not limited to food packaging alone but to others like chemical packaging, paints, drugs, and other products.

Double Seam Components

Seaming Machine
Source: Pixabay

For double seaming to take place, there are special parts that the seaming machine has to have. Each of the parts serves a specific function. To better understand how double seaming works, you have to know all these components, and they include the following.

Chuck: Also called a seamer head, this is one of the most vital parts that keeps the can in place when the double seaming process is being conducted. The chuck also protects the can from being crushed by the intense pressure erected by the turntable; without that protection, the can may get serious dents that may compromise its structural integrity.

Rollers: Seaming rollers are the parts that are responsible for surviving the seams into place. Most double seaming machines come equipped with two seaming rollers, one handling the can body and the other handling the lid, interlocking the two into one seal. It takes a lot of work to set them right, and you may require the services of a qualified expert to pull it off.

Vacuum Room: Also called the seaming chamber, this is a section of the seaming process that expels the air from the can just before sealing is done. The vacuum created is ideal for preserving the contents of the can for as long as possible since contaminants cannot survive in a vacuum.

Ejector: The ejector is a piece of metallic rod that has a small disc on one end that protrudes from the center of the chuck. It moves in a vertical motion, ejecting the can that has been sealed to make room for the next one. The process of ejection has to be done with care to avoid damaging the can since using too much force may result in the can get a serious dent.

Conveyor Belt: Also called the transport, this is a chain of converter belts that move continuously through the process, moving the body of the can from one section to the next. They feed the can into the machines from one end to the other in a very smooth and seamless fashion.

Feeder Caps: These are automated arms that pick lids and position them over the mouth of the can in the sealing chamber for sealing. They are quite fast and accurate, which is necessary to ensure that packages are able to meet demands.,

Benefits of Double Seaming

Storage Cans

Compared to other forms of seaming, double seaming holds some advantages and this is the reason why packaging suppliers around the world love going with this technique. The following are some of the benefits of using double seaming for packaging.

Best Value: When compared to other seaming techniques, the machines used in double seaming cost a lot, and they require specialized operators. However, double seaming is more reliable as the seal is not only foolproof but the chances of leakage are also eliminated; you will have to exert a lot of pressure and force to pry the lid open. Otherwise, on its own, the can would remain closed.

Extra Protection: WIth double seaming, you are assured of a tight lid that cannot come off on its own. The can could even fall to the ground, and nothing serious would happen to it unless a lot of force is applied to it. This makes double seaming the ideal packaging method for food as well as toxic chemicals, as they are better equipped to keep things from moving in and out of the can once the seal is applied.

Versatile: Double seaming can be used for all kinds of products. From perishable foods to toxic chemicals to beverages. It is highly versatile and can come in handy for manufacturers and packagers who diversify into other products. Whether it is a beer bottle, a can of sardine, or a huge tank of paint, double seaming can be used without any issue.

Fast: Double seaming is a very fast and automated process that can be used to produce a large volume of canned products in a matter of minutes. There are some can seaming machines that are advanced enough to handle tens of thousands of cans in a single day, and this makes the process the perfect one for packagers who deal in fast-moving products like canned food and beverages.

Applications of Double Seaming

Sealed Storage Cans
Source: Pixabay

Double seaming is a very resourceful technique for customizable packaging and has been used for years in the food and beverage industries, among many others. The following are the notable applications of double seaming in today’s world.

Beverage Industry: The beverage industry has been around for years, changing its containers from glass to tin can switch rely heavily on double seaming. From soda, beers, and energy drinks, double seaming is the most used method for sealing these cans to ensure their contents remain fresh for a long time and to keep them safe for human consumption.

Canned Food Industry: Foods are perishable goods, and where seafood and fruits are involved, proper containers are needed to ensure they have a longer lifespan on the shelves. Food requires an airtight seal and double seaming is the best way to achieve this without going overboard.

Medical Industry: The storage of drugs also makes use of double seaming to ensure the drugs don’t come into contact with contaminants. This is ideal for powdery drugs and liquid-based medicine. Double seaming works for all kinds of materials from metallic cans, plastic containers, and even glass.

Chemical Industry: Just like the food and beverage industry, the chemical industry is another big beneficiary of double seamed cans. Chemicals can be toxic to the environment, and for this reason, they have to be sealed tight, something that only a double seaming machine can pull off successfully.

Double Seaming Process

A double seaming process goes through three main stages, each serving a specific function before transferring the product to the next. The principle behind it is not that different from other seaming techniques. The three stages include the following.

Compression

This is the first stage of double seaming, and it involves the application of force to the main body of the can, holding it in place as the seaming process is done. The can is then pushed to the turntable, where the chuck gets hold of the id and positions it over the mouth of the can. Once the lid is over the can. The can and the lid are then pushed to the next stage for the interlocking process to start.

First Roller Operation

This is a necessary operation that kicks off the interlocking process. It begins by hooking the lid over the can by pushing the flange of the lid to fit onto the edge of the main body of the can. The roller continues phishing that lid towards the chuck, and this causes the edge of the lid to fold nicely over the can, forming the first hook before quickly moving on to the final stage in quick succession.

Second Roller Operation

The second roller then takes hold of the body can, folding it into the hook of the can to create a second layer forming the double seam. The second stage makes use of pressurized force to force the two edges into each other, creating a hermetic seal that cannot be opened without the use of considerable force or a knife to cut it open. Once the edges are interlocked into each other, the double seam process is now complete, and the can is ready for use however you want it.

Double Seam Defects

There is no perfect process in the manufacturing world, and something is reliable as double seaming does come with its own set of defects. The following are some expected defects that result from double seaming.

Wooling

Wooling
Source: https://doubleseam.com

Also called silvering, wooling is a condition where a part of the lid or the can body is shaved off accidentally, causing a pile-up of metallic parts in the seaming header area. These parts usually come in the form of sine silver strands in the case of tin cans and can block the cover feed rails if nothing is done about it quickly enough.

Common causes of wooling include a worn-out first seaming roller, the lid being loosely set on the body of the can, or the turntable being too tight with a lot of pressure applied. Some possible solutions include loosening the rollers, adjusting the pressure on the turntables, and clearing the feed rails if the fine threads pile up.

Vee

Vee
Source: https://doubleseam.com

A Vee is a sharper and a pointed extension that appears on the edge of the sealed lead. Sometimes it appears in sections, or it may go all around the can. The Vee is visible to the naked eye, and you can even feel it when you pass your hands around the can. In some very severe cases, the vee sometimes folds back over itself, distorting the shape of the can completely.

Possible causes include excessive seaming, product entrapment, or a worn-out seaming roller. The defect can be rectified by replacing the worn-out rollers, checking with the manufacturer, or reducing the pressure in the turntables.

Sharp Seam

Sharp Seam
Source: https://doubleseam.com

This is a unique condition where the completed seam has a very sharp edge on the top part of the inside edge just over the can cover. A good seam is supposed to be smooth and even, but in this case, there’s a 90-degree drop creating a sharp edge that could be an injury hazard.

The most common causes of this include an operation seaming roller that is set too right or a seaming chuck that has been worn out due to overuse. Re-adjusting the sealing roller and replacing the worn-out chuck are the things you can try to make things right.

Mushroomed Flange

Mushroomed Flange
Source: https://doubleseam.com

This is an extended edge that stretches over the top of the can to form a long body hook. This can distort the shape of the can, and in some cases, it may pose a risk to anyone unfortunate enough to pass their hands over the sharp edge.

The most common causes of this defect include the use of excessive pressure in the seam header, using a worn-out chuck, or using a damaged can flange. Replacing all the worn-out parts and reducing the actionable pressure in the seam header will do the trick.

False Seam

can seaming
Source: https://doubleseam.com

A false seam occurs when the body of the can and lid are not interlocked properly but appear to be folded over each other. On a closer inspection, you will realize that there’s enough space to allow contaminants to sneak in and leakages to happen. 

A  common cause of this condition is the use of a bent flange, a damaged lid, misaligning the lid when putting it over the can, and using excess pressure in the seaming roller. Using the right lids and aligning everything as directed by the instructions would help you get rid of this defect once and for all.

Droop

Droop
Source: https://doubleseam.com

A droop manifests itself when a small part of the seam stretches below the edge of the bottom seam. These droops are noticeable and can give the tin a very unnatural look. Although modern seaming machines are getting better at smoothing out this defect, there are still instances where it pops up.

Common causes of the defect include the use of worn-out seaming rollers, improper formation of clever curls, using a body hook that’s way too long for the can, and the use of excessive pressure on the turntable. Getting new replacements for the worn-out parts and calibrating the pressure will set things right.

Creasing

can sealing
Source: https://doubleseam.com

Also called scoring, this is common in aluminum cans, and it is the process where the outer edge of the lid is creased by a part of the hook. This manifests itself in the form of a catch that pushes the lit outwards, affecting the ability of the can to keep the ingredients from leaking. Sometimes it appears as small dents around the lid. 

A common cause of this defect includes the use of a can seaming roll that is too tight, which then increases the stress on the lid. The can neck being too short can also lead to creasing. Simply use the right lids and reduce the tightness on the chuck to rectify the problem.

Conclusion

Double seaming is a very effective process when it comes to packaging, and it is no wonder that every packager has invested in the double seaming machines. There are many other variations in the market that you can check out if you plan to get into the can packaging business. For more information, check out our website and get some valuable tips.

Send Your Enquiry
en_USEnglish