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A double seam is a canning process for sealing a tin can by mechanically interlocking the can body and a can end (or lid).
Originally, the can end was soldered or welded onto the can body after the can was filled. [1] However, this introduced a variety of issues, such as foreign contaminants (including lead and other harmful heavy metals). The double seam was later developed as a cheaper and safer alternative and quickly replaced the welded seam.
The double seam is made using a double seamer, which can have just one or a number of heads or seaming stations. The double seam is formed by mechanically interlocking five layers of material together: three layers of the can end and two layers of the can body. Each seaming head typically consists of two rolls, a first operation roll and second operation roll, and a chuck. Some seaming machines have two first operation rolls and two second operation rolls and a few machines use a method called "rail seaming" which requires no rolls. During the seaming operation, the can end is lowered on to the filled can body and held down by the chuck, which acts as an anvil to the seaming operation. The first operation roll then engages the can end against the can body thereby folding the end curl around the flange of the body. In some seaming machines, this is done as the can is turning at high speed. In other seaming machines, the can is stationary and the first operation roll (or rolls) spins around several times to ensure a complete first operation. After the first operation is complete, the first operation roll disengages from the can and the second operation roll then engages the can. The purpose of the second operation is to iron out the double seam into its final shape and remove the voids between the layers of can and end material. In practice, ironing out all of the can and end material in a double seam without leaving some voids is impossible without the use of a sealing compound.
The production of a high-quality double seam is dependent on several factors, including conformity to the set can and end specifications, the quality of the seamer tooling used and its compliance with the can and end being used, the condition of the seaming machine and the setup of the seaming rolls, lifter pressure and other components. When the machinery is set up correctly and the incoming materials (cans, ends, tooling, etc.) comply to the set specifications, the result should be [2] ideal first and second operation seams.
A problem in any one of these factors and others can contribute to seam defects that have an adverse effect on the ability of the can to withstand foreign contamination and keep the product from leaking or reduce its shelf life. Below is a list that can be used as a reference. [3]
In the United States, the production and quality of double seams is regulated by the US Department of Health and Human Services - Food and Drug Administration (FDA) and the Department of Agriculture (USDA). The plant's responsibility towards the government depends on the product being canned. The FDA regulates all components of canning low acid canned foods, including handling of empty containers, glass, metal and plastic containers. FDA regulations require that at least one double seam can per seamer must be visually inspected every 30 minutes. Additionally one can per line must be cut open and inspected with a micrometer or a seam scope, which projects a magnified image of the seam, at least every four hours. [4] The USDA regulates canning of animal products. [5] Additionally, X-rays may be used to inspect the seam as part of the visual inspection
A flange is a protruded ridge, lip or rim, either external or internal, that serves to increase strength ; for easy attachment/transfer of contact force with another object ; or for stabilizing and guiding the movements of a machine or its parts. Flanges are often attached using bolts in the pattern of a bolt circle.
120 is a film format for still photography introduced by Kodak for their Brownie No. 2 in 1901. It was originally intended for amateur photography but was later superseded in this role by 135 film. 120 film survives to this day as the only medium format film that is readily available to both professionals and amateur enthusiasts.
Canning is a method of food preservation in which food is processed and sealed in an airtight container. Canning provides a shelf life that typically ranges from one to five years, although under specific circumstances, it can be much longer. A freeze-dried canned product, such as canned dried lentils, could last as long as 30 years in an edible state.
A jerrycan or jerrican is a fuel container made from pressed steel. It was designed in Germany in the 1930s for military use to hold 20 litres of fuel, and saw widespread use by both Germany and the Allies during the Second World War.
In rail transport, a derailment is a type of train wreck that occurs when a rail vehicle such as a train comes off its rails. Although many derailments are minor, all result in temporary disruption of the proper operation of the railway system and they are a potentially serious hazard.
In professional wrestling, a pin is a move where a wrestler holds an opponent's shoulders to the mat in an attempt to score a fall. A pinfall is a common victory condition, where the attacker pins an opponent and the referee makes a three count before the opponent gets released from the pin.
Sheet metal is metal formed into thin, flat pieces, usually by an industrial process.
In manufacturing, a countersink is a conical hole cut into a manufactured object, or the cutter used to cut such a hole. A common use is to allow the head of a countersunk bolt, screw or rivet, when placed in the hole, to sit flush with or below the surface of the surrounding material. A countersink may also be used to remove the burr left from a drilling or tapping operation, thereby improving the finish of the product and removing any hazardous sharp edges.
A defect detector is a device used on railroads to detect axle and signal problems in passing trains. The detectors are normally integrated into the tracks and often include sensors to detect several different kinds of problems that could occur. Defect detectors were one of the inventions which enabled American railroads to eliminate the caboose at the rear of the train, as well as various station agents placed along active routes to detect unsafe conditions. The use of defect detectors has since spread overseas to other railroad systems.
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is similar to the rolling of dough. Rolling is classified according to the temperature of the metal rolled. If the temperature of the metal is above its recrystallization temperature, then the process is known as hot rolling. If the temperature of the metal is below its recrystallization temperature, the process is known as cold rolling. In terms of usage, hot rolling processes more tonnage than any other manufacturing process, and cold rolling processes the most tonnage out of all cold working processes. Roll stands holding pairs of rolls are grouped together into rolling mills that can quickly process metal, typically steel, into products such as structural steel, bar stock, and rails. Most steel mills have rolling mill divisions that convert the semi-finished casting products into finished products.
A can seamer is a machine used to seal the lid to the can body. The lid or "end" is usually tinplated steel (food) or aluminum (drinks) while the body can be of metal, paperboard or plastic.
A pleat is a type of fold formed by doubling fabric back upon itself and securing it in place. It is commonly used in clothing and upholstery to gather a wide piece of fabric to a narrower circumference.
A pond liner is an impermeable geomembrane used for retention of liquids, including the lining of reservoirs, retention basins, hazardous and nonhazardous surface impoundments, garden ponds and artificial streams in parks and gardens.
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A fitting or adapter is used in pipe systems to connect sections of pipe or tube, adapt to different sizes or shapes, and for other purposes such as regulating fluid flow. These fittings are used in plumbing to manipulate the conveyance of fluids such as water for potatory, irrigational, sanitary, and refrigerative purposes, gas, petroleum, liquid waste, or any other liquid or gaseous substances required in domestic or commercial environments, within a system of pipes or tubes, connected by various methods, as dictated by the material of which these are made, the material being conveyed, and the particular environmental context in which they will be used, such as soldering, mortaring, caulking, plastic welding, welding, friction fittings, threaded fittings, and compression fittings.
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In North America, a roll-off is usually an open-top dumpster characterized by a rectangular footprint, utilizing wheels to facilitate rolling the dumpster in place. The container is designed to be transported by special roll-off trucks. There are two types of delivery trucks for the bins based on bin size, and they are: Hook lift bins and Roll-off bins. Roll-offs are commonly used to contain loads of construction and demolition waste or other waste types. While most roll-off containers have a swinging door on the end for easier disposal of waste, some roll-off containers are not open-top and are used with commercial or industrial trash compactors.
Sewing is the craft of fastening or attaching objects using stitches made with needle and thread. Sewing is one of the oldest of the textile arts, arising in the Paleolithic Era. Although usually associated with clothing and household linens, sewing is used in a variety of crafts and industries, including shoemaking, upholstery, sailmaking, bookbinding and the manufacturing of some kinds of sporting goods. Sewing is the fundamental process underlying a variety of textile arts and crafts, including embroidery, tapestry, quilting, appliqué and patchwork.
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