Cannibalization of machine parts
Cannibalization of machine parts, in maintenance of mechanical or electronic systems with interchangeable parts
Interchangeable parts
Interchangeable parts are parts that are, for practical purposes, identical. They are made to specifications that ensure that they are so nearly identical that they will fit into any device of the same type. One such part can freely replace another, without any custom fitting...

, refers to the practice of removing parts or subsystems necessary for repair from another similar device, rather than from inventory
Inventory means a list compiled for some formal purpose, such as the details of an estate going to probate, or the contents of a house let furnished. This remains the prime meaning in British English...

, usually when resources become limited. The source system is usually crippled as a result, if only temporarily, in order to allow the recipient device to function properly again.

Cannibalization is usually due to unavailability of spare part
Spare part
Spare Parts may also refer to:* Spare Parts , by Status Quo* Spare Parts is a Doctor Who audio drama.* Spare Parts , by Servotron* "Spare Parts" , by Bruce Springsteen* "Spare Parts"...

s, due to an emergency situation, long resupply times, physical distance, or insufficient planning or budget. Cannibalization can also be due to surplus inventory. At the end of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 a large quantity of high quality, but unusable war surplus equipment
Military surplus
Military surplus are goods, usually matériel, that are sold or otherwise disposed of when no longer needed by the military. Entrepreneurs often buy these goods and resell them at surplus stores. Military surplus rarely includes weapons or munitions, though they are occasionally found in such stores...

 such as radar devices made a ready source of parts to build radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...


Diminishing manufacturing sources

Sometimes, removing parts from old equipment is the only way to obtain spare parts, either because they are no longer made, are obsolete, or can only be manufactured in large quantities. In logistics, this is known as Diminishing Manufacturing Sources (DMS).

This is often the case in the military, and ships
A warship is a ship that is built and primarily intended for combat. Warships are usually built in a completely different way from merchant ships. As well as being armed, warships are designed to withstand damage and are usually faster and more maneuvrable than merchant ships...

 and aircraft
Military aircraft
A military aircraft is any fixed-wing or rotary-wing aircraft that is operated by a legal or insurrectionary armed service of any type. Military aircraft can be either combat or non-combat:...

, as well as other expensive equipment that is produced in limited quantities. Such was the case with the aircraft carrier USS Kitty Hawk
USS Kitty Hawk (CV-63)
The supercarrier USS Kitty Hawk , formerly CVA-63, was the second naval ship named after Kitty Hawk, North Carolina, the site of the Wright brothers' first powered airplane flight...

, the sole survivor of a class of three ships built during the early-1960s. The ship herself is over forty years old, and having manufacturers build individual custom replacement parts would be highly impractical, and thus decommissioned ships, such as the USS Independence
USS Independence (CV-62)
The fifth USS Independence is a of the United States Navy. It was the fourth and final member of the Forrestal-class conventional-powered Supercarrier...

, have been utilized for the necessary parts to keep the Kitty Hawk in operation.

Another example is the Union Pacific's 4-8-4
Under the Whyte notation classification of steam locomotives, 4-8-4 represents the wheel arrangement of four leading wheels on two axles , eight powered and coupled driving wheels on four axles, and four trailing wheels on two axles .Other equivalent classifications are:UIC classification: 2D2...

 locomotive 838 is used as a spare parts source for 844
Union Pacific 844
Union Pacific 844 is a 4-8-4 steam locomotive owned by Union Pacific Railroad. It was the last steam locomotive delivered to Union Pacific and is unique in that it is the only steam locomotive never retired by a North American Class I railroad....

 since the type has been out of production for decades and the builder itself is no longer in existence.

One strategy used to combat DMS is to buy additional inventory during the production run of a system or part, in quantities sufficient to cover the expected number of failures. This strategy is known as a "lifetime buy". An example of this is the many 30- and 40-year-old railway locomotives being run by small operators in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

. These operators will often buy more locomotives than they actually require, and keep a number of them stored as a source of spare parts.
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