JACKING OIL PUMP - provides oil supply when the turbine is placed on barring (slow rotation to stop the turbine from sagging or hogging)

JET COMPRESSOR - A device employing a venture tube so that a high pressure stream flowing through the nozzle creates a lower pressure or a vacuum into which the gas to be compressed flows. The gas is discharged from the nozzle with the expanded high-pressure medium.

JOULE - English Scientist James Prescott Joule (1818 - 1889)

JOULE - The unit used to measure heat, work, and energy in the metric system. Its symbol is J. It is the amount of energy required to move an object of 1 kg mass to a height of 1 m. Also called a newton-metre.

JOULE-THOMSON EFFECT - The change in gas temperature which occurs when the gas is expanded adiabatically from a higher pressure to a lower pressure. The effect for most gases, except hydrogen and helium, is a cooling of the gas.

JOURNAL - That part of a shaft or axle that rotates relative to a radial bearing.