Glossary

Inertance, Hydraulic - A quantity related to the inertial forces required to accelerate or deceleration a fluid in a conduit or a passage. It is analogous to electrical inductance.

Inertial Load - The reaction force resulting from the acceleration of a mass and is equal to the product of the mass and the acceleration, and always acts in a direction opposite to that of the actuator motion.

Inertial Load - The reaction force resulting from the acceleration of a mass and is equal to the product of the mass and the acceleration, and always acts in a direction opposite to that of the actuator motion.

Jack - A single-acting cylinder that can be pressure actuated in only one direction.

Kinetic Energy - The energy that a substance or body possesses by virtue of its mass (weight) and velocity.

Knockout - A device to strip the part from the punch or die.

Lapping-in - Polishing a surface such as a valve seat to obtain a smooth mating surface.

Lap - The relative axial position relationship between the fixed and movable flow metering edges with the spool at null. Lap is measured as the total separation at zero flow of straight line extensions of the nearly straight portions of the normal flow curve, drawn separately for each polarity, expressed as per cent of rated input parameter.

Leakage, Center Position - This refers to the amount of leakage associated with spool lap conditions for a given clearance.

Learning Control System - A system designed to recognize familiar features and patterns of a situation and then, based on its past experience or learned behavior, react in an optimum manner.

Linear Actuator - A device which converts pressure energy into linear motion with a limited stroke; i.e., a hydraulic cylinder or ram.

Linear Equation (Function) - An equation of the first degree (which always maps as a straight line).

Linearity - A measure of deviation from proportional relationship in the ratio of valve output to input. The degree to which the normal flow curve conforms to the normal flow gain line with other operational variables held constant. When output varies in direct proportion to the input, the valve is considered linear.

Load Sensing System - A closed-circuit system with load/pressure feedback. It combines the advantages of an open-center system and constant pressure closed-center systems while avoiding their major disadvantages.

Lumped Parameter Model - A mathematical model which treats all variables of a system element (lumped) as if they acted at only one point in the element. The converse is a distributed system.