HYDRAULIC CYLINDERS HYDRAULIC TERMS
COMMON HYDRAULIC TERMS A
Accumulator - A container which stores fluids under pressure as a source of hydraulic power. It may also be used as a shock absorber. Actuator - A device which converts hydraulic power into mechanical force and motion. (Examples: hydraulic cylinders and motors.) Aeration - The presence of dispersed air bubbles in the system’s hydraulic fluid. Aeration can result in severe erosion of pump components when the bubbles collapse as they suddenly encounter high pressure when entering the discharge area of the pump. ANSI - American National Standards Institute ASAE - American Society of Agricultural Engineers (sets standards for many hydraulic components for agricultural use) Back Pressure - The pressure encountered on the return side of a system. Ball Valves - These valves are manual shut-off valves. They differ from needle valves in that they cannot meter the flow of oil. These valves can be used to shut off the flow of oil while repairs are made to the system or for shutting off the flow in one particular line of a circuit, etc. Base plate - The end of the cylinder opposite the rod end. Some device, such as a cross tube or a clevis, is welded directly onto the base plate and used to secure the cylinder. Bleed - The process by which air is removed from a hydraulic system. Bore - The inside diameter of the cylinder tube. Breakout Pressure - The minimum pressure which starts moving an actuator. Breather Plug - A vent installed into a port on a hydraulic cylinder to allow a double-acting cylinder to be used in a single-acting application. Bypass - A secondary passage for fluid flow. B C Case drain - An external port used to drain off the small amount of oil that collects in the seal and bearing pockets of a hydraulic motor or pump. This oil has slipped through clearances between the gear sides and the housing. If the oil is not drained, the pressure inside the housing would blow out the shaft seal. This becomes a problem only when two or more hydraulic motors are connected in a series. Cast Iron Ring - This is a style of piston seal that is a non-positive seal. It is made from cast iron and is like the piston rings on and engine piston. Cavitation - A phenomenon which occurs when the pressure at a point in a hydraulic system is lowered below the vapor pressure of the oil in the system. This allows bubbles of oil vapor to form in the oil. If this occurs at the pump inlet, the quick pressure rise inside the pump forces these bubbles to collapse violently. This can cause erosion of metal parts, noise and vibration. Check Valve - These valves are most often a ball, or poppet, and spring design. Oil is allowed to flow unrestricted in one direction by pushing the poppet off its seat. Oil is blocked in the other direction by forcing the poppet onto its seat and closing off the flow path. Applications include load holding, directing flow into other accessory valves, and any other application where backflow is unwanted. Circuit - A series of component parts connected to each other by fluid lines or passages. Usually part of a “system”. Clevis - A “U” shaped bracket used for mounting a cylinder to an application. A clevis is either located at the rod end or on the end cap or both. The clevis is two narrow tangs that have a machined hole to receive a common pivot pin. Closed Center System - A hydraulic system in which the control valves are closed during neutral, stopping oil flow. Flow in this system is varied, but pressure remains constant. Closed Center Valve - A valve in which inlet and outlet ports are closed in the neutral position, stopping flow from pump. Closed loop circuit - Once the fluid has been circulated, much like an open loop system, the oil is recirculated at low pressure back to the pump inlet, rather than being returned to the reservoir. This type circuit is more adaptable to hydraulic motor applications.
180
Made with FlippingBook flipbook maker