Pressure Relief Valve - These are “safety valves”. They serve to set a limit to the rise in pressure in a line or circuit. There are two categories; direct-acting and pilot-operated relief valves. The direct-acting is one in which the poppet is half closed by direct force of a mechanical spring. Any increase in pressure past the “cracking pressure” will cause the poppet to be unseated and allow a small part of the oil to escape. Advantages of the direct-acting relief valve are that they are less expensive than the pilot-operated type and they have a faster response time. Pilot-operated reliefs hold the poppet on its seat by adjustable pilot pressure. The pilot pressure can be supplied internally or externally and is most often from the pump line. When the pump line pressure rises higher than the adjustment set on the relief, the poppet becomes unseated and oil is directed back to tank. When pump line pressure drops below the control setting, the poppet can re-seat and close the valve. The pilot-operated reliefs can be more accurately adjusted and are used more often as the main relief in hydraulic systems. PSI - Pounds per square inch (of pressure) PTO Pump - This pump is operated by the power take-off shaft of a tractor or other piece of equipment. As opposed to the standard gear pump, which has a shaft of its own that couples to drive a motor or engine. Pump - A device which converts mechanical force into hydraulic fluid power. Basic design types are gear, vane, and piston units. P R Rated Pressure - The operating pressure which is recommended for a component or a system by the manufacturer. Regenerative Circuit - A circuit in which pressure fluid discharged from a component is returned to the system to reduce flow input requirements. Often used to speed up the action of a cylinder by directing discharged oil from the rod end to the piston end. Regulator - Hydraulic regulators maintain the output pressure of a hydraulic system at a set value, minimizing fluctuations in a pressurized line. A hydraulic regulator is typically made of steel, coated steel, or stainless steel and comes with a variety of connections. Hydraulic regulators are designed to hold a tight seal even as the pressure in the line rises. Hydraulic regulators may be used in land-based applications or may be specially designed to work underwater. Relief Valve - A valve which limits the pressure in a system, usually by releasing excess oil. Remote - A hydraulic function such as a cylinder which is separate from its supply source. Usually connected to the source by flexible hoses. Rephasing Cylinder - Rephasing cylinders are two or more cylinders plumbed in series or parallel, with the bores and rods sized such that all rods extend and/or retract equally when flow is directed to the first, or last, cylinder within the system. Reservoir - A container for keeping a supply of working fluid in a hydraulic system. Restriction - A reduced cross-sectional area in a line or passage which normally causes a pressure drop. (Examples: pinched lines or clogged passages, or an orifice designed into a system.) Retainer ring - A ring that screws down over the outside diameter of a cylinder tube and holds the gland in place on a welded cylinder. Retracted length - The length of a cylinder measured from the center of the mounting hole on the rod end to the center of the mounting hole on the base end when the piston and rod are in the “in” position. The shortest overall length of a cylinder. Rod - The chromed shaft, attached to the piston inside the cylinder tube, the end of which extends out of the gland of the cylinder and is attached to an application by a clevis, cross tube, or a hole bored directly through the rod. The rod also serves and dynamic sealing surface for the rod seal. RPM - Revolutions per minute Rubber shields - A bearing number is followed by the suffix 2RS indicates that the bearing is sealed on both sides with two rubber shields.
Prices subject to change. For the most accurate pricing, please refer to our website at Baileyhydraulics.com or call one of our Customer Experience Representatives at 1-800-800-1810. 195
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