Atmospherically vented counterbalance valves with pilot assist are meant to control an overrunning load. Low pilot Ratio requires a high pilot ratio pressure in order to lower the load, but it permits a more precise and smooth control of the motion. Most counterbalance valves are available with a variety of pilot ratios and are interchangeable, making it easy to find the correct ratio for the system. Thus, the selection of counterbalance valves represents a compromise between stability (low pilot ratio) and efficiency (lower required pilot pressure, high pilot ratio). Please call us to inquire with questions on special applications. The black line and the red line are direct acting designs where it takes a greater pressure difference to increase the flow, making them less likely to react to transient pressure changes. Required fields are marked *. by the pilot ratio. The line connected between the valve and cylinder’s rod side acts on a small piston area (1 square inch) inside the valve. The pilot ratio refers to the ratio, or difference, between the pilot pressure area and the relief area as shown in Figure 1. For example: with a relief setting of 4,000psi and a load pressure of 2500psi for a 4:1 vs a 6:1 pilot ratio, the pilot pressure required to open the valve varies by only 125psi which is only 5 percent of the load pressure and 3 percent of the set pressure. 5:1 pilot ratio, vented counterbalance valve Capacity: 60 gpm (240 L/min.) The stiffness of the spring relates directly to the responsiveness of the valve to pressure fluctuations. Description: Counterbalance Valve 3:1 Pilot Ratio 30GPM, T-2A Series 2 Packaging Condition Details: Open Manufacturer's Packaging, box shows signs of wear. The ratio of these areas is usually 3:1 or 4:1. Matching this selective pilot ratio to particular equipment sometimes corrects the problem. A��common challenge in the design of hydraulically operated machines is selecting the right pilot ratio to use within the overcenter valve. A counterbalance valve, comprising: a valve body having a longitudinal chamber; and a load port, a valve port, and a pilot port all of which are configured to communicate with the longitudinal chamber; a piston positioned within the longitudinal chamber, the valve having an adjusting means that increases pilot ratio when pilot pressure exceeds an outer spring's biasing force. The line connected between the counterbalance valve and cylinder’s rod-end port acts on a small piston area (1 in. Most counterbalance valves come with a pilot ratio anywhere from 1.75:1 to 12.0:1. A counterbalance valve, comprising: a valve body having a longitudinal chamber; and a load port, a valve port, and a pilot port all of which are configured to communicate with the longitudinal chamber; a piston positioned within the longitudinal chamber, the valve having an adjusting means that increases pilot ratio when pilot … In this article, we���ll try to clear up some of these details and provide some considerations for choosing an efficient solution in the overcenter value. May have holes, tears, tape, and/or label removal damage. 2013/0233409, are provided with load-sensing, hydromechanically setting features. With this counterbalance valve design, the back-pressure Pv at port V2 is additive with the ratio 1 : 1 to the relief setting Pt and with the ratio (R + 1) / R to the theoretical pilot pressure Ppil for piloted opening. Learn how your comment data is processed. As the load pressure increases, changes in pilot ratio have very little effect on stability or performance.��. counterbalance valve. Circuits with counterbalance valves can be unstable. Adjustment - No. ADJUSTMENT TYPE Parker offers counterbalance valves with adjustable and non-adjustable pressure settings. Let discovery the system where counterbalance valve with a 3:1 pilot ratio adjusted for pressure setting 3000 psi and with a load pressure 2000 psi at port 1. But, sometimes, on motors high pilot ratios will provide adequate dynamic control. Pilot assist at port 3 lowers the effective setting of the relief valve at a rate determined by the pilot ratio. We’ll assume the 3:1 ratio. Functional Group: Products : Cartridges : Counterbalance : 3-Port Non-vented : Standard, 3:1 Pilot Ratio Model: CBCA-LHN Product Description Counterbalance valves with pilot assist are meant to control an overrunning load. Pilot Ratio Seals Optional Pressure Setting Pressure Range Code Pilot Ratio A 3:1 B 4.5:1 C 7:1 CB101 Counterbalance Cartridge Valve Body Material Port Size THIRD-ANGLE PROJECTION Technical Information Code Seals / Kit No. Pilot assist at port 3 lowers the effective setting of the relief In the real systems with hydraulic actuators like cylinder or motor it is necessary to consider the actuator’s area ratio because the pressure what applied to pilot port 3 also applied to input of actuator and through actuator’s area difference – to port 1. To overcome a spring force of 1,800 … But, sometimes, on motors high pilot ratios will provide adequate dynamic control. Required fields are marked *. to Max. This paper investigates the dynamic behavior of a pilot . September 9, 2014 This action causes the valve to open at a lower pressure. SUN HYDRAULICS CBBALHN 3:1 pilot ratio, restrictive counterbalance valve Without significant hysteresis, this valve would always be unstable. Your email address will not be published. Technical Features Counterbalance valves should be set at least 1.3 times the maximum load induced pressure. Counterbalance valves should be set at 1.3 times the load induced pressure. The pilot area divided by the relief area equals the pilot ratio. The pilot pressure required to open the valve will depend on the pilot ratio that is the ratio between the relief area and the pilot area. 3:1 pilot ratio, standard capacity counterbalance valve L C ap city: 15 gpm (60 /min.) Pilot Ratio (pr) is defined as the geometrical ratio between the area on which the load acts (port 1) and the pilot area (port 3). 3. Pilot ratio — Pilot area ratio 3 (default) | positive scalar. Enter the load mass and actuator dimensions in the text boxes, or use the slide bar. A 10:1 pilot ratio means that the force on the spool, generated by the pilot pressure is 10 times higher than the force generated by the same pressure from the system. Sun counterbalance cartridges can be installed directly into a cavity machined in an actuator housing for added protection and improved By Maurice A. J. Ashmore,��Global Chief Engineer SICV & HIC,��Eaton���s Hydraulics Business,��Warwick UK. The result is that with a 10:1 pilot ratio the load starts to move at a lower supply pressure and with a lower pressure drop across the valve. If a counterbalance valve is used to support a cylinder, the total pressure at the cylinder side of the valve is a sumation pressure required to overcome the spring force plus any pressure drop caused by the flow of oil through the valve. Backpressure at port 2 does not affect the valve setting because the spring chamber references the vent (port 4). Selecting a pilot ratio In general, higher pilot ratios work well for consistent, stable loads, and lower pilot ratios for unstable or variable loads. The pilot … Your email address will not be published. Bringing a higher rate of spring and more rigidity to the system, the platform can help users avoid the loss of machine control and ensure safety for personnel and property. So selecting a counterbalance valve is a balancing act (pardon the pun) between valve efficiency and load control, with the valve flow resistance and pilot ratio being the two main factors to be considered. On our e-commerce ready for delivery thermal relief ��� not so much as a full relief... A 3:1 pilot ratio 3:1 is very common and works in most cases to variations pilot., sometimes, on motors high pilot ratios will provide adequate dynamic control and troubleshooting of the to! ( default ) | positive scalar many capacities, pressure must be with... Your email address will not be published as follows: pilot pressure changes resistance and lower ratios... In context, imagine driving in your car with the overcenter valve with a free flow.. 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