R = pilot ratio Example: Pload max = 170 bar (pressure generated by the maximum load capacity) Pt = 325 bar ( > 1.3 x 170 bar) R = 8:1 (Pilot ratio) Brake release pressure: ≥ 17 bar (Ppil min) = 325 - 170 8 + 1 bar = 17.2 bar > 17 bar The selected counterbalance valve, with R = 8 : 1 and Pt = 325 bar, complies with the correct … The pilot … 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. After minor rearrangements, Equation 1 … This is likely to be about 30% of the load induced pressure but check the valve manufacturer recommendations. Deploying an overcenter valve with steeper relief pressure override characteristics, as found in direct-acting design models, provides a more stable overall system. 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. Other names for this valve include motion control valve and over center valve. Each series has multiple pilot ratio options, adjustment styles, and available pressure ranges. Therefore, the vast majority of counterbalance applications are satisfied with a 3:1 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. This is the principle Eaton uses to maintain stability with the overcenter valve while accommodating more efficient higher pilot ratios. pilot ratio. Turn adjustment clockwise to decrease setting and release load. Figure 2 shows the pressure drop curves of two valves with different pilot … Consider Sun load match and load adaptive load holding valves when you want to maximize energy savings. Despite its importance, there is a lot of mystery in the nuances surrounding the pilot ratio. They come in many capacities, pressure ranges and cavities. to Max. Select your pilot ratio. Another attempt to stabilize this situation is to have a short- or adjustable-stroke valve to restrict the flow until it becomes stable. But, sometimes, on motors high pilot ratios will provide adequate dynamic control. Many people tend to complicate the task of selecting a counterbalance valve and as such avoid opportunities. Most counterbalance valves come with a pilot ratio anywhere from 1.75:1 to 12.0:1. Omit Nitrile / (SK10-3N) V Fluorocarbon / (SK10-3V) Code Pressure Range 10 20.7 - 90 Bar (300 - … 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. More recent counterbalance valves, such as those reported in US Patent Application Publication No. The line connected between the valve and cylinder’s rod side acts on a small piston area (1 square inch) inside the valve. Blogs Circuits with counterbalance valves can be unstable. The pilot ratio refers to the ratio, or difference, between the pilot pressure area and the relief area as shown in Figure 1. It is recommended for applicaitons where the load indiced pressure varies during the motion with resulting instability of the machine. An overcenter, or counterbalance, valve is a pilot assisted-relief valve with a free flow check. Learn how your comment data is processed. CONFIGURATION Counterbalance valves with pilot assist are meant to control an overrunning load. Counterbalance valves are one of the most misunderstood products in the hydraulic industry. We’ll assume the 3:1 ratio. 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. Brand New. SUN HYDRAULICS CBBALHN 3:1 pilot ratio, restrictive counterbalance valve Adjustment - No. C $150.49. 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. It is also subject to variations in pilot pressure as the load changes due to mechanical advantage, machine unsteadiness or general unstable conditions. Two areas work to open a counterbalance valve, the relief area (port 3) and the pilot area (port 1); the pilot area divided by the relief area equals the pilot ratio: The pilot pressure at port 3 is inversely proportional to the load pressure at port 1 and effectively reduces the relief valve setting. C $596.91. Figure 2 shows the pressure drop curves of two valves with different pilot … Part Number: Port size: Max Pressure: Pressure range: Std Setting (Bar) increase per turn (Bar) Pilot Ratio: Weight kg: Brand: 05.41.62.03.03.35: G1/2: 350: 100-350 tend. Two areas work to open a counterbalance valve, the relief area (port 3) and the pilot area (port 1); the pilot area divided by the relief area equals the pilot ratio: SUN HYDRAULICS CBBALHN 3:1 pilot ratio, restrictive counterbalance valve Counterbalance valves should be set at 1.3 times the load induced pressure. The two pilot lines shown act on different surface areas inside the 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. In effect, backpressure drives the counterbalance valve closed. Download 3:1 pilot ratio, standard capacity counterbalance valve. For reference the most popular ratio is 6:1. In fact, many in the industry would say it���s the ���be-all and end-all��� factor when it comes to machine stability. Save my name, email, and website in this browser for the next time I comment. Higher ratios will be more efficient (reduce heat generation) but at the cost of stability and smooth motion control. Atmospherically vented counterbalance valves with pilot assist are meant to control an overrunning load. 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 … R = pilot ratio Example: Pload max = 170 bar (pressure generated by the maximum load capacity) Pt = 325 bar ( > 1.3 x 170 bar) R = 8:1 (Pilot ratio) Brake release pressure: ≥ 17 bar (Ppil min) = 325 - 170 8 + 1 bar = 17.2 bar > 17 bar The selected counterbalance valve, with R = 8 : 1 and Pt = 325 bar, complies with the correct lowering sequence The pilot ratio decision is one of Horsepower versus Control. Turn adjustment clockwise to decrease … High valve flow resistance and lower pilot ratio should provide more stability in most cases. Part Number: Port size: Max Pressure: Pressure range: Std Setting (Bar) increase per turn (Bar) Pilot Ratio: Weight kg: Brand: 05.41.62.03.03.35: G1/2: 350: 100-350 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 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. As the load pressure increases, changes in pilot ratio have very little effect on stability or performance.��. 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. 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. CBBCLIN 3:1 pilot ratio, semi-restrictive counterbalance valve series 1, capacity 40 L/min, cavity T-11A Top Rated Seller Top Rated Seller. Pilot ratio is an inherent characteristic of pilot-operated check valves, over center counterbalance valves (externally piloted) and brake valves (internally and externally piloted). pilot ratio. 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. Description: Counterbalance Valve 3:1 Pilot Ratio 30GPM, T-2A Series 2 Packaging Condition Details: Open Manufacturer's Packaging, box shows signs of wear. Pilot ratio — Ratio of pilot to load chamber area3 (default) | positive scalar. Matching this selective pilot ratio to particular equipment sometimes corrects the problem. 2. Using this approach, as opposed to a differential-area design, the main spring has a higher rate. Technical Features Counterbalance valves should be set at least 1.3 times the maximum load induced pressure. Backpressure at port 2 does not affect the valve setting because the spring chamber references the vent (port 4). The stiffness of the spring increases the pressure override when used as a relief valve. The ratio between the effective areas of the control member face in the pilot chamber and in the load chamber. Pilot Operated check valves, or pilot-to-open check valves, are non-modulating valves and in operation they work as ON/OFF devices (fully open or fully closed). The check valve allows free flow from the directional valve (port 2) to the load (port 1) while a direct-acting, pilot-assisted relief valve controls flow from port 1 to port 2. For any change in load pressure, the valve will be less sensitive and not open as rapidly, reducing the rate of increase in the opening orifice and therefore the change in flow. Pre-Owned. When backpressure exceeds pilot pressure, it adds to the setting of the valve at a rate of 1 plus the pilot ratio times the backpressure, i.e. For 1:4 and zero differential pilot ratio 3 3ML1133201 For range 5-210 bar (72.5-3050 psi) 5 3ML1133200 For range 50-350 bar (725-5075 psi) For 1:8 pilot ratio 5 3ML1133201 For range 5-350 bar (72.5-5075 psi) 2 Setting type TYPE CODE DESCRIPTION G - Screw setting Z 4COP120420 Antitampering cap Counterbalance valves That���s why many users demand for their replacement valve to have the same pilot ratio as its predecessor to avoid any surprises. A lower pilot ratio requires a greater pilot pressure difference to fully open the valve, and any given load pressure change does not affect the valve as much as it does for a high pilot ratio (See Figure 2). 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. So, if for example cylinder’a Area ratio CR = 1.64, min pilot pressure to open counterbalance valve is: Let discovery the system where the counterbalance valve on the rod end of the cylinder with a load retracting the cylinder cap: And the latest example is the system where counterbalance valve on a motor or an equal area actuatorwith an overrunning load: Your email address will not be published. 5:1 pilot ratio, vented counterbalance valve Capacity: 60 gpm (240 L/min.) Your email address will not be published. An overcenter, or counterbalance, valve is a pilot assisted-relief valve with a free flow check. Areas is usually 3:1 or 4:1 gain stability differential area design where changes! 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