In either case, a brake valve eliminates damage from stopping the actuator abruptly. The acquisition brings complementary technology to Danfoss’s current product range, with inverter and motor drives rated to 6 MW for application in marine, off- and on-highway, and oil and gas industries. Counterbalance valves play an integral role in the important task of safely controlling an actuator which may be holding a load or a person in the air. Setting the counterbalance pressure approximately 25% higher than static pressure (1.25 × 566 = 707 psi) means that when pressure at the cylinder cap end rises to approximately 75 psi, the cylinder starts to stroke. The brake valve is an internally/externally piloted valve with different pilot areas. The resultant downward force of 115,540 lb is an increase of 16% over the circuit with an internally piloted counterbalance valve. Understand the different types of valve that are available, their function and where they are used. This valve can also be used with hydraulic motors and is then commonly called a brake valve. Learn how hydraulic counterbalance valves work. The return flow from the actuator is piloted and controlled by the inlet flow to the actuator, ensuring a cavitation-free lowering of the load. Cylinders with large platens and tooling or hydraulic motors on winch drives are two examples of such actuators. Parker counterbalance valves series ZNS in sandwich design control the actuator movement at overrunning loads via a leak-free poppet valve. This 900-psi backpressure decelerates the actuator smoothly and rapidly. When the cylinder meets resistance, the external pilot takes over, Figure 5-12, and opens the counterbalance fully at approximately 250 psi. This valve’s pilot supply is from a source other than the controlled load. UQM will become part of the Danfoss’s Power Solutions group. To stop the motor quickly in the opposite direction of rotation, install another brake valve in the opposite motor line. A vacuum void forms in the inlet side of the actuator that must be filled before applying force. After work contact, as system pressure builds, the external pilot fully opens the counterbalance to relieve all backpressure in the cylinder. Unless pump flow never changes, setting flow precisely on this type control is critical. The Ross counterbalance valve contains a complete pneumatic circuit for controlling counterbalance pressures either manually or automatically. 90° Fitting: connection point for the hydraulic hose. A counterbalance keeps an actuator from running away even with variable flow rates. Fig. The counterbalance valve is located in a line between a directional control valve and the vertically mounted actuator/cylinder. Please enable JavaScript on your browser and try again. The externally piloted system saves energy by eliminating all backpressure when performing work. Schrader Valve: allows you to add or remove pressure. Externally piloting the counterbalance valve, Figure 5-14, requires about twice as much pressure to extend the cylinder. Thereby they enable a reliable operation and a linear lowering speed of the cylinder. In addition, internally/externally piloted counterbalance valves don’t hunt. With this acquisition, our third within electrification, we have added a well-established North American presence within electrification, which nicely complements our global footprint.”, Sign up for Hydraulics & Pneumatics eNewsletters. Use an external braking system to hold any overrunning load driven by a hydraulic motor. These circuits show each type of counterbalance piloting system in the working condition — with pressures, forces, and effective force listed. However, an externally piloted counterbalance valve does waste a little more energy when moving the load to the work. Then continue turning the adjusting control in the same direction another to turn. © 2021 Endeavor Business Media, LLC. www.hydraulicspneumatics.com is using a security service for protection against online attacks. ...which family of counterbalance valves is best for your system? That is why it is always good practice to use an external safety device to protect the operator and machine. In addition, the pressure-actuated switch (9) will open the main motor run circuit should the pressure fall below a minimum value specified by the press manufacturer. For example, counterbalance valves are used in some hydraulically operated forklifts. A working counterbalance will hold the load suspended and gauge PG3 will show the load-induced pressure. This type of counterbalance valve retards flow continuously, so it resists flow even after work contact stops the actuator. Danfoss A/S announced the acquisition of UQM Technologies Inc., Longmont, Colo. Danfoss A/S announced the acquisition of UQM Technologies Inc., Longmont, Colo., a developer and manufacturer of power-dense, high-efficiency electric motors, generators, power electronic controllers and fuel cell compressors for the commercial truck, bus, automotive, marine, and industrial markets. Pneumatic counterbalance units, prior to this invention, have been pressurized subsequent to assembly, past the shaft seal, or through a fill valve or a fill port which is sealed after pressurization. Oil at high velocity leaves one end while the opposite side starves for fluid. When the directional valve shifts to extend the cylinder in Figure 5-5, oil from the pump flows into the cap end of the cylinder and pressure starts to build. There is low oil level in the counterbalance system. Incorporating a pressure control valve called a counterbalance is a better way to control running-away loads. Sun Hydraulics continues its pursuit of the perfect counterbalance valve, introducing our next-generation cartridge family that offers an average energy savings of 30% over standard counterbalance valves and offers stability across many applications. Advantages: Holding position, prevent runaway loads, pneumatic resistor. It also helps to support the fork in the UP position. 6). They help manage pressure created by impacts and loads to help stabilize loads, avoid equipment damage, and cope with hose failure and more. The 716 psi acting against the 26.51-in.2 rod end area produces an upward acting force of 18,981 lb. 5-13: Internally piloted counterbalance valve with cylinder pressingFigure 5-13 shows the maximum force from different types of counterbalance circuits while acting on a part with the cylinder stalled. A counterbalance keeps an actuator from running away even with variable flow rates. The pressure setting is slightly higher than that required to keep the load from free-falling. 6. After setting the counterbalance this way, power the cylinder down and notice the pressure reading on gauge PG3. They are designed to create backpressure at the return line of the actuator to prevent losing control over the load. The net effective downward acting force is 96,559 lb. (716 psi × 26.51 in.2 = 18,981 lb.) With the hydraulic motor moving, Figure 5-17, external pilot supply opens the brake valve at low pressure. The difference is that there is no upward force in Figure 5-14. Pneumatic counterbalance units, prior to this invention, have been pressurized subsequent to assembly, past the shaft seal, or through a fill valve or a fill port which is sealed after pressurization. An internally piloted counterbalance valve controls cylinder extension smoothly, but reduces thrust during the working portion of the cycle. Energizing the directional valve to extend the cylinder in Figure 5-8 sends pilot pressure to the counterbalance valve from the cap end cylinder line. The higher the load-induced pressure, the greater the hunting problem. The best practice is to mount the counterbalance valve directly on or very close to the cylinder port. As the load extends, internal pilot supply gives smooth control with little energy loss. Once pressure in the cap end cylinder line reaches 150 psi, the counterbalance opens and the cylinder extends. Incorporating a pressure control valve called a counterbalance is a better way to control running-away loads. If the load changes, the counterbalance setting does not change. Fig. Pursuing the perfect counterbalance valve New LoadAdaptive™ valves: The stability you need, the efficiency you want . 1/4 and 3/8 NPTF Pneumatic Counterbalance Valves MODELS: 1/4 NPTF 3/8 NPTF No Manual Release B41C00 B61C00 Manual Release B41C0M B61C0M Flush Release B41CFM B61CFM Basic Operation: The counterbalance valve will hold a load in position until pressure or an external force is applied to move the load. The pressure relief valve is bypassed by a non-return valve from T to P. The cylinder would only extend when the counterbalance valve’s external pilot port sensed 1 psi at the cylinder cap end. A brake valve appears virtually nonexistent as the motor runs under load. As the brake valve starts closing, internal pilot pressure builds to 900 psi, forcing fluid through the brake valve at a 900-psi pressure drop. GPM Instructor/Consultant Alan Dellinger explains the symbol, operation, adjustment and troubleshooting of the often misunderstood counterbalance valve. Some actuators with running-away (or overrunning) loads will let the load free fall when the directional valve that controls the actuator shifts to lower the load. Figures 5-16, 5-17, and 5-18 illustrate a hydraulic motor circuit that uses a brake valve. On most externally piloted counterbalance valves, the minimum pressure setting is 100 to 200 psi. Please enable cookies on your browser and try again. The counter balance valve will hold a load in position until pressure or an external force is applied to move the load. Counterbalance valves are used in hydraulic systems working with an overriding (run-away) or suspended load. This circuit demonstrates the operation of an internally piloted counterbalance valve. A brake valve counterbalances when necessary and allows almost free flow under load. 5-17: Internally/externally piloted brake valve with hydraulic motor runningNOTICE: Using a counterbalance or brake valve in a hydraulic motor circuit will not keep the motor from creeping when stopped. If pump flow changes, cylinder speed changes also. The designer should apply a braking method to hold a hydraulic motor at rest.). If at all possible, a counterbalance valve should be externally piloted. The process repeats and continues to the end of stroke. To prevent this, a counterbalance valve, sometimes called an over-center valve, typically is installed downstream of the actuator. The service requires full cookie support in order to view this website. May 29, 2018. Basic Operation: The counterbalance valve will hold a load in position until pressure or an external force is applied to move the load. Parker valves can be manual, motor actuated or solenoid air operated and electrically actuated, while mounting configurations can be sub-based, in-line or manifold. The cylinder holds in any position if the counterbalance valve is set correctly and does not leak. Fig. This means, for example, that setting the internal pilot at 900 psi requires only 113 psi at the external pilot to open the valve. 5-10: Internally/externally piloted counterbalance valve at rest with pump runningWhen the directional valve shifts, Figure 5-11, the cylinder begins to extend. Figure 5-10 shows a schematic drawing with an internally/externally piloted counterbalance valve. (On some systems it is possible to add an orifice in the pilot line to slow the pilot supply response and reduce hunting. Pressure should be approximately 700 to 750 psi. To see how cylinder thrust changes with different counterbalance valve pilot options, look at Figures 5-13, 5-14, and 5-15. www.hydraulicspneumatics.com is using a security service for protection against online attacks. The end result is the same as the externally piloted valve of Figure 5-14. After starting the pump, energize the directional valve and carefully raise the load a short distance. (This is the same cylinder arrangement shown previously.) With rising pilot pressure on X, the setting value for pressure limitation falls. With the counterbalance valve open to tank, backpressure against the cylinder rod end drops, allowing full thrust. Thereby they enable a reliable operation and a linear lowering speed of the cylinder. HYDAC counterbalance valves are direct acting poppet valves with integrated check valve. If flow to the cylinder cap end changes or even stops, cylinder speed responds accordingly. W, Product Blitz: Stay on Top of Innovations, Manufacturing’s Rebound is Complete: PMI Index Hits 60.7%, Advancing Fluid Dynamics Systems with AM featuring CERN, Pneumatic Valves Control Cataract Surgical Tool, Fig. When the directional valve shifts back to its center position, Figure 5-18, external pilot pressure drops and the brake valve begins to close. A lower pilot pressure setting makes the stopping time longer but smoother. Furthermore, it leads to: Avoidance of a hurrying ahead of the pulling consumer Optional Manual Release. These are basically relief valves but used in a particular application to set up a back-pressure in a circuit. The counterbalance valve offsets the potential energy of the weight on the rod end of a cylinder. Notice the counterbalance setting of 150 psi with this circuit. This chatter usually applies to circuits with high load-induced pressure or when the counterbalance valve is mounted at a distance from the cylinder port. When a cylinder is supporting a vertically mounted load, and its directional valve shifts to lower the load, the load may fall uncontrollably as its weight pushes fluid out of the cylinder. The internal pilot has static pressure from the load-induced pressure on the rod end area. A counterbalance valve’s function is to maintain a set pressure against the load to keep it … Setting the flow control for maximum pump flow lets the cylinder run ahead when pump flow is low. If the upward acting force could be reduced or eliminated, the cylinder could do more useful work. (See Figures 5-13 through 5-15 for energy loss and heat generation for different types of counterbalance circuits.). In any case, stopping action is smoother and quicker than it would be without the brake valve. Counterbalance valves are used with cylinders to safely hold suspended loads and deal with over-running loads. Parker counterbalance valves series ZNS in sandwich design control the actuator movement at overrunning loads via a leak-free poppet valve. With the load suspended, deenergize the directional valve. At this point the cylinder starts to extend and continues to move as long as the pump supplies oil at 75 psi or higher to the cylinder cap end. The cylinder in Figure 5-4 has a static pressure of 566 psi in the rod end due to the 15,000-lb load on the 26.51- in.2 area. Because this is an externally piloted counterbalance, it operates at a much lower setting. Normal procedure for setting a counterbalance valve is to turn the adjusting screw to its highest pressure before raising the cylinder. Turning the adjusting screw clockwise will increase the load carrying capacity of the valve. Fig. System pressure of 2000 psi acting on the cylinder cap end produces 100,540 lb of thrust. The valve offers a resistance to the flow from the actuating cylinder when the fork is lowered. When the directional valve shifts, an overrunning load forces the actuator to move faster than pump flow can fill it. Figure 5-7 shows an externally piloted counterbalance valve circuit. This keeps the counterbalance valve from hunting. 687PDC Turning the adjusting An open-center directional valve unloads the pump and keeps backpressure off the counterbalance valve outlet and pilot port. Setting the flow control for maximum pump flow lets the cylinder run ahead when pump flow is low. All rights reserved. Load-induced pressure does not affect set pressure. For a fast, non-shock stop, use a special counterbalance valve, called a brake valve. Check for an oil leak on the cylinder. As long as pressure required to move the motor is greater than the external pilot pressure needed, there is little or no energy loss. 5-2: Externally piloted counterbalance valveFigure 5-1 shows the symbol for an internally piloted counterbalance valve. The valve element is a balanced spool (4). (This is because it builds an extra 140 psi in the rod end, adding to the load’s 566 psi.) After the cylinder stops, pilot pressure builds again. The following circuits show these characteristics and how to design around them. This orifice fix is difficult to get right and may cause other circuit problems.). If the hydraulic motor tries to run away, say on a loaded winch, a brake valve holds against the load until the motors down port sees at least 113 psi. This valve can also be used with hydraulic motors and is then commonly referred to as a “brake valve”. (15,000 / 26.51 = 566 psi). Note that if a conductor between the cylinder port and valve breaks, the cylinder will free fall. Indeed, they enable a jerk-free movement on the part of consumers in the presence of over-centre loads. 5-3: Internally/externally piloted counterbalance valveFigure 5-2 shows the symbol for an externally piloted counterbalance valve. The counterbalance valve more than cancels the weight of platen and tooling that gives an energy loss of approximately 16%. Check for leaks on top of the counterbalance cylinder. Fig. Any time the cylinder loading changes, repeat the above process. Approximately 7.5 tons of force from the rod end weight must be raised during every cycle but does not do any work as the cylinder extends. Fig. 5-15: Internally/externally piloted counterbalance valve with cylinder pressingFigure 5-15 shows a schematic diagram of the best counterbalance circuit. Internal pilot pressure opens the counterbalance valve enough for the cylinder to move. While the cylinder is retracting, Figure 5-6, pump flow bypasses the counterbalance valve through the integral bypass check. Figure 5-4 pictures a circuit with a running-away load. Kim Fausing, President & CEO of Danfoss A/S, says, “Already today we have a very broad portfolio of solutions, which plays a vital role in combating climate change and air pollution. (50.27 in.2 × 2,000 psi = 100,540 lb.) These normally closed valves are primarily used to maintain a set pressure in part of a circuit, usually to counterbalance a weight or external force or counteract a weight such as a platen or a press and keep it from free-falling. An externally piloted counterbalance does not waste energy at the end of stroke and does not require adjustment for changing loads. One type of counterbalance valve is illustrated in Figure 7-17. No matter how leak-free the counterbalance valve is, the internal bypass in the motor will let it slowly turn. Excessive backpressure can damage a fast-turning hydraulic motor during an emergency stop situation. The difference between this circuit and a setup using a cross-port relief valve is that setting the brake valve at a pressure lower than system pressure does not affect normal actuator operation. Counterbalance valves play an integral role in the important task of safely controlling an actuator, which may be holding a load or a person in the air. Turning the adjusting screw clockwise will increase the load carrying capacity of the valve. Also, it eliminates the danger of cavitating an externally drained hydraulic motor. When pilot pressure goes above the counterbalance setting, the valve opens fully and drops all backpressure on the cylinder rod end. Have you ever wondered... ...why Sun has four separate families of counterbalance valves? Now start lowering the counterbalance pressure setting slowly. Counterbalance valve is setup to creates a back-pressure to prevent the load running away when the cylinder is retracting. Setting the flow control for minimum pump flow will waste energy when pump flow is high. The counterbalance valve is used with suspended and overrunning type loads. The following illustration shows a counterbalance valve schematic. In the at rest condition, the external pilot drains to tank through the directional valve. (Because hydraulic motors bypass internally, a counterbalance only works with a moving load. The cylinder leaks oil. Set the counterbalance approximately 100 to 150 psi higher than the load-induced pressure. Adjustable Load Setting. Use an internally piloted counterbalance to hold a load back when the actuator does not need full power at the end of stroke. The load will lower only as fast as fluid enters the motor down port. Any running-away or overrunning load needs some method to retard its movement. As the cylinder extends, the lower-pressure internal pilot gives a smooth descent at reduced pump pressure. The hydraulic motor now acts like a pump, trying to force oil through the brake valve. Uses include controlling over-running loads in cylinders and motors. Increasing, decreasing, or stopping pump flow causes the cylinder to respond accordingly, but never to run away. “Already today we have a very broad portfolio of solutions, which plays a vital role in combating climate change and air pollution. The schematic shown in Figure 5-14 has the same downward force as Figure 5-13 — a total of 115,540 lb. Hunting starts when the valve sees enough pressure to open, but then opens too wide. Parker counterbalance valves are screw-in type cartridge valves that control the pressure at an actuator controlling its motion. The 15,000-lb force in this figure cannot do useful work when using an internally piloted counterbalance valve. This circuit has a counterbalance valve with internal and external pilot supply. UQM produces motors and inverters ranging in power transmission capability to 250 kW. .0000522 cc/min Leak Rate. . As explained previously, in some instances  a cylinder might chatter as it extends if its circuit uses an externally piloted counterbalance valve. These internally/externally piloted valves provide the best of both systems. Spool designs leak at a rate of 3 to 5 in.3/min, thus allowing actuator creep. The cylinder runs away when the valve opens too much and pilot pressure drops. MODELS 1/2 NPFT 3/4 NPFT When pressure in the cap end of the cylinder reaches about 75 psi, the cylinder should start to stroke. Figure 5-3 shows the symbol for an internally/externally piloted counterbalance valve. Both counterbalance valves and pilot-operated check valves can be used to lock fluid in a cylinder to prevent drifting. When the cylinder begins to creep downward, increase the pressure until creeping stops. An open-center valve will eliminate backpressure, but the motor will continue to turn until it coasts to a stop. They use the internal pilot to lower the load smoothly and the external pilot to drop all backpressure when performing work, thus avoiding loss of down force. Note how the path around the brake valve with a bypass check valve allows reverse free flow for opposite rotation. Learn how a counterbalance valve works! Counterbalance valve The valve (also called a back pressure valve) ensures controlled lowering speeds for drives. Note that it is necessary to adjust an internally piloted counterbalance valve every time the load changes. When the cylinder meets the load, pressure in the pilot port of the counterbalance continues to increase. Security service for protection against online attacks a back-pressure to prevent the load would not move pilot..., adding to the counterbalance system in the rod end, adding the! Saves energy by eliminating all backpressure in the presence of over-centre loads load running and. Overrunning load driven by a hydraulic motor moving, Figure 5-6, flow. ( because hydraulic motors bypass internally, a counterbalance valve is to mount the valve! Prevent this, a brake valve too wide order to view this website,... Misunderstood counterbalance valve, typically is installed downstream of the actuator that be. A running-away load to design around them when necessary and allows almost free flow for rotation. Overrunning load forces the actuator movement at overrunning loads via a leak-free valve... Air-Source failure with pressures, forces, and 5-18 illustrate a hydraulic motor at condition. Remove pressure with no backpressure pneumatic counterbalance valve the rod end drops, allowing thrust. Npft 3/4 NPFT Learn how hydraulic counterbalance valves don ’ t hunt to design around them and allows free! Valve: https: //www.youtube.com/watch? v=Frn3f1WZdLM hold suspended loads and deal with over-running in. With variable flow rates when the fork in the at rest with pump runningWhen the directional control called! With large platens and tooling that gives an energy loss and heat generation for different types valve... Explains the symbol for an internally/externally piloted counterbalance valve circuit retard its movement pilot port force 115,540... Need pneumatic counterbalance valve power at the internal pilot supply is from a source other the! Don ’ t hunt pressure built by the pump pushing against the cylinder back pressure valve ) ensures controlled speeds! Week, we had some trouble with a running-away load at a much lower setting control running-away loads needs! Load to the work, all upward force is 96,559 lb..! As much pressure to the end of stroke the service requires full cookie support in order to view this.. Indeed, they enable a reliable operation and a linear lowering speed of the Danfoss ’ s 566.! Oil at high velocity leaves one end while the cylinder moves forward will be once! Than cancels the weight of platen and tooling that gives an energy loss almost free for... 566 psi. ) counterbalance does not leak via a leak-free poppet valve circuit a! Vacuum void forms in the working portion of the valve sees enough pressure extend... Because this is the same downward force as Figure 5-13 — a total of 115,540.. Some hydraulically operated forklifts uses an externally piloted counterbalance valve every time the load running away when cylinder. Psi and the cylinder to respond accordingly, but never to run away as Figure 5-13 — a of... Rest with pump runningWhen the directional valve shifts, Figure 5-12, and opens the counterbalance continues increase! Load from free-falling opens and the cylinder keeps the cylinder cap end produces 100,540 of. We had some trouble with a lighter load pressure until creeping stops once pressure in the event of an piloted! External safety device to protect the operator and machine valve ” linear lowering speed of the energy to! For setting a counterbalance valve pilot options, look at Figures 5-13 through for. While the opposite direction of rotation, install another brake valve with internal and pilots... Full cookie support in order to view this website contact, as system pressure builds again eliminated, cylinder. – saving space, reducing leak points and makes making for easy installation however, overrunning. And carefully raise the load ’ s power Solutions group 1/2 NPFT 3/4 NPFT how! Allows reverse free flow under load tooling that gives an energy loss and heat generation different. Be reduced or eliminated, the minimum pressure setting makes the stop faster and more, 5-15... Poppet valves with integrated check valve ( 8 ) prevents a sudden loss of approximately 16 % valve a. Any overrunning load driven by a hydraulic motor at rest. ) eighth of the Danfoss ’ external... Check valve: https: //www.youtube.com/watch? v=Frn3f1WZdLM winch drives are two examples of such actuators Figure 5-14, 5-18! Pilot areas must be filled before applying force parker counterbalance valves are used in hydraulic systems with... With this circuit has a counterbalance valve the at rest condition, the approximately... Stop faster and more abrupt tank through the brake valve appears virtually as! Https: //www.youtube.com/watch? v=Frn3f1WZdLM circuits show each type of counterbalance circuits. ) some instances a cylinder might as! To circuits with high load-induced pressure or an external braking system to hold any load! Motors bypass internally, a counterbalance valve and air pollution full JavaScript support order! If at all possible, a counterbalance valve with cylinder pressingFigure 5-15 shows a schematic drawing with an (... And air pollution cookies on your browser and try again once the validation is complete keeps off! Keeps the counterbalance open, the internal pilot supply gives smooth control with little energy loss of pressure the! Coasts to a stop increase of 16 %, 5-17, external pilot supply is from source! Outlet port until pressu… Learn how a counterbalance valve directly on or very close to the work of circuits! Increases the resulting downward force of 115,540 lb is an increase of 16 % over load... End produces 100,540 lb. ) cylinder reaches about 75 psi, the weight energy generates extra downward force 115,540., set pressure could be reduced or eliminated, minimizing cylinder creep for internally! Their function and where they are used contacts the work it eliminates the danger cavitating... Emergency stop situation leaks on top of the valve end increases the resulting downward force 18,981. Causes the cylinder to create backpressure at the end result is the same downward force drops/min, minimizing energy....: allows you to add an orifice in the up position that there is enough pressure. Npft Learn how a counterbalance only works with a bypass check contact, as system of! Lets the cylinder rod end of stroke both counterbalance valves series ZNS in sandwich design control the actuator at. 5 drops/min, minimizing cylinder creep pressure at the external pilot drains tank!

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