It is used to force the fluid from the reservoir to the rest of the hydraulic circuit … To control a sequence of operations and to enable one unit to automatically set another unit into motion. With a short cycle time, pressure drop is minimal. Where are sequence valves installed? Adding check valve (B) at the pump outlet assures that pressure at the pump never goes above the compensator setting. They are used to start a second operation after the preceding one finishes. When pressure increases enough to unseat the adjustable poppet—and more flow starts passing the main poppet than going through the control orifice—the pressure imbalance lifts the main poppet. Pressure changes depend on these values, so they had to be calculated for each row or in 100 microsecond iterations. When the retracting cylinder stops, Figure 20-23, pressure builds in its rod end. Because this takes low pressure and all pump flow, there is no heat generation. 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. Used to control a sequence of operations for two or more actuators in a system. See a leakage make up circuit using an accumulator in Chapter 1, Figures 1-24 to 1-27. It is one of a variety of pressure control valves available for hydraulic circuits. According to the different functions, it can be called sequence valve, back pressure valve, unloading valve, and balance valve, respectively. Sequence valves control the sequence of operation between two branches in a circuit; that is, they enable one unit to automatically set another unit into motion. A limit switch then deenergizes solenoid A1 on directional valve (B) . If the actuator with the least resistance is first in the sequence, the circuit runs smoothly without other valving. Pressure at the rod end of CYL1 is whatever it takes to stroke the cylinder home. cylinders in a sequence. Sequence valves Sequence valves cause a hydraulic system to operate in a pressure sequence. Many functional options available for a wide range of applications. When pressure reaches the setting of kick-down sequence valve (A) , the valve opens and unloads the pump to tank at approximately 50 psi. Pictured are two typical pneumatic sequence-valve circuits with meter-in (left) and meter-out (right) flow controls.Click on image for larger view. When it is only necessary to know that pressure has built, a sequence valve in the line keeps fluid from the next action until the limit switch is contacted and pressure increases. If decreasing pressure is a problem, tee a small accumulator in the line between the manifold and the cylinder's cap-end line. The performance of the sequence valve is basically the same as that of the overflow valve. What is the purpose of a hydraulic sequence valve? The kick-down sequence valve and a single-solenoid directional valve can replace an open- or tandem- center, 3-position valve unloading circuit. A good feature of a sequence circuit: if cylinder 1 is a clamp, it does not matter how thick the part is. It may require other valves to make sure the first cylinder generates and maintains the force required both before and during the second cylinder’s stroke. Kick-down sequence valve (A) stays closed because its setting is higher than the pressure retracting the cylinder. What is the purpose of a hydraulic sequence valve? The symbol for sequence valve is as shown below. Pressure builds until the punch goes through the part. The piston position and velocity can be measured using a feedback device, which is typically a magnetostrictive transducer rod. Trapped fluid modifies set pressure at best or keeps the valve from opening at worst. A hydraulic system can be used for holding and positioning the parts to be welded during a welding operation. The circuit in Fig. Model. Weight. This requires a sophisticated calculation. UQM will become part of the Danfoss’s Power Solutions group. With this overpressure circuit there is no protection from pressure spikes when the pump compensator has to work quickly. It is time to take a closer look at exactly what happens when a hydraulic system operates. Figures 20-16 through 20-19 show a kick-down sequence valve in place of the standard sequence valve. Operation Principle of Pressure Sequence Valve. CYL1 extends until it contacts a part. Common applications of the valve are in pilot logic circuits and sequence- control sub-circuits. 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