The Clamp cylinder maintains force because the modular pilot-operated check traps 700-psi fluid in it. See a leakage make-up circuit using an accumulator in Chapter 1, Figures 1-24 to 1-27. Figures 20-4 through 20-11 provide schematic drawings for a two-cylinder sequence circuit. With this sequence circuit, Clamp cylinder pressure cannot drop below 700 psi while the Work cylinder strokes. The schematic drawing notes the valve pressure settings. Component series 30 size 10，25, 32 Maximum operating pressure 315 bar Maximum flow 600 l/min. Their utilisation is in the case where influence shouldn't happen on the cracking pressure by the tank dynamic pressure. Direct-acting sequence valves are employed in low flow applications such as providing signals to operate directional control valves or to positively release a brake before a machine can function. Most sequence circuits require a heat exchanger, especially when they cycle rapidly. Pump flow goes to the Clamp cylinder, extending it to the work. The use of modular valves and manifolds shortens piping time while reducing the number of potential leakage points. Sometime we feel need, for various mechanism and operation of machines, of operation of hydraulic cylinders in a sequence. The function of the valve is similar to that of the two-stage relief valve in Figure 3, except that once the main spool has lifted, the 'kickdown’ jet is connected to the output port. After the work is contacted, Figure 20-18, energize solenoid A2 on directional valve DV02. The pilot-operated check still maintains 700 psi or higher on the Clamp cylinder, holding the work firmly while the Work cylinder retracts. Once the first actuator has completed its cycle, the sequence valve opens, allowing the second actuator to move. All rights reserved. (See further explanation in conjunction with Figures 20-23.). The valve is not affected by the back pressures and therefore it allows the circuit pressure be be used by both circuits. CYL1 extends until it contacts a part. When an external force tries to retract the cylinder, the cylinder is free to move when pressure in its cap port rises a little above compensator setting. Oil now goes to CYL2 and sequence valve (D) . The cylinder extends until it meets the part. You can also choose from 1 year, 6 months, and 1.5 years pressure sequence valve, as well as from metal check valves, ball valves pressure sequence valve, and whether pressure sequence valve is … The inlet to a pressure-compensated pump should never see a pressure higher than its compensator setting. A good feature of a sequence circuit: if cylinder 1 is a clamp, it does not matter how thick the part is. UQM will become part of the Danfoss’s Power Solutions group. Figure 20-4 shows a two-cylinder sequence circuit at rest. A reducing valve drain can usually be combined with the drains from other reducing valves or sequence valves but should never be teed into a main tank return line. Energizing solenoid B1 on directional valve (A) , Figure 20-9, starts returning the cylinders to their at-rest positions. Lernen Sie die Übersetzung für 'pressure sequence valve' in LEOs Englisch ⇔ Deutsch Wörterbuch. The extra cost of special manifolds for this arrangement is a good investment. This function is achieved by draining the spring chamber separately to tank. Figure 20-2 pictures the symbol for an externally piloted sequence valve. Gauges are placed to show working pressures as the sequence progresses. Figure 6-15 shows an installation of two sequence valves that control the sequence of operation of three actuating cylinders. Where the output flow is used to drive cylinders directly, two-stage valves are usually more appropriate. An important feature of all pressure sequence valves is a separate drain connection from the spring chamber. Isolation check valve (B) in the pump outlet line before the sequence valve keeps reverse flow and excess pressure away from the pump. © 2021 Endeavor Business Media, LLC. As pressure passes through 300 psi (as seen on gauges PG1, 2, and 3), CYL2 is still stationary. When an outside force starts pushing back against the cylinder, pressure in its cap end increases. Pressure sequence valves sense a change in pressure in a system and transmit a hydraulic signal when the set pressure has been reached. 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. Sequence Valve functions and applications. Pressure at the outlet port of the sequence valve is that required to overcome resistance in the secondary circuit when it is not above relief valve or pressure compensator setting. Figure 1 (a) Normally closed sequece valve with intergral reverse-flow check valve. If pressure at CYL1 drops for any reason, sequence valve E shuts enough to keep system pressure at 500 psi or higher if possible. (Note that a kick-down sequence valve causes less heat generation, but does not hold pressure on the primary circuit.). In general, this kind of valve is often used. With two or more cylinders controlled by a single directional valve, the cylinder with the lowest resistance always strokes first. See a leakage make up circuit using an accumulator in Chapter 1, Figures 1-24 to 1-27. When using flow controls with sequence circuits, meter-in flow control is the only workable option. Because of sequence valve (D) , pressure at the rod end of CYL2 stays at 300 psi. The kick-down sequence valve and a single-solenoid directional valve can replace an open- or tandem- center, 3-position valve unloading circuit. This means there is usually a high pressure drop across a sequence valve that results in wasted energy. It remains open even if conditions in the downstream circuit cause the circuit pressure to fall below the control setting. Pump flow goes to the Clamp cylinder through the pilot-operated check valve to extend the Clamp cylinder. When the component is undamped, the pressure falls and the sequence valve closes. Figure 20-11. Pressure may have to reach 900 psi before flow passes through the valve, but when it starts passing, a kick-down sequence opens fully. When the retracting cylinder stops, Figure 20-23, pressure builds in its rod end. The pressure sequence valves is a pressure relief valve with an additional check valve for bypassing purpose. With this type of sequencing circuit, the first cylinder may lose holding power when the second directional valve shifts. Hydraulic sequence valve is also type of pressure control valve. After a kick-down sequence valve reaches set pressure, flow passes through unrestricted. Figure 2 ‘Circuit breaker’ or ‘kickdown’ sequence valve. This allows full pressure to appear on both cylinders when they stall, instead of the pressure having to divide between them. This is because, unlike a conventional relief valve, a high pressure can occur in the output port during the normal course of operation. This sequence-valve relief works anywhere in the circuit to protect any line from overpressure. After the Work cylinder retracts fully, deenergize solenoid A1 and energize solenoid B1 on the directional valve, retracting the Clamp cylinder to its home position. In Figure 20-5, solenoid A1 is energized and CYL1 is extending. In Figure 4 when the directional control valve is switched to the 'tramline' condition, cylinder A will extend followed by cylinder B. The main difference is that a sequence valve always has an external drain line — and often has a bypass check valve for reverse flow. Relief valves make it possible to avoid this hazard. If decreasing pressure is a problem, tee a small accumulator in the line between pilot-operated check valve (C) and the cylinder. The outlet of sequence valve (A) goes directly to tank. If the actuator with the least resistance is first in the sequence, the circuit runs smoothly without other valving. A sequence valve always has an external drain port to keep from trapping leakage oil. When pressure on CYL2goes higher than 500 psi, there is no energy loss, hence no heat. Repeat the pressure setting sequence if the outlet pressure does not return to the desired setting. Sequence valve is used to feed 2 cylinders in sequence: it provides flow to the secondary circuit when a primary circuit function has reached the pressure setting. To retract the Work cylinder, deenergize solenoid A2 as in Figure 20-15. Pressure Sequence Valves Sequence Valve is different from a Relief Valve in that the spring chamber is vented directly to atmosphere instead of to the outlet port on the valve. The main reason this overpressure relieving circuit is better than a circuit with a standard relief valve is that adjusting the pump compensator not only changes system pressure, but also automatically raises relief pressure. When the Clamp cylinder makes a limit switch, as in Figure 20-14, it energizes solenoid A2 on directional valve DV02. (b) Clamping application. With a sequence-valve spring setting of 65 psi, it will not open to tank until pressure after check valve (B)goes at least 65 psi higher than pump compensator setting, as in Figure 20-26. Because this takes low pressure and all pump flow, there is no heat generation. 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, BOOK 2, CHAPTER 23: Three fluid power circuits, BOOK 2, CHAPTER 22: Synchronizing cylinder movement, Danfoss Agrees to Buy Eaton’s Hydraulics Business, Danfoss Development Center to Boost Vehicle Testing and Design, New Control Option Makes Pump More Versatile. Any sequence circuit may fail to operate correctly at any time because of outside influences. A sequence valve is somewhat similar to a relief valve except that, after the set pressure has been reached, the sequence valve diverts the fluid to a second actuator or motor to do work in another part of the system. Pilot-operated check valve (C) traps oil in the cap end of CYL1 — note gauge PG3 — so it does not relax and release the part. A separate directional valve for each cylinder is one way to sequence such a circuit. When oil passes through sequence valve (D) , it first sends a pilot signal to open pilot-operated check valve (C) . The composite valve that can have reverse flow is called a one-way sequence valve. In some circuits the pilot signal to open the valve is from a source other than the line feeding it. Some designs use a spring acting directly on the spool or poppet, others are pilot-operated. Unlike relief valves, sequence valves generate a constant pressure at the inlet port irrespective of the pressure on the outlet port. A sequence valve is a pressure-operated, normally closed, poppet or spool valve that opens at an adjustable set pressure. One 4-way directional control valve controls both cylinders. Operation: The VektorFlo ® sequence valve operates as a pressure sensitive, normally closed element in a clamping system. An important feature of all pressure sequence valves is a separate drain connection from the spring chamber. If the Work cylinder only requires 450 psi to extend, the 300-psi energy loss generates heat. To retract the Work cylinder, deenergize solenoid A2 as in Figure 20-19. Consider a machining operation where the workpiece must be clamped with a certain force before it is extended to make contact with the cutting tool. The cylinder retracts until the end of stroke or until it contacts a dead stop. Sequence valves often generate a great deal of heat because the first actuator to move takes higher pressure than the subsequent actuators. This pressure drop results in heat, because its energy does not do useful work. However, relief valve (D) may cause problems, as stated in Chapter 1, page ACC7. If decreasing pressure is a problem, tee a small accumulator in the line between the manifold and the cylinder's cap-end line. When it is necessary to positively locate an actuator, always use a limit switch or limit valve. For reverse flow capabilities, use the integral bypass check valve shown in the symbol. The accumulator circuit almost eliminates pressure spikes — plus it gives faster actuator response at the start of a cycle. A single screw-in cartridge sequence valve — added to the bar manifold in the pump line between the clamp valve and the working cylinder valves — can eliminate multiple sequence valves. The pressure drop allows kick-down sequence valve (A) to close (or reset) for the retract cycle. An external pilot-operated sequence valve opens and allows flow when a remote operation reaches a certain pressure. When the cylinder that must move first has the highest resistance, a single directional control will not work. A pressure drop of more than 50 psi across a kick-down sequence valve keeps it full open. Some designers use a relief valve with a pressure-compensated pump to reduce pressure spikes as the pump rapidly goes from full flow to no flow. UQM produces motors and inverters ranging in power transmission capability to 250 kW. (Valve (A) has a low-pressure spring rate between 50 and 250 psi.) A sequence valve is somewhat similar to a relief valve except that, after the set pressure has been reached, the sequence valve diverts the fluid to a second actuator or motor to do work in another part of the system. The cylinder extends at the pressure required to move it. This circuit has some heat generation but makes sure the Clamp cylinder never goes below a certain pressure while the Work cylinder extends and retracts. The pump, unloading through kick-down sequence valve (A) at about 50 psi, is ready for a cycle. 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. Figure 20-25 shows internally piloted, externally drained, low-pressure sequence valve (A) teed into the pump outlet. Cylinder 2 will not extend until pressure at cylinder 1 reaches 600 psi. Figure 20-20 shows the circuit at rest. When the Work cylinder has retracted fully, deenergize solenoid A1 and energize solenoid B1 on the directional valve. When pressure is 350 psi at CYL1, reducing valve (B) shuts and holds. Without controlling these forces, the power components and expensive equipment could get damaged. Cartridge Valves. In this condition, the input pressure necessary to hold the valve fully open has only to overcome the resistance caused by the secondary circuit pressure and the light spring situated behind the main spool. Upon reaching set pressure, the valve opens enough to let excess pump flow pass on to the second operation. If the Work cylinder only requires 450 psi to advance to the work, system pressure drops to 450 psi with minimal heating. Any other time the sequence valve stays closed because its inlet never sees pressure higher than compensator setting. When CYL2 bottoms out, as in Figure 20-8, pressure at gauges PG1 and PG5 goes to 750 psi and the system relief valve starts dumping fluid to tank. Figure 20-3 shows the symbol for a kick-down sequence valve. Pressure valves with a switching task are referred to as pressure valves with fixed throttle: sequence valves and unloading valves. PSVP-10: 20: 10: PSVP-10_520-P-060720-en : This unit is a direct acting, screw in cartridge style, poppet type, adjustable, soft shift (shock free), hydraulic hi-lo pressure sequence valve. Version “P” The compression spring (3) holds the control spool (2) in initial position, the valve is blocked. 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