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Contents Technical Support 5 How to Get Technical Support Before You Contact MTS 5 5 If You Contact MTS by Phone 6 Problem Submittal Form in MTS Manuals 7 Preface 9 Before You Begin Conventions 9 10 Documentation Conventions 10 Introduction 13 About the Servovalve Servovalve Function 14 14 Servovalve Applications Single Servovalves Dual Servovalves 16 17 18 Three-Stage Servovalves 19 252 Servovalve General Specifications 252 Servovalve Flow Ratings 20 21 252 Servovalve Performance Char
Maintenance 33 Replace the Servovalve Filter Element Adjust the Mechanical Null Troubleshooting Guide 4 Contents 33 35 39 Series 252 Servovalve Product Information
How to Get Technical Support Technical Support How to Get Technical Support Start with your manuals The manuals supplied by MTS provide most of the information you need to use and maintain your equipment. If your equipment includes software, look for online help and README files that contain additional product information. If you cannot find answers to your technical questions from these sources, you can use the Internet, e-mail, telephone, or fax to contact MTS for assistance.
If You Contact MTS by Phone Know information from prior technical assistance Identify the problem Know relevant computer information Know relevant software information If you have contacted MTS about this problem before, we can recall your file based on the: • MTS notification number • Name of the person who helped you Describe the problem and know the answers to the following questions: • How long and how often has the problem occurred? • Can you reproduce the problem? • Were any hardware or
Problem Submittal Form in MTS Manuals • Name • Company name • Company address • Phone number where you can be reached If your issue has a notification number, please provide that number. A new issue will be assigned a unique notification number.
Problem Submittal Form in MTS Manuals 8 Technical Support • In the back of many MTS manuals (postage paid form to be mailed to MTS) • www.mts.
Before You Begin Preface Before You Begin Safety first! Other MTS manuals Before you use your MTS product or system, read and understand the Safety manual and any other safety information provided with your system. Improper installation, operation, or maintenance can result in hazardous conditions that can cause severe personal injury or death, or damage to your equipment and specimen. Again, read and understand the safety information provided with your system before you continue.
Conventions Conventions Documentation Conventions The following paragraphs describe some of the conventions that are used in your MTS manuals. Hazard conventions Hazard notices may be embedded in this manual. These notices contain safety information that is specific to the activity to be performed. Hazard notices immediately precede the step or procedure that may lead to an associated hazard. Read all hazard notices carefully and follow all directions and recommendations.
Documentation Conventions Hypertext links The electronic document has many hypertext links displayed in a blue font. All blue words in the body text, along with all contents entries and index page numbers, are hypertext links. When you click a hypertext link, the application jumps to the corresponding topic.
Documentation Conventions 12 Preface Series 252 Servovalve Product Information
Introduction The MTS Series 252 Servovalves are designed for use with actuators requiring 3.8 to 227 L/min (1 to 60 gpm) of fluid flow. Contents About the Servovalve Servovalve Function 14 14 Servovalve Applications 16 252 Servovalve General Specifications 252 Servovalve Flow Ratings 20 21 252 Servovalve Performance Characteristics 23 m m 252 Servovalve Dimensions 22 Revision C Revision G Series 252.3x Servovalve Series 252.2x/4x Servovalve Note The Series 252.
About the Servovalve About the Servovalve The heart of a servohydraulic system is the servovalve. It is the final control element in most MTS closed-loop systems. The servovalve responds to command signals generated by the software and processed by the controller and output through the valve driver module. The servovalve regulates the direction and flow of the hydraulic fluid entering the actuator from the hydraulic pressure ports.
Servovalve Function First Stage Coil Magnets Upper Pole Flexure Tube Armature Lower Pole Nozzle Flapper Second Stage Feedback Wire Spool Filter Fixed Orifice Manifold Pressure from Power Actuator Actuator Rod Piston LVDT (inside rod) Functional Diagram Moving the spool Stopping the spool A command from the controller causes the armature to rotate clockwise or counterclockwise (depending on the polarity of the command).
Servovalve Applications Stopping actuator movement When the actuator has moved the desired amount, the valve drive command decreases to zero. Hydraulic fluid flow to the actuator stops, and so does the actuator. Servovalve Applications Servovalves are suitable for a variety of applications. They may be mounted directly to a linear or rotary actuator, or single or dual servovalves may be mounted to a manifold, which in turn is mounted to an actuator.
Single Servovalves Single Servovalves Single servovalves may be mounted to a manifold or directly to an actuator. The purpose of a manifold is to adapt the ports of the servovalve to the ports of the actuator. This is a cross section of a single servovalve showing how its ports are aligned. A manifold realigns the ports to match a given actuator.
Dual Servovalves Dual Servovalves Dual servovalves are sometimes mounted to a manifold. The manifold is a metal block that connects the ports of each servovalve to the ports of the actuator. Mounting two servovalves to a manifold doubles the flow rate. Manifold Manifold To/From To/From Actuator Actuator Supply Supply Return Return Supply Supply Pressure Pressure To/From To/From Actuator Actuator This is a cross section of dual servovalves mounted to a manifold.
Three-Stage Servovalves Three-Stage Servovalves A small (252) servovalve may be mounted to a larger (256) servovalve, enabling the fluid flow from the smaller one to be used to move the spool of the larger one. This configuration enables the control signal to effectively regulate a flow rate substantially greater than the full-flow rating of the smaller servovalve. 256 252 m m m The Series 252 Servovalve provides the first two stages of the Series 256 Servovalve (a three-stage servovalve).
252 Servovalve General Specifications 252 Servovalve General Specifications Parameter Specification Maximum operating pressure 31 MPa (4500 psi)* Minimum operating pressure 1.4 MPa (200 psi) Operating temperature range -40°C to +135°C (-40°F to +275°F) Revision G only -20°C to +135°C (-40°F to +275°F) Rated full-flow input signal current 25 mA (series) 50 mA (differential) 50 mA total (parallel) Coil resistance 80 Ω per coil Seals Viton Weight 252.2X/.4X Revision C 252.2X/.
252 Servovalve Flow Ratings 252 Servovalve Flow Ratings The following table lists typical flow ratings for the Series 252 Servovalves. Model Number* Full-Flow Rating† 90° point at 10% Command Null Flow‡ 252.21 4.0 L/min (1.0 gpm) 230 Hz 1.10 L/min (031 gpm) 252.22 9.5 L/min (2.5 gpm) 230 Hz 1.44 L/min (0.40 gpm) 252.23 19.0 L/min (5.0 gpm) 230 Hz 2.27 L/min (0.60 gpm) 252.24 37.0 L/min (10.0 gpm) 170 Hz 2.27 L/min (0.60 gpm) 252.25 56.0 L/min (15.0 gpm) 160 Hz 2.27 L/min (0.
252 Servovalve Performance Characteristics 252 Servovalve Performance Characteristics The flow versus frequency performance curves are shown in the following figures. They indicate the typical performance capabilities of the servovalves at various frequencies. The curves are derived by driving the servovalve at the indicated frequency with a sine wave control signal and ± full current to the coil.
252 Servovalve Dimensions 252 Servovalve Dimensions The following figures show the dimensions of the Series 252 Servovalves. Null Adjust Pin Electrical Connector Mount with 5/16-18 x 1.50 LG SHCS (4) (Leaves .38 for THD engagement) Model 252.2x/4x Servovalve Dimensions (Revision C) Model 252.
252 Servovalve Dimensions Model 252.
2 Servovalve Installation Installation The servovalve can be installed on an actuator or a Series 256 Servovalve. This section includes the following: 252 Servovalve Installation 25 252 Servovalve Cable Connections 28 Five-Port Operation—252.2x Servovalve 29 Five-Port Operation—252.3x Servovalve 30 Important If you are replacing an existing servovalve and you encounter any component interference or alignment issues, contact MTS Technical support.
252 Servovalve Installation Control Port No. 1 Mounting Holes (4 places) Return Port Locating Pin Return Port Control Port No. 2 Control Port No. 1 Pressure Port Mounting Holes (4 Places) Locating Pin Control Port No. 2 Pilot Pressure Port (optional) Pressure Port Auxiliary Pilot Pressure Port Servovalve Locating Pin Note For mounting the Model 252.2x and 252.4x servovalves use four 5/16-18 x 1-1/2 in. ASTM A574 socket head cap screws and the Model 252.3x servovalve uses four 3/8-16 x 1-3/4 in.
252 Servovalve Installation 8. Apply low hydraulic pressure to the servovalve so that the hydraulic fluid gradually fills the filter cavity. 9. Apply high hydraulic pressure and check for leaks at the servovalve hydraulic connections and at the base of the servovalve.
252 Servovalve Cable Connections 252 Servovalve Cable Connections The following figure shows the connector wiring for the servovalve. The correct wiring configuration is determined by the requirements of the device used to control the servovalve. See the appropriate controller manual for information on servovalve connections.
Five-Port Operation—252.2x Servovalve Five-Port Operation—252.2x Servovalve The Model 252.2x Servovalve can easily be changed from four to five ports. The servovalve can be configured for pilot stage oil supply through the internal pressure “P” port, or from a separate supply line through the “X” port. Standard configuration is internal pilot operation with a screw and seal washer in the “X” port.
Five-Port Operation—252.3x Servovalve Five-Port Operation—252.3x Servovalve The Model 252.3x Servovalve can easily be changed from four to five ports. The fifth port provides hydraulic pressure to the spool even when station pressure is removed. The following procedure describes how to open the fifth port and block a secondary port to the filter. The five port configuration can be changed back to a four port configuration.
Five-Port Operation—252.3x Servovalve A. Use the threaded screw driver (#2 -56) to connect to the plug. Push the plug into the secondary port until it seats into the port . Secondary Secondary filterfilter port port B. Remove the threaded screw driver from the plug. C. Use a 1/8 inch Allen driver to install the Allen set screw removed in Step B into the secondary filter port. 5. Reassemble the filter. A.
Five-Port Operation—252.
Replace the Servovalve Filter Element Maintenance Maintaining the Series 252 Servovalves typically involves changing the filter element (Model 252.3x only) and setting the mechanical null adjustment. Except for these procedures, further disassembly, inspection, or repair of the servovalve is not recommended and may void the servovalve warranty. MTS does not recommend changing the 35-micron filter element in the Models 252.2x/.4x Servovalve (revision C).
Replace the Servovalve Filter Element Socket Head Screws (4) 1 3 4 Filter Cover Plate 2 Filter Plug Filter Plug O-Rings Filter O-Ring Filter Filter Cover Filter Housing Model 252.2x/.4x Filter Location (Revision G only) Model 252.3x Filter Assembly 1. Ensure that system hydraulic pressure has been reduced to zero before proceeding. To do this, turn off the hydraulic power unit and exercise the actuator until it stops moving. Turn off electrical power to the controller. For the Models 252.
Adjust the Mechanical Null B. Remove the filter plug by threading one of the socket head screws, removed in Step A, into the filter plug and pulling it out of the filter housing. Remove the filter cover plate. C. Remove the filter plug O-rings from the filter plug. D. Remove the filter O-ring from the filter. E. Remove the filter. F. Lightly lubricate the filter O-ring with clean hydraulic fluid, install it on the replacement filter, and insert the filter into the housing. G.
Adjust the Mechanical Null WARNING Do not perform the following procedure without clearing the path of motion of the actuator. Sudden and unexpected actuator rod movement can cause serious injury to personnel and/or damage to equipment. Ensure that all personnel, specimen/structures, and tools are away from the path of motion of the actuator (crush zone). 1. Exercise the actuator. The actuator should be exercised to warm it up.
Adjust the Mechanical Null CAUTION Do not apply more than 1.36 N•m (12 lbf-in.) of torquing force to the adjustor pin. Excessive torquing may shear off the adjustor pin eccentric. If the pin does not turn using very little force, gently loosen the self-locking nut more, then try turning the pin again. C. Check that the scribe mark on the adjuster pin is pointed toward the base (oriented in the lower 180° of the adjustment range).
Adjust the Mechanical Null G. See your controller manual to complete the valve balance procedure. 4. Set the magnetic null adjustment (Newer Series 252.3X servovalves). 38 Maintenance A. Using a flat screwdriver, slowly rotate the magnetic null adjustment on the top of the servovalve while monitoring the command and feedback signals until the command equals feedback. B. See your controller manual to complete the valve balance procedure.
Troubleshooting Guide Troubleshooting Guide The table below provides the symptom, probable cause, and remedy for some common servovalve malfunctions that may be encountered. Before diagnosing a servovalve malfunction, ensure that: • The servovalve is getting the proper command. • The servovalve is getting full system pressure and flow. • The hydraulic fluid in the system is clean.
Troubleshooting Guide 40 Maintenance Series 252 Servovalve Product Information
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