NUCLEARENVIRONMENT VELOCITY - TO-DISPLACEMENTCONVERTER MOD~L BENTL NEVADA

Transcription

1 Manual No. TW ' NUCLEARENVIRONMENT VELOCITY - TO-DISPLACEMENTCONVERTER MOD~L BENTL NEVADA

2 8ENTLY NEVADA r'\ V..WoridWider~serVice... Copyright<D 1987 Bently Nevada Corporation All Rights Reserved No part of this publication may be reproduced, transmitted, stored in a retrieval system nor translated into any human or computer language, in any form or by any means, electronic, mechanical, magnetic, optical, chemical, manual or otherwise, without the prior written permission of the copyright owner, Bently Nevada Corporation, Post Office Box 157, Minden, Nevada USA. Copyright infringement is a serious matter under the United States and Foreign Copyright Laws. is a Registered Trademark of Bently Nevada Corporation. Manual No. TW First Printing: NOV Rev C: APR 1987 ii,.

3 CONTENTS Page SECTION 1 - DESCRIPTION AND OPERATION SECTION 2 - INST ALLA TION General. ReceivingInspection.... InstallationConsiderations RadiationResistance GeneralEnvironment Protection Powerand SignalConnections TransducerIsolation/ShieldGrounding SECTION 3 - MAINTENANCE General V-D Converter Test and Calibration V-DConverterTest Setup Procedure V-DConverterCalibrationCheckProcedure GainCheck Recalibration %DownCheck OutputBiasCheck SECTION 4 - RECOMMENDED SPARE PARTS APPENDIX A - SPECIFICATIONS

4 SECTION 1 DESCRIPTION AND OPERATION The Model Velocity-to-Displacement (V-D) Converter (Figure 1-1) is a single encapsulated unit designed to operate in a nuclear radiation environment. The V-D converter is connected between a seismic velocity transducer and a displacement monitor to condition the velocity signal and convert it to a displacement signal for input to the monitor. Circuitry for the V-D converter is encapsulated within a stainless steel case. The case flange is drilled for mounting. The input and output terminals are contained in two three-terminal barrier type strips mounted at the case top surface. A calibration resistor (fixed) is located between the terminal strips. The V-D converter accepts a velocity signal from a velocity Seismoprobe and performs a single integration process. The resulting output signal is a displacement signal having a scale factor determined by the V-D converter circuit. The V-D converter circuit also performs fault detection functions: if the transducer or the extension wiring becomes either open or shorted to common, the output bias voltage goes to within 3 volts of either VT supply (-24 Vdc) or common respectively INCH 18.1 mm} 16 PLACES; t' INCH mml 6.32 UNC TERMINAL 16 PLACES} INCH mml L1.96INCH-J mml Figure 1-1. Nuclear Velocity-to-Displacement Converter

5 CAUTION If casing velocity measurements are being made for overall protection of a machine, thought should be given to the usefulness of the measurement for each application. Most common machine malfunctions (unbalance, misalignment, etc.) occur on the rotor and originate as an increase (or at least a change) in rotor vibration. In order for any casing measurement alone to be effective for overall machine protection, a significant amount of rotor vibration must be faithfully transmitted to the machine casing or mounting location of the transducer. In addition, care should be exercised in the physical installation of the velocity transducer on the bearing housing or machine casing. Improper installation may result in a decrease of the transducer amplitude and frequency response and! or the generation of false signals which do not represent actual vibration. Refer to the appropriate instruction manuals and Application Notes.

6 SECTION 2 INSTALLATION GENERAL This section contains receiving inspection, power and signal connections, and V-D converter mounting considerations. The exact installation instructions will depend upon the application and machine configuration where the V-D converter is to be used. RECEIVING INSPECTION Inspect the V-D converter as soon as it is received and unpacked to determine if any in-transit damage has occurred. All shipping forms and invoices should be retained. If any shipping damage is apparent, file a claim with the carrier and submit a copy to Bently Nevada Corporation. Include the V-D converter model number with all correspondence. The user will be advised concerning repair or replacement in accordance with terms and conditions of sale. INST ALLA TION CONSIDERATIONS Radiation Resistance The transducer and cabling from the transducer to the V- D converter are constructed with approved materials that provide resistance to degradation from nuclear radiation environments. The V-D converter electronic circuits, however, undergo changes in operating characteristics when irradiated. These changes require recalibration as described in Section 3 of this manual.

7 Changes in the electronic circuit caused by irradiation can be either prevented or reduced by the following methods.. REDUCING THE INTENSITY OF RADIATION RECEIVED ELECTRONIC CIRCUITRY TO AN ACCEPTABLE LEVEL. BY THE Intensity reduction can be achieved by either installing the electronic circuitry in an area having a local radiation level that is less than one rad (air) per hour, or by shielding the circuit from radiation. The recommended method of shielding is to enclose the V-D converter in a lead-lined (user supplied) weatherproof housing. The design of the shield is dependent upon the highest radiation levels of the housing location.. PERIODIC RECALIBRATION The V-D converter can be recalibrated as necessary to maintain the scale factor within factory specification. The frequency of racalibration is dependent upon the environment in which the unit is mounted. It is recommended that V-D converter calibration be checked initially at one-month intervals. From these checks, a practical recalibration schedule can be determined. General Environment Protection The V-D converter should be installed such that it receives protection from corrosive environments, moisture, and weather. The V-D converter is not normally affected by vibration, dust, humidity, or most gasses. However, it is necessary to mount it in a location where it is not subjected to temperatures in excess of 2120 F (1000 C). CAUTION Temperatures in excess of 2120 F (100 C) may cause permanent damage to the V-D converter. 2-2 "

8 POWER AND SIGNAL CONNECTIONS All power and signal connections between the velocity Seismoprobe and V-D converter, and between the V-D converter and the monitoring device must be made in the field. The Seismoprobe is connected to the V-D converter through a three-wire shielded cable. A second three-wire shielded cable connects the V-D converter power and output signal terminals to the monitoring device. Transducer Isolation! Shield GroundinK The designs and applications of BNC monitoring systems are such that the transducer isolation and shield grounding practices outlined in this section should be implemented during installation. Proper isolation and shield grounding ensure that a minimum amount of noise will be induced in the signal conductors. Variations in transducer applications can require different isolation! shield grounding techniques. If the transducer applications described in this manual do not cover the user's installation, contact Applications Engineering, Bently Nevada Corporation for additional information. Transducer Isolation The circuitry within the V-D converter is isolated from the case; therefore, no isolation technique is required for mounting. Shield Grounding The shield of each field wiring cable should be earth grounded at only one end; the other end should remain unconnected. All shields of field wiring connected to monitors in the same rack should connect to the same earth ground. If safety barriers are not used in the field wiring, each monitor-end shield connects to the COM terminal of the respective rack signal module. The signal module COM terminals are connected to ground by a user-installed jumper wire connecting a specific remote reset terminal (common) to the earth ground terminal, as shown in Figure 2-l. Routing of the wire is at the user's discretion. If safety barriers are used, shields are connected to the earth ground bus, as shown in Figure 2-1.

9 t-.:> I ~ VELOCITV SEISMOPROBE (lnternallv ISOLATED) I C B A SHIELD OPEN V-D CONVERTER (INTERN ALL V ISOLATED) I C our B A I SHIELD GROUND CONNECTION COM Vr SHIELD OPEN SHIELD GROUND CONNECTION XDCR POWER COM INPUT LINE 1 GND POWER SUPPL V SIGNAL TERMINAL STRIP / \ } REMOTE RESET { - 4-~ 5 / 18 AWG INSULATED (USEDWITHOUT JUMPER BARRIERSONLV) LINE 1 NEUT/LINE 2 GND Figure 2-1. Shield Grounding, V-D Converter Field Wiring 1-3 ::E 00 0 t-.:> ~ ~ C) 0

10 SECTION 3 MAINTEN ANCE GENERAL This section covers test setup and calibration check procedures for the V-D converter. Table 3-1 lists the equipment recommended to perform the calibration check procedures. If the recommended equipment or its equivalent is not available, calibration check procedures should not be attempted; instead, the nearest Bently Nevada Corporation Field Office should be contacted, or the unit should be returned to the factory or a testing laboratory for calibration. Table 3-1. Recommended Maintenance Equipment MINIMUM RECOMMENDED ITEM SPECIFICATIONS EQUIPMENT Signal Sine wave output, Hewlett- Packard Model 3111 Generator 0 to 10 Volts 4 to 100 Hz peak-to-peak Oscilloscope DC to 1000 Hz Tektronix Model A5110N Differential Inputs with Calibrated Vertical Amplifiers and Time Base Power Supply -24 Vdc, 20 ma Hewlett-Packard Model 6215A Frequency 5-Digit Display, Hewlett-Packard Model 5314A Counter 1 megohm input impedance. less than 30 pf shunt capacitance 4 to 100 Hz Digital 0 to 30 Vdc Hewlett-Packard Multimeter 0 to 50k Ohm Model 3465A/B Potentiometer 50k Ohm Metal Film 1.27k Ohm 1% 1/4W Resistors 1.24k Ohm 1% 1/4W Electrolytic 10 uf, 50V Capacitor

11 V-D CONVERTER TEST AND CALIBRATION V-D Converter Test Setup Procedure a. Connect test equipment and make all connections as shown in Figure 3-1. b. Use the floating (differential) inputs of the oscilloscope as shown. V-D Converter Calibration Check Procedure When performing the following procedures, if a measured value does not fall within the given limits, the V-D converter must be recalibrated or rejected. Gain Check a. Adjust the signal generator until an input frequency of 63.7 Hz is indicated on the frequency counter. b. Adjust the signal generator for an input amplitude of 1.6 volts peak-to-peak, as measured on the oscilloscope. c. The output amplitude of the V-D converter as measure on the oscilloscope should be 0.77 to 0.83 volts peak-to-peak. Recalibration Perform necessary. this procedure if recalibration of the V-D converter is a. Unsolder and converter. remove the calibration resistor from the V-D b. Connect the 50k ohm potentiometer (as a variable resistor) between the calibration resistor terminals. c. Adjust the input signal to 31.8 Hz and 1.6 volts peak-to-peak.

12 OSCILLOSCOPE. + COM 0 + _0 COM SIGNAL GENERATOR 24V SUPPLY + VELOCITY-TD-DISPLACEMENT CONVERTER -24 VDC A COM CAL. B 10 fj. F K 1% OUTPUT C R CAL.. HI DIGITAL MUL TIMETER LOW 50K COM FREQUENCY COUNTER IN.OSCILLOSCOPE MUST HAVE FLOATING DIFFERENTIAL INPUT ON BOTH CHANNELS TO PREVENT GROUNDING OF THE INPUT SIGNAL. UCONNECT ONLY IF RECALIBRATION IS REQUIRED. Figure 3-1. V-D Converter Test Setup

13 d. Adjust the potentiometer until the V-D converter output is 1. 6 volts p eak-to-p eak. e. Disconnect the 50k ohm potentiometer (without changing setting) and measure its resistance. f. Select one or two 1% 1/4 watt metal film resistors to obtain a fixed resistance Solder the within fixed 1% of resistor the measured potentiometer resistance. to the V-D converter calibration resistor terminals. 10% Down Check a. Adjust the signal generator until an input frequency of 4.2 Hz is indicated on the frequency counter. b. Set the oscilloscope to dc-coupled input, and adjust the signal generator for an input amplitude of 0.6 volts peak-to-peak, as measured on the oscilloscope. c. The output amplitude of the V-D converter as measured on the oscilloscope should be 3.80 to 4.30 volts peak-to-peak (dc coupled). d. Disconnect the oscilloscope. Out,eut Bias Check a. Using the Digital Multimeter (DMM), measure -4.8 to -7.4 volts dc bias at the V-D converter OUTPUT terminal. b. Disconnect the A, B, and C terminals individually and check the output bias for a voltage more positive than -1.5 Vdc or within 6.4 Vdc of VT. Allow 30 seconds before checking the output bias voltage. c. Reconnect the inputs, wait 30 seconds, and check that normal bias of -4.8 to -7.4 Vdc is present.

14 SECTION 4 RECOMMENDED SPARE PARTS Bently Nevada Corporation recommends that at least one velocity-todisplacement converter assembly be kept on hand as a spare. If the V-D converter is located in a remote area or is used on an extremely critical application, several spares may be desired. To order a replacement assembly, specify the complete catalog number (model number plus option numbers) as shown in Table 4-1. Spare V-D converters are shipped from the factory fully tested.' When a V-D converter is replaced, the procedures in Section 3 of this manual need not be performed, except to verify proper system performance. Table 4-1. Recommended Spare Parts QU ANTITY PER SYSTEM DESCRIPTION PART NUMBER 1 Veloci ty-to- Displacement Converter

15 APPENDIX A SPECIFICATIONS Following are specifications for the Model Velocity-to-Displacement Converter: Input Transducer Type 3-wire velocity Seismoprobe Model Output Scale Factor 100 mvi mil (3.9 VImm) :t2% displacement with 500 mv/in.lsec input Frequency Range 300 to 60,000 rpm Power Requirement -16 to -26 Vdc (V T); -24 Vdc nominal. 20 ma max normal operation, 46 ma max with signal input and output both shorted to ground. Calibration Resistor Fixed, factory calibrated. Supply Voltage Rejection Ratio 60 db Input Amplitude Range 0 to 8 volts peak-to-peak. Output Amplitude Range 0 to 3.7 volts peak-to-peak. Output Bias 6.1 V :t 1.3 Vdc Output Impedance 50 Ohms Failure Modes An open or short in the velocity pickup or field wiring causes the output bias voltage to go within 6.4 volts volts of of VT' common. or to Other within shorts 1. 5 or improper connections are not necessarily indicated.

16 Current Limiting Output is current limited to 30 ma. Case Isolation Case isolated from circuitry at greater than 20 megohms at voltage less than 30 Vdc. Operating and Storage Temperature -58 F to 212 F ( -50 C to 100OC) Thermal Radiation Mounting Weight Case Drift Resistance Dimensions Less than 3% over operating temperature ranges. One V-D C9nverter was type-tested to 3.4 x 10 rads (air). Change in scale factor was approximately 400%. Unit was able to be recalibrated after above exposure. See Figure kg (10.7 oz) 300 series stainless steel Calibration Terminals Gold plated Calibration Terminal Insulator Nylon Barrier Label Strips Glass reinforced polyester Mylar and acetate