Part Number 40585-01 Rev. H (09/07)

Installation Manual

37506A Digital Tachometer

37506A Digital Tachometer Installation Manual

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Copyright © 1988 Bently Nevada LLC All rights reserved.

The information contained in this document is subject to change without notice. The following are trademarks of General Electric Company in the United States and other countries: ACM, Actionable Information, Actionable Information to the Right People at the Right Time, ADRE, Asset Condition Management, Asset Condition Monitoring, Bently ALIGN, Bently BALANCE, Bently DOCUVIEW, Bently LUBE, Bently Nevada, Bently PERFORMANCE, Bently RELIABILITY, CableLoc, ClickLoc, Data Manager, Decision Support, DemoNet, Dynamic Data Manager, Engineer Assist, FieldMonitor, flexiTIM, FluidLoc, Helping You Protect and Manage All Your Machinery, HydroScan, HydroView, Key ∅, Keyphasor, Machine Condition Manager 2000, MachineLibrary, Machine Manager, MicroPROX, Move Data, Not People, Move Information, Not Data, NSv, Prime Spike, PROXPAC, Proximitor, REBAM, RuleDesk, SE, Seismoprobe, Smart Monitor, Snapshot, System 1, System Extender, TDXnet, TDIXconnX, The Plant Asset Management Company, TipLoc, TorXimitor, Transient Data Manager, Trendmaster, TrimLoc, Velomitor Contact Information The following ways of contacting Bently Nevada are provided for those times when you cannot contact your local representative:

Mailing Address 1631 Bently Parkway South Minden, Nevada USA 89423 USA

Telephone 1.775.782.3611 1.800.227.5514

Fax 1.775.215.2873 Internet www.ge-energy.com/bently

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Additional Information

Product Disposal Statement Customers and third parties, who are not member states of the European Union, who are in control of the product at the end of its life or at the end of its use, are solely responsible for the proper disposal of the product. No person, firm, corporation, association or agency that is in control of product shall dispose of it in a manner that is in violation of any applicable federal, state, local or international law. Bently Nevada LLC is not responsible for the disposal of the product at the end of its life or at the end of its use.

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Contents

Section 1 — Description and Operation ...............................................1 Bently Nevada Catalog Number ................................................................................................ 1

Section 2 — Installation..........................................................................2 General......................................................................................................................................... 2 Receiving, Inspection, Handling, And Storage .............................................................................. 2 Probe Installation Procedures ........................................................................................................ 3 Tach Driver / Proximitor® Installation.......................................................................................... 6 Tachometer Installation................................................................................................................. 6

Section 3 — Calibration and Maintenance ...........................................8 Events/Revolution Range Programming........................................................................................ 8 Transducer/Input Power Options ................................................................................................... 9 Condition Circuits (Hysteresis and Threshold) ............................................................................ 10

Section 4 — Troubleshooting ..............................................................11 Field “Pitfalls” ............................................................................................................................ 11

Section 5 — Circuit Flow Diagram ......................................................13

Section 1 - Description and Operation

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1. Description and Operation The Bently Nevada 37506A Digital Tachometer numerically displays revolutions per minute (rpm) of rotating shafts. The input to the tachometer is supplied from either a special probe/tach driver or a probe/Proximitor transducer configuration provided by Bently Nevada LLC.

The probe, which must observe a shaft timing mark (such as a keyway, gear, projection, or slot) is an eddy current device that does not contact the shaft.

The tachometer has an internal power supply which optionally provides either +15 Vdc for the tach driver or -18 Vdc for the Proximitor. These power supply options, as well as the source voltage (115 Vac, 60 Hz or 220 Vac, 50 Hz) are field selectable via internal jumpers inside the tachometer.

1.1.1 Bently Nevada Catalog Number 37506-AXX A: Power Requirement

0 1 115 Vac, -18 Vdc Proximitor, Louvered Display

0 2 115 Vac, +15 Vdc Tach Drive, Louvered Display

0 3 220 Vac, -18 Vdc Proximitor, Louvered Display

0 4 220 Vac, +15 Vdc Tach Drive, Louvered Display

0 5 115 Vac, -18 Vdc Proximitor, Non-Louvered Display

0 6 115 Vac, +15 Vdc Tach Drive, Non-Louvered Display

0 7 220 Vac, -18 Vdc Proximitor, Non-Louvered Display

0 8 220 Vac, +15 Vdc Tach Drive, Non-Louvered Display

The tach driver or Proximitor provides an RF signal that radiates from the probe tip. The notch, projection, or gear passing by the probe tip creates a pulse at the output of the tach driver or Proximitor that is connected to the input of the tachometer.

The tachometer contains an input board that conditions the tach input signal for the period counter. Programming for the events per revolution range is accomplished by field adjustable switches for 1 through 99 events per turn of the shaft. Also, a hysteresis adjustment is provided to avoid false triggering of the tachometer by vibration or runout of the observed surface. Refer to Section 3 for the location of the switches and the procedures for setting events per revolution range programming and hysteresis.

After proper installation, the tachometer provides continuous rpm display without further adjustment. There are no operational controls for the tachometer.

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2. Installation 2.1 General

The following is required for a complete tachometer installation. Item Quantity

37506A Tachometer 1 Tach Driver TD 15A or Proximitor (3300XL, 3300 or 7200 series). 1 Signal Cable (3-conductor with overall shield). 1 Probe (compatible with Proximitor or tach driver). 1 Extension Cable, Coaxial (matched to the probe and tach driver, or probe and Proximitor).

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This section contains receiving inspection, handling, and storage procedures, and installation procedures for installing the tachometer, the probe, extension cable, and the tach driver or Proximitor, which are normally shipped as separate units and must be interconnected at the installation site by the user.

2.2 Receiving, Inspection, Handling, And Storage All equipment should be removed from shipping containers and visually inspected to ensure there is no shipping damage. If shipping damage is apparent, file a claim with the carrier and submit a copy of the claim to Bently Nevada. Include the part number and serial numbers on all correspondence.

If no damage is apparent and the equipment is not going to be used immediately, Bently Nevada recommends returning the equipment to the shipping container and resealing. The equipment should be stored in an environment free from potentially damaging conditions such as high temperature, excessive humidity, or a corrosive atmosphere.

The equipment is durable; however, reasonable handling care should be exercised during installation. When cable connectors are part of the equipment, they must be properly protected from physical abuse or contamination by oil, water, or other substances. Wrap the connector with Teflon tape to prevent damage either during storage or during installation.

Section 2 - Installation

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2.3 Probe Installation Procedures The probe should, if possible, be mounted on a radial plane. The axial motion of the shaft might produce a voltage sufficient to trigger the tachometer counting circuit and provide an inaccurate rpm display.

Probe size and shaft characteristics must be selected to provide maximum accuracy of the tachometer. In general, the smaller the shaft, the smaller the probe should be. See Table 2-1 for detailed dimensions of the trigger notch/hole based on the probe.

Table 2-1. Probe Type and Shaft Characteristics

Shaft Marker Dimensions

Probe* Hole Notch Gap (mils, Vdc) 125 0.2" dia x

80 mils deep Slot 0.20" x 0.40" x 80 mils deep

10 – 20 mils

190 0.3" dia x 80 mils deep

Slot 0.30" x 0.50" x 80 mils deep

20 – 50 mils, -4 to –10 Vdc

300 0.5" dia x 80 mils deep

Slot 0.45" x 0.65" x 80 mils deep

20 – 50 mils, -4 to –10 Vdc

7200, 3300 and 3300XL**

0.5" dia x 100 mils deep

Slot 0.50" x 0.70" x 100 mils deep

10 – 80 mils**, -1 to –15 Vdc

Gear/Projection Minimum Maximum All All Tooth Width =

1/2 Tooth width = Tip

All All Tooth Spacing = Tip

Tooth Spacing = 2 x Tip

Same as above

* Check the availability of probes prior to requesting Technical Support or additional systems. Some probes listed may be obsolete and no longer supported, but are noted for informational purposes. ** The linear range of the probes may be reduced due to –18 Vdc supplied from the tachometer.

The probe and tach driver (or Proximitor) operating on eddy current principles produces an output voltage proportional to the gap distance measured between the probe face and the observed surface.

The probe gap distance (Table 2-1) is measured from the nearest point being observed. The probe is supplied with a high frequency RF signal from the tach driver (or Proximitor). The signal sets up an electrical field, which induces eddy currents into any conductive surface with which the field comes into contact.

The tachometer is triggered by pulse type signals from the tach driver. For this reason, the tach driver is calibrated to give the maximum voltage change for each mil of gap change and to ignore low amplitude runout (output is nonlinear with respect to gap change). The shaft mark or gear being observed must be of sufficient size to provide a high voltage spike from the tach driver.

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EXAMPLE: Assume a 3300XL 8mm Proximitor system is observing a shaft with an 80-mil projection. The probe is mounted 25 mils from the projection (the highest point). Since the projection stands 80 mils above the shaft surface, the probe is 105 mils from the shaft surface and the probe output will be more negative than -16 volts. Once per turn, as the projection passes the probe, the voltage will change to approximately -4 volts, producing a signal like the following:

EXAMPLE: With the probe observing a shaft with an 80-mil notch or keyway and probe gap set to 25 mils, the voltage will be approximately –4 volts. Once per turn, as the notch passes the probe, the voltage will change to more negative than -16 volts. The figure below shows the basic signal pattern for a notch.

2.3.1.1 Events/Revolution

If the shaft had a keyway on both sides, the once per turn signal would appear as follows:

Three events would produce three pulses per turn, 10 events would produce 10 pulses per turn, and so on. Each tachometer can be field calibrated to observe a specific number of events per turn. Once calibrated, the probe must see this number of events to record one revolution.

-16 Volts

-4 Volts

-16 Volts

-4 Volts

-16 Volts

-4 Volts

Section 2 - Installation

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2.3.1.2 Probe Mounting

The probe should be mounted at the proper distance from the highest point on the shaft or gear to be observed. It should be mounted on a rigid surface that will not vibrate appreciably. After installation and gapping (preferably with a feeler gauge) the probe should be locked securely in place. If the probe is to observe a projection on the shaft, the gap must be measured between the probe and projection (line up the probe mounting hole before installing the probe). If a notch or keyway is being observed, the gap should be set between the shaft and the probe face.

The notch, keyway, or projection, should be at least 80 mils deep and at least one and one half times as wide as the probe.

DO NOT mount the probe over a notch or gear teeth that are narrower than the probe face. This will reduce the pulse required to trigger the tachometer.

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2.4 Tach Driver / Proximitor Installation The tach driver or Proximitor is factory calibrated to the probe tip size, the observed material, and 15 electrical feet of probe lead and extension cable. The 95-ohm extension cable is articulated at one-foot physical length for each foot of electrical length. The 50-ohm probe lead is roughly calculated at two electrical feet for each physical foot of length.

EXAMPLE: For a probe with 1 1/2 feet of probe lead (three electrical feet) a 12 foot 95 ohm extension cable must be used with the TD15A, the 3000 and 7200 series proximitors. 7200 Series probes use 95-ohm cable where electrical feet equals physical feet. 3300 Series probes use 75-ohm cable where electrical feet equals physical feet.

As an option, other electrical cable lengths are available with TD15A or Proximitors. Cabling from the tach driver or Proximitor to the tachometer should be three wire # 22 AWG, or larger, shielded cable.

2.5 Tachometer Installation The tachometer is designed for panel mounting. Figure 2-1 shows the panel cutout required. The tachometer is cantilever-mounted with support bolts required only at the faceplate. The faceplate of the tachometer is made weatherproof by the gasket provided.

Figure 2-1 Panel Cutout

Section 2 - Installation

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Power required is 95 to 125 Vac, 60 Hz, or 195 to 250 Vac, 50 Hz depending upon the option selected. Power connections are made at the rear of the tachometer (see Figure 2-2).

Note: The rear of the tachometer, behind the faceplate, is not

weatherproof.

Figure 2-2 System Interconnect

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3. Calibration and Maintenance 3.1 Events/Revolution Range Programming

Events/revolution are determined by switches Sl and S2 (refer to Figure 3-1). From one through 99 events/turn are available. Sl is the most significant digit (MSD), S2 is the least significant digit (LSD).

Minimum rpm = 50/events per turn.

Example: at one event per turn, minimum rpm = 50

at 50 events per turn, minimum rpm = 1

Maximum rpm = 468,000/events per turn

Example: at five events per turn, maximum rpm = 93,600

at one event per turn, maximum rpm = 468,000

(Display will read 68, 000)

At any intermediate value, rpm = input frequency (Hz) x 60/events per turn.

Figure 3-1 Switch and Option Jumper Locations

SWITCHES

S2

JUMPER LOCATIONS

W1B

W1A

W1C

W2B

W2A

S1

Section 3 - Calibration and Maintenance

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3.2 Transducer/Input Power Options Programming for transducer options is accomplished by jumper according to Table 3-1. These options should be installed by Bently Nevada personnel.

Jumper positions are shown in figure 3 -1.

Table 3-1. Transducer Option Programming

Option Display Option

Probe Interface System*

Transducer Voltage ± 5%

Input Power

Jumper installed

-01 Louvered 3000 Series 7000 Series 3300 Series** 7200 Series** 3300XL Series**

- 18 Vdc 115 Vac W1A W1B W2A

-02 Louvered TD15A + 15 Vdc 115 Vac W1A W1B W2B

-03 Louvered 3000 Series 7000 Series 3300 Series** 7200 Series** 3300XL Series**

- 18 Vdc 220 Vac W1C W2A

-04 Louvered TD15A + 15 Vdc 220 Vac W1C W2B

-05 Non-Louvered 3000 Series 7000 Series 3300 Series** 7200 Series** 3300XL Series**

- 18 Vdc 115 Vac W1A W1B W2A

-06 Non- Louvered TD15A + 15 Vdc 115 Vac W1A W1B W2B

-07 Non- Louvered 3000 Series 7000 Series 3300 Series** 7200 Series** 3300XL Series**

- 18 Vdc 220 Vac W1C W2A

-08 Non- Louvered TD15A + 15 Vdc 220 Vac W1C W2B

* Check the availability of probes prior to requesting Technical Support or additional systems. ** 3300XL, 3300 and 7200 Series Proximitor use -24 Vdc. -18 Vdc is compatible for these transducers when intrinsic safety barriers are not used. Tachometer will accept input from Proximitor powered from external -24 V dc supply.

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3.3 Condition Circuits (Hysteresis and Threshold) The 37506A incorporates an automatic threshold adjustment circuit. There is no manual adjustment for threshold. The variable hysteresis resistor (R10) is accessible through the side of the tachometer (Figure 3-2). It has been factory adjusted for noise immunity, which should be adequate for most all vibration and runout. Should there be an excessive amount of noise at the tachometer inputs, this resistor can be adjusted in a clockwise direction to increase the hysteresis to a maximum of two volts.

If the triggering level is misadjusted, erratic or erroneous readings will be displayed. While watching a constant speed, adjust Rl0 until a stable, reasonable reading appears on the display.

Figure 3-2 Hysteresis Adjustment Access Hole

Section 4 - Troubleshooting

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4. Troubleshooting The digital tachometer is constructed of high quality components to give dependable service. Occasionally a malfunction may occur due to rough usage. If a malfunction occurs, and all external connections are secure, do not attempt to troubleshoot the digital tachometer. Check continuity of all external connections. If the digital tach still malfunctions, return it, along with a description of the problem, to the nearest Bently Nevada field service office.

4.1 Field “Pitfalls” The following list describes the most common problems or “pitfalls” found by our servicemen in the field.

1. Probes mounted at an extreme angle from the perpendicular to the centerline of the shaft.

2. Insufficiently rigid probe mounting brackets, resulting in resonance within the frequency of interest and of large amplitudes.

3. Conduit attached to a small probe body, putting excessive strain on the body.

4. Probes gapped incorrectly.

5. Insufficient protection of the probe lead and the extension cable.

6. Poor oil seals in the probe cable conduit, filling the Proximitor housing with lube oil.

7. Screwing in the probe with the extension cable connected to the probe, resulting in broken wires, etc.

8. Improper length of probe extension cables for a particular probe lead length and Proximitor type.

9. Probe cables coming from a common conduit with no identification, resulting in probe/Proximitor/tach driver cross wiring.

10. Use of the Proximitor to tachometer cables shield as common conductor, resulting in ground loops.

11. Proximitor/tach driver to tachometer cable running parallel to power lines, with shield not grounded, resulting in ac pickup problems.

12. Cross wiring between the Proximitor/tach driver and tachometer.

13. Loose wire shorting to the Proximitor/tach driver.

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14. Steam condensing in the Proximitor/tach driver housing, causing a short circuit.

Section 5 - Circuit Flow Diagram

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5. Circuit Flow Diagram