4C-9437 Portable Hydraulic Tester , 1U-8761 Portable Hydraulic Tester (Canceled), 4C-9675 Portable Hydraulic Tester , 1U-9951 Portable Hydraulic Tester (Canceled){0599, 0738} Caterpillar

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Introduction

Important Safety Information

Illustration 1	g02139237
Think Safety

European Union Compliant, CE marked

Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools to perform these functions properly.

Improper operation, lubrication, maintenance, or repair of this product can be dangerous and could result in injury or death.

Do not operate or perform any lubrication, maintenance, or repair on this product until you have read and understood the Tool Operating Manual.

Safety precautions and warnings are provided in this manual and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons.

The hazards are identified by the "Safety Alert Symbol" and followed by a "Signal Word" such as "DANGER", "WARNING", or "CAUTION". The Safety Alert "WARNING" label is shown below.

A non-exhaustive list of operations that may cause product damage are identified by "NOTICE" labels on the product and in this publication.

Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The warnings in this publication and on the product are, therefore, not all inclusive. If a tool, procedure, work method, or operating technique that is not recommended by Caterpillar is used, the operator must be sure that the procedures are safe. The operator must also be sure that the product will not be damaged or made unsafe by any unspecified procedures.

The information, specifications, and illustrations in this publication are based on information that was available at the time that the publication was written. The specifications, torques, pressures, measurements, adjustments, illustrations, and other items can change at any time. These changes can affect the service that is given to the product. Obtain the complete and most current information before you start any job.

When replacement parts are required for this product Caterpillar recommends using Caterpillar replacement parts or parts with equivalent specifications including, but not limited to, physical dimensions, type, strength, and material.

Literature Information

This manual contains safety information, operation instructions and maintenance information and should be stored with the tool group

Some photographs or illustrations in this publication may show details that can be different from your service tool. Guards and covers might have been removed for illustrative purposes.

Continuing improvement and advancement of product design might have caused changes to your service tool, which are not included in this publication.

Whenever a question arises regarding your service tool or this publication, consult Dealer Service Tools (DST) for the latest available information.

Safety Section

The Safety section lists basic safety precautions.

Read and understand the basic precautions listed in the Safety section before operating or performing maintenance and repair on this service tool.

General Information Section

The General Information section describes tooling functions and features. The section provides useful information on individual parts, additional tooling, and resources.

Operation Section

The Operation section is a reference for the new operator and a refresher for the experienced operator.

Photographs and illustrations guide the operator through correct procedures for using the tool group.

Operating techniques outlined in this publication are basic. Skill and techniques develop as the operator gains knowledge of the service tool and the tools capabilities.

Maintenance Section

The Maintenance section is a guide to tool inspection, cleaning, storage, and tool disposal

Service Parts Section

The Service Parts section is a reference for parts identification and available part numbers.

Safety Icon Nomenclature

Personal Protection/Important Information

Illustration 2	g02166423
Personal Protection/Important Information

Prohibited Action

No smoking

Hazard Avoidance

Crushing hazard (foot)

Crushing hazard (hand)

Pinch point

Fire hazard

Electrical Shock - Hazard

Fire hazard

Safety Section

Show/hide table

At operating temperature, the hydraulic tank is hot and under pressure. Hot oil and components can cause personal injury. Do not allow hot oil or components to contact skin. Remove the filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand. Remove the filler cap slowly in order to relieve pressure.

Show/hide table

Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

General Information Section

Introduction

Illustration 3	g02792180

The Hydraulic Testers are made of a number of instruments combined to safely and accurately measure flow, pressure, temperature, and speed. There are four models. The 1U-8761 Portable Hydraulic Tester and 4C-9437 Portable Hydraulic Tester have a threaded inlet and outlet port. The port connection is a 1-5/16-12 UN O-ring boss. Thread type is stamped on the turbine block near the inlet and outlet port. The 1U-9951 Portable Hydraulic Tester and 4C-9675 Portable Hydraulic Tester have a modified SAE-type 1-1/2" flange connection. An O-ring is used as a face seal and the flange held in position by four 1/2" UNC bolts.

Additional Contact Information

For additional product support questions concerning this tool, contact the Caterpillar Dealer Service Tools Hotline at:

Flow

The flow meter consists of an axial turbine mounted in the aluminum base block. The oil flow rotates the turbine and the speed is proportional to the oil velocity. The speed of the turbine is measured by a magnetic sensing head (magnetic reluctance transducer) which transmits a pulse to an electronic circuit. Each pulse is generated by a pass of the turbine blade. The electronic circuit amplifies the pulse and converts to a number of pulses per second. The DC current is read on ammeter which is calibrated in liters per minute or gallons per minute.

Pressure

Pressure Measurement

The tester is fitted with 64 mm (2.5 inch) diameter, 414 bar (6000.0 psi), dual-scale glycerine filled pressure gauge. The pressure gauge is connected to a shuttle valve built into the turbine block with a copper capillary tube. The shuttle valve has a connection to both sides of the Testers loading valve and automatically connects the highest pressure to the pressure gauge. For example, under normal flow conditions, the gauge will measure the pressure in the turbine tube. Under reverse flow conditions, the oil goes through the loading valve and then through the turbine tube. The pressure gauge will measure the oil pressure in front of the loading valve.

Pressure Loading

Resistance to the oil flow can be changed by the pressure loading valve. This valve is not a relief valve but a positive displacement, pressure balanced shut-off valve. Because of the pressure balancing, relief valve can be operated at pressures up to 414 bar (6000.0 psi), with flow in either direction. The valve also incorporates two safety discs described below.

Pressure Protection

Built into the loading valve are two safety discs which will prevent the loading valve from being used for creating excessive pressure. The standard safety discs on the 1U-8761 Portable Hydraulic Tester and 4C-9437 Portable Hydraulic Tester are designed to break at 435 bar (6300.0 psi), on the 1U-9951 Portable Hydraulic Tester and 4C-9675 Portable Hydraulic Tester at 380 bar (5500.0 psi). Safety discs with lower pressure ratings are available. All of the discs are color-coded for easy identification. These discs are precision made and other pieces of metal should never be substituted.

Temperature

Temperature is measured by a precision thermistor which is built into the magnetic reluctance transducer. The thermistor is very close to the oil flow, being separated and protected from the pressure by a thin stainless steel disc. The electrical output from this thermistor is not linear, output is linearized by a Wheatstone bridge circuit incorporated in the Testers printed circuit board. Output can be read on the ammeter which has been calibrated in degrees Celsius.

Speed

The Tester can be used for measuring RPM by using the photo-tachometer or mechanically driven tachometer accessory. The tachometer is connected to the Tester at the DIN socket on the left side of the instrument deck. The photo-tachometer is used for measuring higher speeds, up to 9000 RPM, and the mechanical tachometer for speeds up to 3000 RPM. The RPM range varies a little for different models. When the photo-tachometer is used, two "D" size batteries must be fitted to the auxiliary battery holder, located at the back of the Tester case. The batteries provide power for the photo-tachometer light bulb. The mechanically driven tachometer does not require the additional batteries.

Troubleshooting

If the Tester does not work, the most common problem is no flow reading. Usually no flow reading is due to a battery fault or jammed turbine.

Troubleshooting Procedures

Checking the Battery (for electric circuit)

Turn the selector switch to the "B" test position. See if the needle on the ammeter goes to the right of the "B" line marked on the scale. If not, replace the battery.

To replace the battery, remove the two small pozidrive screws and the battery cover. Battery cover is immediately below the ammeter on the top deck of the instrument. Install a new 9-Volt transistor radio battery. Use an alkaline battery if possible. A carbon-manganese battery will operate the Tester successfully, but has a much shorter shelf life and is inclined to leak in the battery holder. Make sure that the press buttons are clean and free from any corrosion. Replace the battery cover and check.

Do not leave the switch in the "B" test position which can quickly run down the battery. Normal current consumption of the Tester is less than three milliamp, but on the battery test position current consumption has been increased to ten milliamp. Although the battery saving circuit will cut off the supply after approximately 1 hour, a considerable part of the batteries life can be wasted.

Cleaning the Turbine Assembly

Illustration 4	g02792185

If the flow meter still does not work after checking the battery, remove the turbine assembly, see Figure 4.

Take out the circlip with a pair of circlip pliers. Use a pair of soft-nosed pliers, gently grip one of the blades of the turbine flow straightener and pull gently. Do not rotate the assembly. This action can cause one of the flow straightener blades at the rear of the turbine to catch on the magnetic pick-up.

Examine the turbine assembly carefully and see if there are any pieces of O-ring or PFTE tape wrapped round the turbine. Carefully remove any obstruction and wash the whole turbine assembly in an organic solvent such as kerosene or denatured alcohol. Blowing gently alone the axes of the flow straightener should make the turbine spin freely without any vibration. Check that the turbine tube is free from debris. Magnetic particles tend to stick to the end of the transducer.

The corner of one of the blades of the flow straightener has been clipped off at an angle of about 45°, in replacing the turbine assembly. With the Tester horizontal, this blade should be in the 1 o'clock position inside the turbine tube. The bottom of the recess at the inlet port has been staked to provide two small ridges. The blade should be placed between the ridges preventing the complete turbine assembly from being rotated by flow forces.

Put the turbine back in the correct rotational position. Rotating the assembly can change the distance between the tip of the turbine blades and the face of the magnetic pick-up. The gap can be too large resulting in a signal that is too weak and the Tester will not give good low flow readings. Alternatively, the turbine blades may come too close to the transducer and accuracy will be affected by magnetic detenting. In extreme cases, blades may actually touch the face of the transducer so that the turbine will not spin.

Checking the Magnetic Reluctance Transducer

To carry out the necessary tests and adjustments to the transducer, the instrument panel assembly must be removed from the Tester.

Loosen the six pozidrive head screws and lift the panel above the box 2 to 3 cm (0.79 to 1.18 inch). Lifting panel will allow access to the nut that connects the capillary tube to the bottom of the pressure gauge. You can hold the instrument deck above the box by using two small pieces of wood. Two sticks, approximately 2 x 2 cm (0.79 x 0.79 inch) and about 25 cm (9.84 inch) long will work.

Disconnect the capillary tube from the pressure gauge. (Use a 5/8" across flats spanner on the nut and a 9/16" across flats spanner on the gauge.) Lift the deck clear. The printed circuit board, which is attached to the underside of the deck, will still be connected to the magnetic reluctance transducer. The transducer sticks out from the top surface of the turbine block. Disconnect the wires by removing the insulating tape around the DIN plug and socket and gently pull the two apart.

Illustration 5	g02792188

Connect a multimeter to pins 2 and 3 on the transducer socket. Measure the resistance of the transducer coil which should be approximately 3,000 ohms. If the resistance is low, the coil has shorted out. If high, a wire has probably broken. Make sure that the DIN socket is properly soldered to the wires from the transducer. The plastic sleeve can be easily slid back if the small metal clip is depressed, allowing access to the soldered connections. Repairing a broken transducer is not practical. A new one should be installed, see Section ""Installing a New Transducer" ". After a new transducer assembly has been screwed into position, adjust transducer, see ""Adjusting the Magnetic Reluctance Transducer" ".

Adjusting the Magnetic Reluctance Transducer

Another reason for no flow may be the magnetic reluctance transducer is not adjusted properly. If the ammeter works correctly on the battery check, and the turbine runs freely, the problem is in the wiring, electronic circuit, or transducer.

To check the transducer, be sure that transducer is correctly adjusted. Adjustment is critical to the accuracy of the flow measurement. To ensure correct adjustment, reconnect the DIN plug and socket so that the signal can show on the ammeter. Turn the selector switch to "flow". Loosen the outer hexagon sleeve nut of the transducer (use a 1" across flats spanner) and turn counterclockwise about half a turn. Using an air line, blow a small quantity of compressed air into the inlet port of the turbine tube so that the turbine spins freely. Make sure that the loading valve is open. If the valve is closed, the air can go down one side of the turbine tube and back-up the other. Effectively trying to rotate the turbine in opposite directions, so turbine does not turn at all.

Turn the transducer body clockwise. Body has 13/16" across flats hexagon. As the transducer approaches the turbine blades, a signal should begin to register on the ammeter. Continue turning the transducer until the face of the transducer eventually comes into contact with the tip of the turbine blades. Do carefully otherwise the turbine bearing can be damaged or the spindle bent. The turbine will immediately stop, there will be no signal to the ammeter. The needle will quickly go back to zero.

The transducer should be rotated back about 1/8 turn or 45° counterclockwise to give the correct clearance to the turbine. Holding the turbine boy firmly in position, tighten the outer hexagon sleeve. Do not over tighten the hexagon sleeve nut, there is the possibility of stretching the body of the transducer, resulting in failure.

Illustration 6	g02792191

Illustration 7	g02792192

To check the sensitivity of the transducer, blow a small amount of air through the turbine. Measure the minimum steady reading that can be obtained on the ammeter. On both the "hi" and "lo" scales, this measurement should not be more than the bottom 4% of the scale. A 1U-9951 Portable Hydraulic Tester or 4C-9675 Portable Hydraulic Tester on "hi" should read down to 20 L/min (5.3 US gpm).

If the minimum reading cannot be obtained slide back the plastic sleeve on the DIN socket or plug. With the two halves still connected, attach a voltmeter to pins 2 and 3. Switch to the "lo" flow setting and spin the turbine with air so that the ammeter shows maximum flow.

The voltmeter should indicate at least 1 V and could be considerably more. If you get a 1-Volt-plus reading, try adjusting the transducer closer to the turbine to see of the minimum reading can be obtained. Disconnect the voltmeter before varying out this test as test can reduce the signal going to the Testers electronic circuit. How much effect the voltmeter would have depends upon the input impedance. If the 1-Volt reading cannot be obtained or adjusting the transducer to get the required minimum reading, is impossible, the transducer should be replaced.

Checking the Ammeter

Flow and RPM are displayed on a 100 microamp moving coil ammeter mounted on top of the instrument panel. The ammeter is sturdily constructed and will take shocks up to 100 g without damage. However, if the Tester is dropped, Tester can be damaged.

If the Tester has a good battery, and the needle on the ammeter does not move when the selector knob is turned to the "B" test position, ammeter is broken. Confirmed by gently shaking the Tester. If the needle does not move or moves in a sluggish manner, the ammeter should be replaced.

To install a new ammeter, remove the instrument panel of the Tester, see Section ""Checking the Magnetic Reluctance Transducer" ". Loosen the three small hexagon nuts. One of the nuts also supports the PCB bracket. Disconnect the wires from the two terminals. Install a new ammeter with the correct scale. The pin wire goes to the "+" terminal, the green/black wire to the other. If the wires are connected incorrectly, the meter will try to read backwards. After installing a new ammeter, the Tester must be recalibrated, see Section ""Recalibrating the Flow Meter" ".

Recalibrating the Flow Meter

After installing the ammeter, the flow and RPM meter sections of the Tester must be recalibrated.

A label with the appropriate meter factors for the instrument is on the underside of the instrument panel. There are a number of Hz for a given flow rating on both "high" and "low" flows. A similar frequency rating for the tachometer circuit. If for any reason this information is missing, the frequency figures can be supplied by Caterpillar Service Technology. The serial number stamped on the side of the turbine block is needed.

Illustration 8	g02792282
Tester Calibration of Electronic Circuits

To recalibrate the flow and RPM meters, connect the DIN plug, which connects to the transducer, to an appropriate frequency generator. A standard audio frequency generator is not accurate enough. Accuracy should be better than ±0.5 Hz. Caterpillar can supply an 8T-5200 Frequency Generator which includes appropriate connecting leads. Figure 8 shows how to connect the 8T-5200 Frequency Generator .

Apply a frequency to pins 2 and 3. Turn the selector switch to the required scale and frequency as shown on the label applied to the circuit. Adjust the ammeter reading with one of the four potentiometers mounted on the edge of the printed circuit board. These potentiometers are shown clearly on drawing FT2312A and Figure 8. The adjustment screws on these potentiometers are locked in position with a small quantity of silicone rubber. The silicone rubber is easily removed. After adjustment, the screws should be relocked to prevent any possibility of movement due to vibration. A silicone rubber used for sealing the edge of bathtubs is suitable. Small tubes of this silicone rubber manufactured by Dupont are widely available.

If the turbine has been replaced, the Tester must be recalibrated on a flow calibration stand. Oil at a known flow rate must be passed through the Tester and the potentiometer adjusted so that the ammeter shows the correct reading. Factory calibration is carried out with oil at 46° C (114.8° F), viscosity 28 centistokes.

The Electronic Circuit

Illustration 9	g02792288

Illustration 10	g02792289

Illustration 11	g02792290

A problem in the electronic circuit, is difficult to find and can be very time consuming. Installing a new printed circuit board which is supplied complete with wire harness is easier and cheaper to install. Figures 10 and 11 show the wiring color code for soldering to the wafers on the selector switch. A complete description of the electronic circuit, however, follows.

Drawing FT1993, Figure 9 shows the basic schematic layout of the electronic circuit that is used in Caterpillar portable flow meters. The circuit carries out the following functions:

• Stabilized power supply

• Wheatstone bridge circuit for temperature measurement

• Schmitt trigger and mono-stable for pulse counting

• Timer for switching battery off made up of oscillator, counter, and switch.

Stabilized Power Supply

Components (see Figure 9): (IC4A), (D4), (R15), (R16), (R17), (R27), and (C11)

Item (D4) is a band-gap reference diode which is used to set up a reference voltage across the operational amplifier (IC4A). The voltage at which the amplifier is set is determined by voltage divider made up of resistors (R16) and (R17). This circuit is set to give a precise 4-volts output. This voltage will remain stable over a fairly wide range of input voltage, load, and temperature conditions. The circuit automatically takes care of the change in voltage from the battery as power is consumed. The circuit is efficient, the total power loss being around 9 mw. (R27) is a high value resistor which ensures that (IC4A) always turns on. (C11) is fitted as a precaution to prevent (D4) from oscillating.

Wheatstone Bridge Circuit for Temperature Measurement

Components (see Figure 9): (R18), (R20), (R21), (R22) and (R23), (RV4) and (IC4B)

(R22) and (R21) make up one pair of legs of the bridge and have equal values. (R20) and (R18), the thermistor which is not shown, make up the other leg of the bridge. (R18) is a resistor in series with the thermistor and is used to give better linearity. The thermistor is incorporated inside the magnetic reluctance transducer and is close to the oil flow and therefore sensitive to the oil temperature.

The 4-Volt output from the stabilized power supply is too high for the bridge circuit. Ay this level high power can cause self-heating of the thermistor. The voltage is reduced to the appropriate level by (IC4B). This operational amplifier is used with variable resistor (RV4) to calibrate the bridge circuit by adjusting the voltage level to the appropriate value.

The ammeter, calibrated in degrees C, is connected by appropriate switches across the bridge to the junctions of (R21) / (R20) and (R22) / (R18). (R23) is a ballast resistor for the meter. Change in resistance of the thermistor with temperature is not linear. The use of the Wheatstone Bridge Circuit enables a more linear output to be achieved.

Schmitt Trigger and Mono-stable for Pulse Counting

Schmitt Trigger Components (see Figure 9): (IC4C), (R10), (R11), (R12) and (R13), (R14) and (C4)

Mono-stable Components (see Figure 9): (IC5), (C1), (C2), (D3), (R7), (R6), (R3), (R4), (R5), (RV1), (RV2), and (RV3)

Flow measurement is carried out by monitoring the speed of an axial turbine which is rotated by the oil flow. The turbine speed has a nearly linear relationship with the oil velocity. As the cross-sectional area of the oil is constant over a wide range of velocities. The turbine speed can be directly related to rate of flow. The turbine speed is monitored by a magnetic reluctance transducer. The transducer gives an output in the shape of a sine wave each time a turbine blade passes the face. The frequency of this sine wave is therefore directly related to the turbine speed.

The sine wave is fed into the Schmitt trigger circuit. The sine wave input turns the amplifier (IC4C) on and off for both positive and negative parts of the sine wave. Inputs create a clean, square wave output. The output is differentiated into a spike by the capacitor (C3) and the balancing resistors (R8) and (R9). The spike is used to trigger the mono-stable.

(IC5) gives a regular pulse output whose height (voltage) is determined by the stabilized power supply. The length (time) is controlled by capacitor (C1) and the resistors (R3), (R4), (R5) and (RV1), (RV2) and (RV3) .

The resistors are used in pairs for three switchable circuits. These pairs allow the mono-stable output to be calibrated for different settings depending upon the way (RV1), (RV2), and (RV3) are adjusted. Each pulse coming from the mono-stable for a given setting will have a constant amount of energy. The number of pulses will be directly proportional to input frequency and therefore to the turbine speed. These pulses are fed directly to an ammeter which is connected between the negative rail and the junction of resistors (RV6) and (RV7). The pulses are integrated by the meter movement and the meter deflection is directly proportional to the turbine speed and therefore flow rate.

Timer for Switching Battery Off

The timer is made up of an oscillator, counter, and switch.

• Oscillator

Components (see Figure 9): (IC1A) and (lC1B), (C9), (C10), (R23), (R24)

The first part of the timer is made up of an oscillator. The output of the oscillator is fed to the counter (IC2) .

• Counter

Components (see Figure 9): (IC2), (lC1C), (lC1D), (C8), and (R25)

(IC2) is a 14-bit binary counter which is set to zero when the circuit is first turned on. The output from the oscillator is counted by (IC2). When count reaches 8192 (2¹³), (IC1C) and (IC1D) are reversed to give an output to the switch which disables the oscillator.

• Switch

Component (see Figure 9): (IC3)

(IC3) is a quad bilateral gate which is connected in parallel to provide the necessary current-carrying capacity. An output from the counter circuit brings all these gates high and interrupts the battery voltage to the circuit.

Note: Components (C6), (C2), and (C7) are used for decoupling purpose. R1 and R2 are used as a voltage divider and load when checking battery voltage. (D1) protects the circuit in case the battery is connected incorrectly.

Temperature

If the unit reads low, but fails to show the temperature when the switch is turned to the appropriate position, there is an electrical problem. A fault may have developed in the wiring, a wire may have come loose from the selector switch. A fault may develop if one of the wires coming out of the transducer in which the temperature measuring thermistor is buried has broken. A fault may also develope if there is a problem in the electronic circuit which may mean replacing the electronic circuit.

To ensure that the temperature circuit is correctly adjusted and the thermistor is in good order, perform the following tests.

Disconnect the DN plug and socket between the transducer and the printed circuit board. On the plug half, connect a 10,000 ohm, half-perecent-accuracy resistor across pins 1 and 2 (see Figure 11) to the wire that connects to the printed circuit board. Turn the selector switch to "temperature" and the ammeter should read 50.5°C. If the reading is incorrect, make adjustments by turning the potentiometer on the edge of the printed circuit board, see Figures 8 and 9.

To check the thermistor, connect an accurate avometer or multimeter to pins 1 and 2 on the socket. The half that is connected to the transducer. Measure the resistance. The resistance for the appropriate temperature is shown in Table 2.

Installing a New Transducer

Remove the instrument panel assembly, see Section ""Checking the Magnetic Reluctance Transducer" ". Loosen the hexagon sleeve nut (turn counterclockwise) with a 1" across flats spanner. Remove the transducer and sleeve by turning the transducer body counterclockwise with a 13/16" across flats spanner.

Before installing the new transducer, make sure that the internal O-ring is inserted inside the hexagon sleeve nut. Replace the copper washer between the top of the turbine block and the hexagon sleeve nut. The transducer must be adjusted to the correct position. See Section ""Adjusting the Magnetic Reluctance Transducer" ". Do not over tighten the hexagon sleeve nut. Overtightening might stretch the transducer body and separate the magnet from the core of the coil and make the transducer inoperative. After the transducer has been locked into the correct position, pressure test the turbine block. Make sure no oil leaks past the transducer into the instrument box. See Section ""Pressure Test" ".

Checking the Pressure Gauge

If the pressure gauge does not indicate pressure or is suspected of registering the incorrect pressure, remove gauge from the Tester. Check gauge on a comparator, dead weight machine, or with the 5P-8558 Calibration Group .

To remove pressure gauge, remove the instrument panel see Section ""Checking the Magnetic Reluctance Transducer" ". Loosen the two long clamp screws with a screwdriver. Rotate the clamp until the square hole in the clamp is in line with the square boss of the pressure gauge.

Pressure Test

Connect the pressure gauge, which has a 1/4"-19 BSPF thread, to a comparator or dead weight tester. Check at 10%, 50%, and 90% of the scale. All the readings should be within ± 1.6% of the full scale reading.

If the pressure gauge is properly calibrated, check the capillary tube that connects the pressure gauge to the turbine block for contamination. Remove the two recessed hexagon plugs. One on the loading valve end of the turbine block, the other on the back of the turbine block near the outlet port. These two plugs are item (29) on assembly drawing FT2218A. Remove any contamination and wash through with denatured alcohol.

When replacing the capillary tube or pressure gauge, replace the small copper washer that forms the seal, item (1.1), part no. FT0804.

Changing the Safety Discs

Illustration 12	g02792296

Illustration 13	g02792297

If the loading valve fails to change the pressure when oil is being pumped through the Tester, replace the safety discs. Remove the complete loading valve assembly from the turbine block.

Remove the four screws that hold the flange to the side of the turbine block, see Figure 12 and 13. Gently pull out the complete assembly. In a vice gently grip the 30mm diameter of the valve poppet, the cylindrical part with the two slots. Unscrew the hexagon-head safety disc holder (5/8" on 1U-9551, 4C9675 11/16" on 1U8761 and 4C9437). Underneath, there should be two safety discs separated by a disc spacer.

Remove the damaged discs and install two new discs with the correct pressure rating. The safety discs are supplied flat, gently form in the hand to a truncated cone shape by needing discs round the disc spacer. Drop the first one in position. Place the disc spacer on top. Put the second safety disc in position and screw the safety disc holder, which also has an internal conical shape, in position on top. Do not over tighten. The maximum torque required is 55 N·m (40.6 lb ft). Over tightening the safety disc holder can cause the safety discs to fail at a lower pressure. Do not substitute other pieces of metal. Safety discs are carefully controlled during manufacture to ensure bursting at the correct pressure.

Two discs must be used. When flow is reversed through the Tester, pressure is applied to the opposite face of the disc. One disc will quickly fatigue and fail at much lower than normal bursting pressure. When pressure is applied to the safety disc, disc deforms away from the pressure. Pressure then applied to the opposite side, buckles the small bulge back in the opposite direction. This work hardens the material and results in abrupt and quick fatigue failure. When two discs are used, discs bulge in towards one another with an air gap between them.

When replacing the loading valve assembly in the aluminum turbine block, note that there is a pin protruding inside the cavity. The pin must line up with one of the slots cut into the loading valve poppet to prevent the loading valve poppet from rotating. Make sure O-ring (3.8), is in good condition. O-ring fits under the flange of the loading valve and at the edge of the cavity in the turbine block. Replace if necessary.

Loading Valve

Illustration 14	g02792307

The loading valve is a pressure-balanced shutoff design. Figure 14 shows a cross section of the valve. The valve poppet (21) can be moved into the outlet port of the turbine block to restrict or completely block the flow. The poppet is prevented from rotating by the plug (37) and is moved backwards and forwards by the spindle (3.6) .

The spindle has a left and thread for normal opening and closing. When the spindle is rotated clockwise, the valve closes. The spindle has a small collar and is held in its axial position by two small thrust bearings. One on either side of the collar. Pressure balancing is achieved by equalizing the pressure on both ends of the valve poppet. The small angled hole which comes through to the bottom of the left hand threaded hole allows the necessary transfer of fluid. The fluid gets to the end of the poppet via a slot cut into the spindle thread. The poppet also contains the safety discs which are described in Section ""Changing the Safety Discs" ".

If loading valve is difficult to turn when the Tester is being used, and at higher pressures the handle becomes almost impossible to turn. A problem with the pressure balancing is indicated. The most likely cause is a blocked pressure balancing hole through the poppet. Cleaned by pushing a small piece of wire through to clear the obstruction. Wash with denatured alcohol and blow through with compressed air from an air line.

Another reason could be a leaking seal (18) at one end of the poppet. This seal is a special low-friction type and a standard O-ring should not be substituted. If the spindle seal (3.9) is leaking, then take the whole bonnet assembly apart to replace. Remove the loading valve assembly from the turbine block and unscrew the poppet (21). Take off the knob (3.1) by first knocking out the spiral pin (3.10) with a 1/8" dia. pin punch. Undo the retaining ring inside the bonnet with a tubular pin spanner. Remove the first thrust bearing and two thrust washers. Pull out the spindle and remove the second thrust bearing and two thrust washers. Remove the bearing ring (3.5) and pull out the seal (3.9). A new seal should be inserted and the procedure described above reversed. Do not tighten the retaining ring (3.12). The spindle should have about 9.25 mm (0.364 inch) axial float.

Checking the Turbine Assembly

To check that the turbine assembly is in good condition, remove the turbine assembly, see Section ""Cleaning the Turbine" ". Blow gently along the straightener blades. The turbine should spin freely. If the turbine bearing is worn, the vibration can be clearly felt with the fingers. If the bearing is faulty, the whole turbine assembly should be replaced. Changing the turbine bearings is possible. Removing the turbine without damaging the spindle or the flow straightener, is difficult. Rebalance the turbine, if necessary.

Assembling The Instrument Box

When assembling the instrument box (5) to the turbine block, a new cork gasket (25) should be used. Apply Loctite screw lock, or similar material, to the screws. Do not over tighten the screws or the gasket may be crushed and extruded between the block and the side of box.

Tachometer

The photo-tachometer and mechanical tachometer use the same pulse counting circuit as the turbine. The photo-tachometer scale on the ammeter is based on the generation of 1 pulse per revolution of the photo-tachometer. If two separate pieces of reflector tape are used on the revolving shaft, the photo-tachometer will get 2 pulses per revolution. The revolution and the reading on the ammeter must be divided by 2.

For the photo-tachometer to function correctly, two 'D' size batteries must be inserted in the battery holder in the side of the case. The positive (+) terminal goes to the battery holder cover. The 'D' cells provide power for the bulb in the photo-tachometer head and also for the photo-tach amplifier. The signal from the light-dependent resistor built into the photo-tachometer head is small. In bright light conditions, the photo-tachometer may appear to work without the 'D' cells. The reading on the ammeter may or may not be correct. Without power to the amplifier, the pulse counting circuit may double count the weak signal.

The mechanical tachometer gives a good electrical output of 3 pulses per revolution and no battery is required.

The tachometer circuit can be calibrated in the same way as the flow circuit, see Section ""Recalibrating the Flow Meter" ". In place of a frequency generator, the photo-tachometer head can be pointed at a fluorescent light. If the mains frequency is 50 Hz, the ammeter should read 6,000 RPM and for 60 Hz, 7,200 RPM.

Service Tools

In addition to the usual small tools, the following are required:

Illustration 15	g02792308

• To remove instrument panel:

No. 2 Pozidrive screwdriver

9/16" across flats open ended spanner

5/8" across flats open ended spanner

• To remove transducer:

1" across flats open ended spanner

13/16" across flats open ended spanner

• To remove instrument case from turbine block:

5/16" Allen key made into a 'T' wrench

9/16" hexagon spanner

• To remove loading valve knob:

1/18" diameter pin punch.

• To remove loading valve anti-rotation plug:

1/2" hex socket spanner (1U8761 and 4C9437)

9/16" socket spanner (1U9551 and 4C9675)

• To remove loading valve assembly:

5/16" Allen key (1U8761 and 4C9437)

3/4" hex socket with ratchet handle and short extension (1U9551 and 4C9675)

• To remove retaining ring holding bearing on loading valve:

Special pin spanner, see sketch

• To remove turbine assembly:

Thin nosed circlip pliers

Soft nosed pliers

• To remove safety discs:

11/16" hex socket spanner (1U8761 and 4C9437)

5/8" hex socket spanner (1U9551 and 4C9675)

• To remove handle from case:

1/2" across flats open ended spanner

• For electrical work:

5mm, 6mm, 7mm across flats box or socket ended spanner, small electricians screw driver

Temperature controlled soldering iron,

8T-5200 Frequency Generator or audio frequency generator with accuracy of ±.5 Hz up to 1200 Hz

• To remove plugs to shuttle valve:

1/4" hex Allen key

Service Parts

Note: The FT part numbers are not Caterpillar designed fabricated tool drawings. The numbers are the manufacturers drawing numbers.