Signature Tests for Certain 789B And 793B Off-Highway Trucks{7601} Caterpillar

Signature Tests for Certain 789B And 793B Off-Highway Trucks{7601}

Usage:

793B 1HL

Off-Highway Truck/Tractor:: 789B (S/N: 7EK1-UP); 793B (S/N: 1HL1-UP)

Introduction

This Special Instruction enables dealers and the customers to benefit from use of the Cat VIMS to measure and record machine data while the truck is operated under specific sets of conditions. Every effort has been made to provide the most current and relevant information known to Caterpillar Inc.. Since Caterpillar makes ongoing changes and improvements to products, this Special Instruction must be used with the latest technical information available from Caterpillar to ensure that such changes and improvements are incorporated where applicable.

For VIMS / DSN Support contact the local technical communicator.

Summary

This Special Instruction describes signature tests that can be run on an operational 789B or 793B Off-Highway Truck equipped with VIMS to record and analyze vital machine information data. The data can be compared to earlier data from the same machine or to other similar machines in the fleet to assist in identifying major component degradation or problems that have gone undetected by more conventional inspections.

Signature tests are run under three different conditions:

Stationary Tests with engine running

Moving Truck Tests

Haul Cycle Tests

After the tests have been run and data downloaded from the VIMS, the truck can be put back on the ready line. Data is analyzed using off-board VIMS.

Data from signature tests is primarily used as a trending indicator. If tests are run when the truck is new, then repeated at 2,000 service hours or 4,000 service hours, the rate of degradation for various machine systems can be monitored and repairs can be scheduled in a cost effective manner.

Data from the signature tests can also be used for evaluation of truck performance. Some system-specific data analysis techniques are described that can be used to identify potential problems with the truck. These problems are such that it is unlikely that they are severe enough to cause a fault to be displayed on the monitor, logged on the event recorder, or be noticed by the operator. However, early identification of problems will allow timely trouble shooting and repair scheduling, if needed. As a result, unscheduled repairs can be reduced.

If the truck meets the requirements for the signature tests, the truck can be expected to give normal performance on the haul road.

Recording Test Conditions

Many of the tests described in this Special Instruction will require keeping a record of the conditions (grade of road and surface condition) under which the tests were run. A paper or electronic file that describes the test conditions should be maintained.

A recommended method for creating an electronic reference file is to use the text editor in Windows Program Manager. To create the text file, access Windows Program Manager. From the Accessories Program Group, select and open the Write Program Item by double clicking the Write icon. Type in the desired text that describes the particular conditions relating to the test. Name and save the file to the desired subdirectory that contains the data logger file for the current machine. Double clicking the file name in File Manager with the Mouse will enable the selection and reading of the text file at a later date.

Important Safety Information

Most accidents involving 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 correctly.

Note: Read and understand all safety precautions and warnings before operating or performing lubrication, maintenance, and repair on this product.

Basic safety precautions are listed in the "Safety" section of the Service or Technical Manual. Additional safety precautions are listed in the "Safety" section of the owner/operation/maintenance publication. Specific safety warnings for all these publications are provided in the description or operations where hazards exist.

WARNING labels have also been put on specific hazards. If these hazard warnings are not heeded, bodily injury or death could occur to you or other persons. Warnings in this publication and on the product labels are identified by the following symbol.

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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 operation, lubrication, maintenance and repair information.

Caterpillar Inc. 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, ensure that it is safe for the technician and others. Additionally, ensure that the product will not be damaged or made unsafe by the operation, lubrication, maintenance, or repair procedures you choose.

The information, specifications, and illustrations in this publication are based on information available at the time the information was written. Such information as specifications, torque, pressures, measurements, adjustments, illustrations, and other data can change at anytime, which can affect the servicing of the product. Make sure to obtain the most complete and most current information before starting any job. Caterpillar dealers have the most current information available.

Stationary Tests

Purpose

The purpose of the stationary tests is to record key information on the engine, power train system, and electrical system that is monitored by the VIMS sensors. Stationary tests can be run on the vehicle near the truck shop. Access to a haul road is not required. Information from the stationary tests can be compared to the following:

Expected normal values

Earlier tests ran on the same machine, or

Tests that have been run on similar machines.

When the information is compared, the overall condition of the machine systems can be determined without the need for more time consuming installation of service tools.

The data logger and event recorder should be downloaded and cleared before beginning these tests. All five tests can be completed sequentially with the data logger turned on at the beginning of Test 2 and left on for the remaining tests. Estimated time to run all five tests is 0.5 hours, if the machine is running at operating temperature. If systems are not warmed. additional time will be required.

Test 1: Brake System Testing and Operating Temperatures

The purpose of this test is to warm the machine to normal operating temperatures and to determine if secondary brake system is functional. The test is not intended to measure maximum brake holding effort. Brake holding effort required to hold a machine at a specific engine rpm will vary from machine to machine due to differences in engine setting, power train efficiency, and in brake holding capability.

Engine rpm at beginning of machine movement, with secondary brake applied, should be compared with the engine rpm the specific machine was able to hold on a prior test.

Start the engine and allow air system pressure to build up to maximum operating pressure.

Warm the engine and power train such that:
1. Coolant outlet temperature is between 79° C (175° F) to 90° C (195° F).
1. Converter outlet oil temperature is between 82° C (180° F) to 90° C (195° F).
1. Transmission outlet temperature is between 79° C (175° F) to 90° C (195° F).

Apply secondary brake.

Move the transmission shift lever to first gear range forward.

Release the parking brake.

Gradually accelerate the engine to 1200 rpm.

The machine should not move forward.

If the secondary brake does not function properly, have necessary repairs made.

Repeat this test with the service brakes. If truck creeps forward at full engine speed, have necessary repairs made before continuing the stationary tests.

Set the parking brake and shut down the engine.

Test 2: Starting Test

The purpose of this test is to record engine cranking speed. If the truck has a prelube system installed, prelube oil pressure and system voltage drop during prelube will also be recorded.

Note: This test will deplete the air system, run only if an alternate air source is available for recharging the air system.

Set the ground level shut off in the "FUEL OFF" position.

Turn key switch to the on position, allow VIMS to go through self-test.

Verify that air pressure is 827 kPa (120 psi). If not, recharge the air system.

Turn ON the data logger.

Crank the engine until cranking stops because of low air pressure.

Turn the data logger OFF.

Recharge the air system.

Set the ground level shut off in the "RUN" position.

Test 3: Unloaded Engine Test

The purpose of this test is to record electrical system charging voltage and engine lubrication pressure as engine speed is increased. The time required to recharge the air system pressure is also recorded.

Turn key switch to the ON position, allow VIMS to go through self diagnostic test.

Turn the data logger ON.

Wait 10 seconds.

Start the engine.

Run engine at low idle for 10 seconds.

Leave transmission in neutral and gradually increase engine speed from low idle to high idle in 15 seconds. Hold at high idle for 10 seconds.

Reduce engine speed to low idle.

With transmission still in neutral, snap accelerate engine speed from low idle to high idle two times with 15 seconds between accelerations.

Reduce engine speed to low idle.

Test 4: Converter Stall Test

The purpose of this test is to record the engine response time against converter stall.

Note: Do not apply the parking brake during the converter stall test. On VIMS equipped machines, applying the parking brake with the transmission in gear will cause a category 3 parking brake warning message to lock on the message center. This condition will prevent the serviceman from observing when the category 2 warning occurs from hot converter oil temperature during the stall test.

Position the machine on ground level at least 50 m (164 ft) from other machines, structures, or people.

Put blocks behind the wheels to prevent movement of the machine.

Apply the service brake and retarder. Shift the transmission to first gear forward and turn on the data logger.

Quickly accelerate the engine from low idle to maximum speed. Hold for 5 to 10 seconds at maximum engine speed.

Reduce the engine speed to low idle. Hold for 60 seconds.

Repeat step 2.

Repeat step 3.

With transmission in first gear, accelerate the engine to maximum speed. Hold until the high torque converter oil temperature warning comes on (Level 2).

Reduce the engine speed to low idle.

Shift transmission to Neutral.

Turn data logger OFF.

Allow system to cool to normal ranges.

Test 5: Double Stall Test

The purpose of this test is to record the engine response time against converter stall and the implement hydraulic system pump.

Note: Do not apply the parking brake during the converter stall test. On VIMS equipped machines, applying the parking brake with the transmission in gear will cause a category 3 parking brake-warning message to lock on the message center. This condition will prevent the serviceman from observing when the category 2 warning occurs from hot converter oil temperature during the stall test.

Turn data logger ON.

Accelerate engine to high idle with transmission in Neutral.

Raise the body.

Slow engine to low idle.

Lower the body.

Raise the body with engine still at low idle.

Lower the body.

With the service brakes applied, move the body raise lever to "BED DOWN" position, move the transmission shift lever to first gear forward range.

Accelerate engine to maximum speed and hold until the high torque converter oil temperature warning comes on (Level 2).

Lower the engine speed to low idle, shift transmission to "NEUTRAL", and move the body raise lever to "FLOAT" position. Allow the truck to cool for 60 seconds.

Repeat steps 8 and 9.

Repeat step 10.

Turn the data logger OFF.

Moving Vehicle Tests

Purpose

The purpose of the moving vehicle tests is to record key information on the engine, power train system, and suspension system that is monitored by the VIMS sensors. Moving vehicle tests should be run on a section of haul road where the grades are known and can be expected to be available at a later date. To aid in repeating the test at a later date, the following parameters should be recorded:

Rolling radius of tires. Calculate this value by using the distance traveled for five revolutions.

Estimate of the rolling resistance of the haul road used for the tests.

Ambient temperature.

Altitude.

Barometric pressure.

Dew point.

As with the stationary tests, information from the moving vehicle tests can be compared to:

Expected normal values,

Earlier tests ran on the same machine, or

Tests that have been run on similar machines in the same fleet.

When the information is compared, the overall condition of the machine systems can be determined without the need for more time consuming installation of service tools.

Note: Before beginning the Moving Vehicle tests, make sure that the Stationary Test 1 has been completed and that the truck is at normal operating temperature and that the secondary brake system is functional.

Test 1: Unloaded Truck - Level Road Test

This test will enable information to be recorded to evaluate the payload monitoring system calibration and suspension strut pressures.

Turn the data logger ON.

Coast to a stop from 8 km/h (5 mph) to 16 km/h (10 mph).

Turn the data logger OFF.

Test 2 [ERG1] Unloaded Truck Retarding

This test is intended to log information on the performance of the ARC and to ensure that retarder system is operating correctly.

Use a relatively permanent road for this test that has a grade that is typical for the mine site operation. A permanent road section is desirable so that similar tests can be run at a later date. Keep a paper or electronic record of the road grade and surface condition for later reference.

Turn the data logger ON.

Descend the grade at a safe speed using the Automatic Retarder Control.

Turn the data logger OFF.

Test 3: Loaded Acceleration Test - Level Surface

This test is intended to log information on the response of the engine, CTS, transmission shifting, and strut pressures.

Turn the data logger ON.

Snap accelerate the truck from first gear through sixth.

Without using the service brakes or retarder, coast to a stop by downshifting from sixth gear to first.

Accelerate the truck back to 8 km/h (5 mph) to 16 km/h (10 mph).

Shift to Neutral and coast to a stop without using the service brakes or retarder.

Turn the data logger OFF.

Test 4: Loaded Uphill Grade

This test is intended to log information on the performance of the engine, boost, exhaust temperature and total vehicle performance.

Turn the data logger ON.

Run the truck up the grade in a constant gear.

Record the time required for a measured distance up the grade and note the gear used for the test.

Turn the data logger OFF.

Repeat the test a second time.

Test 5: Loaded Truck Retarding

This test is intended to log information on the performance of the ARC, and brake cooling performance.

Use a fully loaded truck for this test. Load the truck to rated capacity. Placement of the load is not critical but should be balanced for safe operation.

Turn the data logger ON.

Descend the grade using the correct retarding gear and the Automatic Retarder Control.

Turn the data logger OFF.

Repeat the test using one gear higher to descend the grade.

Step 4 is intended to record the brake cooling performance. The brake oil temperature warning (Level 2) will likely come on. When the brake oil temperature warning occurs, brake to a slower speed and shift to the correct gear for the slope.

Normal Haul Cycle Tests

Purpose

The purpose of the haul cycle tests is to record key information on the engine, power train system, and suspension system that is monitored by the VIMS sensors while the truck is operating on a normal haul cycle. As with the stationary and moving vehicle tests, information from the haul cycle tests can be compared to:

Expected normal values,

Earlier tests ran on the same machine, or

Tests that have been run on similar machines.

When the information is compared, the overall condition of the truck systems can be determined without the need for more time consuming installation of service tools.

Logged data from a haul cycle can be used to assist in Fleet Management and haul road improvements.

Note: Before beginning the Haul Cycle Tests, make sure that the Stationary Test 1 has been completed. It is important that secondary brake system be functional. The truck should also be at normal operating temperature as described in Stationary Test 1.

Test 1: Long Uphill Haul

For this test, the loaded truck should be run on the longest uphill section of the job site haul road. If haul is more than 30 minutes, log only the loaded portion.

The data logger should be downloaded and cleared before beginning this test.

Test 2: High Speed Haul

For this test, the loaded truck should be run on the highest speed section of the job site haul road. If the haul is more than 30 minutes, log only the loaded portion.

The data logger should be downloaded and cleared before beginning this test.

Test 3: Typical Haul Cycle

For this test, the loaded truck should be run on the most typical haul cycle at the job site. If the haul is more than 30 minutes, log only the loaded portion.

The data logger should be downloaded and cleared before beginning this test.

Download Data and Clear VIMS

At the completion of the Truck Signature Tests, the data logger and event recorder should be downloaded and cleared.

None of the tests described in this Special Instruction should cause VIMS to display a level 3 warning to the operator or log a level 3 event. If any level 3 events are present, the events should be investigated and appropriate repair made.

Use the methods described in the Service Manual for troubleshooting.

Analysis of Signature Test Data

Engine

Problem 1: Exhaust Temperature Split Too High

Exhaust temperature split is the difference between the right exhaust temperature and the left exhaust temperature taken at the same time. Left and right exhaust temperatures are measured at full load conditions during the following tests.

Stationary Test 4 - Converter Stall.

Stationary Test 5 - Double Stall.

Moving Test 5 - Loaded Uphill Grade.

The exhaust temperature split will likely be highest for the Double Stall test.

A normally performing engine has some variation in the bank-to-bank exhaust temperature, typically less than 20° C (36° F). An exhaust temperature split greater than 50° C (90° F) or a step change in the exhaust temperature split occurs, this split may indicate a serious problem.

Probable Cause:

Faulty exhaust temperature sensors.

Defect in fuel injectors.

Leak or break in fuel line between fuel manifold and cylinder head.

Wrong valve lash.

Air inlet system has a leak.

Exhaust system has a leak.

Air inlet or exhaust system has a restriction.

Wrong fuel Injector lash.

Incorrect fuel injection timing calibration.

Bent or broken push rod.

Problem with electronic control system.

Note: Refer to Testing and Adjusting, SENR5596, "3512 and 3516 EUI Engines for Caterpillar Built Machines ", for troubleshooting the engine.

Problem 2: Engine Has Low Oil Pressure

A decrease in engine oil pressure, although the pressure is still within the acceptable range since the last test is an indication that parts are beginning to fail such as:

Engine bearings
Engine oil pump
Engine oil pump relief valve

Engine oil pressure versus engine speed data can be derived from several of the stationary tests. Stationary Test 3 - Unloaded Engine Test is the best source since the engine speed is raised slowly. The Data Logger plot shown at the right is a typical run.

This data can be reduced to produce a plot of engine oil pressure versus engine speed. Since VIMS does not have the capability of plotting one sensor output versus another sensor one of several alternate approaches can be used. Two approaches are:

Using VIMS Analysis, read the actual values of oil pressure and engine speed and plot the values in another program such as a spreadsheet.

Using VIMS Analysis, export the data to a separate file and then import this file into a spreadsheet or other data analysis or plotting program.

The graph shown in Illustration 2 is generated using the data from the Data Logger run as plotted in the Illustration 1.

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Illustration 1	g02931879

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Illustration 2	g02931878
Engine Oil Pressure

The straight-line curve in Illustration 2 represents the oil pressure versus engine speed warning level that is used by the Engine Control Module and VIMS to provide low oil pressure warning. Oil pressure is checked against these curves according to engine speed. Refer to System Operations, Testing and Adjusting, SENR5596, "3512 and 3516 EUI Engines for Caterpillar Built Machines ", for further definition of this oil pressure map.

The measured oil pressure for this engine is well above the warning level curves. The change in slope of the measured oil pressure occurs at the engine speed where the relief valve is beginning to open. As an engine and lubrication system wears, the speed at which the relief valve begins to open will increase. When a 20 percent increase in engine rpm is necessary to generate maximum oil pressure, this increase may be an indicator that repair or rebuild is needed.

If the same viscosity oil is used and the oil temperature is the same and there are significant changes in oil pressure, determine the reason and make repairs as needed.