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Tech Tips Service Call: AC Dielectric Testing of a Category C Telescopic Aerial Device Tools Required: • AC Dielectric Tester • Insulating Outrigger Pads • Safety equipment to create a dielectric test area Model(s): L13I, L17I, TL Tech-Tip 93 Released: 6/19/2019...
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Tech Tips Tech Tip Safety Rules Danger Failure to obey the instructions and safety rules in the appropriate Operator's Manual and Service Manual for your machine will result in death or serious injury. Many of the hazards identified in the operator’s manual are also safety hazards when maintenance and repair procedures are performed.
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Tech Tips Step 1 In the interest of safety, the dielectric testing area should be separated from the normal work area by means of a barrier to keep anyone unassociated with the procedure out of the testing area. If a barrier is not available, use a spotter(s).
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Tech Tips Consult the ID Placard to determine whether the unit is insulated or non-insulated. If the unit is insulated, the qualification voltage and rating of the unit will be shown. Verify that the boom is designed as insulated before proceeding with the dielectric test.
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Tech Tips Step 2 Complete a thorough daily inspection of the unit, including running all boom functions through their full range of motion before beginning any dielectric testing. Daily inspection criteria can be found in the unit specific operators and maintenance manuals.
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Tech Tips Step 3 Drive the unit into the dielectric testing area and onto the insulating platforms (pads) centered under the tires. Engage the park brake, place the transmission in neutral and turn on the PTO. Set the unit up for operation by deploying the outriggers onto insulating platforms (pads) centered under the outrigger foot, reference Figure 1.
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Tech Tips Step 4 To begin setup for testing the upper boom, install jumpers between components in the following locations as shown in Figure • Turntable above rotation to pedestal below rotation (#1) • Turntable above rotation to lower boom (#2) •...
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Tech Tips Step 5 Attach the current meter return to the back of the truck. If a ground lug or loop is available, attach the return there. Attach the voltage source from the AC Dielectric Tester to the boom tip. This may be attached at the same location as the jumpers that were installed at the boom tip.
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Tech Tips Step 6 Position the lower and upper booms both at 45 degrees. Extend the upper boom to the minimum extension decal (if equipped). Visually check that all jumpers, voltage source from the AC Dielectric Tester, and return are still connected once unit is in position.
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Tech Tips Step 7 Plug in and turn on the dielectric tester. Raise the voltage control to the required voltage listed on the test sheet. Monitor the volt and current meters to verify the test is working correctly. If the current meter reads zero verify all connections.
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Tech Tips The upper boom Qualification and Periodic readings are shown below. Qualification testing is done on a new unit install or after a major component such as a boom is replaced. Periodic testing is done once a year to verify dielectric integrity of the unit.
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Tech Tips Step 8 Once testing is complete bring the upper and lower booms down to the ground mount position. Disconnect the voltage source from the boom. Step 9 Remove the following jumpers: • Turntable above rotation to pedestal below rotation (#1) •...
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Tech Tips Step 11 Attach the voltage source from the AC Dielectric Tester to the knuckle side of the lower boom and install jumpers between components in the following locations as shown in Figure 4 below: • Lower boom to knuckle (#1) •...
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Tech Tips Raise the lower boom to at least a 45 degree angle. Visually check that all jumpers, voltage source from the dielectric tester and the return are still connected once the unit is in position. Step 12 Plug in and turn on the dielectric tester. Raise the voltage control to the required voltage listed on the test sheet.
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Tech Tips The lower boom Qualification and Periodic readings are shown below. For a Chassis Insulating System (Lower Boom Insert) Qualification test, the reading should be no higher than 3000 µA for 3 minutes at 50 KV. For a Chassis Insulating System (Lower Boom Insert) Periodic/Maintenance test the reading should be no higher than 3000 µA for 1 minute at 35 KV.
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Tech Tips Once testing is complete bring the lower boom down and disconnect the voltage source from the boom. Remove all of the jumpers from the following locations indicated in Figure • Lower boom to knuckle (#1) • Lower boom link to knuckle (#2) •...
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Tech Tips Step 15 Attach the voltage source from the AC Dielectric Tester to the control handle using a spring with the cable going over the top of the platform as shown below. Tech-Tip 93 Released: 6/19/2019...
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Tech Tips Step 16 Reach under the upper control cover and attach the current meter return to a fitting that is attached to the upper control valve as shown below. (Cover removed for clarity) Tech-Tip 93 Released: 6/19/2019...
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Tech Tips Step 17 Elevate the platform to at least 4 feet above the ground. Visually check that all jumpers, the voltage source from the dielectric tester, and the return are still connected once the unit is in position. Step 18 Plug in and turn on the dielectric tester.
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Tech Tips The Single Stick Qualification and Periodic readings are shown below. For a Single Stick Control AC Qualification and Periodic/ Maintenance test the reading should be no higher than 400 µA for 3 minutes at 40 µA=Microamp Step 19 Once testing is complete lower the platform to the ground mount position.
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