795F AC and 795F AC XQ Off-Highway Trucks Caterpillar

Illustration 1	g06332002
Pantographs used on the 795F AC Trolley System

The instructions provided here are specifically for trolley system use. If a haul truck is unable to get on a trolley line, the operator shall continue up the ramp using the power from the diesel engine. Follow the mine site procedures to notify the proper person or persons describing the problem encountered.

Refer to Electrical Shutdown and Voltage Discharge for information on de-energizing the Power Train Electrical System on the truck.

Operating in Trolley Line Mode

Only trucks that are loaded should travel on the trolley line. All recommendations for diesel operation apply for trolley operation with the addition of the following recommendations:

1. Trucks operating on trolley will be faster than when operating on diesel. Because of the faster speed, all safety and warning recommendations must be followed closely.

2. If something is in the path of a truck while on the trolley line and the operator wants to go around it, the operator must completely disengage from the trolley line and use diesel power. After driving around the object, the truck must be fully under the trolley line before the trolley engage switch is pressed by the operator to begin the trolley engage sequence.
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   NOTICE
   Always keep the pantographs in the down position when not in use on trolley. Never drive near or under the trolley lines with raised pantographs unless the truck is properly aligned with the trolley line. If this procedure is not followed, pantograph and line damage will occur.

3. Trolley-assist is to be used for loaded uphill haul only. Trucks must have the dump body at least half loaded, or more, before going uphill on the trolley line. Empty trucks are not to go uphill on the trolley line because the increased speed will result in accelerated carbon brush wear.

Getting On the Trolley Line

When operating a trolley truck, follow the procedure listed below to get on the trolley line:

1. Approach the trolley line equipped portion of the haul road at a speed to allow for smooth transition into trolley assist propulsion. The truck must be traveling at least 8 km/h (5 mph) when the trolley engage switch is pressed for the trolley sequence to start.

2. Align the truck with the entrance area of the trolley line system. The operator should align to the sighting paddle hanging down from the trolley line arm. The sighting paddle should be at a position so the operator aligns to have it directly in front of them. Often two lines are marked on the upper portion of the windshield. The operator steers the truck to keep the sighting paddle between these windshield lines.
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   Illustration 2	g06332007
   Trolley system switch

3. With the accelerator pedal still depressed, press the top of the trolley system switch and hold for 0.5 seconds to raise the pantographs and start the trolley engage sequence.

   The engage sequence takes 5 to 8 seconds:

   1. Once started by the pressing of the operator trolley engage switch, the pantographs will raise to contact the overhead cables.

   2. After the pantographs are in contact with the lines, the voltage is measured.

   3. Once the voltage is detected within operating limits, the trucks voltage is set to a close value.

   4. Next, the contactors in the trolley cabinet are closed. The power for the wheel motor is now coming from the overhead lines.

   5. Finally, the engine speed is commanded down to 1300 rpm.

      Note: If the drive system does not detect proper voltage, the pantograph will lower after approximately 10 seconds and a fault message will be issued. The operator can try the engage sequence again once the pantographs are fully lowered.

      Pantograph position can be seen from the operator cab by referencing the position of the flag on each pantograph.

Operation While on the Trolley Line

1. The directional control lever must remain in the D or L position while on trolley line.

2. Truck speed is regulated by throttle pedal, limited by the active speed limit.

   Note: In the L position, the speed limit is 11 km/h (7 mph).

3. If slowing is required while on trolley line, release the throttle pedal. The truck will remain on the trolley line as long as the speed remains above 8 km/h (5 mph). Once the speed is below 8 km/h (5 mph), the truck will automatically complete the trolley disengage sequence and switch back to diesel mode.

   The disengage sequence takes 5 to 8 seconds:

   1. Once started by the pressing of the operator trolley disengage switch, the engine speed will be commanded to high idle.

   2. The power being taken from the trolley line will decrease to the diesel level. The truck will slow down.

   3. Load is applied to the engine to lower the power being taken from the line.

   4. Once power from the line is detected below a limit, the contactors in the trolley cabinet are opened.

   5. The wheel motor power is now coming from the diesel engine.

   6. Finally, the pantographs are lowered.

4. If stopping is required while on the trolley line, release the throttle pedal and depress the brake pedal as necessary. Use of the brakes will cause the trolley to activate the rapid disengage sequence and the truck will switch back to diesel mode.

   The rapid disengage sequence takes 1 to 2 seconds:

   1. At the same time the pantographs are commanded to drop, the contactors are commanded to open and the engine speed is commanded to high idle at the same time that the pantographs are commanded to drop.

   2. The load will transfer to the engine but the truck will likely come to a stop and anti-roll may engage.

While Operating on the Trolley

• If a serious fault is detected, such as over current, ground fault, etc. while on the trolley line, the truck will rapidly disengage and switch back to diesel mode automatically.

• If the pantograph becomes disconnected from the trolley line for any reason, the truck will rapidly disengage and switch back to diesel mode automatically.

• If the brake or retarder lever is used while on trolley line, the truck will rapidly disengage and switch back to diesel mode automatically.

• If the truck speed drops below 8 km/h (5 mph) while on trolley line, the truck will disengage and switch back to diesel mode automatically.

• To obtain trolley operation again, ensure that the truck is properly aligned under the trolley line and press the trolley engage switch to start the engage sequence. The tuck speed must be over 8 km/h (5 mph) before the engage sequence will start and raise the pantographs.

Getting Off the Trolley Line

As the truck approaches the end of the trolley line, it must exit the line properly. There should be a sign or signal near the end of the line indicating to the operator to press the trolley disengage switch.

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Illustration 3	g06332007
Trolley system switch

1. At the designated location, the operator must press the bottom of the trolley system switch. This will lower the pantographs and start the disengage sequence to change over from trolley mode to diesel mode.

2. As a part of the trolley disengage sequence, the truck speed will decrease and the engine speed will increase to high idle.

3. The system will switch over to diesel mode once the engine is up to full speed as smoothly as possible.

4. After the truck is in diesel mode, the pantographs are lowered. The operator can now steer the truck out from under the trolley line.

   The operator shall follow the procedure for getting off the trolley line in the event an operator is required to get off a trolley line to drive around an obstruction such as rocks or disabled equipment. The operator will then drive around the obstacle and follow the procedure for getting onto the trolley line.

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DO NOT touch the pantographs unless the engine is off, the drive system has been de-energized, and grounded per the discharge procedure. Failure to follow these instructions may result in injury or death.

Refer to Electrical Shutdown and Voltage Discharge for information on de-energizing the Power Train Electrical System on the truck.

Line Status Signals

Line status signals are recommended to advise operators whether segments of trolley lines are energized and ready to accept traffic. A different status signal light should be used for each section of the trolley line that is energized. The lights are mounted to allow the driver to check the status of the line that the truck is approaching, so that the trolley can be disengaged before a de-energized section of line is reached. Each section of line that is energized by a substation is recommended to have a separate line status signal. Since it is important that a driver press the trolley disengage switch before the truck reaches a de-energized section of ramp, the drivers must constantly monitor the line status signals then press the trolley disengage switch if the line status signals ahead indicates that an approaching section of line is not ready to accept trucks. After proceeding past the section of line, if the next line status signal indicates that the line is ready to accept traffic, the operator should press the trolley engage switch as previously instructed and continue operating on trolley.

Trolley Disconnect

Trucks operating on trolley may be rejected from a trolley assist line for several reasons:

1. System voltage drop - The trolley line is capable of output to a certain rating. If too many trucks are using a section of line at one time, the voltage will drop. The truck system will first reduce the power drawn from the line and the truck will go slower. If the voltage drops below the minimum, the truck will complete the disengage sequence and switch to diesel operation automatically.

2. No throttle signal - If, at any time while on trolley, the operator releases the throttle pedal, the truck speed will slow down. When truck speed is below 8 kph (5 mph), the truck system will automatically start the trolley disengage sequence. If the truck rolls back, the anti-roll feature will hold the truck stationary. Move the directional control lever to the P position to keep the truck stationary.

3. Electrical system malfunction - If an abnormal condition is detected in the truck electrical system, it will automatically start the trolley disengage sequence. The truck will switch back to diesel mode and the pantographs will lower.

   If a truck is rejected while the operator has the throttle pedal depressed, the transition back to a diesel mode will occur. The operator will notice the truck speed decrease from trolley speed to diesel speed however the truck will not stop and the operator can proceed up the ramp. If the operator releases the throttle pedal, the truck will stop in ether mode.

Traffic Consideration for Trolley Line Operation

Trucks operating on trolley assist will travel faster than trucks unable to operate on the trolley line, most support equipment, and some maintenance equipment. Because of this speed difference, trucks operating on the trolley line will be able to overtake some slower moving vehicles if allowed. To maintain the highest level of effectiveness and efficiency of the trolley system, it is important that all personnel operating equipment in the pit area reacts properly to trolley assisted haulage equipment and be aware of the proper procedures to allow faster moving haulage trucks to overtake the slower moving vehicles when possible.

Approaching Slow Moving Vehicles in a Trolley Assisted Truck

As trucks operating on trolley assist approach slower moving vehicles, the truck operator must begin to reduce the trolley truck speed. Operators must be looking far enough ahead to begin speed reduction before the truck gets too close behind the slow moving vehicle, less than 30 m (100 ft).

Note: Haul trucks must maintain a minimum following distance between equipment or vehicles of 30 m (100 ft) going uphill or traveling on level ground, and 60 m (200 ft) going downhill.

If a slower moving vehicle, traveling in front of a trolley assisted haulage truck, does not take the required action allowing the faster truck to overtake, the truck should reduce speed adequately to maintain proper follow distances. If proper following distances cannot be maintained while operating on trolley assist, and the slow-moving vehicle does not, or cannot, take the required action to allow overtaking, the trolley assisted truck should switch back to diesel mode, if necessary. If the slower moving vehicle takes the necessary action to allow the trolley assisted truck to overtake them, the trolley assisted truck will obtain maximum speed and overtake the slower moving vehicle as quickly as possible.

Operating Slow Moving Vehicles on Trolley Assist

Personnel operating any vehicle on a trolley assist ramp that is moving slower than trolley assisted trucks should be aware of the following general safety considerations:

1. Whenever a trolley assisted truck is capable of overtaking slower moving vehicles, the slower moving vehicle, if possible, should take the required action to allow the faster moving truck to travel up the trolley ramps without interruption.

2. It may not always be possible to take the action required to allow a trolley assisted haulage trucks to overtake a slower moving vehicle. Personnel should not jeopardize the safety of themselves or others if conditions do not permit overtaking.

3. Permitting a trolley assisted truck to overtake a slower moving vehicle helps the trolley system become more efficient and cost effective. It is not necessary for a trolley assisted truck to be able to overtake all slower moving vehicles. The trolley assisted truck can travel slower up the ramp under trolley power, if necessary, to maintain safe traffic patterns or traffic flows. Minimum trolley speed is 8 km/h (5 mph).

Truck Failure While on The Trolley Line

If the truck becomes immobile while under the trolley line, perform the following:

1. Stop the truck using the service brakes and move the directional control lever to the P position to apply the parking brake.

2. The pantographs should automatically lower. If the pantographs are still raised, then shut off the engine to bleed the hydraulic pressure and force them to lower.

3. Contact proper mine personnel to get the substation de-energized and grounded.

   Remain in the cab of the truck and warn all personnel not to approach or touch the truck until the substation is de-energized and grounded.

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If the pantograph is attached to the trolley line, DO NOT touch the truck while standing on the ground. Failure to follow these instructions may result in injury or death.