PR-275 PAVEMENT PROFILER During Operation Caterpillar

The operating pressures in the wheel and cutter drive systems are interdependent. If the load on the cutter system is increased by increasing the depth of cut, the load on the wheel drive system will also be increased, and the pressures in both systems will rise. If the load on the wheel drive system is increased by increasing the travel speed, the load on the cutter drive system will also be increased, and the pressures in both systems will rise.

To reduce the pressures in the wheel and/or cutter drive systems, one or more of the following can be done:

1. Reduce the depth of cut being made.

2. Reduce the the working speed.

3. Increase the cutter speed. (The cutter should always be at full speed while working).

The auxiliary system pressure should always be 2,000 psi. The pressure can be changed with the adjusting screw on the auxiliary pump.

Hydraulic Oil Filter Indicator Light

If the hydraulic oil filter indicator light comes on after the hydraulic oil temperature has reached 100°F, shut the engine down immediately and change the return filter elements. The indicator light is turned on by a pressure switch that is activated only when the hydraulic oil returning to the oil tank is bypassing the oil filter and the oil cooler. Since the oil cooler is being bypassed, the hydraulic oil temperature will rise rapidly when working and cause the engine to automatically shut down in a short time. See page 4-41 for procedures for changing the filter elements.

Hydraulic Oil Temperature

It is extremely important that the hydraulic oil temperature be checked periodically during operation. Continuous operation of the machine with high hydraulic oil temperatures will cause rapid wear and failure of pumps and motors.

If the hydraulic oil temperature rises to 210°F and remains there or continues to rise, shut the engine down and thoroughly clean the exterior surfaces of the hydraulic oil cooler and radiator. Use an air hose to remove any loose material and then, if necessary, use a steam cleaner to remove any remaining material. Also check the condition of the engine coolant and, if the coolant shows signs of system corrosion, flush and clean the cooling system.

If the hydraulic oil temperature rises to 210°F and remains there after the radiator and oil cooler have been cleaned, change the return filter elements immediately. If the hydraulic oil temperature reaches 220 to 225°F, a temperature sensor will automatically shut the engine down.

NOTE: THE WATER SPRAY SYSTEM PROVIDES WATER TO A WASHDOWN NOZZLE THAT SHOULD BE USED DAILY TO WASH THE OIL COOLER AND RADIATOR CORES.

Central Lubrication Light

If the central lubrication low level alarm light comes on during operation, the lubrication reservoir should be refilled as soon as possible. The grease pumped through the cutter bearings by the system not only lubricates the bearings, but also flushes the dust caused by the cutting operation out of the bearings. Continued operation with a low lubricant level will cause bearing failure.

Water Spray System

Although it may not appear to be important, the water spray system is one of the key factors to effective machine operation. If the system does not work properly, it can cause very rapid wear of the cutter bits and excessive dust will settle in the radiator and oil cooler cores, causing an automatic shutdown of the engine because of overheating. It is therefore important that the operator constantly watch for any indication of plugging of the nozzles. If the nozzles appear to be plugging up, the operation should be stopped, the nozzles cleaned, the strainer screen removed and cleaned, and the filter element changed. If the water in the tank is excessively dirty, drain the tank and refill with clean water.

To avoid needless down time:

1. Always use the cleanest water possible.

2. Check the water system pressure gauges periodically during the day. If the pressure drop across the filter is more than 20 psi, replace the filter element (see page 3-25).

3. Visually check operation of the spray nozzles periodically during the day.

If the machine is to be parked outside in freezing weather, the water spray system must be drained immediately after stopping operation. Open all drain valves in the water pump and at the bottom of the water tank. Dump the water from the water filter bowl.

Replacing Water Filter Element

1. Unscrew filter bowl from head.

2. Empty the water from the bowl, take out the old element (cartridge) and remove the seal plate from the element.

3. Clean all parts and replace the gasket (O-ring), if necessary.

4. Place the seal plate on the bottom of a new element and insert into the bowl.

5. Screw the bowl onto the head. DO NOT OVER TIGHTEN. HAND TIGHTEN ONLY.

6. Start the spray system and check for leaks.

Cutting Asphalt

The operator must be particularly alert when cutting asphalt because the physical properties of a given type of asphalt vary considerably with ambient temperatures. When the asphalt is cool it is harder and more brittle making it easier for the cutter bits to cut. As the asphalt gets warmer it gets soft and gummy, creating a drag on the cutter bits. The possible cutting speed in a given type of asphalt will vary between winter and summer, morning and afternoon, and between shaded and unshaded areas. The operator must be alert for changes in the asphalt and make the required changes in the machine settings.

Avoid cutting large amounts of asphalt and then cutting concrete with the same set of bits. Asphalt tends to wear the supporting metal away from around the carbide tip, leaving the carbide center shaft exposed. If the exposed carbide tips then hit concrete, they may break off at the level of the supporting metal. This same problem may be encountered when cutting asphalt overlaid on concrete if the bits occasionally hit the concrete base. Replace the bits anytime the distance from the end of the supporting metal to the holder is 1 1/4 inch or less.

Caring For The Cutter

The life of the cutter bits will vary greatly with the type of material being cut, the temperature and the speed of operation. Check the length of the bits periodically during the day and be sure they are replaced if they get worn down to a length of 1 1/4" from the tip of the bit to the holder. If the bits are not replaced when required, the holders will start hitting the concrete and will be severely damaged or even torn from the cutter. IT IS MUCH EASIER TO REPLACE THE BITS THAN TO REPLACE HOLDERS!!

Uneven bit wear can result from a variety of reasons. One cause is the cutting of long stretches of material that are not as wide as the cutter. Another possible cause is the cutting of asphalt overlaid on concrete in such a way that the cutter bits are hitting concrete on one section of the cutter and hitting only asphalt on another section. Jobs where cutting deep at the curb and "feathering out" on the off-side for an overlay, will experience extremely uneven wear from one end of the cutter to the other. If the machine is to be used to cut an accurate cross slope, the cutter bits should be checked for uneven wear and replaced if uneven wear has occured. The machine will not cut an accurate cross slope unless the bits are all the same length.