Hydraulic Pressure Gauge

Most types of construction equipment are equipped with hydraulic pressure guages. When operating this equipment, you must watch for leaks. Consult the operator's manual for the pressure at which the equipment should be operated. Should the pressure not reach the operating range or should you detect a leak, be sure to document and report either or both.

Hydraulic Temperature Gauge

Most types of construction equipment are also equipped with hydraulic temperature gauges. In most cases, if the hydraulic temperature exceeds the recommended temperature, it is because the fluid level is 100 low.

Should the fluid level be correct and the equipment overheats, you are overworking the hydraulic system. Stop your machine and check the hydraulic fluid level. Be careful because the hydraulic fluid is hot and the hydraulic system may be pressurized. If the fluid level is normal, let the machine sit at idle to cool the hydraulics.

Fuel Level Gauge

When prestart inspecting a piece of equipment, you should visually check the fuel. During the day, watch the fuel gauge to ensure it shows a slow depletion of fuel. Should the fuel gauge not move in a reasonable amount of time, assume the fuel _{gauge is broken.} In this case, check the fuel visually from time to time to ensure that you do not run out of fuel.

HYDRAULIC SYSTEMS

Hydraulic systems on equipment are used to transmit power for steering and controlling the operation of mechanical components. The basic components of a

hydraulic system (fig. 4-9) consist of a reservoir, strainer and falters, pump, control valves, hydraulic cylinders, hoses, couplers, accumulators, and on some systems, a hydraulic motor.

HYDRAULIC RESERVOIR

The hydraulic reservoir is the fluid storehouse for the hydraulic system. It contains enough fluid to supply the normal operating needs of the hydraulic system and an additional supply to replace fluid lost through minor leaks. Additionally, the reservoir allows the settling of any impurities and separation of air from the fluid before reuse in the system.

The basic hydraulic reservoir (fig. 4-10) has a space above the fluid even when they are full. This space allows the fluid to foam, and thus purge itself of air

Figure 4-9.-Basic hydraulic system.

Figure 4-10.-Basic hydraulic reservoir.

bubbles that normally occur as the fluid flows from the reservoir, through the system, and back to the reservoir.

The air vent allows the air to be drawn in and pushed out of the reservoir by the ever-changing fluid level. An air filter is attached to the air vent to prevent drawing atmospheric dust into the system.

Because it is essential that the fluid in the reservoir be kept at the correct level at all times, the sight gauge is provided to allow the normal fluid level to always be seen The baffle plate segregates the outlet fluid from the inlet. This allows the fluid time to dissipate air bubbles, contaminants to settle, and the return fluid to cool before it is picked up by the pump.

The proper hydraulic fluid level must be maintained. In some systems low fluid level causes overheating because the fluid does not have enough time to cool in the reservoir before it gas back into the pump. Also, some systems will not work at all because the fluid is so low in the reservoir that air gets into the pump.

Before adding hydraulic fluid, know what type to use and make sure it is clean. Clean around the filler cap or tube so there is less chance that dirt can get into the system.

STRAINERS AND FILTERS

Hydraulic systems have a strainer and one or more filters that remove the impurities that would eventually contaminate the hydraulic fluid. The strainer is normally located in the reservoir or in the inlet line to the pump. The filter is normally located so only a small amount of fluid is lost when the element is changed. The falter is equipped with a valve that allows the fluid to bypass the filter element should it become clogged. The falter element is usually of the paper cartridge, canister, or edge type and is similar to those used in engine _{lubrication systems.} Regular filter maintenance, performed by the mechanics, is necessary to prevent contaminated fluid from being recirculated in the system.