Hydraulic Power Packs

HYDRAULIC POWER PACKS

1. What is a Hydraulic Power Pack?

• A hydraulic power pack is a self-contained unit (stand-alone unit) that is used instead of a built-in power supply for hydraulic machinery.

• It works to apply the hydraulic pressure needed to drive motors, cylinders, and other complementary parts of a given hydraulic system.

• The hydraulic power pack is also called as hydraulic power unit.

2. Components of a Hydraulic Power Pack

• A hydraulic power pack has:

(i) a hydraulic reservoir, which houses the fluid,

(ii) regulators that allow users to control the amount of pressure the power pack delivers to a valve,

(iii) pressure supply lines and relief lines,

(iv) a pump and

(v) a motor to power the pump.

• The various components of a hydraulic power pack are presented in Table 16.16.

Table 16.16. Components of a hydraulic power pack

1. A hydraulic reservoir (or tank). A hydraulic reservoir holds the enclosed oil. This is a storage unit designed with enough volume for the oil in the pipes to drain into it. It also ensures that the oil is stored and maintained in the best possible condition. Common auxiliaries for a reservoir include filler/breathers and drain ports, level gauge, level switches and inspection covers.

2. Regulators. Regulators control and maintain the amount of pressure that the hydraulic power pack delivers.

3. Pressure supply lines and relief lines. The supply line supplies fluid under pressure to the pump and the relief lines relieve pressure between the pump and the valves. The relief lines also control the direction of flow through the system.

4. Motor. Motor is used to power a pump.

5. Pump. A pump to perform two actions. Firstly, it creates a vacuum at the pump inlet and with the help of atmospheric pressure, forces fluid from the reservoir into the inlet line. This fluid is then fed to the pump. The pump then delivers this fluid to the pump outlet and force feeds it into the hydraulic system.

6. Other components:

 (a) Filters: Filtration is a critical part of a hydraulic power pack, ensuring wear is minimised and efficiencies are maintained. Basic suction strainers do not allow large contaminants to enter the pump. Pressure filters are normally configured at the pump outlet and ensure only filtered oil enters the hydraulic system. Contamination within the system is filtered out by the return filter before it enters the hydraulic reservoir. 

(b) Pressure control valves that limit or control the hydraulic pressure within the hydraulic system.

(c) Directional control hydraulic valves (manual, electrical, pneumatic or hydraulic operated) direct the oil flow around the system to operate actuators, motors or other functions.

(d) Cooling is another other key consideration, where efficiencies within a system or machine will produce heat in the oil; this must be cooled to ensure long life and high-efficiency.

(e) Accumulators: These are containers that can be attached to the hydraulic actuators. They collect oil from the pump and are intended to build and maintain fluid pressure to supplement the motor pumping system.

(f) Coolers and heaters: As part of the temperature regulation process, an air cooler can be installed near or behind the filter unit to prevent temperatures from rising the above operational parameters. Likewise, a heating system, such as an oil- based heater, can be used to elevate temperatures when necessary.

(g) Power unit controllers: The hydraulic controller unit is the operator interface containing power switches, displays, and monitoring features. It is necessary for installing and integrating a power unit into a hydraulic system, and can usually be found wired into the power unit. Oil level and temperature protection switch, pressure switches and filter clogging switches are quite common.

• A typical schematic of hydraulic power pack is illustrated in Fig.16.14.

• Using fluid to transmit power from one location to another, hydraulic power packs can generate massive amounts of power which can be used to drive hydraulic machinery. 

• Hydraulic power packs come in many different shapes and sizes, some are very large and stationary whereas others are much smaller and more compact. In fact, some hydraulic power packs are so compact that they can easily be transported even in a small van.

• Types of hydraulic power packs: Power packs can be two types based on their size and portability. They are:

(i) Stationary power pack, or

(ii) Portable power pack.

• Identification of hydraulic power packs: The only real way to identify hydraulic power packs is through its main components. No matter the size of the unit, all power packs will have the following: a hydraulic reservoir, regulators, a pump, motor, pressure supply lines and refief lines.

3. How Does a Hydraulic Power Pack Work?

• A hydraulic system employs enclosed fluid to transfer energy from one source to another, and subsequently create rotary motion, linear motion, or force. The power unit/pack provide the power needed for this transfer of fluid.

• Unlike standard pumps, hydraulic power units use multi-stage pressurization networks to move fluid, and they often incorporate temperature control devices. The mechanical characteristics and specifications of a hydraulic power unit dictate the type of projects for which it can be effective.

• Some of the important factors that influence a hydraulic power unit's performance are pressure limits, power capacity, and reservoir volume. In addition, its physical characteristics, including size, power supply, and pumping strength are also significant considerations.

4. Applications of Hydraulic Power Packs

Mobile hydraulics applications increasingly employ hydraulic power packs. Some of the hydraulic power pack applications include dump trailers, electric sanitation trucks, snow plow, and telescopic logistics equipment like the dock leveler, car tailgate, wing trucks, electric push cart, and electric pallet lift, car lift, scissors lift, electric operating table, etc.