NEW HYDRAULIC PUMPS

OBJECTIVE :

Branch of science concerned with the practical applications of fluids, primarily liquids, in motion. It is related to fluid mechanics (q.v.), which in large part provides its theoretical foundation. Hydraulics deals with such matters as the flow of liquids in pipes, rivers, and channels and their confinement by dams and tanks. Some of its principles apply also to gases, usually in cases in which variations in density are relatively small. Consequently, the scope of hydraulics extends to such mechanical devices as fans and gas turbines and to pneumatic control systems.

Hydraulic Elements

In hydraulic-power systems there are five elements: the driver, the pump, the control valves, the motor, and the load. The driver may be an electric motor or an engine of any type. The pump acts mainly to increase pressure. The motor may be a counterpart of the pump, transforming hydraulic input into mechanical output. Motors may produce either rotary or reciprocating motion in the load.

Hydraulic Pumps

The pumps run constant speed, usually by an electric motor, take the oil from the supply reservoir and deliver it at sufficient volume and pressure to do the work required.

Types of pumps

• gear pumps
• vane pumps
• plunger pumps
• piston pumps

Gear pumps

The gear pumps is probably the simplest kind of commercial medium- pressure
Constant-delivery pump. This type of pumps has been used for many years for raising and circulating (pumping) various kinds of liquids. Its wide use in the hydraulic transmission power is due to:
a. The large volume at medium pressure of which it is capable
b. It’s quiet running at high speed, owing to ball bearing, helical gears etc
c. Its small dimension
d. Its simplicity, low first cost and unkeep.

Vane pumps

The vane type pump has advantages in size, weight, quiet running, and long life, and is highly efficient. The diagrammatic is term “hydraulically” balanced” because there are two diagrammatically  opposing pumping chamber which, being opposite each other, cancel out thrust forces imposed by the pumping action.

Plunger pump

The plunger type pump lends it self radialy to variable delivery, high presser, and smooth flow and, alone or together with a constant-delivery unit, is an important piston, or plunger, which fits closely in its cylinder, draw in the oil as it moves outward and expels the oil as it is pushed back. These pumps have five or more radial cylinders, each of course, with its plunger.

Piston pump

Piston pumps generate a pumping act by causing piston to reciprocate within piston bore.
The pumping mechanism of piston pump basically consists of a cylinder barrel, piston with shoes, shawsplate, shoeplate, shoeplate bias spring, and port plate.

Hydraulic valves

The purpose of valves is to control the flow of oils. The flow is through passages called port, in through the suction (intake or inlet) port, out through the presser (outlet) port. Valves may be operated mechanically, electrically, or hydraulically, and for most action may be automatic. Very sensitive valves for controlling the slightest movement (inches) even 0.001 in. of heavy tables are not uncommon. Frequently two or more, and quite often several, valves are incorporated in the same hydraulic system.

Types of valves pilot valves

Pilot valves is operated usually by dogs on a sliding table (or by hand) to release a comparatively small amount of oil to actuate some larger valve.

2. Relief valve

A relief valve may be adjusted to open at a predetermined presser

3. Check valve

A check valve permits a one- way flow only.
4. Reverse valve
A reverse valve is for the purpose of changing the direction of the flow of oil to the driven unit.

5. Resistance valve (foot valve)

It offers resistance in one direction of the flow.

6. Control valve

It may cover a variety of uses, such as starting, stopping, speed changing, and quite often the movement of other valves for various purposes.

 Hydraulic drive system

A hydraulic drive system is a drive or transmission system that uses pressurized hydraulic fluid to drive hydraulic machinery. The term hydrostatic refers to the transfer of energy from flow and pressure, not from the kinetic energy of the flow.
A hydraulic drive system consists of three parts: The generator (e.g. a hydraulic pump), driven by an electric motor, a combustion engine or a windmill); valves, filters, piping etc. (to guide and control the system); the motor (e.g. a hydraulic motor or hydraulic cylinder) to drive the machinery.

Hydraulic Cylinder

Hydraulic cylinders (Also called linear hydraulic motors) are mechanical actuators that are used to give a linear force through a linear stroke. Hydraulic cylinders are able to give pushing and pulling forces of millions of metric tons with only a simple hydraulic system. Very simple hydraulic cylinders are used in presses; here, the cylinder consists of a volume in a piece of iron with a plunger pushed in it and sealed with a cover. By pumping hydraulic fluid in the volume, the plunger is pushed out with a force of plunger-area pressure.