MECHANICAL HYDRAULIC PUMPS

2009-11-06T14:01:00.000-08:00

Gear pumps

Gear pump is a fixed positive displacement pumps, and can be divided into external and internal gear types.

External Gear Pumps

A gear pump produces flow by carrying fluid in between the teeth of two meshing gears. One gear is driven by the drive shaft and turns the idler gear. The chambers formed between adjacent gear teeth are enclosed by the pump housing and side plates.

A partial vacuum is created at the pump inlet as the gear teeth unmeshed.

Fluid flows in to fill the space and is carried around the outside of the gears. As the teeth mesh again at the outlet end, the fluid is forced out.

Under the optimum condition the volumetric efficiencies of gear pumps run as high as 93%.

Internal Gear Pumps

Internal gear pumps have an internal gear and an external gear. Because these pumps have one or two less teeth in the inner gear than the outer, relative speeds of the inner and outer gears in these designs are low. For example, if the number of teeth in the inner and outer gears were 10 and 11 respectively, the inner gear would turn 11 revolutions, while the outer would turn 10. This low relative speed means a low wear rate. These pumps are small, compact units.

for more information watch the above vedio and ask me if you have any problem,.........

2009-08-17T12:45:00.000-07:00

General Components of Centrifugal Pumps
A centrifugal pump has two main components:
a . A rotating component comprised of an impeller and a shaft.
b. A stationary component comprised of a casing, casing cover, and bearings.

Stationary Components
Casing :
Casings are generally of two types: volute and circular. The impellers are fitted inside the casings.

1.Volute casings are a curved funnel increasing in area to the discharge port. As the area of the cross-section increases, the volute reduces the speed of the liquid and increases the pressure of the liquid.( Volute casings are building a higher head ).

2.Circular casing have stationary diffusion vanes surrounding the impeller periphery that convert velocity energy to pressure energy. Conventionally, the diffusers are applied to multi-stage pumps.( circular casings are used for low head and high capacity )

Suction and Discharge Nozzle
The suction and discharge nozzles are part of the casings itself. They commonly have the following configurations.

1. End suction/Top discharge The suction nozzle is located at the end of, and concentric to, the shaft while the discharge nozzle is located at the top of the case perpendicular to the shaft. This pump is always of an overhung type.
2. Top suction Top discharge nozzle The suction and discharge
nozzles are located at the top of the case perpendicular to the shaft. This pump can either be an overhung type or between-bearing type

2. Side suction / Side discharge nozzles The suction and discharge nozzles are located at the sides of the case perpendicular to the shaft. This pump can have either an axially or radially split case type.

Now ;that’s the most important stationary components.
There’s also (Seal Chamber , Gland , Throat Bushing , Internal circulating device , Mechanical Seal ).

Rotating Components

1. Impeller The impeller is the main rotating part that provides the centrifugal acceleration to the fluid. They are often classified in many ways.
a- Based on major direction of flow in reference to the axis of rotation:

Radial flow
Axial flow
Mixed flow
b- Based on suction type
Single-suction: Liquid inlet on one side.
Double-suction: Liquid inlet to the impeller symmetrically
from both sides.
c- Based on mechanical construction
Closed: Shrouds or sidewall enclosing the vanes.
Open: No shrouds or wall to enclose the vanes.
Semi-open or vortex type.

2. Shaft
The basic purpose of a centrifugal pump shaft is to transmit the torques
encountered when starting and during operation while supporting the impeller and other rotating parts. It must do this job with a deflection less than the minimum clearance between the rotating and stationary parts.

There’s also (Shaft Sleeve , Coupling ).
But ;that’s the most important stationary components.

2009-07-23T10:19:00.000-07:00

Centrifugal Pump

Working Mechanism of a Centrifugal Pump
A centrifugal pump is one of the simplest pieces of equipment in any process plant. Its purpose is to convert energy of a prime mover (a electric motor or turbine) first into velocity or kinetic energy and then into pressure energy of a fluid that is being pumped. The energy changes occur by virtue of two main parts of the pump, the impeller and the volute or diffuser. The impeller is the rotating part that converts driver energy into the kinetic energy. The volute or diffuser is the stationary part that converts the kinetic energy into pressure energy.

Generation of Centrifugal Force

The process liquid enters the suction nozzle and then into eye (center) to the impeller. When the impeller rotates, it spins the liquid sitting in the cavities between the vanes outward and provides centrifugal acceleration.As liquid leaves the eye of the impeller a low-pressure area is created causing more liquid to flow toward the inlet. Because the impeller blades are curved, the fluid is pushed in a tangential and radial direction by the centrifugal force. This force acting inside the pump is the same one that keeps water inside a bucket that is rotating at the end of a string.The figure below depicts a side cross-section of a centrifugal pump indicating the movement of the liquid.

Conversion of Kinetic Energy to Pressure Energy
The key idea is that the energy created by the centrifugal force is kinetic energy.The amount of energy given to the liquid is proportional to the velocity at the edge or vane tip of the impeller. The faster the impeller revolves or the bigger the impeller is,then the higher will be the velocity of the liquid at the vane tip and the greater the energy imparted to the liquid.

This kinetic energy of a liquid coming out of an impeller is harnessed by creating a resistance to the flow. The first resistance is created by the pump volute (casing) that catches the liquid and slows it down. In the discharge nozzle, the liquid further decelerates and its velocity is converted to pressure according to Bernoulli’s principle.

Therefore, the head (pressure in terms of height of liquid) developed is approximately equal to the velocity energy at the periphery of the impeller expressed by the following well-known formula:

H=(V^2)/(2*G)

Where

-H=Total head developed in feet.

-V=Velocity at periphery of impeller in (ft/sec).

-G=Acceleration due to gravity (32.2 feet/sec^2).

This head can also be calculated from the readings on the pressure gauges attached to the suction and discharge lines.

V=(N*D)/229

Where

-V=Velocity at periphery of impeller in (ft/sec).

-N=The impeller RPM (revolution per minute).

-D=Impeller diameter in inches.

2009-06-14T10:41:00.000-07:00

HYDRAULIC PUMPS

Hydraulic pumps convert the mechanical energy transmitted by its prime mover (electronic motor, internal combustion engine) into hydraulic working energy.
The type of pump used in an industrial hydraulic system is a positive displacement pump, there are many types of positive displacement pumps.
For this reason, we must be selective and concentrate on the most popular.These are vane, gear, and piston pumps.
So, now we need to know types of pump?

PUMP TYPES

Non positive displacement pumps:
Centrifugal pumps are used to pump large volumes of fluids at relatively low pressures. Like other non positive displacement pumps, they share the common advantages of low noise level, and the ability to pump nearly all fluids without damage to internal parts. Propeller pumps are also non positive displacement pumps.

Positive displacement pumps:
Positive displacement pumps transfer a constant amount of fluid for each cycle of operation. If this internal pump volume can not be adjusted, the pump is considered to have a fixed displacement. If the internal volume of the pump is adjustable, the pump is considered to be variable volume displacement pump. While the drive speed also can be used to change the volume flow rate for a positive displacement pump, this is a less desirable altrnative than varying the internal displacement to change pump output.

Positive displacement pumps are essentially four basic types:
1-Gear pumps (fixed displacement only by geometrical necessity):
· External gear pumps.
· Internal gear pumps.
· Lobe pumps.
· Gerotor.

2-Screw pumps (fixed displacement only).

3-Vane pumps:
· Unbalanced vane pumps (fixed or variable displacement).
· Balanced vane pumps (fixed displacement only).
4-Piston pumps (fixed or variable displacement):
· Axial flow.
· Radial flow.

2009-05-08T10:33:00.000-07:00

FLUID POWER

FLUID POWER MEAN USING PRESSURIZED OIL OR AIR TO ACCOMPLISH WORK, MOST HYDRAULIC SYSTEMS USE PETROLEUM OILS OR WATER, AND AIR IN PNEUMATIC SYSTEMS.

FLUID POWER IS USED IN INDUSTRIAL LIFT TRUCKS, LOADERS, ROBOTIC ARMS, AND LANDING GEAR OF AIRCRAFT AND MORE …………..

BUT, WHAT ARE THE FIELDS WE NEED FLUID POWER FOR?
ALMOST EVERYTHING LIKE INDUSTRIAL, CONSTRUCTION, AGRICULTURE, MARINE,
OFFSHORE,………….

WHY WE DON’T USE ELECTRICAL POWER INSTEAD OF FLUID POWER?
THERE ARE A LOT OF REASONS LIKE;

1- TRANSMISSION OF HIGH FORCES WITHIN A SMALL SPACE.
2- HIGH ENERGY DENSITY.
3- ENERGY STORAGE CAPABILITY.
4- RAPID REVERSAL DUE TO LOW COMPONENT MASSES.
5- UNIFORM MOTION.
6- DESIGN FREEDOM IN THE ARRANGEMENT OF COMPONENTS.
7- OVERLOAD PROTECTION.
8- WIDE TRANSMISSION RATIO.
9- LONG SERVICE LIFE.
10- ENERGY RECOVERY CAPABILITY.
AND SO……………

NOW WE CAN SEE WHY FLUID POWER EVEN WITH ITS TERRIBLE DISADVANTAGES LIKE;

1- PRESSURE AND FLOW LOSSES IN PIPES AND CONTROL DEVICES.
2- FLUID VISCOSITY SENSITIVE TO TEMPERATURE AND PRESSURE.
3- LEAKAGE PROBLEMS.
4- COMPRESSIBILITY OF THE HYDRAULIC FLUID.

NOW, WE CREATE A GENERAL IDEA ABOUT FLUID POWER
THEN ,WHAT IS THESE WORDS MEAN (PUMP, TURBINE, AND COMPRESSOR)?

WELL THEY ARE HYDRAULIC DEVICES SIMILAR AT THE SHAPE AND THE INTERNAL COMPONENTS ,THEY ALL CONSIST OF BLADES ,SHAFT, AND EXTERNAL CASE, BUT SO DIFFERENT IN PURPOSE……..

LOOK;
PUMP IS A HYDRAULIC DEVICE THAT CONVERTS THE MECHANICAL ENERGY TRANSMITTED BY ITS PRIME MOVER (ELECTRICAL MOTOR, INTERNAL COMBUSTION ENGINE) INTO HYDRAULIC WORKING ENERGY.

TURBINE IS THE REVERSE OF THE PUMP ,IT IS CONVERTS THE HYDRAULIC ENERGY INTO MECHANICAL ENERGY TO PRODUCE ELECTRICITY, LIKE RIVER DAM TURBINES.

COMPRESSOR IS THE SAME LIKE PUMP CONVERTS THE MECHANICAL ENERGY INTO HYDRAULIC WORKING ENERGY BUT THE DIFFERENT IS THE WORKING FLUID; HOW?
IN PUMPS WE USE WATER OR PETROLEUM OILS,
BUT IN COMPRESSORS WE USE THE AIR.

THERE IS VERY IMPORTANT QUESTION NOW?!

IS TURBINE DEAL WITH THAT TOW DIFFERENT FLUIDS?
YES, THERE IS STEAM TURBINE FOR WATER , AND GAS TURBINE FOR AIR.

Privacy policy

2009-04-04T03:43:00.000-07:00

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