HYDRAULIC PUMPS:HYDRODYNAMIC PUMPS.

HYDRODYNAMIC PUMPS

Hydrodynamic or non-positive-displacement pumps such as centrifugal or turbine designs are used primarily in the transfer of fluids where the only resistance encoun­tered is that created by the weight of the fluid itself and friction.

Most non-positive-displacement pumps (Figure 3-1) operate by centrifugal force where fluids entering the center of the pump housing are thrown to the outside by a rapidly driven impeller. There is no positive seal between the inlet and outlet ports, and pressure capabilities are a function of rotating speed.

Although they provide smooth continuous flow, the output of a hydrodynamic pump is reduced as resistance is increased. It is possible to completely block off or dead­ head the outlet while the pump is running. For this and other reasons, non-positive­ displacement pumps are seldom used in hydraulic systems.

HYDROSTATIC PUMPS

Hydrostatic or positive-displacement pumps, as their name implies, provide a given amount of fluid for every stroke, revolution, or cycle. Except for leakage, their output is independent of outlet pressure or back pressure from the system. This properly makes them well suited for use in the transmission of power.

ROTARY PUMPS

All rotary pumps have rotating parts, which trap the fluid at the inlet port and force it, through the discharge port, into the system. Gears, screws, lobes, and vanes are com-

FLUID POWER DYNAMICS-0259

monly used to move the fluid within the pump. Rotary pumps are classified as posi­tive, fixed-displacement type.

Rotary pumps are designed with very small clearances between their rotating and sta­tionary parts to minimize slippage from the discharge side back to the suction side of the pump. They are designed to operate at relatively moderate speeds, normally below I ,800 rpm. Operation at higher speeds can cause erosion and excessive wear.

There are numerous types of rotary pumps and various methods of classification. They may be classified by the shaft position, the type of driver, their manufacturer’s name, or their ser­vice application. However, classification of rotary pumps is generally made according to type of rotating element. A few of the more common types include the following.

Incoming search terms:

Related posts:

Case studies:Benefits given by the use of environmental temperature control using reciprocating PD p...
Case studies:Upgrade of an oil refinery's pumping systems including installation of variable speed d...
System and process requirements:Process requirements
Valves and Sensors:Air flow measurement
Energy and Efficiency:Overall advantages of compressed air
CONTROL VALVES:Globe Valves
Air flow rate evaluation:The influence of temperature and Conveyed material influences.
Pipelines and valves:Steps
Design procedures:The use of equations in system design and Logic diagram for system design.
Conveying capability:The influence of materials and Low pressure conveying – Part I.
HYDRAULIC PUMPS:Centered Internal Gear
Hydraulic fluid:Applications of hydraulic systems
Graphic symbols.
Pressure measurement.
SUMMARY OF THE FIRST LAW OF THERMODYNAMICS

Leave a comment

Your email address will not be published. Required fields are marked *