Diaphragm Pump:Design & Working

Prepared By:- Sidra Hafeez

Definition: It’s a metering pump that displaces a predetermined

volume of liquid in a specific period.This pump is a positive displacement machine;also

known as controlled volume or chemical injection pump.

Working: It is a device that uses an elastomeric part to

transport a fluid.The diaphragm is moved back ‘n forth by a

reciprocating mechanism.The eccentric drive is there which gives more

fluctuation i.e. at the end of stroke; it gives jerks which affects the flow.

IntroductionHistory:-

In the 1940s, the USA started an extensive program to help synthetic elastomer achieve a worldwide breakthrough.

Using high quality elastomer material,new technical possibilities eventually opened up for the design and working of diaphragm pumps.

Later hydraullically driven diaphragm compressors come onto the market that were able to produce high pressures of up to 4,000 bar.

Principle:An elastomer diaphragm is moved up ’n down by an eccentric.The pump transfers, evacuates, and compress completely oil free.

Features:Uncontaminated transfer, no pollution of media.100% maintenance freeCompact designSmooth runningEasy installation

CharacteristicsHave good suction lift characteristics, some are

low pressure pumps with low flow rates; others are capable of higher flows rates, dependent on the effective working diameter of the diaphragm and its stroke length. They can handle sludges and slurries with a good amount of grit and solid content.

Suitable for discharge pressure up to 1.200 bar Have good dry running characteristics.Are low-shear pump

Construction

Elastic DiaphraghmPump HeadThe HousingThe Connecting RodClearanceThe Diaphragm Fixing

ScrewTransfer CompartmentOutlet Pressure valve Inlet Pressure Valve

Diaphragm Pump

Design Of DiaphragmControl Parameters: Max. speed = 250 rpmDiameter to stroke ratio= d/L=2

Design Parameters1. DischargeDischarge =area*stroke length *speedQmax = Π/4*d2*L*speed

Continued….2. Chamber DiameterD= 3d3. Chamber DepthL= L/2+4mm clearance4. Eccentricitye= 1/25. Control Volume

=Π/4*d2*L

Double Acting

Diaphragm Pump

WorkingWhen the volume of a chamber ofeither type of pump is increased (the diaphragm moving up), the pressure decreases, and fluid is drawn into the chamber. When the chamber pressure later increases from decreased volume (the diaphragm moving down), the fluid previously drawn in is forced out. Finally, the diaphragm moving up once again draws fluid into the chamber, completing the cycle. This action is similar to that of the cylinder in an internal combustion engine.

Working of Diaphragm Pump

Working Of Liquid Diaphragm Pump

High Speed Liquid Diaphragm Pump

A special type of pump based on the technology of diaphragm pump. Employes a mechanical drive for transfering,evacuating and compressing

gases. Are also used for siphoning off liquids or air-liquid mixtures.

Features Small Diaphragm strokes Low rotational speeds Stiffer diaphragms and use of diaphragm supports Drive ‘n shaft support more robustly constructed

Pros & ConsA major advantage of diaphragm pump is

that the pumped liquid does not come in to contact with most of working parts of the pump

The diaphragm pump furthur advantageous over over oil lubricated pumps such as it is an oil free pump, it has high gas tightness capacity, is highly reliable etc.

Cause a pulsating flow that may cause water hammer

Implications:Can be used to make artificial hearts.Are used to make air pumps for the filters on

small fish tanks.Can be up to 97% efficient.Have good self priming capabilities.Can handle highly viscous liquids.Are available for industrial, chemical and

hygienic applications

Criteria For Selection Of A pumpType of gasRequired Pneumatic performanceGas temperatureTemperature of surroundingOther conditions related to the surroundingType of motorPossible constructionl parametersMounting position and orientationOperation conditions

Future ScopesPrinciples of diaphragm pump can be used to

make miniature pump i.e. Micropump which’ll be useful for space and medical applications.Following is micro pump concept.

There is range of NASA experiments instruments and applicatipons where miniature pumps are needed.

To address such needs, a piezo electrically actuated miniature metering pump used to pump liquids at adjustable flowrates.

Any Questions??????