What Do You Mean By A Pump?
A Pump Is A Device That Transfers Energy To A Fluid Passing Through It. In Practice, Pumps Change Both The Velocity And The Pressure Of The Fluid Passing Through It, The Ratio Of These Energy Changes Depends Upon The Type And The Speed Of The Pump In Use.
What Are The Main Types Of Pumps?
Main Types Of Pumps
1. Displacement Pumps
2. Kinetic Pumps
What Do You Mean By Displacement Pump? Also Briefly Explain Types Of Displacement Pump.
1. Displacement Pumps
In Displacement Pumps The Volume Of The Pump Chamber Is Alternately Increased To Draw The Liquid In (suction) And Then Decreased To Force The Liquid Out (delivery). This Is Done By A Reciprocating Motion Of A Piston Or Plunger Within A Cylinder, Or By A Rotary Motion Of Specially Designed Vanes, Gears Or Rotors.
Positive Displacement Are Provided Fitted With Relief Valve Safeguard The System
Types Of Displacement Pump?
i) Reciprocating Pump: A Reciprocating Pump Has 'to And Fro' Motion Provided By A Direct Acting Steam Driven Piston, Or Through Mechanisms That convent Rotary Motion To Reciprocating Motion (e.g. Cranks, Eccentrics Etc.).Due To Fluctuating Motion Of The Piston, The Delivery And Pressure Is Not Steady. To Improve The Overall Performance, The Pump Is Arranged As Double Acting And Fitted With An Accumulator (air Vessel) On The Discharge Side Of The Pump To Achieve A Near Steady Pressure.
Reciprocating Type Pumps Are Suitable For Delivering Smaller Quantities Of Liquids At High Pressures. They Are Self-priming And Can Handle High Suction Lifts. However Their Construction Is Complicated And Uneconomical Except For Limited Applications E.g. Bilge Pumps, Stripping Pumps, Etc.
ii) Rotary Pumps
Rotary Types Of Displacement Pumps Are Commonly Used On Board Ships In Place Of Reciprocating Pumps.
A Rotary Pump Continuously Scoops The Fluid From The Pump Chamber By Means Of Gears Or Screws, Or Vanes Etc. When Rotated, Liquid Gets Trapped In Small Pockets Created By The Moving Element And It Gets Transferred From The Suction Side To The Delivery Side.
Types Of Rotary Pumps
The Sliding Vanes Or Blades Fit Into The Slots In The Rotor. Ahead Of The Slots And In The Direction Of Rotation, Grooves Admit The Liquid Being Pumped By The Vanes, Moving Them Outward With A Force Of 'locking Pressure That Varies Directly With The Pressure That The Pump Is Operating Against. The Grooves Also Serve To Break The Vacuum On The Admission Side. The Operating Cycle And The Action Of Centrifugal Force And Hydraulic Pressure Hold The Vanes In Contact With The Casing.a) A Gear Pump Has Intermeshing Gears Or Lobed Members Enclosed In A Suitably Shaped Housing. The Efficient Of These Pumps Depends Upon The Accuracy With Which The Component Parts Are Machined And Fitted I.e. Working Clearances. Gear Pump Is The Simplest Type Of Positive Delivery Pumps And Most Commonly Used On Board Ship For Handling Small Quantities Of Fluids -usually Oils, E.g. Lubricating Oil Transfer Pumps, Auxiliary Diesel Engine Lubricating Oil Pump, Oil Separator Pumps Etc. Delivery Rate Depends Directly Upon The Speed Of The Pump.
B) A Lobe-pump Like A Gear Pump And Was The Earlier Type Of Mechanical Pumps Used For Supercharging Of Main Engine. Now You Will Find It Being Used A Sewage Pump.
C) A Vane Type Pump Operation Is Also Based On The Principle Of Increasing The Size Of The Cavity To Form A Vacuum, Allowing The Space To Fill With The Incoming Liquid, And Then Forcing The Fluid Out Of The Pump Under, Pressure By Diminishing The Volume.
Types Of Screw Pump
a) Single-screw- Rotating Within A Accurately Bored Cylinder -mono-pumps As Commonly Known For Marine Application Has One Power Rotor Within A Semi-flexible Stator, And This Type Can Handle Highly Abrasive Liquids And Can Also Pump Liquids Containing Fairly Large Solid Particles.
b) Two-screw- Either With Intermeshing Contact, Or Separately Driven And Synchronised To Run With Positive Clearance.
C) Three-screw -with Three Screw On Parallel Axis. The Central Screw Is Power Driven And Drives Two Outer Idler Screws. The Assembly Of Three Screws Is Usually Supplied In A Single Element.
Bhupesh Srivastava is a Marine Engineer by profession and sailing as a 3/E on FG vessels. He loves reading, writing and blogging. He loves to write about Marine Automation, MEP and Marine Auxiliary machines.
Procedures for starting, stopping and taking on load GeneratorsPrecaution Must Be Taken While Starting And Taking ....
>> READ MOREAll that you need to know about Breathing ApparatusA Breathing Apparatus Normally Known As The BA Set ....
>> READ MORE10 points you should know about EEBD/ELSAEmeregency Scape Breathing Device (EEBD) / Emergen ....
>> READ MOREFAQ Orals MEP (Auxiliary Boilers)What Would You Do If You Had A High Chloride Level ....
>> READ MOREIntroduction of new CPR Ring by MAN B&WA Number Of Incidents Came In Focous With High Top ....
>> READ MOREConsequences of Low Load Operation of Diesel GeneratorsQ. What Is A Cylinder Liner Protection Ring & What ....
>> READ MOREAll you need to know about Classification societiesWhat Do You Mean By Classification Society? ....
>> READ MORECentrifugal Pumps Vs Positive Displacement PumpsThe pumps behave very differently when considering ....
>> READ MOREMarinelookout is an intiative by seagoing Mariners to make life easy for the marine fraternity either at sea or at MMD. With Marinelookout we deals with several areas of maritime industry like - Day to day MMD oral Questions. Specific blogs inscribing the questions faced. Separate ePariksa section which prepares you for the written exams of MEO Class IV. Pre Sea Section is for the Cadets at College, which provides them the gateway to Sea. Its to help them understand the basic topics in a simplified manner. Marinelookout has a very dedicated team of young guns who are fired up to perform. We also have Chief Engineers and Masters who make us a complete organization.In the upcoming years we are going to create a marine knowledge hub over the internet. Its just a matter of time, be with us now and you can avail the fruits ever.