PUMP || WHAT IS MEAN BY PUMP? || CLASSIFICATION OF PUMPS || TYPES OF PUMPS

          A Pump is a machinery or device used to move or compress Fluids (Liquids or Gases ) or Slurries, by using mechanical action. The mechanical energy available from the the motor into potential, kinetic and thermal energy imparted to the liquid flow.
          "Pump is a mechanical device, which converts the mechanical energy into pressure energy of the liquid" which is subsequently converted into potencial energy as the liquid is lifted from a lower to higher level.

          Pumps are widely used in industries like power plants, chemical, petrolium, paper, metallurgy etc., There are many different types of pumps and each pump have different working principle. Type of pump which you need depends upon the application. The basic requirement of any pump is it's reliability, durability and efficiency. 

          There are many types of pumps are the in the industry, the type pump we need depend on application, including;
          1) The type of fluid
          2) The volume of liquid
          3) The distance/head

Classification of Pumps

Pumps are divided into two major categories: 

            a) Dynamic (or Kinetic)pumps

            b) Positive displacement (or Displacement) pumps

a) Dynamic pumps:

          Dynamic or Kinetic pumps include all pumps that impart fluid velocity and the resulting momentum to the fluid as it moves past or through the pump impeller and subsequently convert some of that velocity into additional pressure in a diffusing flow passage.

          These pumps generally have lower efficiency than positive displacement pumps. However they do operate at relatively higher speeds, thus providing higher flow rates in relation to the physical size of the pump. These pumps require less maintenace than positive displacement pumps.

Classification of Dynamic pumps:

          i. Centrifugal pumps

          ii. Vertical/Horizontal pumps

          iii. Submersible pumps

          iv. Fire fighter pumps

          v.   

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a) Positive displacement pumps:

          A positive displacement pump makes a fluid trap in a fixed amount and forcing (displacing) that trapped volume by the moving element (Piston, Plunger, Rotor, Lobe, or Gear) from the pump casing (or cylinder) into the discharge pipe, and, at the same time raises the pressure of the liquid. So displacement pump doesn't develop pressure; it only produces a flow of fluid.

          Some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant through each cycle of operation.

Classification of Positive displacement pumps:

v Diaphragm pumps

v Gear pumps

v Piston/Plunger pumps

v Screw pumps

v Lobe pumps

v Ejectors 
v Mono block pumps

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Reverse Osmosis (RO)

          Reverse Osmosis (RO) is a water purification technique that uses a semi-permeable membrane to get rid off ions, molecules and larger contaminants (particles) from fresh water.

What is Reverse Osmosis (RO)?

Image Courtesy: https://www.freshwatersystems.com/blogs/blog/reverse-osmosis-faqs

          To understand the purpose and method of Reverse Osmosis we should understand initially the naturally occurring process of Osmosis.

          Osmosis is a naturally occurring phenomenon and one of the foremost vital processes in nature. This is a method where less concentrated molecules (saline solution) will tend to migrate to more concentrated solution. The objective is an equalized solution.

          The examples of Osmosis are 'Cholera', 'plant roots drawing (absorb) water from the soil' and 'our kidney absorb water from our blood'.

          In the below diagram we showed how osmosis works. A solution that is less concentrated will have a natural tendency to migrate to a solution with a higher concentration. For example, if a container filled with water with a low salt concentration and another container filled with water with high salt concentration and that they were separated by a semi-permeable membrane, then the water with the lower salt concentration would begin to migrate towards the water container with the higher salt concentration, until concentration becomes equal on both sides.

Semi-permeable membrane:
          A semi-permeable membrane is a synthetic or biological membrane that will permit some atoms or molecules to pass but not others. A simple example for semi-permeable membrane is a screen door. It permits air molecules to go through but not pests or something larger than the holes within the screen door. Another example is blood brain barrier, it allows what ever the brain needs and what ever harmful is kept out. The membranes surrounding the organelles.

Reverse Osmosis:
          Reverse osmosis is simply the opposite of osmosis method. Osmosis happens naturally without ant energy required. To reverse the method of osmosis we need to use some energy to the more saline solution. A Reverse Osmosis membrane is a semi-permeable membrane that acts like a filter having extremely tiny pores that enables the passage of water molecules however not the majority of dissolved microscopic contaminants like salts, organic, microorganism and pyrogens. However, we need to "push" the water through the reverse osmosis membrane (or semi-permeable membrane) by applying pressure that is greater than the naturally occurring osmotic pressure in-order to de-salinate (de-mineralize or de-ionize) water in the method, allowing pure water through while holding back majority of contaminants.
          In the below diagram we showed the method of Reverse Osmosis. When pressure is applied to the concentrated solution the water molecules are forced through the semi-permeable membrane and the contaminants are not allowed through.

PROGRESSIVE CAVITY PUMPS : SCREW PUMPS

VARIOUS MATERIALS USED FOR SINGLE POINT CUTTING TOOLS

          Different machining applications require different tool materials. In those conditions along with general properties of cutting tools they require some unique properties. 

Basic properties that cutting must posses are:

§ Tool material must be at least 30 to 50% harder than the work piece material.

§ High temperature stability i.e., Tool material must show high red hardness

§ High toughness

§ High wear resistance and long life

§ High thermal conductivity

§ Lower coefficient of friction

§ Chemically inert to the working material and lubrication fluid.

§ Flexibility in fabrication and low cost

Different elements used in cutting tool materials and their properties are 

Element	Properties
Tungsten	Increases hot hardness Hard carbides formed Abrasion resistance
Molybdenum	Increases hot hardness Hard carbides formed Improving resistance
Chromium	Depth hardenability during heat treat hard carbides are ormed improving abrasion resistance some corrosion resistance
Vanadium	combines with carbon for wear resistance retards grain growth for better toughness
Cobalt	Increases hot hardness, toughness
Carbon	Hardening element forms carbides

          Different cutting tool materials used for cutting operations. In practice we use high carbon steel, high speed steel(HSS), non-ferrous cast alloys, cemented carbides, ceramics and sintered oxides, diamond, and cubic boron nitride(CBN).

1. High Carbon Steel tools:

§ Carbon tool steel is one of the inexpensive metal cutting tool.

§ It’s composition is C = 0.8 to 1.5%, Si = 0.1 to 0.4% and very small amount of Mn = 0.1 to 0.4%. and also other materials like Cr, V are added to change properties like hardness and grain size.

§ It is used for low-speed machining & soft metals like free cutting steels, aluminium and brass and used as Twist drills, chisels etc.

§ These tools possesses good machinability.

§ These tool loose hardness above 250°C so these can’t be used for high temperature applications.

§ Hardness of tool is about HRC = 65.

§ Used at cutting speed of 5m/min.

2. High speed steel (H.S.S):
          High speed steel is an alloy element. The main constituents are Tungsten, molybdenum and chromium etc., Generally used HSS tools composition is 18-4-1.
            18 - Tungsten is used to increase hot hardness and stability.
            4 – Chromium is used to increase strength.
            1 - Vanadium is used to maintain keenness of cutting edge.
In addition to these 2.5% to 10% cobalt is used to increase red hot hardness.
Rest of the content is iron

§ H.S.S is used for drills, milling cutters, single point cutting tools, broaches, dies, reamers etc.

§ It looses it’s hardness above 600°C temperature.

§ Some times tungsten is completely replaced by Molybdenum.

§ These tools are two types they are T-type : Tungsten predominant metal & M-type : Molybdenum predominant metal

§ Molybdenum based H.S.S is cheaper than Tungsten based H.S.S and also slightly greater toughness but less water resistance.

§ Coolant should be used for better tool life.

3. Non – ferrous cast alloy tools:
          It is an alloy having composition of Cobalt – 40 to 50%, Chromium – 27 to 32%, Tungsten  – 14 to 29%, Carbon – 2 to 4%

§ It can not heat treated and are used as cast form.

§ It looses it’s hardness above 800°C.

§ It will give better tool life than H.S.S and can be used at slightly higher cutting speeds.

§ They are weak in tension and like all cast materials tend to shatter when subjected to shock load or when not properly supported.

4. Cemented carbides:

§ Cemented carbide cutting tool is Produced by powder metallurgy technique with sintering at 1000°C.

§ Cutting speed range is 60-200 m/min, this is 6 to 8 times that of H.S.S.

§ They doesn’t loose their hardness up to 1000°C.

§ Compressive strength is more than tensile strength.

§ They are very stiff and their young’s modulus is about 3 times that of the steel.

§ High wear resistance.

§ High modulus of elasticity.

§ Low coefficient of thermal expansion.

§ High thermal conductivity, low specific heat, low thermal expansion.

§ Hardness is upto HRC- 90.

5. Ceramics and sintered oxides:

          Most common Ceramics and sintered oxides are basically made of Al₂O₃ and SiN. These are made by powder metallurgy technique with sintering.

§ Used for very high speed (300-600m/min). These are 10 times faster than HSS.

§ Used for continuous cutting only.

§ Can withstand up to 1800°C.

§ These tools are chemically inert and Have very abrasion resistance.

§ Having high compressive strength.

§ Used for machining CI and plastics.

§ Has less tendency to weld metals during machining.

§ No coolant is required.

§ Generally used ceramic is sintered carbides.

§ Another ceramic tool material is silicon nitride which is mainly used for CI.

6. Cubic Boron Nitride (CBN):

§ This is the second hardest material after diamond.The trade name is Borozone.

§ Consists of atoms of Nitrogen and Boron and produced by power metallurgy process.

§ Used as a substitute for diamond during machining of steel.

§ Used as abrasive grinding wheels.

§ Excellent surface finish is obtained.

§ Hardness HRC- 95.

§ Speed 600-800m/min

7. Diamond:

Diamond is the hardest metal known in the world and also costly.

§ Diamond possesses

Extreme hardness

Low thermal expansion.

High thermal conductivity.

High melting point

Very low coefficient of friction.

§ Diamond tools give good surface finish and dimensional accuracy.

§ Speeds ranging 1500 to 2000m/min.

§ These are not recommended for ferrous metals because of the diffusion of carbon atoms from diamond to work-piece.

§ Can withstand above 1500°C.

A synthetic (man made) diamond with polycrystalline structure is recently introduced and made by powder metallurgy process.