Posted tagged ‘flow’

Vertical screw conveyors

September 8, 2011


01-Vertical screw conveyors- Vertical screw pump- Vertical screw conveyor design- Vertical screw conveyor calculations

A vertical screw conveyor conveys material upward in a vertical path. It requires less space than some other types of elevating conveyors. Vertical screw conveyor can handle most of the bulk materials provided there is no large lump. The maximum height is usually limited to 30m.

A vertical screw conveyor consists of a screw rotating in a vertical casing. The top bearing for the screw shaft must be designed to stand against radial and thrust loads. A suitable inlet port at the lower end and a discharge port at the upper end of the casing are provided. Feeding a vertical screw conveyor deserves careful consideration. Most materials are fed to the vertical conveyor by a straight or offset horizontal feeder conveyor. The ideal operation of a vertical screw conveyor is to have a controlled and uniform volume of material feeding.

Uneven feeding and start stop operation may adversely affect the performance of the vertical screw conveyor in terms of speed, capacity and horse power.

Average capacities and speeds of vertical conveyor

Nominal diameter of screw in mm Capacities in m3/hr Speed of screw
150 10 Up to 400 RPM
250 35 300 RPM
300 75 250 RPM
400 170 200 RPM

Vertical screw conveyors or some special design of vertical screw conveyor finds wide application in ship unloading.

01-Vertical screw lift- Vertical screw elevator- Vertical screw feeder- vertical screw conveyor-vertical screw pump

Practical experience with these conveyors has shown that the resistance factor for vertical conveyors is higher than those of the horizontal conveyors. Resistance factor λ may be taken as 5.5 to 7.5 for grains. 6.5 to 8.3 for salt.

01-screw conveyor design calculation- screw conveyor power calculation- screw conveyor efficiency- screw conveyor theory- screw conveyor formulae- screw conveyor flow rates

The driving power of the loaded screw conveyor is given by:

P = PH + PN + Pst

Where,

PH = Power necessary for the progress of the material

PN = Driving power of the screw conveyor at no load

Pst = Power requirement for the inclination of the conveyor

Power necessary for the progress of the material PH:

For a length L of the screw conveyor (feeder), the power PH in kilo watts is the product of the mass flow rate of the material by the length L and an artificial friction coefficient λ, also called the progress resistance coefficient.

PH = Im.L. λ.g / 3600 (kilowatt)

= Im.L. λ / 367 (kilowatt)

Where,

Im = Mass flow rate in t/hr

λ = Progress resistance coefficient

Each material has its own coefficient λ. It is generally of the order of 2 to 4. For materials like rock salt etc, the mean value of λ is 2.5. For gypsum, lumpy or dry fine clay, foundry sand, cement, ash, lime, large grain ordinary sand, the mean value of λ is 4.0.

In this connection it should be noted that the sliding of the material particles against each other gives rise to internal friction. Other resistance due to grading or shape of the output discharge pattern contributes to the resistance factor. That is why the parameter λ is always higher than that due to pure friction.

Drive power of the screw conveyor at no load, PN:

This power requirement is very low and is proportional to the nominal diameter and length of the screw.

PN = D.L / 20 (Kilowatt)

Where,

D = Nominal diameter of screw in meter

L = Length of screw conveyor in meter

Power due to inclination: Pst

This power requirement will be the product of the mass flow rate by the height H and the acceleration due to gravity g.

Pst = Im.H.g / 3600

= Im.H / 367

H should be taken positive for ascending screws and will be negative for descending screws.

Total power requirement:

The total power requirement is the sum total of the above items

P = (Im (λ.L + H) / 367) + (D.L /20) (Kilowatt)

Vibratory conveyor / Oscillating Conveyor

September 8, 2011


01-vibrating conveyor- vibrating conveyor systems-vibrating conveyor parts-shaker conveyor-inertia conveyor-reciprocating conveyor-oscillating conveyor

A vibratory conveyor essentially consists of an open or closed trough or pipe, generally horizontal but not always so, and which is elastically supported on a base structure or suspended from an overhead structure by springs. The trough or pipe is caused to oscillate at high frequency and small amplitude by an appropriate drive mechanism. Vibratory conveyors are commonly employed in industry to carry a wide variety of particulate and granular types of bulk materials. The fundamental action of the vibrating troughs on the bulk material loaded on it is to throw the particles upward in the forward direction so that the material performs series of short hopping movement and propagates at a certain speed.

Oscillating conveyors are utilized to convey sand or other granular particles at a desired rate. The conveyor is generally placed under a vibrating shakeout or a grid to eliminate direct handling of hot sand by the belt conveyor. In the process of reciprocation, the oscillating conveyor cools the hot sand to some extent which increases the life of the return sand conveyor belt.

An important characteristic of vibratory conveyor is the ease with which the flow rate of the conveyed material can be controlled by adjusting the amplitude and or frequency of the vibration. This particular aspects of such conveyor has led to the wide spread application of vibrating trough as feeders employed to supply material in controlled amount to various machines. When the trough is replaced by a screen, the vibratory conveyor may serve as vibrating screen, which has wide application in various industries. A distinction must be made between feeders and conveyors. A feeder is used as a discharge device under a storage hopper or bin and is subjected to varying head loads. A conveyor requires regulated feed rate and must not operate under varying head load conditions.

Construction details of Oscillating Conveyor:

01-vibrating conveyor parts-oscillating conveyor design-oscillatory motion design-vibrating trough conveyors-vibrating oscillatory machine-vibrating machine

01-vibrating conveyor parts-vibrating conveyor design-vibrating conveyor components-vibrating feeders-vibrating machine-vibrating motor-horizontal motion vibrating bed-motion of vibrating systems

MATERIAL HANDLING

August 23, 2011

Bases on Design features and operational characteristics, material handling equipment may be broadly classified as:

01-classification of material handling equipment

Hoisting Equipment’s:

01-hoisting equipments-Pillar-Type-Jib-Crane-cantilever crane

It constitute a group of equipment which are employed mainly for lifting or lowering of unit load or piece goods in batches. This group of equipment’s can be further sub classified into:

1. Pure Hoisting Machineries

    • Jack
    • Winches
    • Hand Hoists
    • Pulley Blocks

2. Cranes

    • EOT Crane
    • Jib Crane
    • Cantilever Crane

3. Elevators

    • Lift
    • Bucket Elevators

Conveying Equipment’s:

01-automatic conveyor system-material handling system-material handling equipments

It comprises of a number of equipment which are employed for handling principally bulk load (occasionally piece goods or unit load may also be handled) in continuous flow. Such machines do not have separate lifting or lowering gear. This group of equipment also can have further sub classifications as:

1. Belt Conveyor

2. Hydraulic Conveyor

3. Pneumatic Conveyor

4. Apron Conveyor

5. Screw Conveyor

6. Flight Conveyor

Surface/ Overhead Equipment’s:

01-Toyota_Forklift-surface equipment-handling unit load-bulk load

These are the group of equipment’s which are employed for handling unit load or bulk load in batches on a horizontal surface. This group of equipment may be further sub classified into:

1. Truck and Lorries

2. Railway Cars and Wagons

3. Fork Lifts

4. Overhead mono-rail / Equipment

5. Scrapers and Skidders

Types of Material Handling Equipment Loads:

It usually classified into:

1. Unit Load

2. Bulk Load

Unit Load:

Unit loads are those which are counted by numbers or units. A component of a machine, a complete machine, a structural element, a beam, a girder, building block are some examples of unit load.

01-hoisting machineries-niko_jib_crane_floor_mounted-cantilever cranes


Sometimes certain quantities of free flowing materials can be placed in a container and can be handled as unit load. Hoisting equipment are primarily used for handling unit load. Unit loads are usually specified by it’s weight.

Bulk Load:

When the load is in the form of particles or lumps of homogeneous materials or powder like materials, which can not be counted by numbers, it is called as “Bulk load”.

01-bulk load material handling equipment's-railway cars-railway wagons

Examples are:


Sand, Cement, Coal, Mineral, Stone, Clay etc.,

A bulk material may be classified by it’s:

1. Bulk Density

2. Lump-Size

3. Flowability

4. Abrasiveness

5. Miscellaneous Characteristics

METALLURGY

August 23, 2011

Definition:

The Process of producing components from metallic powder parts made by powder metallurgy may contain non-metallic constituents to improve the bonding qualities and properties.

Number and variety of products made by powder metallurgy are continuously increasing:

    1. Tungsten Filaments for Lamps
    2. Contact Point relays
    3. Self lubricating bearings
    4. Cemented carbides for cutting tools etc.

02-PowderManufacturing-metallurgy-particles

 

Characters of Metal Powders:

  • Shape:

It is influenced by the way it’s made. The shape may be spherical (atomization) (Electrolysis) flat or angular (Mechanical crushing). The particle shape influences the flow characteristics of powders.

  • Particle Size (Fineness) and size distribution:

Particle Size and Distribution are important factors which controls the porosity, Compressibility and amount of shrinkage. Proper particle size and size distribution are determined by passing the powder through a standard sieves ranging from 45 to 150 micrometer mesh.

  • Flowability:

The ability of the powders to flow readily and conform to the mould cavity. The flow rate helps to determine to possible production rate.

  • Compressibility:

It’s defines as the volume of initial powder (Powder loosely filled in cavity) to the volume of compact part. Depends on particle shape & size distribution.

  • Apparent Density:

The Apparent density depends on particle size is defined as the ratio of volume to weight of loosely filled mixture.

  • Green strength:

It refer to strength of a compact part prior to sintering. It depends on compressibility and helps to handle the parts during the mass production.

  • Purity:

Impurities affects sintering & Compacting Oxides & Gaseous impurities can be removed from the part during sintering by the use of a reducing atmosphere.

  • Sintering ability:

It is the ability which promotes bonding of particles by the application of heat.

 

Powder Metallurgy Process steps:

 

01-powder-metallurgy-process-step by step


 

01-powder metallurgy processes-mixing-finished product

 

02-finished product 

Manufacture of Metal Powders:

Methods:

  • Mechanical pulverization:

Machining, Drilling or Grinding of metals is used to convert them to powders.

  • Machining:

It Produces coarse particles (Flack form) especially Magnesium powders.

  • Milling or Grinding:

It suitable for brittle materials.

  • Shorting:

The process of dropping molten metal through a Sieve or small orifice in to water. This produces Spherical particles or larger size. Commonly used for metals of low melting point.

03-mechanical pulverization-milling-powder

04-crushing-shredding-conveyors-powder

 

  • Atomizing:

In this molten metal is forced through a nozzle, and a stream of compressed air, stream or Inert gas is directed on it break up into five particles. Powders obtained in irregular in shapes. Atomization commonly used for aluminium, Zinc, Tin, Cadmium and other metals of low melting point.

03-atomization-powder metallurgy

 

  • Electrolytic deposition:

It’s used mainly for producing iron and copper powders. These are dense structure with low apparent density. It consists of depositing metal on cathode plate by conventional electrolysis processes. The Cathode paltes are removed and the deposited powder is scraped off. The powder is wasted, dried, screened & oversized particles are milled or ground for fineness. The powder is further subjected to heat treatment to remove the work hardening effect.

  • Chemical reduction:

It’s used for producing iron, Copper, Tungsten, Molybdenum, Nickel & Cobalt powder process consists of reducing the metal oxides by means of carbon monoxide or Hydrogen. After reduction, the powder is usually ground & Sized.

 

Forming to shape:

    1. The process of mixing the powders is called Blending.
    2. The Loose powders are formed in to shape by compacting.

METALLURGY

August 23, 2011

Definition:

The Process of producing components from metallic powder parts made by powder metallurgy may contain non-metallic constituents to improve the bonding qualities and properties.

Number and variety of products made by powder metallurgy are continuously increasing:

    1. Tungsten Filaments for Lamps
    2. Contact Point relays
    3. Self lubricating bearings
    4. Cemented carbides for cutting tools etc.

02-PowderManufacturing-metallurgy-particles

 

Characters of Metal Powders:

  • Shape:

It is influenced by the way it’s made. The shape may be spherical (atomization) (Electrolysis) flat or angular (Mechanical crushing). The particle shape influences the flow characteristics of powders.

  • Particle Size (Fineness) and size distribution:

Particle Size and Distribution are important factors which controls the porosity, Compressibility and amount of shrinkage. Proper particle size and size distribution are determined by passing the powder through a standard sieves ranging from 45 to 150 micrometer mesh.

  • Flowability:

The ability of the powders to flow readily and conform to the mould cavity. The flow rate helps to determine to possible production rate.

  • Compressibility:

It’s defines as the volume of initial powder (Powder loosely filled in cavity) to the volume of compact part. Depends on particle shape & size distribution.

  • Apparent Density:

The Apparent density depends on particle size is defined as the ratio of volume to weight of loosely filled mixture.

  • Green strength:

It refer to strength of a compact part prior to sintering. It depends on compressibility and helps to handle the parts during the mass production.

  • Purity:

Impurities affects sintering & Compacting Oxides & Gaseous impurities can be removed from the part during sintering by the use of a reducing atmosphere.

  • Sintering ability:

It is the ability which promotes bonding of particles by the application of heat.

 

Powder Metallurgy Process steps:

 

01-powder-metallurgy-process-step by step


 

01-powder metallurgy processes-mixing-finished product

 

02-finished product 

Manufacture of Metal Powders:

Methods:

  • Mechanical pulverization:

Machining, Drilling or Grinding of metals is used to convert them to powders.

  • Machining:

It Produces coarse particles (Flack form) especially Magnesium powders.

  • Milling or Grinding:

It suitable for brittle materials.

  • Shorting:

The process of dropping molten metal through a Sieve or small orifice in to water. This produces Spherical particles or larger size. Commonly used for metals of low melting point.

03-mechanical pulverization-milling-powder

04-crushing-shredding-conveyors-powder

 

  • Atomizing:

In this molten metal is forced through a nozzle, and a stream of compressed air, stream or Inert gas is directed on it break up into five particles. Powders obtained in irregular in shapes. Atomization commonly used for aluminium, Zinc, Tin, Cadmium and other metals of low melting point.

03-atomization-powder metallurgy

 

  • Electrolytic deposition:

It’s used mainly for producing iron and copper powders. These are dense structure with low apparent density. It consists of depositing metal on cathode plate by conventional electrolysis processes. The Cathode paltes are removed and the deposited powder is scraped off. The powder is wasted, dried, screened & oversized particles are milled or ground for fineness. The powder is further subjected to heat treatment to remove the work hardening effect.

  • Chemical reduction:

It’s used for producing iron, Copper, Tungsten, Molybdenum, Nickel & Cobalt powder process consists of reducing the metal oxides by means of carbon monoxide or Hydrogen. After reduction, the powder is usually ground & Sized.

 

Forming to shape:

    1. The process of mixing the powders is called Blending.
    2. The Loose powders are formed in to shape by compacting.

INTERVIEW QUESTIONS:GERNAL:

August 22, 2011
  • Explain the Second Law of Thermodynamics.
    The entropy of the universe increases over time and moves towards a maximum value.

 

  • How do you measure temperature in a Wet Bulb Thermometer?
    Wet bulb temperature is measured in a wet bulb thermometer by covering the bulb with a wick and wetting it with water. It corresponds to the dew point temperature and relative humidity.

 

  • What is Bending moment?
    When a moment is applied to bend an element, a bending moment exists in the element

 

  • What are the points in the Stress Strain curve for Steel?
    Proportional limit, elastic limit or yield point, ultimate stress and stress at failure.

 

  • Define Reynolds number.
    Reynolds number is the ratio of inertial force and viscous force. It is a dimensionless number. It determines the type of fluid flow.

 

  • What is a Newtonian fluid?
    A Newtonian fluid possesses a linear stress strain relationship curve and it passes through the origin. The fluid properties of a Newtonian fluid do not change when any force acts upon it.

 

  • How many Joules is 1 BTU?
    1 BTU is equal to 1055.056 joules.

 

  • What is PS?
    PS is Pferdestarke, the German unit for Horsepower.

 

  • Explain Otto cycle.
    Otto cycle can be explained by a pressure volume relationship diagram. It shows the functioning cycle of a four stroke engine. The cycle starts with an intake stroke, closing the intake and moving to the compression stroke, starting of combustion, power stroke, heat exchange stroke where heat is rejected and the exhaust stroke. It was designed by Nicolas Otto, a German engineer.

 

  • Explain the nomenclature of a 6203-ZZ bearing.
    6 is the type code, which shows it is a single-row ball bearing, 2 is the series, means light, 03 is the bore, which is 17 mm and ZZ is the suffix meaning double shielded bearing.

 

  • What is Gear ratio?
    It is the ratio of the number of revolutions of the pinion gear to one revolution of the idler gear.

 

  • What is Annealing?
    It is a process of heating a material above the re-crystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material.

 

  • Define Torque.
    Torque is defined as a force applied to an object that results in rotational motion.

 

  • What is Ductile-Brittle Transition Temperature?
    It is the temperature below which the tendency of a material to fracture increases rather than forming. Below this temperature the material loses its ductility. It is also called Nil Ductility Temperature.