Posted tagged ‘size’

Design of Screw Conveyor

September 8, 2011

01-screw conveyor-screw conveyor design-screw conveyor design calculations-screw conveyor housing- screw conveyor flights- screw conveyor formulae- screw conveyor flow rates

The size of screw conveyor depends on two factors

1. The capacity of the conveyor

2. The lump size of the material to be conveyed (Maximum dimensions of the particle)

Usually there are three ranges of lump sizes which are considered for selection of screw size. These are:

· A mixture of lumps and fines in which not more than 10% are lumps ranging from maximum size to one half of the maximum, and 90% are lumps smaller than one half of the maximum size.

· A mixture of lump and fines in which not more than 25% are lumps ranging from the maximum size to one half of the maximum, and 75% are lumps smaller than one half of the maximum size.

· A mixture of lump only in which 95% or more are lumps ranging from maximum size to one half of the maximum size and 5% or less are lumps less than one tenth of the maximum size.

The allowable size of a lump in a screw conveyor is a function of the radial clearance between the outside diameter of the central pipe and the radius of the inside of the screw trough, as well as the proportion of the lumps in the mixture.

The lump size of the material affects the selection of screw diameter which should be at least 12 times larger than the lump size of a sized material and four times larger than the largest lumps of an un-sized material.

Example, if screw diameter is 250mm means radial clearance is 105mm, & Maximum lump size is 60mm of 10% lumps.

Capacity of Screw Conveyor:

01-screw conveyor capacity calculation-screw conveyor manufacturers-screw conveyor shaft- screw conveyor capacity- screw conveyor components- screw conveyor bearings

 

The capacity of a screw conveyor depends on the screw diameter, screw pitch, speed of the screw and the loading efficiency of the cross sectional area of the screw. The capacity of a screw conveyor with a continuous screw:

Q = V. ρ

Q = 60. (π/4).D2.S.n.ψ.ρ.C

Where,

Q = capacity of a screw conveyor

V = Volumetric capacity in m3/Hr

ρ = Bulk density of the material, kg/m3

D = Nominal diameter of Screw in m

S = Screw pitch in m

N = RPM of screw

Ψ = Loading efficiency of the screw

C = Factor to take into account the inclination of the conveyor

 

Screw Pitch:

Commonly the screw pitch is taken equal to the diameter of the screw D. However it may range 0.75 – 1.0 times the diameter of the screw.

 

 

 

 

01-screw conveyor pitch- screw conveyor inlet- screw conveyor output- screw conveyor blade- screw conveyor motor

Screw Diameter:

 

Nominal Size D Trough height from center of screw shaft to upper edge of the trough Trough width C Thickness of Tough Tubular shaft (d1 * Thickness)

Outside diameter of solid shaft

Coupling diameter of shaft
Heavy Duty Medium Duty Light Duty
100 63 120 2 1.6 33.7*2.5 30 25
125 75 145 2 1.6 33.7*2.5 30 25
160 90 180 5 3.15 1.6 42.4*2.5 35 40
200 112 220 5 3.15 2 48.3*3.5 40 40
250 140 270 5 3.15 2 60.3*4 50 50
315 180 335 5 3.15 76.1*5 60 50
400 224 420 5 3.15 76.1*5 60 75
500 280 530 5 3.15 88.9*5 70 75

RPM of Screw:

The usual range of RPM of screw is 10 to 165. It depends on the diameter of screw and the type of material (Max RPM of screw conveyor is 165)

Loading efficiency:

The value of loading efficiency should be taken large for materials which are free flowing and non abrasive, while for materials which are not free flowing and or abrasive in nature, the value should be taken low:

Ψ = 0.12 to 0.15 for abrasive material

= 0.25 to 0.3 for mildly abrasive material

= 0.4 to 0.45 for non abrasive free flowing materials

Inclination Factor:

The inclination factor C is determined by the angle of screw conveyor with the horizontal.

 

Angle of screw with the horizontal 10° 15° 20°
Value of factor C 1 0.9 0.8 0.7 0.65

Types of screw flight:

The screw of the conveyor may be right hand or left hand, the right hand type being the usual design. The threads of the screw may be single, double or triple.

The flight of the screws may be made in either of the two ways:

1. As Helicoids

2. As Sectional flight

Helicoids Flight:

They are formed from a flat bar or strip into a continues helix. The threads are thinner at the outer edge and thicker at the inner edge.

01-screw conveyor types- screw conveyor trough- screw conveyor theory- screw conveyor thrust bearings- screw conveyor torque-helicoid flights-continues helix-flight of screws

Sectional flights:

Sectional flights are formed from a flat disc and the thickness of the thread is uniform throughout. A continuous helix is made by joining a number of sectional flights together on a piece of pipe and butt welded them. Various styles of screw flights are in use, depending on the service required.

01- screw conveyor technology- screw conveyor incline- screw conveyor introduction- screw conveyor inlet- screw conveyor information- screw conveyor output-sectional flights-continuous helix-short pitch

Some of the typical configurations are:

1. Short pitch or continuous flight:

If the conveyor is required to handle dry granular or powdered materials that do not pack, this style of flight may be selected. It is of regular construction and recommended for inclined conveyors having a slope of 20 or more, including vertical conveyors. This style is extensively used as feeder screw.

2. Ribbon flight:

If the conveyor is to handle lumpy, clinging, sticky, gummy or viscous substances, this type flight may be selected. It consists of continuous helical flight formed from steel bar and secured to the pipe by supporting lugs.

01-screw conveyor part- screw conveyor pitch- screw conveyor power- screw conveyor length- screw conveyor layout- screw conveyor lift- screw conveyor loading-ribbon flight-cut flight

3. Cut flight:

In this type of flight screws have notches cut in the periphery of the flight. These notches supplement the conveying with moderate mixing action. They are recommended for conveyors required to handle light, fine, granular or flaky materials.

01-screw conveyor length- screw conveyor layout- screw conveyor lift- screw conveyor loading-cut flight-screw flight-sectional flight

4. Cut and folded flights:

This type of flight is characterized by notches as in cut flight, together with folded segments. This type of flight creates agitation and aeration resulting in better mixing. This type of flight is used to handle light or medium weight materials having fine, granular or flaky materials.

5. Some screw conveyors have cut flight with paddles mounted at regular intervals. The paddles counteract the flow of material past the flight resulting in greater agitation and mixing.

6. Sometimes screws are made of stainless steel to suit special requirements, like the sanitation requirements for handling food, drugs and other hygienic materials.

X RAY DIFFRACTION

August 23, 2011

It’s useful for studying Crystal structure

This method have the details about

    • Grain size (or) Crystal size
    • Orientation of the crystal
    • Cold worked, Distorted and Internally stressed crystals
    • Re-Crystallization
    • Preferred orientation etc

Methods of Examining and Measuring the condition of Crystal Structure

    1. The Laue back reflection method
    2. The Rotating Crystal method
    3. The DeBye- Scherrer (or) Powder method:

The Laue back Reflection method:

It’s applicable to single crystals (or) poly-Crystalline masses.

When a beam of Mono chromatic (i.e. of Single Wavelength) X-Ray is directed as a narrow pencil at a specimen of a metal diffraction takes place at certain of the crystallographic planes.


03-laue method- x-rays sheild

01-laue back reflection- method-X-ray-diffraction

01-electron-waves-travel-x-rays03-LaueBack reflection

02-lauemethod

The Rotating Crystal method:

It’s a useful method for determining angles and positions of planes.

Crystallographic planes are brought in to reflecting positions by rotating a crystal (Specimen) about one of it’s axis while simultaneously radially it with a beam of mono chromatic x-Rays.

If crystal orientation planes are known, the angles and directions can be calculated.

04-rotating-crytal-method-x-ray-diffration-crystal-structure

05-diffractometer-x ray detector-rotation crystal

The DeBye- Scherrer (or) Powder method:

The narrow pencil of monochromatic X-Rays is diffracted from the powder and recorded by the photographic film as a series of lines of varying armature.

By the Bragg Equation:

nλ=2d Sinθ

Where,

λ– Wave length of X-ray

d- Spacing of the atomic planes

θ – Angle of reflection

06-debye-scherrer-powder-method

 

 

 

 

 

07-debye-scherrer-powder-method

X RAY DIFFRACTION

August 23, 2011

It’s useful for studying Crystal structure

This method have the details about

    • Grain size (or) Crystal size
    • Orientation of the crystal
    • Cold worked, Distorted and Internally stressed crystals
    • Re-Crystallization
    • Preferred orientation etc

Methods of Examining and Measuring the condition of Crystal Structure

    1. The Laue back reflection method
    2. The Rotating Crystal method
    3. The DeBye- Scherrer (or) Powder method:

The Laue back Reflection method:

It’s applicable to single crystals (or) poly-Crystalline masses.

When a beam of Mono chromatic (i.e. of Single Wavelength) X-Ray is directed as a narrow pencil at a specimen of a metal diffraction takes place at certain of the crystallographic planes.


03-laue method- x-rays sheild

01-laue back reflection- method-X-ray-diffraction

01-electron-waves-travel-x-rays03-LaueBack reflection

02-lauemethod

The Rotating Crystal method:

It’s a useful method for determining angles and positions of planes.

Crystallographic planes are brought in to reflecting positions by rotating a crystal (Specimen) about one of it’s axis while simultaneously radially it with a beam of mono chromatic x-Rays.

If crystal orientation planes are known, the angles and directions can be calculated.

04-rotating-crytal-method-x-ray-diffration-crystal-structure

05-diffractometer-x ray detector-rotation crystal

The DeBye- Scherrer (or) Powder method:

The narrow pencil of monochromatic X-Rays is diffracted from the powder and recorded by the photographic film as a series of lines of varying armature.

By the Bragg Equation:

nλ=2d Sinθ

Where,

λ– Wave length of X-ray

d- Spacing of the atomic planes

θ – Angle of reflection

06-debye-scherrer-powder-method

 

 

 

 

 

07-debye-scherrer-powder-method

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.

MEASUREMENT

August 23, 2011

Calibration:

01-the weighing scale-weighing machines-balance-calibration example

If a known input is given to the measurement system the output deviates from the given input, the corrections are made in the instrument and then the output is measured. This process is called “Calibration”.

Sensitivity:

Sensitivity is the ratio of change in the output signal to the change in the input signal.

Readability:

01-electroniccaliper-VERNIER CALIPER-DIGITAL VERNIER CALIPER-DIRECT MEASUREMENTS-ACCURATE-PRECISION MEASUREMENTS-CALIBRATED INSTRUMENTS-readability

Refers to the ease with which the readings of a measuring instrument can be read.

True size:

Theoretical size of a dimension which is free from errors.

Actual size:

Size obtained through measurement with permissible error.


01-true size-actual size-feet size-example-shoe-footwear

Hysteresis:

All the energy put into the stressed component when loaded is not recovered upon unloading. so the output of measurement partially depends on input called Hysteresis.

01-tachometer-digital tachometer-hysteresis due to pressure of force

Range:

The physical variables that are measured between two values. One is the higher calibration value Hc and the other is Lower value Lc.

01-range - read values from 0 to 11000 rpm - bezel meter - tachometer

Span:

The algebraic difference between higher calibration values to lower calibration values.

Resolution:

The minimum value of the input signal is required to cause an appreciable change in the output known as resolution.

Dead Zone:

It is the largest change in the physical variable to which the measuring instrument does not respond.

Threshold:

The minimum value of input signal that is required to make a change or start from zero.

01-threshold-minimum input given to start the engine-bike kick start action

Backlash:

The maximum distance through which one part of the instrument is moved without disturbing the other part.

01-backlash - continuous rotation possible without applying brake-SINGLE 3-PHASE AC ASYNCHRONOUS ELECTRIC MOTOR

Response Time:

The time at which the instrument begins its response for a change in the measured quantity.

Repeatability:

The ability of the measuring instrument to repeat the same results during the act measurements for the same quantity is known as repeatability.

Bias:

It is a characteristic of a measure or measuring instruments to give indications of the value of a measured quantity for which the average value differs from true value.

Magnification:

It means the magnitude of output signal of measuring instrument many times increases to make it more readable.

01-magnification-objective lens-magnify-loupe-ring

Drift:

If an instrument does not reproduce the same reading at different times of measurement for the same input signal, it is said to be measurement drift.

Reproducibility:

It is the consistency of pattern of variation in measurement. When individual measurements are carried out the closeness of the agreement between the results of measurements of the same quantity.

Uncertainty:

The range about the measured value within the true value of the measured quantity is likely to lie at the stated level of confidence.

Traceability:

It is nothing establishing a calibration by step by step comparison with better standards.

01-traceability-calibration step by step-vacuum calibration

Parallax:

An apparent change in the position of the index relative is to the scale marks.

 

 

01-parallax-error-measurement of length-eye view

MEASUREMENT

August 23, 2011

Calibration:

01-the weighing scale-weighing machines-balance-calibration example

If a known input is given to the measurement system the output deviates from the given input, the corrections are made in the instrument and then the output is measured. This process is called “Calibration”.

Sensitivity:

Sensitivity is the ratio of change in the output signal to the change in the input signal.

Readability:

01-electroniccaliper-VERNIER CALIPER-DIGITAL VERNIER CALIPER-DIRECT MEASUREMENTS-ACCURATE-PRECISION MEASUREMENTS-CALIBRATED INSTRUMENTS-readability

Refers to the ease with which the readings of a measuring instrument can be read.

True size:

Theoretical size of a dimension which is free from errors.

Actual size:

Size obtained through measurement with permissible error.


01-true size-actual size-feet size-example-shoe-footwear

Hysteresis:

All the energy put into the stressed component when loaded is not recovered upon unloading. so the output of measurement partially depends on input called Hysteresis.

01-tachometer-digital tachometer-hysteresis due to pressure of force

Range:

The physical variables that are measured between two values. One is the higher calibration value Hc and the other is Lower value Lc.

01-range - read values from 0 to 11000 rpm - bezel meter - tachometer

Span:

The algebraic difference between higher calibration values to lower calibration values.

Resolution:

The minimum value of the input signal is required to cause an appreciable change in the output known as resolution.

Dead Zone:

It is the largest change in the physical variable to which the measuring instrument does not respond.

Threshold:

The minimum value of input signal that is required to make a change or start from zero.

01-threshold-minimum input given to start the engine-bike kick start action

Backlash:

The maximum distance through which one part of the instrument is moved without disturbing the other part.

01-backlash - continuous rotation possible without applying brake-SINGLE 3-PHASE AC ASYNCHRONOUS ELECTRIC MOTOR

Response Time:

The time at which the instrument begins its response for a change in the measured quantity.

Repeatability:

The ability of the measuring instrument to repeat the same results during the act measurements for the same quantity is known as repeatability.

Bias:

It is a characteristic of a measure or measuring instruments to give indications of the value of a measured quantity for which the average value differs from true value.

Magnification:

It means the magnitude of output signal of measuring instrument many times increases to make it more readable.

01-magnification-objective lens-magnify-loupe-ring

Drift:

If an instrument does not reproduce the same reading at different times of measurement for the same input signal, it is said to be measurement drift.

Reproducibility:

It is the consistency of pattern of variation in measurement. When individual measurements are carried out the closeness of the agreement between the results of measurements of the same quantity.

Uncertainty:

The range about the measured value within the true value of the measured quantity is likely to lie at the stated level of confidence.

Traceability:

It is nothing establishing a calibration by step by step comparison with better standards.

01-traceability-calibration step by step-vacuum calibration

Parallax:

An apparent change in the position of the index relative is to the scale marks.

 

 

01-parallax-error-measurement of length-eye view