Sieving – Definition, Principle, Mechanism, Types, Benefits, Disadvantages, Practice Problems and FAQ

The majority of the objects we encounter on a daily basis are a combination of two or more pure substances. These pure substances must be taken out of the mixture in order to be used separately. You must have seen, for instance, that we don't instantly make chapatti with the flour we buy from merchants. We use specific separation techniques to separate the flour from the associated pollutants.

For separating the flour from bran or other contaminants, we typically use sieve plates. These sieve plates enable the smaller contaminants to pass through the plate's perforations and remain on the sieve while allowing the finer flour particles to flow through. Sieving is the process of removing particles from a mixture based on differences in particle size. For separating coarse from fine particles, sieve plates are used.

Plates used in sieves have bottoms that are mesh- or perforated-like, allowing only particles of a certain size to pass through. Depending on its use, mesh size might change from one location to another. For instance, sieving is also used to remove wheat husks and stones. In this case, we utilise sieve plates with a larger mesh size than the one used to separate flour.

Similar to this, we use a strainer (sieve) to separate the tea from the tea leaves when preparing tea.

On this concept page, we will get to know more about sieving!

TABLE OF CONTENTS

• Sieving – Introduction
• Sieving – Mechanism
• Sieving – Principle
• Sieving – Types
• Sieving – Benefits
• Sieving – Disadvantages
• Practice Problems
• Frequently Asked Questions – FAQ

Sieving – Introduction

Sieving is a separation method based on particle size differences. The sieve retains larger particles. Sieving is the process of using a sieve to separate materials of various sizes of materials. With the support of a netting or perforated bottom vessel through which the material is agitated or poured, the material is exposed to mechanical forces of vertical and lateral movement.

Sieving – Mechanism

Only particles of a specific size can pass through sieve screens, which have blended or perforated bottoms. Mesh sizes might vary depending on where they are used. Sieving can also be used to separate the husk from wheat. In this case, we utilise sieve plates with a larger mesh size than those used for flour separation. Sieving is a technique for separating particles from a mixture based on particle size differences.

Sieving – Principle

Depending on the method used, the sample is moved horizontally or vertically during sifting. As a result, the particles and the sieve move relative to each other. The selection of a method is mostly determined by the dispersion status or the level of granularity of the sample. Particle size estimation by sieve analysis is the oldest and most well-known approach. The mass or volume defines the particle size distribution. This allows for the rapid and accurate separation of relatively broad particle sizes.

Sieving – Types

Different types of sieves with varied hole sizes are used to separate the coarse from the fine and coarse aggregates. These varied forms include:

• Vibratory sieving
• Horizontal sieving
• Tap sieving
• Air jet sieving

Vibratory Sieving

• The sample is propelled upwards by the sieve bottom's vibrations and then falls back down owing to gravity forces.
• The amplitude represents the vertical vibration elevation of the sieve bottom.
• The sample material is evenly distributed across the entire sieve area as a result of this simultaneous effect.
• The particles are transported vertically, spin freely, and then return to their statistical orientation.

Horizontal Sieving

• Sieves rotate in horizontal rings in a plane in a horizontal sieve shaker.
• Few particles change their alignment on the filter as a result of the horizontal sifting motion.

Tap Sieving

• A vertical motion produced by a tapping force is overlaid on a horizontal movement in a tap sieve shaker. As a result, sieving times are longer.
• The tapping motion provides the particles with a stronger impulse, the fraction of small particles in specific materials, which is usually higher.
• The fraction of tiny particles in light materials like flour, on the other hand, is lower.

Air Jet Sieving

• The air jet sieve is a single-sieve sieving machine, which means that only one sieve is needed for each sieving procedure.
• A vacuum cleaner is linked to the sieving equipment, which creates a vacuum within the chamber and draws in fresh air through a revolving nozzle.
• The air stream is increased and blown against the sieve as it passes through the tiny slit of the nozzle, scattering the particles.
• The air jet is dispersed across the entire sieve surface above the mesh and pulled in at a low speed through the grid.
• As a result, finer particles are carried into the vacuum cleaner through mesh holes.

Sieving – Benefits

• In comparison to other methods, it is quicker.
• It is a traditional approach for separation, which does not need considerable skill.
• It is a very cost-effective strategy because it does not require the installation of costly equipment.
• It's utilised on construction sites or in grain mills.

Sieving – Disadvantages

• It is unable to differentiate two identically sized substances in a mixture.
• The size and form of particles in relation to the sieve width are two criteria that have been recognised as influencing the operation of this equipment.

Practice Problems

1. What are the different types of sieving?

Solution: Different types of sieves with varied hole sizes are used to separate the coarse from the fine and coarse aggregates. These varied forms include

1. Vibratory sieving
2. Horizontal sieving
3. Tap sieving
4. Air jet sieving

2. What are the benefits of sieving?

Solution: The following are some of the benefits of sieving.

• In comparison to other methods, it is quicker.
• It is a traditional approach for separation, which does not need considerable skill.
• It is a very cost-effective strategy because it does not require the installation of costly equipment.
• It's utilised on construction sites or in grain mills.

3. What are the disadvantages of sieving?

Solution: The following are the disadvantages of sieving.

• It is unable to differentiate two identically sized substances in a mixture.

• The size and form of particles in relation to the sieve width are two criteria that have been recognised as influencing the operation of this equipment.

4. What is sieving?

Solution: Sieving is a separation method based on particle size differences. The sieve retains larger particles. Sieving is the process of using a sieve to separate materials of various sizes of materials. With the support of a netting or perforated bottom vessel through which the material is agitated or poured, the material is exposed to mechanical forces of vertical and lateral movement.

Frequently Asked Questions – FAQ

What are the factors affecting sieving?

The operation of sieves is affected by a variety of factors, including

1. Particle size and shape.
2. The sieve's mesh size.
3. The quantity of debris on the sieve's surface.
4. The speed at which the material is moving in relation to the sieve surface.
5. When particles accumulate and clog the sifting mesh, the sieve becomes blinding.

What is the principle of sieving?

A mixture of particles of various sizes is sieved by passing it through a sieve or screen. The sieve retains the larger particles while allowing the smaller ones to pass through its pores.

Are filtration and sieving the same?

Particles that are too large to fit through the sieve's holes are retained during sieving.

A multilayer lattice is used in filtering to hold onto particles that can't travel through the filter's convoluted channels.

What are the industrial uses of sieving?

• In today's pharmaceutical, food, and beverage industries, sieves are essential.

• A filter, sieve, or commercial food strainer of some kind is used in every food preparation process.

• For product purity and hygiene, the pharmaceutical industry depends on a variety of sieves.

Related Topics