Milling and Mills

Represented by:-ketaki patil

Contents

• Introduction

• What is milling

• Types of mills

• Details of routine mill maintenance schedule

• Checking the operation of a mill

• How to improve efficiency

• Saftey at work

Introduction

Milling is a unit operation which is

carried out to convert the grains, cereals,

pulses into flour.

What is milling ???

Receiving of raw material/ grains

Washing

Sorting & grading

Dehulling

Toasting/roasting

Mixing

Milling

Packaging

Labeling

Storage

How flour is milled

• During the milling process, different parts of the wheat

grain are used to make different types of flour. White

flour is made from the endosperm only.

• Whole meal flour uses all parts of the grain: the

endosperm, the wheat germ and the bran layer. Brown

flour contains about 85% of the original grain, but

some bran and germ have been removed

Types of milling

• In grain milling there are two basic

methods i.e. dry & wet grinding the

moisture content of the grains is

about 16%, while in wet milling it is

higher

• Dry milling Wet milling

• Advantages Advantages

• Better efficiency No dust problem Easier milling

• Disdvantage Disdvantage

• Danger of explosion Formation of lumps

• if moisture is too high

Types of mills

• Traditional mill

• Hammer mill

• Roller mill

• Pan mill

• Colloidal mill

• Fixed head mill

• Ball mill

• The edge runner mill

• Disc beater mill

• Milling we mean that reduction of grain to fine particles so that it is more adaptable to culinary manipulation.

• The first mills of either mortar & pestle in the simplest form in concavity in a stone which held grain in place while it was poured with the smaller rock.

Traditional mill• Consist of two circular stones

placed on each other which is rotated by manually i.e. by hands or animals or slaves in ancient time.

• Lower stone is stationary and upper one is moving.

• The material is fed from hole of upper stone

• The ground material was collected from outer edges of lower stone.

Hammer mill

• It is most widely used equipment for food size reduction by impact forces.

• It is used to produce wide range of particles like from medium to fine.

• Hammers or beaters are provided for size reduction, so it called as hammer mill.

• It is based on impact and shear force

Roll mill• It is the main type of milling equipment

used for fine grinding of cereals

• They consist counter rotating rolls pair

• Grinding in the roll mill depend upon kind,

consistency, and texture, dimension of roll

i.e. length & diameter of product.

• It is based on compression and shear force

Pan mill

• Consists of two to four heavy rolls rotating around an axis the centre of pan in which product to be ground is fed.

• They are used in crushing & grinding products such as olives and other oil containing seeds.

Colloidal mill

• This consist of various flat disks.

• This will help in increase in efficiency of product.

• Mostly this mill is used for oilseeds.

Ball mill

• Material to be ground is enclosed in a horizontal cylinder or cone and tumbled with a large number of steel balls or artificial stones, which crush and break material .

• It is having limited application in food industry but they are using grinding food colors

• Based on impact and shear force

Details of routine mill maintenance

DailyMaintenance

Mechanical• check and grease bearings, replace if faulty• check pulley wheels for cracks and replace to avoid damaging belts.• check bolts and nuts for tightness.• check the oil level in diesel engines and top up with the correct oil if required

Electrical • clean flour dust off motors and other electrical equipment• when a machine is not in use, make sure that power is switched off atthe mains and that equipment has not been left switched on. This is veryimportant when power cuts occur, because when power returns amachine that has been left on can injure an operator or cause a fire.

Cont…

Housekeeping store tools and equipment in pre-determined places to help find themnext time and to help notice when they have gone missing.• always keep walkways clear of tools and equipment• clean diesel engine cooling fins every day to prevent dust settling

Weeklymaintenance

check hammers for wear and replace if necessary check that locking nuts on the shaft are tight.• check that fan bolts have not loosened as the fan then becomes verydangerous.• check the bearing mountings as this area is prone to cracking

Monthlymaintenance

check the body casting and welds for cracks• tighten floor nuts and look for any cracks in the mill foundation• check the fan key and make sure that the fan is a slide fit on the shaft foreasy removal. If the blades are worn always replace with the correctthickness of steel and then check for balance• check that cables are secured and there is no sign of insulationbreakdown• check the acid level in batteries that are used to start diesel engines.Keep the terminals clean.47

Material used for mills

• Typical Feasible

Alloy steel Ceramics

carbon steel Lead

Cast iron Nickel

Stainless steel Tin

Aluminium Titanium

Copper Thermoplastic

Magnesium Thermosets

Saftey should be carried out…

• 1) personal protective equipments- PPE’S :-– it consist of goggles, hand gloves,

safety shoes, lab coat, mask etc…

2) Do not wear any ornaments, jewelry, bangles etc..

3) Do not wear loose clothes e.g sari..

4) Should apply IP (iso propyl alcohol) or sanitizer before working

How to improve Efficiency

Operators should maintain following things i.e. process cycle :-

1)Load /unload time

2) cut time

3) Idle time

4) Tool replacement time

5)Feed rate

6)Spindle speed

“Our work is never so important that we can not

take the time to do it safely”

- Cadbury pvt ltd