air cooling and ventilation

8/10/2019 Air Cooling and Ventilation

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Air cooling and ventilation

Sheikh Kashif

Faiz

Vaswee Dubey


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What Is Industrial Ventilation?

Environmental engineers view:

The design and application of equipment forproviding the necessary conditions for maintainingthe efficiency, health and safety of the workers

Industrial hygienists view:

The control of emissions and the control ofexposures

Mechanical engineers view:

The control of the environment with air flow. This canbe achieved by replacement of contaminated air withclean air


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Hazards of Poor or No Ventilation

Lack of oxygen (headache, fatigue, Asphyxiation,

particularly in confined spaces)

Excessive heat, cold, and humidity

Toxic fumes (e.g.- Lead, cadmium, zinc)

Toxic vapors (e.g.- Benzene, toluene, TCE, MEK)

Toxic gases (e.g.- Hydrogen Sulphide, ammonia)

Dusts (causing poisoning or gradually reduced lungcapacity)

Fire/explosion


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Control philosophy

The correct recognition and careful

evaluation of the hazards are extremelyimportant and will constitute the basis

of appropriate control measures


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Generalized Diagram:--

Methods of Control

Desired control priority for chemical hazards

1. Source control

2. Pathway control

3. Receiver control


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Pathway Controls

Pathway controls generally are not as desirable as

source controls:-

Exposures are reduced, but not eliminated

(general ventilation)

The source hazard still remains

Pathway controls often are costly

Operation cost

Pathway control systems must be maintained


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Industrial Ventilation

Ventilation is a primary engineering control

available to eliminate or reduce the

concentration of gases, dusts, vapors,

smoke, and fumes present in the work

environment .

Ventilation is defined as the process of

supplying air to, or removing air from, any

space by natural or mechanical means.


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Purpose

To dilute airborne contaminants to

acceptable levels

To prevent hazardous air contaminants fromdispersing into the working environment

(LEV)

To prevent fire and explosion

To create a comfortable environment in the

plant - i.e. The HVAC system


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Types of Ventilation

General Dilution Ventilation(Pathway control)

- Mechanical Ventilation (involves Fans)

- Natural Ventilation(with natural air movement caused by

thermal gradient or any other)

Local Exhaust Ventilation (Source control)

Heating Ventilation and Air conditioning

System (to control temp. & humidity)


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Natural Ventilation MechanicalVentilationPreferred if significant

health hazards exist

General or Dilution Ventilation


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Clean AirSupply

Zone of ContaminantRelease

Operators BreathingZone

DischargeOpening

Direction of air flow must remove contaminants from workersbreathing zone

Principle of General Ventilation


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Recomme

nded

Practices


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General Dilution Ventilation

If (TLV


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Local Exhaust Ventilation-Source

Control

Capture or contain contaminants at their source

Typical Local Exhaust

Ventilation system

Components of Local

Exhaust SystemDuct


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Hoods - any point where air is drawn into the

ventilation system to capture or control

contaminants.

Ducts - the network of piping that connects the

hoods and other system components.

Fan - air-moving device that provides the energy to

draw air and contaminants into the exhaust system &

through the ducts and other components.

Air Cleaner - a device to remove airborne

materials that may be needed before the exhaust air

is discharged into the community environment.


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Use of Enclosures

--ed power consumption

-- less collection efficiency

--ed flow rate to have sufficient

capture velocity

-- more collection efficiency

--less flow rate required

--less power consumption


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Benefits of ENCLOSURES

Using techniques such as enclosures,

control capabilities are maximized

Air volumes requirements are drastically

minimized

Reduces required make-up air and

associated costs


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VENTILATION IN GARMENT INDUSTRIES


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TEMPERATURE

Cold temperatures are rarely a

problem for workers in garment

factories. Occasionally, workers inthe computer design rooms

experience cold temperatures.

Such environments are optimal for

the computer and not for the

workers.

Many garment workers

experience

hot, humid conditions, especiallythose in the ironing section.

There

are a number of control

measures

that can be introduced to reduce

the temperature.


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Temperature affects

productivity

A workers ability to do his/her job is affected byworking in hot environments. One of the mostimportant conditions for productive work ismaintaining a comfortable temperature inside the

workplace.

There are two main ways in which heat (or cold)gets into the factory:

Directlythrough windows, doors, air bricks etc;

Indirectlyby conduction through the actual fabric ofthe building namely the roof, walls and floor.


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There are a number of measures thatmanagement can take to try to reduce thesuns heat from entering the factory. These

include:

ensuring that the external walls are smooth intexture and painted in a light colour to help to

reflect the heat

improving the heat reflection of the roof

improving heat insulation of walls and ceilings

ensuring that the factory is shaded as far as

possible by natural means (trees, bushes,hedges etc) or with shades on windows, doors


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Controlling heat in the workplace

There are a number of basic approaches to tackling heat

hazards in garment factories:

ENGINEERING CONTROLS :

the use of increased general ventilation throughoutthe factory by opening windows, by ensuring that airbricks, doors etc are not blocked

the use of spot cooling by the use of fans to reducethe temperature in certain sections of the factory

the use of local exhaust ventilation systems in hotspots such as the ironing section to directly removethe heat as close to the source of the heat as possible

the use of air conditioners/coolers.


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CHANGING WORK PRACTICES :

increasing the number and duration of rest periods

introducing job rotation so that workers are notalways doing so-called hot work

doing hot work in the coolest part of the day

providing more workers to reduce the work load sothat workers spend shorter times in hotenvironments.


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In garment factories fans are located to

reduce the temperature in

certain locations. Here these workers

have fans behind them to cool down this

work

area.

Fans are used throughout garmentfactories to reduce the

temperature.


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National Standard for workplace

temperature

Prakas 147 on Thermal Environment at the Workplacespecifies:

Employers shall create a thermal environment that meets

acceptable standards.

The thermal environment shall be in conformity withworkers health and shall not disturb their work.

The thermal environment shall be measured by thetemperature shown on the thermometer at theworkplace.

In a building or a workshop with normal condition, each

worker shall have a space of at least 10 cubic meters.


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The workplace shall be protected from the ultra heat of the sun. The

production method which does not generate heat should be

adopted.

If the production generates extreme heat, the employer shall reduce

the heat by:

- having the heat generating parts insulated

- having the heat absorbed and diverted from the original source.


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Ventilation

It is not only essential to provide a comfortabletemperature inside the factory, one must also ensure :

an adequate supply of fresh air

the removal of stale air

the prevention of any build up of contaminants (dust,

spot cleaning chemicals, etc).

Many Cambodian garment factories rely on the principle of general

ventilation by allowing the free flow of air through the factory from one side

to the otherreferred to as horizontal air-flow.


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General ventilation in a

factory: if you have ventilation

systems or freestanding fans in thefactory, make sure thatthey increase the

natural flow of airthrough the factory andnot try to blow airagainst any prevailingwind.

ensure that hot, staleair that rises to thefactory roof can easilybe removed and

replaced with fresh air.


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make sure that all fansare well maintained andregularly cleaned so that

they work efficiently.

ensure that the air-flowto and from fans is notblocked .

try to ensure that anyhot processes such asthe ironing section issited next to the down

wind wall so that theheat is extracted directlyoutside rather than beingspread around thefactory.


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In cases where there is a build up of contaminants or heat in specific

areas of the factory, local exhaust ventilation has to be used to

remove the hazard. This type of ventilation uses suction and hoods,

ducts, tubes etc to remove the hazard as close to the source aspossible and extract it to the outside environment. It works on a principle

similar to that of a vacuum cleaner but on a much larger scale.


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National Standard for

ventilationPrakas 125 on Air Circulation and the Cleaning of the Workplacerequires:

An employer shall make an arrangement to have a good/cleanatmosphere at the workplace in order to maintain the health andsafety of the employees.

Air circulation in a workplace without a dirty atmosphere may bepossible by blowing in air naturally or artificially.

If dangerous substances in the workplace cannot be eliminated, theemployer must remove the hazard as close to the source as possibleto the outside environment in accordance with the EnvironmentalProtection Law.

This regulation also specifies the need for employers to providethe appropriate personal protective equipment if these hazardscannot be controlled by general or local exhaust ventilationsystems.


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Checklist for Temperature and

Ventilation


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Thank you.

References: http://www.globalsources.com/si/AS/Qingdao-

Xinmaosen/6008847210245/pdtl/It-

is/1059121934.htm

29 October, 2014 5:14 p.m.

http://betterwork.com/cambodia/wp-

content/uploadshttp://betterwork.com/cambodia/

wp-content/uploads/2013/05/OSH-manual.pdf29 October, 2014 5:14 p.m.

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