UNIT –
III
CHEMICAL
PROCESS INDUSTRIES IN INDIA.
The effective production executive
knows the value of organization. He realizes that no objective can be attained,
whether it be for production, training, inspection, selling or accident
prevention or elimination does not come about unless all levels of people of
the organizatiion are tuned towards that objective.
A recent review of plants indicates
many differences in safety organixations and a wide variance of authority and
interest from top management down through the organization.
The following points should be
considered first.
(1) Safety
must have top management approval, sanction and support
(2) Responsibility
for safety must restwith the supervisory personnel.
(3) Safety
must be given an equally important consideration with other factors and
(4) Provision
must be made for prompt action in the elimination of mechanical and personal
hazards.
Whatever may be the size of the
firm, the principle and the purpose should be indentical, “Within each and
everyone, at all levels of the organization, a safety consciousness”.
For this a definite programme should
be developed to interest and educate all employees in safety and to secure
their active cooperation to eliminate accidents. Such a programme must be based
on the full assumption of its responsibilities by the management. Safety must
be included in all phases of planning, purchasing, supervision and operation.
We may classify the safety
organization in three general types, namely
(1) Type
A firms. (2) Type B firms (3) Type C firms
TYPE – A FIRMS
Those in which the safety work
is carried by the functional head of
that particular firm.
If no full time safety personnel are
available, the production executives must become expert in their knowledge in
safety problems involved in their particular establishment.
The strength of Type A setup lies on
the fact that it centers its entire
responsibility for all safety effort within each operating unit. It is his duty
to incorporatesafety into each and every part of the day by day activities of
his unit. He must become the best informed andmost safety minded person in his
unit.
The drawback in this type of
organizations is that the supervisory staff occupied with other production
problems finds it difficult to acquire the special knowledge needed to reach a
high standard of safety performance. This means that the knowledge of how to
prevent accidents is gained from the accidents that occur. So the progress is
likely to be slow.
This kind of setup is found more
commonly in firms too small to employ a full time safety engineer.
TYPE – B FIRMS
Those in which the safety work is
directed by a safety engineer reporting to a major executive.
Very large firms use this type of
setup. Its effectiveness depends on two things.
(a) The attitude of the top
management and
(b) The competency and ability of
the safety director.
In such type of industries, the
safety director must first think of the help he can render to each supervisory
staff, second he must try to determine the viewpoint of each so that his help
will be accepted, third he must be sure of his facts and careful in drawing
conclusions and fourth he must keep the boss informed.
TYPE – C FIRMS
Those in which the safety work is
carried out by committees setup for that purpose.
Safety work governed by committees
usually found in establishments too small to justify a full time safety
engineer and where the management prefers the work to be directed by the
members of his staff.
It has the advantage of bringing
together the viewpoints of the group and it’s joint judgement is better than
that of any individual in the group. The disadvantage is the fact that a
committee is the weakest in execution. The prompt, effective& orderly
execution depends on placing the authority in the hands of one person and
faithful discharge by him.
CHEMICAL
HAZARDS
CLASSIFICATION
OF HAZARDS
Chemicals are classified on the
basis of the danger properties. These dangerous properties are
(1) Explosivity, (2) Flammability,
(3)Oxidisability, (4) Toxicity, (5) Corrosivity, (6) Reactivity, (7)
Compressibility.
EXPLOSIVITY
Explosive materials under certain
conditions of temperature shock or chemical action decompose rapidly and evolve
large volumes of gas or excessive heat, thus causing the surround atmosphere to
expand suddenly resulting in explosion. Such inherent explosive materials
aregenerally not handled in the chemical industry except those manufacturing
high explosives.
FLAMMABILITY
Combustioin of materials occur due
to reaction between oxygen and the combustibles present in the materials in the
vaporised or finely divided state. The ease of
burning reduces progressively from gases to dusts to liquids and to
solids.
The index of flammability of a
liquid is called the FLASH POINT which is the lowest temperature at which a
liquid will give off enough vapour and can ignite from a spark or open flame.
FIRE
POINT is the lowest temperature at which a mixture of air and vapour
continues to burn when an open container ignited.
AUTO
IGNITION TEMPERATURE is the temperature at which a material will self
ignite and sustain combustion without
any initiation by spark or flame.
A flammable liquid with a low
boiling point is much more hazardous than a liquid with a higher boiling point.
Limits of flammability are also
known as explosive limits. These represent the percentage by volume of
flammable vapour or gas in air will burn when ignited. Between the lower and
upper limits, fuel- air mixtures are flammable and such mixtures should be
avoided in the normal course.
OXIDISABILITY
Oxidising agents are sources of
oxygen which can sustain fire. Air is the most common oxidising agent. Some
chemicals evolve oxygen at room temperature or on heating.(eg) Peroxides,
Chlorates, Permanganates, nitrites ect fail in this category. It’s always
advisable to segregate oxidising agents from flammable substances so as to
avoid accidental fires.
TOXICITY
Toxic properties of chemicals create
hazardous conditions for life. The chemical may be inherently toxic or
decompose to give toxic chemicals on heating or burning. Toxic substances enter
the human body through the nose during inhalation and through the mouth during
ingestion. The hazard due to toxic nature of chemicals is quantified by some
well publicised methods such as Threshold limit values and Lethal dose.
(eg)
Lead, Arsenic, Silica along with cyanides and isocyanides.
Threshold limit values : These are
expressed as mg/kg of gas or vapour in air. This is the level to which nearly
all workers may be repeatedly exposed day in and day out without adverse
effects.
Lethal dose: Minimum lethal doseis
defined asthe minimum quantity in milligrams per kilogram of bodyness which can
cause fatality among a group of experimental animalas.
CORROSIVITY
Corrosive materials are to be handled
in specific containers and adequate precautions should betaken to avoid severe
burns while handling these liquids. Sometimes dangerous gases can be evolved
due to corrosive action of chemicals or metals.
REACTIVITY
Certain chemicals can react violently
with water or acids and alkalis with evolutioin of gases, heat and fumes. Reactions with other substances can
also cause similar disastrous effects. Some chemicals undergo chain reactions
such as polymerisation on application of heat. Such reactions can also create
unsafe conditions.
COMPRESSIBILITY
This propertyi is present to a very
limited extent in liquids. But when liquids in enclosed spaces are heated, very
high pressures can develop which can rupture the equipment unless pressure is
relieved safely.
In case of gases, application of
pressure compresses the gases considerably and it is normal practice to store
gases under pressure. Some gases liquetyi at moderate pressures and
temperatures and can be stored in properly designed containers as liquefied
gases. A small amount of liquefied gas on vapourising creates a very large
volume of gas which may be toxic or flammable.
In site selection, plant layout and
plot planning. It is possible to make allowances for only certain types of
hazards. For only certain types of hazards.
For this, we breakdown these hazards into first degree hazards and
second degree hazards.
First degree hazards are those which
provide the potential for trouble.Under normal conditions, these hazards do not
cause any damage to either persons or property, but they set stage for
accidents that can cause injury, fire or explosions.
(1) The
presence of flammable or combustible materials
(2) The
presence of heat
(3) The
presence of ignition sources
(4) The
presence of oxygen
(5) The
presence of compressed materials
(6) The
presence to toxic materials
(7) The
possibility of human error
(8) The
possibility of mechanical failure
(9)
The movement of people and equipment
through the plant
When first degree of hazards get out
of hand, the result may be second degree hazards which are capable of directly
inflicting damage to life, limb and property. The second degree hazards are
(a) fire,
(b) explosion, (c) release of toxic chemicals, (d) stumbling, (e) falling and
(f) collision.
In combating all of these hazards,
we draw the lines of defense. The first line of defense consists of trying to
deal the first degree hazards in such a way to avoid the occurrence of second
degree hazards. Success here depends mostly on careful engineering of the
equipment we use. The things we have to consider during plot planning to assist
in first line of defense are
(1) Locating ignition sources upwind
from plants of possible releaseof flammablematerials.
(2) Providing adequate accesways for
movement of equipment and people,
Despite all such efforts, there are
occasions, when second degree hazards, such as fire occur. In the event of a
second degree hazard, how can we minimize the extent of damage to limb, life
and property, is the second line of defense. Here again, we have to look in for
certain things during plot planning itselt.
(1) Separating the most hazardous
areas from areas which are most occupied by people
(2) Strategically locating the fire
fighting equipments
But even then, some damages will
result from these hazards. People do get hurt in modern chemical industries no
matter how carefully we plan against accidents. The third line of defense is to
provide efficient first aid and hospital facilities to care for those who are
all hurt. The essence of the third line of defense is to repair thedamage we
have not been able to prevent.
JOB
SAFETY ANALYSIS
A job is a sequence of seperate
steps or activities that when put together accomplish the work goal.
Identifying the hazards and stressing safe procedures are the part of safety
analysis and should be one of the first steps taken where there is a
possibility of injury to worker.
Here are the steps to follow when
analysing a job.
(1) Select
the job.
(2) Break
the job down
(3) Identify
the hazards and potential accidents
(4) Develop
solutions
SELECT
THE JOB
Job suitable for job safetyi
analysis are those assignments that a line supervisor may make. (eg) Operating
a machine, tapping a furnace or piling ware house goods. They are neither too
broad nor too narrow.
Jobs should not be selected at
random. Those with worst accident experience should be analysed first if JSA is
to yield quickest possible return. In fact some companies make this the local
point of their accident prevention programme.
BREAK THE JOB DOWN
Before the search for hazards begin,
a job should be broken into a sequence of steps, each one describing what is
being done. Avoiding the two common errors (a) making the breakdown so detail
that an unnecessarily large number of steps result. (b) making the breakdown so
general that basic steps are not recorded.
The technique of making a job safety
analysis should involve these steps
(1) Selecting
the right person for observing
(2) Briefing
him on the purpose
(3) Observing
his for the job and trying to break it into basic steps
(4) Recording
each step in the breakdown
(5) Checking
the breakdown with the employee who was observed
While doing so, we have to select a
person who is experienced, capable, cooperative and willing to share ideas.
This person will be easy to work with.
If the person whom we have selected
for job safety analysis is not cooperating, he should be informed about the
purpose (ie) to make a job safe by identifying and eliminating hazards or
controlling hazards. We should explain him that we are going to studyi the job
alone and he is selected on the basis of experience and capability alone.
IDENTIFY HAZARDS AND
POTENTIAL ACCIDENTS
The purpose is to identity all
hazards – both those produced by the environment and those connected with the
job procedure. Each step and thus the entire job must be made safer and more
efficient.
For this, the following observations
should be made.
(a) Is there a danger of striking
against, being struck by or otherwise making injurious contact with an object.
(b) Can he slip or trip? Can he fall
on the same level or to another?
(c) Can the person be caught in,on,
or between the objects?
(d) Can he strain himself by
pushing, pulling or lifting?
(e) Is the observing atmosphere
hazardous? (toxic gas, vapour, mist, fume or dust, heat or radiation.)
We should make close observatiions
and knowledge of the job is required. We have to repeat the job observations as
often as necessary until all the hazards have been identified. We have to
include hazards that can happen as a result of the job. We should make a record
of the type of accident and the cause of it. We have to check with the employee
observed after making the records. We should cross check, with other employees
also, the same. Through observation and discussion we should develop a reliable
list of hazards and potential accidents.
DEVELOP SOLUTIONS
These solutions are based on the
fact that these should prevent the occurrence of poential accidents. The
principal solutions are
(1) Find
a new way to do the job
(2) Change
the physical conditions that create the hazards and
(3) to
eliminate hazards still present, change the job or stleast the frequency that
is must be performed. This solution is particularly helpful in maintenance.
To find a new way to do the job, we
should first determine the work goal of the job and we should see that the work
goal is not altered while trying for newer ways. We should attain is with the
safest way. If we have found a new way to do a job, we should study it
carefully that what are all the other benefits that can occrue. (such as
increased production, less time etc.) These benefits should also be pointed to
the higher management when proposing for change.
It the new way is not found, then we
should try to change the physical condition so that we can eliminate the hazard
or prevent the accident. (such as change in tools, materials, equipment or
location. The third step is to investigate changes in the job procedure. We
should note down what the worker need to do or the worker need not to do to
eliminate the hazards or any potential accidents?If possible, we should try to
analyse how should it be done.
BENEFITS
OF JOB SAFETY ANALYSIS
(1) Giving
the individual training in safe efficient procedures
(2) Giving
pre-job instructions
(3) Instructing
the new man on the job
(4) Making
employee safe contacts
(5) Preparing
for planned safety observations
(6) Reviewing
job procedures after occurrence of
accidents
(7) Studying
the jobs for possible improvement in job methods
APPRAISALS
It is a process of evaluation of the
employee. This process involves 6 steps
1. Establish
performance standards
2.
Communicate performance standards and
expectations to the employee
3.
Measure the performance of individuals
4.
Compare the actual performance of the
individual with the standard
5.
Discuss the appraisal with the employee
6. Initiate
corrective actions if any
Appraisals may be of the following
types.
Individual appraisal : The
shortcoimng of an individual atpraisal are apparent. It is one man’s opinion
and may be biased. Companies with formal plans usually protect themselves by
seeing to it that if individual appraisal is used, the results are reviewed by
the superior of the person who is appraising, in some formal way. This serves
as a definite check against the possibilities of irresponsible evaluation that
may step in the records.
Group appraisal : In
group appraisal the judgement of the immediate superior is supplemented by the
different slants of other executives. The obvious advantages are counter points
to most of the disadvantages cited for individual appraisal.
Multiple appraisal : In
multiple appraisal the suberdinate personnel is appraised independently by
several other qualified officers. The results of such multiple evaluations are
generally consolidated by a staff personnel.
Appraisal by subordinates : Here
employees evluate superiors. In most of the cases they are in no position to
know what is expected of their executives. They may be too young or too
inexperienced to realise the extent of their officer’s responsibility.
PERIODIC STUDY OF PLANT LAYOUT INSPECTION AND
CONSTANT MAINTENANCE :
In a well organized industry, safety
inspections are constantly made. Plant engineers, supervisors and chief of the
workmen all constantly watch over the performance of the workers under their
control. The operations which they perform regularly make them over confident
and sometimes they may neglect the safety regulations in the job. The safety
engineer by inspectioin corrects the worker on the spot. He inspects as a
specialist, keeping his thoughts concentrated on the work and detects and
corrects the unsafe practices and conditions.
Adequate planning and instruction,
training and supervision minimize the hazards. But well planned routine
inspection by a competednt person will discover the hazardous situations
promptly upon their development.
Safety inspections are classified
into 2 types.
1 General safety inspection. 2.
Selective safety inspection
The first type is carried out in
most of the plants as a routine accivity. Inspection is carried out in all the
departments and is done rapidly but not haphazardly. The safety engineer is
through and familiar with the conditions of the plat. He looks for conditions
that may carry hazards and which was absent during their previous inspection.
In the second type he concentrates
on one set of circustances closely and get very effective results. The
objective of an ideal inspection is
1.
To go to the spot directly
2.
To look, observe and learn
3.
To correct as you inspect and
4.
To report to make records constructively
The plant inspection is done with
the aim of finding unsafe conditions both for workers and eachines. The plant
inspector hence concentrates on good house keeping, material handling methods,
adequacy of working space between machines guarding for rotating and revolving
machineries, upkeep of hand tools, proper location of ladder, steps, lifts,
hoists etc. And safe handling them, floors, plat forms, railing etc, electrical
equipments and their switches, lighting, dusts, fumes, gases and vapours,
dangerous substances like acards, location of explosive materials, access to overhead
equipments, location of pressure vessels, compressors and any other conditions
that lead to hazardous conditions.
The inspection must be of continued
plant activity and integrated with production processes. A definite shedule is
drawn regarding what to inspect and how frequently it should be inspected.
After inspection, notes and records are made and corrective actions immediately
initiated.
Inspection of plants are done by
factory safety engineers, government and insurance agencies, factory inspectors,
specialist consultants either regularly or periodically to assess the needs of
safety, proper working area and welfare of personnel.
Plant
maintenance From Safety Point of view:
Proper plant maintenance
specifically preventive plant maintenance is essential in continuing production
safely and profitably. Maintenance is required for plant machines, tools,
equipments, portable tools and buildings. Safely operated machine will never
stop work or bring sudden failures. The cheapest way to operate any machine is
to keep it in good condition as new until obsolescence justifies it’s
replacement.
Safety mindeness in operation and
maintenance are the motto of a good management. Maintenance men should be
experienced engineers and mechanics. They should be alers, capable of learning
the characteristics of machines and show good judgement. Maintenance men should
be trained well in their jobs and safety motivated. In maintenance the
following aspects are given importance.
1.
Careful planning
2.
Hazards anticipated and provisions made
there of
3.
Proper selection of men of the job.
Accidents due to improper
maintenance results in moving machinery, cables breaking, heavy loading,
dizziness and uncosciousness from breathing of fumes and gases and short
circuit of electrical wires. A maintenance job is never completed until the
entire area is restored to order and the machine is kept in operating condition
with all safe guards in place. Loose materials in the floor, grease or oil
clean up are all given importance.
Advantages of plant
maintenance :
1.
Reduced break down and downtime of
machines and labours
2.
Greater safety for worker
3.
Low maintenance and repair costs
compared to break down maintenance
4.
Less stand by or reserve equipments
5.
Better product quality and fewer rejects
6.
Increased equipment life
7.
Better individual morale and industrial
relationship because production workers do not face lay –off or less incentive
due to break down
EFFECTIVE STEPS TO IMPLEMENT
SAFETY PROCEDURES:
Safety education and safety training
are the two modes by which the management can effectively implement the safety
procedures.
Safety
Education :
Safety education deals primarily
with the development of mind, broadening one’s knowledge and understanding.
Education in a specific subject means acquisition of information and
elucidation relating to the subject. Training deals primarily with the
development of skill in performance.
Safety education develops safety
consciousness – a vivid awareness on the importance of eliminating accidents
and creating a mental alertness in identifying conditions and actions that
might cause injury. Safety education of the general working personnel is
valuable in promoting the interest, understanding and active participation of
the workers in safety activities. It improves plant plant performance, adds to
the efficiency and generally adds to a sense of satisfaction in making
operations successfully without losses. Since safety is an intimate part of all
activities it may be integrated right from the school education onwards and
carried out in all training courses for specific tasks, jobs, operations and
professions. Every human activity has some safety incorporated in it and which
must be known to him.
Safety
education lies in effectively
1.
Teaching the essentials of, safe practices
2.
Organising safety programmes
3.
Appraising human attitude and
4.
Fitting new employees to the job
Getting men to work safely is the
motive of safety education. The workmen must be first prepared to accept the
safety codes. Then the information must be present in a powerful manner and
also methodically. Safety posters, films, various types of hazards must be
exhibited and demonstrated to make an impression in the minds of employees.
Safety Training :
In applying the principles of
accident prevention, it is sometimes found that is is better to train the
inexperienced worker rather than to search for the unsafe acts that have
accumulated over a period of time and caused the injury. Sometimes employees
are inherently unsuited to the work they are expected to perform. If a job
study has been made it will indicate the characteristics to look in for men
such as strength, height, weight, skill, judgement of distance, speed of hand
or eye, versatility, perseverance and physical or other qualities. Added to
this the details of operatiion will bring out the specific hazards so that in
the training process they may be given proper instructions on now to avoid the
injury.
Each person starting a job should be
given instructioins to do it properly. Even if he has performed similar type of
job, he needs to know the expectations because each supervisor will have his
own idea of how to do the job. A safety conscious supervisor wants to make sure
the new person is going to work in the safest possible environment and this might
not have been emphasized where the person worked before.
Good instructions contribute to
safety even if is is not specifically on the safe practices. Good instruction
makes an employee a better worker, more satisfied with his company and his job
and more willing to go along with programmes which his company and supervisor
talks more about safety. He also makes his own suggestions to avoid hazards. In
such cases the accidents occurring will be less.
PROPER SELECTION AND
REPLACEMENT OF HANDLING ITEMS:
The subject of handling items is an
exceedingly broad one . All raw matereails parts finished products and wastes
produced or used in the industry must be handled. The handling equipments may
be selected on facters such as characters of materials, size, weight, rate of
handling, distances to be moved , and the purpose of moving. The methods and
procedures used not only vary as between plants but also as between departments
within the plants so that the handling materials is an important function of
over all planning.
Accident experience also shows that
the substitution of suitable mechanical handling for manual methods reduce
accidents to a greate extent. Also the time consumed will be comparatively
less. The volume material to be handled is of greater importance.
Methods of handling objects:
General methods of moving materials
commonly used industries are
1. Hand
lift trucks
2.
Wheel barrows
3.
Overhead travelling creanes
4.
Conveyours
5.
Shovels and
6. Elevators
The basic that unsafe acts of
individual are a factor in majority of the accidents justifies the needs of
mechanical operation wherever possible. The mechanical means must be of safer
design and proper construction and that the personnel selected to operate them
be properly qualified and adequately supervised. Typical hazards are
overloading, poor arrangement of material, operating excessive speeds, lack of
adequate space for operation and lack skill on the part of the operator.
Use of hand tools:
Hand tools of one or the other type
are used in every industry, more particularly in metal working areas, in
maintenance and construction works. We can control accidents directly
attributed to safety and improper hand tools, but we have more difficulty in
controlling the action of the worker who might get injury by way of his
improper work and cause injury to his eye. In such cases, accidents cannot be
avoided but the extent of injury can be avoided by use of goggles.
All heat treating should be done by
those skilled in the art, who understands the properties of the materials used
and know how to apply the required treatment in each case. Materials from the
which hand tools are made should be of good quality and appropriate for the use
to which hand tools will put. A periodic inspection of all tools would include
the collection of those that need dressing, repairing and replacement of tools,
this work should be done only to persons qualified to do it. Tools not in use
should be stored safely on racks designed for them or should be placed in tool
boxes.
RESPIRATORY
PROTECTIVE EQUIPMENTS
REQUIREMENTS
OF PERSONAL PROTECTIVE EQUIPMENTS:
(1) Adequate protection against the
hazards to which the worker will be exposed
(2) Maximum comfort and minimum
weight compatible for protective efficiency.
(3) No restriction of essential movements
(4) Durability and susceptibility of
maintenance on the premises where it is used.
(5) Construction in accordance with
acceptable standards of performance and material
NEED FOR PERSONAL PROTECTIVE
EQUIPMENTS:
In industry it may be possible to substitute
dangerous chemicals by a safer one or to have automatic and mechanical handling
of the substance or to have controlled ventilation of the processes or to plan
and arrange operations such that the personal protective equipments are not
necessary. But sometimes it may not be possible to introduce such measures and
there may be breakdown in the plant. In such cases the use of protective
equipments become necessary. It should be kept in mind that the usage of these
equipments do not eliminate the hazard. These devices are designed to interpose
an effective barrier between a person and harmful objects or radiations.
TYPES OF PERSONAL PROTECTIVE
EQUIPMENTS:
These are divided into 2 broad
groups
(1) Respiratory
protective equipments
(2) Non-
respiratory protective equipments.
RESPIRATORY PROTECTIVE
EQUIPMENTS:
The atmospheric contaminants may
vary from the relatively harmful substances to toxic dusts fumes smokes mists
and vapours and gases. Processes which present hazards of exposure to dangerous
substances should be enclosed or ventilated to minimize the hazard. In enclosed
systems, ventilation is not possible or
become very costly to apply to the degree of safety required. Respiratory
protective equipments should be provided to workers exposed to such hazards. In
any case the usage of respiratory protective equipments should e considered the
last resort or as a stand by protection and never a substitute for effective
engineering control.
CLASSIFICATION
OF HAZARDS:
Types of hazards to which the worker
will be exposed is the basis of selection of the right type of respiratory
protective equipments. Hazards may be classified under
(1) OXYGEN DEFICIENCY : Atmosphere
in confined spaces such as vats, tanks holds of ships etc, may contain air with
oxygen content much lower than the normal. (21% by volume) It may be ude to dilution or
displacement of the air by other gasesor vapours or because of loss of oxygen
due to decay of organic mateer, chemical reaction and oxidation over a long
period of time. A person breathing air with oxygen content of 16% or less may
exhibit symptoms ranging from increased rate of breathing, acceleration of
pulse rate of unconsciousness and death. Such cases, the respiratory protective
equipment should supply normal air or oxygen to the water.
(2) GASEOUS CONTAMINANTS : These may
be toxic gases. The toxic gases may produce harmful effect even as they are
present in relatively low concentrations. These gases produce undersirable
effects mainly by displacement of oxygen.
(a) Immediately dangerous to life :
These contaminants are gases present in concentrations that would enganger life
of a person breathing them even for a small period of time.
(b) Not immediately dangerous to
life : These are gases present in concentrations that could be breathed by a
person for a short time without endangering life but which may cause possible
injury on a prolonged single exposure or repeated short exposures.
(3) PARTICULATE CONTAMINANTS : These
are all not immediately dangerous to life. They may be solid or liquid or a
mixture of solid and liquid and may be classified into three broad groups.
(a) Toxic particulate contaminants :
These when inhaled may pass from the lungs into the blood stream and are thus
carried to various parts of the body. The effect may be chemical irritation,
systematic poisoning or allergic reactions. Some common examples are Antimony,
Arsenic, Cadmium, Chromic acid, Lead, Mangenese and Chromates.
(b) Fibrous producing dusts: These
dusts do not pass into the blood stream but remain in the lungs and may cause
pulmonary impairment. The common examples are Asbestos, Coal, Bauxite and Free
silica.
(c) Nuisance dusts : These may
dissolve and pass directly into the blood stream or may remain in lungs neither
producing local nor systematic effects.
AIR LINE RESPIRATORS :
It consists of a face piece to which
air is supplied through a small diameter hose. It may be a continuous flow or
demand type.
In
continuous flow type, air is supplied to the face piece continuously. Exhaled
air or excess air entering the face piece escapes to the surrounding
atmosphere. Air supplied should be atleast 110 1pm to enter the face piece. In
demand type, air is supplied to the face piece, when the wearer inhales and the
rate is governed by his volume of breathing. Air from an air compressor or
cylinder is supplied to the face piece through a demand hose which is actuated
by the slight negative pressure created when the wearer inhales. In exhalation,
demand valve closes and exhaled air escapes to the surrounding atmosphere
through exhalation valve.
Air line respirators provide
protection so long as the air supply is maintained. But the wearer’s travel is
limited by the length of the hose. Care should be taken to ensure that the air
supply is respirable and is not contaminated and is free from any objectionable
odours, oil or water mist and rust particles from the supply line.
SUCTION HOSE MASK:
It consists of a full face piece
connected to a larger diameter flexible hose. The wearer draws air by his own
breathing effort. The hose is atached to the wearer’s body by a suitable safety
harness with safety line and inlet end is provided with a filter to arrest
particulate matter. Air can be drawn in by the werer upto 30 ft. Length of the
hose.
PRESSURE HOSE MASK:
This hose mask is similar to suction
hose mask except that air is forced through a large diameter hose by a hand or
motor operated blower. This should be operated until the mask is in use.
SELF CONTAINED COMPRESSED AIR
OR OXYGEN BREATHING APPARATUS:
This is a device by means of which
the use r obtains respirable air or oxygen from compressed air or oxygen
cylinder which is an integral part of the apparatus. In demand type
self-contained breathing apparatus, air or oxygen is admitted to the face piece
through a two stage pressure reducing mechanism, only when the wearer inhales
and the quantity of air or oxygen admitted is governed by his breathing . The wearer’s exhaled breath
escapes to the atmosphere.
In compressed oxygen cylinder
recirculating apparatus high pressure oxygen from the cylinder passes through a
pressure reducing and regulating valve into a breathing bag. The wearer inhales
the oxygen through a one way breathing valve and his exhaled breath passes into
the canister containing chemicals to absorb exhaled carbon-di-oxide and
moisture and then through a cooler into the same breathing bag. Oxygen
requirement of the wearer is taken from the supply cylinder only when the
volume of the gas in the bag has decreased sufficiently to allow the supply valve
to open.
From respiratory point of view,
self- contained breathing apparatus has no limitations as to the concentration
of the gas or deficiency of oxygen in the surrounding atmosphere but other
factors may limit. The time that the wearer can remain in a contaminated
atmosphere since many gases are irritating to the skin and can be absorbed in
dangerous amounts through the skin.
OXYGEN
REGENERATING TYPE- RECIRCULATING SELF CONTAINED BREATHING APPARATUS:
In this type apparatus, the moisture
content from the wearer’s exhaled breath reacts with granular chemical in a
cannister to liberate oxygen. Also the exhaled Co2 is absorbed by
the chemicals in the cannister. This oxygen enters the breathing apparatus from
which the wearer inhales through a corrugated breathing tube connecting the bag
to the face piece.
AIR
PURIFVING RESPIRATORS
CANNISTER
GAS MASK:
This consists of a cannister,
containing appropriate chemical, a full face piece and body barness to hold the
apparatus on the body of the wearer. Air is drawn through the cannister by the
wearer and during it’s passage through the chemical in the cannister, the
contaminant present in the incoming air is absorbed, reacted with a
neutraliser. The cannisters are designed for specific gases and it is important
that the appropriate type is used.
The cannister gas mask can be used
only in atmosphere not deficient in oxygen and not containing more than 2% by
volume of most toxic gases. Also the life of the cannister will depend upon the
type of cannister, the concentration of gas and the activity of the wearer.
CHEMICAL CARTRIDGE
RESPIRATORS:
This consists of a half mask
attached to one or two cartidges. Like cannisters, the cartridge are filled
with appropriate chemicals to absorb gases or vapours drawn through them. This
one is a non- emergency gas respirator and it should not be used in an
atmosphere deficient in oxygen. Like cannister gas mask, chemical cartridge
respirator provides respiratory protection for a period that depends on the
type of cartridge used, the concentration of gases or vapour and the wearer’s
activity. It’s recommended for low concentrations of gases or vapours (about
0.1% of organic vapours)
SELF RESCUE TYPE RESPIRATORS:
This is designed to provide the
greatest possible respiratory protection consistent with the practicability of
carrying the device at all times so that it is always available for use during
escape. It consists of a small filter element, a mouth piece, a nose clip and
means of carrying conveniently on the body. The filter elements are similar to
chemical cartridge. The extent of protection afforded is between that provided
by canister gas mask and that provided by a chemical cartridge respirator.
MECHANICAL FILTER RESPIRATORS:
These remove particulate matter from
the inspired air which passes through a filter. These filters may be of the
single use or reusable type. If these respirators are used in heavy
concentrations of particulate matter, the filter will be clogged with gust
particles too quickly and they may have to be replaced every now and then.
Micro filters are special filters
designed to arrest ultra microscopic size of dust particles and these are used
where extra fine dusts are encountered.
COMBINATION OF CHEMICAL AND
MECHANICAL FILTER RESPIRATORS:
They remove toxic gases and vapours
and particulate matter from the inspired air.
SELECTION OF RESPIRATOR:
(1) Nature
of hazard
(2) Severity
of hazard
(3) Type
of contaminant
(4) Concentration
of the contaminant
(5) Period
for which respiratory protection must be provided
(6) Location
of the contaminated area with respect to a source of respirable air
(7) Expected
activity of the wearer and
(8) Operating
characteristics and limitations of the available respirator
CARE OF RESPIRATORS:
Instructions in the use of
respirators, among other things, should include the following.
(1) When
it is to be used
(2) How
it is to be used
(3) Checking
that it is in good operating condition
(4) Fitting
of respirator on the wearer
(5) Proper
use and maintenance of the respirator
NON-RESPIRATORY
PROTECTIVE EQUIPMENTS
HEAD
PROTECTION:
Head protectors must be hard hats
and caps made of aluminium, PVC, fiber glass, laminated plastic or vulcanised
fiber.They may be fitted with brackets, welding masks, protective face screen
or lamp. These caps are provided with replaceable harness which provide
sufficient clearance between the top of the head and shell.
Soft caps and hood are also used for
protection from heat, spark and other dangerous materials and are made of
appropriate materials.
EYE AND FACE PROTECTION:
Numerous eye and face injuries are
caused dusts, flying particles, splashes and harmful radiations. It is
difficult to cover precisely. The various processes in which the worker will be
required to wear goggles. The hazards encountered are
Relatively large flying objects ----- chipping, caulking, sledging
Dust and small flying objects ---- scaling, grinding, woodworking
Splashing of metals ---- casting of metals, vanishing and dipping of
molten metals
Splashing of gases, fumes &
liquids ---- handling of acids and chemicals
Reflected light, glare & radiant
energy -- Foundry work, furnaces,
gas welding & cutting,
arc welding
Eye protectors must be safety
spectacles, mano goggles, welding goggles, foundry goggles, chemical goggles,
welding helmets, face shields and gas tight goggles etc.
HAND AND
BODY PROTECTION:
Protection of hands and arms become
necessary hence workers have to handle materials having sharp edges or when hot
and molten metals, chemicals and corrosive substances are to be handled. The
protective substances may be gauntlet gloves, wrist gloves, mittens, hand pads
and thumb and finger guards and sleeves. It is important that not only the
various parts of the arm and hand are adequately covered but that they should
be covered by a material suitable of with standing the specific hazards
involved.
FOOT AND LEG PROTECTION:
Adequate foot protection may have to
be provided to the workers employed in certain jobs. Risks of injury may be in
handling of heavy materials, caustic and corrosive liquids, wet conditions,
molten metals etc.Common leg and foot protective devices are safety shoes and
boots, foot guards and leg guards. Shoes and boots may be provided with steel
toe- box and inner steel sale and they may be ankle, calf or thigh or hip high.
They may be made of asbestos, neoprene, natural rubber & synthetic rubber.
Leg protectors may be in the form of
leggings which may be knee high and they may be spats which should be lower
shin, ankle and instep. They may be held in position by straps or spring lips
or snap fasteners.
BODY PROTECTION
Sometimes it become necessary to
provide special protective equipment for the body in the form of aprons,
jackets and complete head to toe protective suits. Nature of potential hazard,
degree of hazard involved and nature of activities of the person involved are
important considerations in the selection of safety clothing.
Besides the above five groups, there
are devices for protection against noise in the form of ear- muffs and safety
belts for working in the pits or in confined spaces.
