Saturday, March 14, 2009

Industrial Safety and Security (Subjective Notes) - 4

Q.13. Toxic substances though usefuk in Industry can become a dangerous hazard. Justify.

Ans :- Gaseous contaminants:

These may be toxic or inert gases. The toxic gases may product harmful effect even if they are present in relatively low concentrations. The inert gases produce undesirable effects primarily by displacement or oxygen.

i) Gaseous contaminants immediately dangerous to life:

These gases contaminants present in concentrations that would endanger life of a worker breathing even for a short period of time. In other words, a gas is “immediately dangerous to life” if it is present in certain concentration. Where it is not possible to determine the extent of concentration or the kind of gas is not known, as gases should be considered as “immediately dangerous to life”.

ii) Gaseous contaminants not immediately dangerous to life:

These contaminants are gases present in concentration that could be breathed by a worker for a short time without endangering his life but which may cause possible injury after a prolonged single exposure or repeated short exposure. But even after concentration of the contaminant is known, no exact formula can be applied to determine if the contaminant is immediately dangerous to life or not.

Particulate contaminants: (Dusts, fumes, smokes, mists, fogs):

Majority of particulate contaminants are not immediately dangerous to life. They may be solid, liquid or a combination of solid and liquid and may be classified into three broad groups.

1. Toxic particulate contaminants:

These when inhaled may pass from the lungs into the blood stream and are then carried to the various parts of the body. The effect may be chemical irritation, systematic poisoning or allergic reactions. Common contaminants in this group are antimony, arsenic, cadmium, chromic acid and chromates, lead and manganese.

2. Fibrosis – producing dust:

These dusts do not pass into the blood stream but remain in the lungs and may cause pulmonary impairment. The common examples under this group are asbestos, coal, bauxite and free silica.

3. Nuisance dusts:

These may dissolve and pass directly into the blood stream or may remain in lungs neither producing local or systematic effects.

Combination of gaseous and flarticniate contaminants:

The gaseous and particulate contaminants may be entirely of different substances like carbon monoxide and oxides of nitrogen produced by blasting and the dust from the blasted material or they may be same substances in liquid and vapour from like volatile liquids.

Q. 14 Why is safe guarding of machinery important? How is it ensured?

Ans :- Safeguarding of machinery:

A substantial percentage of reportable accidents in factories are due to machinery.

Therefore, safety legislations in various countries law special emphasis on safeguarding of machinery. Detailed provisions regarding safeguarding of machinery is also contained in the Model Code of Safety Regulations for Industrial Establishments of International Labour Organisation. In some countries, the legislation covers detailed requirements regarding specific machinery and processes in detail in a comprehensive manner while in some others, it is given in concise manner. It is not practicable to bring out detailed regulations in respect of each item of machinery.

Therefore, the Factory Inspectors will have to have sufficient knowledge and experience to understand the requirements which are expressed in general term in the law. For example, in some countries the law specifies some common dangerous parts like setscrews, bolts and keys, flywheels, gearing, cone and cylinder gears etc and supplement it by comprehensive terms such as “other transmission machinery” and “any other dangerous parts of machinery”. Only if the Factory Inspector has knowledge of the manner in which each type of machinery are to be safeguarded can he be in a position to administer the provisions of the law effectively.

Safeguarding of machinery is important, because:

• There could be dangers from machinery.

• Mechanical hazards from machinery.

Types of guards used in machinery are given below:

Fixed Guard:

A guard, which has no moving parts associated with or dependent upon, the mechanism of any machinery and which, when in position, prevents access to a danger point or area is called a fixed guard.

a) Use:

A fixed guard should be used whenever practicable. The guard should by its design, prevent access to the dangerous parts of the machinery. It should be of robust construction, sufficient to withstand the stresses of the process and environmental conditions. It should be fixed in position when the machinery is in motion or is likely to be in motion. It should not be possible to remove or open the guard at any time without the aid of a tool. When it is necessary for work to be fed through the guard, the openings should be sufficient only to allow the passage of material, but should not create a trap between the material and guard.

b) Openings in a fixed guard:

Where an opening is necessary in a fixed guard for the purpose of feeding material by hand, it should not allow the operator access to the dangerous parts. Where it is necessary to provide such an opening, it should be at a sufficient distance from the danger point. Safe opening “x” = Y4+ distance of the guard.

From the danger line “y”
Ø 8

The above thumb rule, if followed in the design should prevent unsafe access. Access through a guard opening which is potentially dangerous can often be prevented by the use of a false table.

If access to the dangerous parts cannot be prevented by the use of a fixed guard with a plain opening, then a funnel of sufficient length should be provided.

c) Adjustable guard:

A fixed guard incorporating an adjustable element, which once adjusted remains in that position during a particular operation is an adjustable guard.


Where it is impracticable to prevent access to the dangerous parts because they are unavoidably exposed during use, (like the cutter on a horizontal milling machine) the use of an adjustable guard may be permissible. An adjustable guard provides for an opening the machinery through which material can be fed, the whole guard or part of it being capable of adjustment, in order that the opening can be varied in height and width to suit the dimensions of the work in hand. The guard should be so designed that the adjustable parts cannot easily become detached and mislaid.

d) Distance guard:

It’s a guard which does not completely enclose a danger point or area but placed sit out of normal reach is a distance guard.


A distance guard is designed and constructed in relating to the danger with object of preventing any part of the body from reaching a danger point or area. It may take the form of a fixed barrier or fence designed to a certain height so as to prevent access to the danger area. However, climbing over this type of safeguard cannot be entirely eliminated.

e) Interlocking guard:

It’s a guard which has a movable part so connected to the machinery controls that –

• The part of the machinery causing the danger cannot be set in motion until the guard is closed and
• Access to the danger point or area is not possible while danger exists.

An interlocking guard includes also a control-guard and a sensing guard.


When a process demands across to a danger area and a fixed guard is impracticable, the provision of an interlocking guard should be considered. The interlocking system may be either mechanical, electrical, hydraulic, pneumatic or any combination of these.

The type and model of operation of the interlock should be considered in relation to the process to which it is applied. The interlocking system should be fail safe.

f) Automatic guard:

It’s a guard which is associated with and dependent upon the mechanism of the machinery and operator so as to physically remove from the danger area and part of a person exposed to danger.


An automatic guard operates by physically removing from the danger area any part of a person exposed to danger. It can be used only where there is adequate time for such removal to take place without introducing any further danger. The movable part of the guard should be positively actuated by the movement of the dangerous part of the machinery. The guard should be securely fastened to the machinery so that it cannot be adjusted or detached without the aid of tools.

g) Self adjusting guard:

It’s a guard which prevents accidental access of a person to a danger point or area but allows the access of a work piece which itself acts as part of the guard, the guard automatically returning to its closed position when the operation is completed. An example of a self adjusting guard to be found on some circular sawing machines. When no timber is passing through the machine, the guard provides complete protection and when the timber is presented in raises the guard which then rests on top of the timber while cutting is in progress.


Safeguarding of machinery to prevent accident is a statutory requirement. The responsibility is dual by employer to provide and employee not to tamper or remove the guards. Inspections as discussed should be possible of equipment without removing these guards. Safety inspections must have a charter the serviceability state of the guards provided.

Q. 15 Inspection have a purpose . They attain more importance when related to safety of human life, and productivity of a unit. Discuss.

Ans :- Introduction: Safety Inspection:

The systematic analysis of hazardous processes and operations has been essential to the safety specialists practice. A system is any unit, organization of operation that can be bounded. Systems analysis views any systems as a totality and emphasizes the effect of possible changes in one part upon all other parts and upon the system as a whole. It is not intended here to prepare the student to be a system analyst but render exposure for inspections as related to safety of plant, machines and operation. Systems safety inspections require imaginative construction of every conceivable situation that could arise within each component of the system during its life expectancy with respect to the effects of its failing as well as its intended action. The line of inspection should be aggressive and obviously would be aided by considerable experience with both the systems and the events of many general.

Each component as inspected in an orderly path through the system should be analyzed with respect to the possibility that it may contribute to an unwanted event. Initiating
questions for the inspection could be:

a) How could each component of the system cause damage or injury? If used properly / improperly.
b) How is the damage or injury apt to occur?
c) Can each hazardous event be prevented How? If not what are the consequences?
d) Can each hazardous event be controlled? To what degree? What are the potential consequences of the limited hazard? Can they be tolerated?

The time spent on inspection would vary depending upon the complexity of the system.

Purpose of Safety Inspection:

Plant safety inspection can bring to light very useful information regarding safety and health status, which will include not only unsafe conditions and unsafe methods of work but also direct and indirect causes leading to them. This is a very useful tool in the hands of the manager and helps him to take corrective action before harm is done.

It also helps the safety management programme in many other ways:

Safety in productivity of Unit:

 Regular inspections carried on the shopfloor cannot escape the notice of the workmen. This effect is an indirect way of demonstrating the management’s interest in the safety and welfare of employees and thus contribute to better shopfloor relations.
 Safety inspection brings to light areas where waster can be decreased, processes can be improved and productivity increased. This results in better management of resources.
 Safety inspections results in contacts with the employees and discussions with them on their difficulties in ensuring safety. Apart from the fact that this will bring forth useful suggestions from employees, such contacts automatically result in better understanding and mutual help, which leads to all round success of the safety programme.

Safety inspection should be objective, regular, systematic and backed with sincerity of

purpose. Defective procedures, lack of objectives, lack of regularity, neglect and half heartedness on the part of the inspection team will make a mockery of the safety management programme in the plant and can even negate achievement by other means.

Safety of human life:

Things to do for safety of human life:

Machines House keeping

Safety in design Layout / passages
Standards of maintenance Condition of flooring
Provision & effectiveness of guards Orderly arrangement
Safe operation Cleanliness
House keeping around the machines, Water logging
Convenience of operation

Electricity: Hand tools

Approach in installation Condition
Condition of installation Use
Protection (Fuse, Earth, Relays) Maintenance standards
Standard of maintenance

Fire protection Environment

Approach to fire points Lighting
Equipment in position Noise
Conditions of equipment Dust / Fumes / Gases
Ignition sources Leakages of chemicals
Storage of flammable materials Spillage of chemicals
Functioning of exhaust systems

Potential for major hazards Action of people

Toxic release Posture
Chances of fire, explosion Methods
High pressure areas Clothing
High temperature areas


Equipment Use of personal protective
Standard of maintenance Equipment
Stacking Orderly behaviour
Ergonomics of handling Discipline

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