Electrical Accident Causes: Electrical accidents can occur due to a number of factors, including: 1. Old wiring 2. Electric cords that run under carpeting 3. Flammable materials left near exposed electrical wiring in the workplace 4. Loose connectors 5. Poor wiring: substandard wiring can lead to electrical fires and electric shock 6. Lack of preventive devices such as ground fault circuit interrupters (a device that monitors and shuts off electric current in the event that the flow fluctuates), threepronged outlets, and polarized plugs 7. Failure to de-energize, lockout & tag out hazards during maintenance, repair or inspections. 8. Use of defective and unsafe tools. 9. Use of tools or equipment too close to energized parts. 10. Not draining off stored energy in capacitors. 11. Using 3-wire cord with a 2-wire plug. 12. Removing the third prong (ground pin) to make a 3-prong plug fit a 2-prong outlet. 13. Overloading outlets with too many appliances. 14. Using the attached electrical cord to raise or lower equipment. 15. Not verifying power is off when making repair (drilling into a 110 Volt a.c. line can kill). 16. Working in an elevated position near overhead lines. Classification of Electric Zone & Types of electric Equipment Recommended
Typical examples of such classifications are given below. Zone 0 Areas Examples are vapour space above closed process vessels, storage tanks or closed containers, areas containing open tanks of volatile, flammable liquid. Equipment for Use in Zone 0 Electrical equipment and circuits can be used in zone o if they are constructed in accordance with following: EPL 'Ga' a) Intrinsic safety (category 'ia') according to IS 5780/IEC 60079-11. Zone I Areas Zone I locations may be distinguished when any of the following conditions exits: a) Flammable gas or vapour concentration is likely to exist in the air under normal operating conditions; b) Flammable atmospheric concentration is likely to occur frequently because of maintenance. Repairs or leakage; c) Failure of process, storage or other equipment is likely to cause an electrical system failure simultaneously with the release of flammable gas or liquid; d) Flammable liquid or vapour piping system (containing valves. meters or screwed or flanged fittings) is in an inadequately ventilated area; and Equipment for Use in Zone 1 EPL 'Gb' a) Flameproof enclosures’ d’ according to IS 2148IIEC 60079-1; b) Pressurised enclosures 'p' according to IS 7389/IEC 60079-2; c) Powder filling 'q' according to IS 7724/IEC 60079-5; d) Oil immersion '0' according to IS 7693IIEC 60079-6 (see Note 6 under 5.2.3); e) Intrinsic safety 'i' according to IS 5780lIEC 60079-11; f) Encapsulation 'rn' according to IS/IEC 60079-18; and g) Electrical heat tracers and equipment which are certified for use in zone I areas. Zone 2 Areas Zone 2 locations may be distinguished when anyone of the following conditions exists: a) The system handling flammable liquid or vapour is in an adequately ventilated area and is so designed and operated that the explosive or ignitable liquids. vapours or gases will normally be confined within closed containers or closed systems from which they can
escape only during abnormal conditions such as accidental failure of a gasket or packing: b) The flammable vapour s can be conducted to the location as through trenches, pipes or ducts: c) Locations adjacent to zone I areas: and d) In case of use of positive mechanical ventilation, as the failure or abnormal operation of ventilating equipment can permit atmospheric vapour mixtures to build up to flammable concentrations.
Equipment for Use in Zone 1 EPL 'Gc' a) Non sparking "n' according to IS/IEC 60079-15; b) Intrinsic safety 'i' according to IS 57801IEC 60079-11; c) Increased safety 'e' according to IS 6381IIEC 60079-7; d) Electrical heat tracers and equipment, which are certified for use in zone 2 areas. Basic needs of Earthling.
To protect human lives as well as provide safety to electrical devices and appliances from leakage current.
To keep voltage as constant in the healthy phase (If fault occurs on any one phase).
To Protect Electric system and buildings form lighting.
To serve as a return conductor in electric traction system and communication.
To avoid the risk of fire in electrical installation systems. Conventional methods of earthling Methods of Earthing | Types of Earthing 1). Plate Earthing: 2). Pipe Earthing: 3). Rod Earthing 4). Earthing through the Waterman 5). Strip or Wire Earthing: 1. Plate type Earthing
Generally for plate type Earthing normal Practice is to use
Cast iron plate of size 600 mm x600 mm x12 mm. OR
Galvanized iron plate of size 600 mm x600 mm x6 mm. OR
Copper plate of size 600 mm * 600 mm * 3.15 mm
Plate burred at the depth of 8 feet in the vertical position and GI strip of size 50 mmx6 mm bolted with the plate is brought up to the ground level.
These types of earth pit are generally filled with alternate layer of charcoal & salt up to 4 feet from the bottom of the pit.
2. Pipe type Earthing
For Pipe type Earthing normal practice is to use GI pipe [C-class] of 75 mm diameter, 10 feet long welded with 75 mm diameter GI flange having 6 numbers of holes for the connection of earth wires and inserted in ground by auger method.
These types of earth pit are generally filled with alternate layer of charcoal & salt or earth reactivation compound
Causes of electrical fires and preventive measure: 1. Most electrical fires are caused by faulty electrical outlets and old, outdated appliances. Other fires are started by faults in appliance cords, receptacles and switches. Prevention Tips: Increase the frequency of checking of electrical appliances, and closely inspect cords and plugs. Replace defective electrical cords as fast as you detect them, and never attempt to repair them yourself. Buy appliances that use quality materials, and follow approved safety standards. Install ground fault circuit interrupters and surge protectors that will guard all major appliances; 2. Light fixtures, lamps and light bulbs are another common reason for electrical fires. Installing a bulb with a wattage that is too high for the lamps and light fixtures is a leading cause of electrical fires. Prevention Tip: Ensure that all light bulbs and lighting devices are plugged into electrical sockets that match the prescribed wattage. Avoid using extension cords for lighting purposes.
3. Misuse of extension cords is another electrical fire cause. Appliances should be plugged directly into outlet and not plugged into an extension cord for any length of time. Prevention Tip: Get the electrician to install power outlets matched to appliances that you frequently use. Avoid plugging appliances into multi-socket extension cords. 4. Space heaters are a major cause of electrical fires. Because these types of heaters are portable, many times people put them too close to combustible surfaces such as curtains, beds, clothing, chairs, couches and rugs. Coil space heaters are especially dangerous in this regard because the coils become so hot they will almost instantaneously ignite any nearby flammable surface Prevention Tip: Ensure that inflammable materials are positioned well away from portable space heaters. Better still, use radiation heaters that do not catch fire on direct contact 5. Wiring that becomes defective with the passage of time Prevention Tip: Call an expert electrician to look over your home. Detect and replace old wiring immediately, and you would be eliminating the biggest threat to electrical fires that your home could be exposed to Lighting & Color: Types of light Source
Lamps Incandesce nt Tungsten Tungsten halogen
Gas Discharge
LED Mercury Low pressure
Mercury Halide (HID)
High pressureHID
Fluorescent CFLs Induction
Sodium Vapour-HID Low Pressure High Pressure
Maintenance of Lighting Installation: CLEANING: Keeping lamps and fixtures clean may be the most important factor in keeping their performance high. Ceilings, and other lit surfaces should also be kept clean, as their reflection of light is sometimes as important as the fixtures themselves. Clean bulbs and fixtures with soft moist cotton cloth, soft-bristled anti-static brush, or lowpower vacuum cleaner. REPLACEMENT: BULBS SHOULD BE REPLACED NOT ONLY WHEN THEY BREAK, BUT ON A SCHEDULE ACCORDING TO HOW THE BRIGHTNESS OF THE LAMP DECAYS OVER TIME.
SOME BULBS LOSE OVER A THIRD OF THEIR INITIAL BRIGHTNESS OVER A FEW YEARS BE SURE TO DISPOSE OF REPLACED BULBS PROPERLY, AS MANY FLUORESCENTS AND OTHER ELECTRIC DISCHARGE LAMPS CONTAIN MERCURY.
VENTILATION: What is industrial ventilation? Ventilation is the mechanical system in a building that brings in "fresh" outdoor air and removes the "contaminated" indoor air. In a workplace, ventilation is used to control exposure to airborne contaminants. It is commonly used to remove contaminants such as fumes, dusts, and vapours, in order to provide a healthy and safe working environment. Ventilation can be accomplished by natural means (e.g., opening a window) or mechanical means (e.g., fans or blowers). Industrial systems are designed to move a specific amount of air at a specific speed (velocity), which results in the removal (or "exhaust") of undesirable contaminants. While all ventilation systems follow the same basic principles, each system is designed specifically to match to the type of work and the rate of contaminant release at that workplace. What is the purpose of a ventilation system? There are four purposes of ventilation: 1. Provide a continuous supply of fresh outside air. 2. Maintain temperature and humidity at comfortable levels. 3. Reduce potential fire or explosion hazards. 4. Remove or dilute airborne contaminants. 5. To maintain the oxygen content of the air and reduce CO2 concentration. 6. To maintain satisfactory thermal environment. 7. To maintain heat balance of the body 8. To prevent acute discomfort and acute injury to the health of the workers. Why have an industrial ventilation system? Ventilation is considered an "engineering control" to remove or control contaminants released in indoor work environments. It is one of the preferred ways to control employee exposure to air contaminants.
Other ways to control contaminants include:
eliminate the use of the hazardous chemical or material,
substitute with less toxic chemicals,
process change, or
Work practice change.
What are the basic types of ventilation systems? There are two types of mechanical ventilation systems used in industrial settings: Dilution (or general) ventilation reduces the concentration of the contaminant by mixing the contaminated air with clean, uncontaminated air. Local exhaust ventilation captures contaminates at or very near the source and exhausts them outside. What are main features of dilution ventilation? Dilution, or "general", ventilation supplies and exhausts large amounts of air to and from an area or building. It usually involves large exhaust fans placed in the walls or roof of a room or building. Dilution ventilation controls pollutants generated at a worksite by ventilating the entire workplace. The use of general ventilation distributes pollutants, to some degree, throughout the entire worksite and could therefore affect persons who are far from the source of contamination. Dilution ventilation can be made more effective if the exhaust fan is located close to exposed workers and the makeup air is located behind the worker so that contaminated air is drawn away from the worker's breathing zone. See Figure 1 for examples of good and poor dilution ventilation design. When used to control chemical pollutants, dilution must be limited to only situations where:
the amounts of pollutants generated are not very high,
their toxicity is relatively moderate, and
Workers do not carry out their tasks in the immediate vicinity of the source of contamination.
It is therefore unusual to recommend the use of general ventilation for the control of chemical substances except in the case of solvents which have admissible concentrations of more than 100 parts per million.
Figure 1
Figure 2
Figure 3
Figure 4 Figures 1 to 4: Examples of recommended dilution ventilation What are the limitations of dilution ventilation? As a method for protecting workers, it is important to know that dilution ventilation:
Does not completely remove contaminants.
Cannot be used for highly toxic chemicals.
Is not effective for dusts or metal fumes or large amounts of gases or vapours.
Requires large amounts of makeup air to be heated or cooled.
Is not effective for handling surges of gases or vapours or irregular emissions.
Regular "floor" or "desk" fans are also sometimes used as a method of ventilation, but these fans typically blow the contaminant around the work area without effectively controlling it. Opening doors or windows can be used as dilution ventilation, but again, this method is not reliable since air movement is not controlled. As a general note, the air or "volumetric" flow rate of dilution ventilation depends largely on the how fast the contaminant enters the air as well as the efficiency that fresh air mixes with workroom air. What is local exhaust ventilation? It is applied at the release point of the contaminant source to reduce the concentration of contaminant below the TLV level. Local exhaust is generally a far more effective way of controlling highly toxic contaminants before they reach the workers' breathing zones. This type of system is usually the preferred control method if:
Air contaminants pose serious health risk.
Large amounts of dusts or fumes are generated.
Increased heating costs from ventilation in cold weather are a concern.
Emission sources are few in number.
Emission sources are near the workers' breathing zones.
What are the components of local exhaust ventilation? A local exhaust system has six basic elements (see Figure 6):
A "hood" or opening that captures the contaminant at the source.
Ducts that transport the airborne chemicals through the system.
An air cleaning device that removes the contaminant from the moving air in the system (not always required).
Fans that move the air through the system and discharge the exhaust air outdoors.
An exhaust stack through which the contaminated air is discharged.
Figure
6
Basic components of a local exhaust system
Comparison of Ventilation Systems Dilution Ventilation Advantages Usually
Local Exhaust Ventilation Disadvantages
lowerDoes
equipment
not
Advantages
completelyCaptures contaminant atHigher
andremove contaminants.
installation costs. Requires
Disadvantages
source and removes itdesign, from the workplace.
lessCannot
maintenance.
be
used
cost
installation
and equipment.
forOnly choice for highlyRequires
regular
highly toxic chemicals. toxic airborne chemicals. cleaning,
inspection
and maintenance. Effective control forIneffective for dusts orCan handle many types small amounts of lowmetal fumes or largeof toxicity chemicals.
contaminants
amounts of gases orincluding vapours.
dusts
combustible
orof
and
metal fumes.
Effective control forRequires large amountsRequires flammable
for
heated
or
smaller
cooledamount of makeup air
gasesmakeup air.
since smaller amounts
or vapours.
of
air
are
being
exhausted. Best ventilation forIneffective for handlingLess energy costs since mobile or dispersedsurges
of
contaminant
vapours
sources.
emissions.
or
gases
orthere is less makeup air
irregularto heat or cool.
Mechanical ventilation: Advantages to a mechanical system.
Mechanical ventilation systems are considered to be reliable in delivering the designed flow rate, regardless of the impacts of variable wind and ambient temperature. As mechanical ventilation can be integrated easily into air-conditioning, the indoor air temperature and humidity can also be controlled.
Filtration systems can be installed in mechanical ventilation so that harmful microorganisms, particulates, gases, odours and vapours can be removed.
The airflow path in mechanical ventilation systems can be controlled, for instance allowing the air to flow from areas where there is a source (e.g. patient with an airborne infection), towards the areas free of susceptible individuals.
Mechanical ventilation can work everywhere when electricity is available.
Disadvantages to a mechanical system:
Mechanical ventilation systems often do not work as expected, and normal operation may be interrupted for numerous reasons, including equipment failure, utility service
interruption, poor design, poor maintenance or incorrect management. If the system services a critical facility, and there is a need for continuous operation, all the equipment may have to be backed up — which can be expensive and
unsustainable. Installation and particularly maintenance costs for the operation of a mechanical ventilation system may be very high. If a mechanical system cannot be properly installed or maintained due to shortage of funds, its performance will be
compromised. Because of these problems, mechanical ventilation systems may result in the spread of infectious diseases through health-care facilities, instead of being an important tool for infection control.
Natural ventilation: Advantages of a natural ventilation system, compared with mechanical ventilation systems.
Natural ventilation can generally provide a high ventilation rate more economically, due to the use of natural forces and large openings.
Natural ventilation can be more energy efficient, particularly if heating is not required.
Well-designed natural ventilation could be used to access higher levels of daylight.
There are a number of drawbacks to a natural ventilation system.
Natural ventilation is variable and depends on outside climatic conditions relative to the indoor environment. The two driving forces that generate the airflow rate (i.e. wind and temperature difference) vary stochastically. Natural ventilation may be difficult to control, with airflow being uncomfortably high in some locations and stagnant in others. There is a possibility of having a low air-change rate during certain unfavourable climate conditions.
There can be difficulty in controlling the airflow direction due to the absence of a wellsustained negative pressure; contamination of corridors and adjacent rooms is therefore a risk.
Natural ventilation precludes the use of particulate filters. Climate, security and cultural criteria may dictate that windows and vents remain closed; in these circumstances, ventilation rates may be much lower.
Natural ventilation only works when natural forces are available; when a high ventilation rate is required, the requirement for the availability of natural forces is also correspondingly high.
Natural ventilation systems often do not work as expected, and normal operation may be interrupted for numerous reasons, including windows or doors not open, equipment failure (if it is a high-tech system), utility service interruption (if it is a hightech system), poor design, poor maintenance or incorrect management.
Although the maintenance cost of simple natural ventilation systems can be very low, if a natural ventilation system cannot be installed properly or maintained due to a shortage of funds, its performance can be compromised, causing an increase in the risk of the transmission of airborne pathogens.
LIGHTING ARRESTOR A lightning stroke is an electric discharge between the atmosphere and an earth-bound object. They mostly originate in the thundercloud and terminate on the ground, called cloud to ground (CG) lightning. Types of lightning strokes Direct stroke Indirect stroke (1) Direct stroke
In direct stroke, the lightning discharge is directly from the cloud to the subject equipment. From the line, the current path may be over the insulator down the pole to the ground. (2) Indirect stroke Indirect stroke results from the electro statically induced charges on the conductors due to the presence of charge clouds. Harmful effects of lightning The travelling waves produced due to lightning will shatter the insulators. If the travelling waves hit the windings of a transformer or generator it may cause considerable damage. Lightning protection system
A lightning protection system is designed to protect a structure from damage due to lightning strikes by intercepting such strikes and safely passing their extremely high currents to ground.
A lightning protection system includes a network of air terminals, bonding conductors, and ground electrodes designed to provide a low impedance path to ground for potential strikes.
Lightning protection systems are used to prevent or lessen lightning strike damage to structures. Lightning protection systems mitigate the fire hazard which lightning strikes pose to structures.
A lightning protection system provides a low-impedance path for the lightning current to lessen the heating effect of current flowing through flammable structural materials.
If lightning travels through porous and water-saturated materials, these materials may literally explode if their water content is flashed to steam by heat produced from the high current. This is why trees are often shattered by lightning strikes.
Because of the high energy and current levels associated with lightning (currents can be in excess of 150,000 amps), and the very rapid rise time of a lightning strike, no protection system can guarantee absolute safety from lightning.
Lightning current will divide to follow every conductive path to ground, and even the divided current can cause damage.
Secondary "side-flashes" can be enough to ignite a fire, blow apart brick, stone, or concrete, or injure occupants within a structure or building.
The fundamental principle used in lightning protections systems is to provide a sufficiently low impedance path for the lightning to travel through to reach ground without damaging the building.
Working Principle of LA:
The Earthing screen and ground wires can well protect the electrical system against direct lightning strokes but they fail to provide protection against traveling waves,
which may reach the terminal apparatus. The lightning arresters or surge diverters provide protection against such surges. A lightning arrester or a surge diverted is a protective device, which conducts the high voltage surges on the power system to the ground.
Fig shows the basic form of a surge diverter. It consists of a spark gap in series with
a non-linear resistor. One end of the diverter is connected to the terminal of the equipment to be protected
and the other end is effectively grounded. The length of the gap is so set that normal voltage is not enough to cause an arc but
a dangerously high voltage will break down the air insulation and form an arc. The property of the non-linear resistance is that its resistance increases as the voltage (or current) increases and vice-versa. This is clear from the volt/amp
characteristic of the resistor shown in Fig The action of the lightning arrester or surge diverter is as under: (i) Under normal operation, the lightning arrester is off the line i.e. it conducts no current to earth or the gap is non-conducting (ii) On the occurrence of over voltage, the air insulation across the gap breaks down and an arc is formed providing a low resistance path for the surge to the ground. In this way, the excess charge on the line due to the surge is harmlessly conducted through the arrester to the ground instead of being sent back over the line. (iii) It is worthwhile to mention the function of non-linear resistor in the operation of arrester. As the gap sparks over due to over voltage, the arc would be a short-circuit
on the power system and may cause power-follow current in the arrester. Since the characteristic of the resistor is to offer low resistance to high voltage (or current), it gives the effect of short-circuit. After the surge is over, the resistor offers high resistance to make the gap non-conducting. Type of LA for Outdoor Applications: There are several types of lightning arresters in general use. 1. Rod arrester 2. Horn gap arrester 3. Multi gap arrester 4. Expulsion type lightning arrester 5. Valve type lightning arrester (1) Rod Gap Arrester 
It is a very simple type of diverter and consists of two 1.5 cm rods, which are bent at right angles with a gap in between as shown in Fig.

One rod is connected to the line circuit and the other rod is connected to earth. The distance between gap and insulator (i.e. distance P) must not be less than one third of the gap length so that the arc may not reach the insulator and damage it.

Due to the below limitations, the rod gap arrester is only used as a back-up protection in case of main arresters.
Limitations:
After the surge is over, the arc in the gap is maintained by the normal supply voltage, leading to short-circuit on the system.
The rods may melt or get damaged due to excessive heat produced by the arc.
The climatic conditions (e.g. rain, humidity, temperature etc.) affect the performance of rod gap arrester.
The polarity of the f the surge also affects the performance of this arrester
Due to the above limitations, the rod gap arrester is only used as a back-up protection in case of main arresters (2) Horn Gap Arrester:
Fig shows the horn gap arrester. It consists of a horn shaped metal rods A and B separated by a small air gap. The horns are so constructed that distance between them gradually increases towards the top as shown.
The horns are mounted on porcelain insulators. One end of horn is connected to the line through a resistance and choke coil L while the other end is effectively grounded.
The resistance R helps in limiting the follow current to a small value.
The gap between the horns is so adjusted that normal supply voltage is not enough to cause an arc across the gap.
(3) Multi Gap Arrester:
Fig shows the multi gap arrester. It consists of a series of metallic (generally alloy of zinc) cylinders insulated from one another and separated by small intervals of air gaps.
The first cylinder (i.e. A) in the series is connected to the line and the others to the ground through a series resistance. The series resistance limits the power arc. By the inclusion of series resistance, the degree of protection against travelling waves is reduced.
In order to overcome this difficulty, some of the gaps (B to C in Fig) are shunted by resistance. Under normal conditions, the point B is at earth potential and the normal
supply voltage is unable to break down the series gaps. On the occurrence an over voltage, the breakdown of series gaps A to B occurs. The heavy current after breakdown will choose the straight – through path to earth
via the shunted gaps B and C, instead of the alternative path through the shunt resistance.
Hazardous Effect of lightning strike
Visual effects (flash): caused by the Townsend avalanche mechanism
Acoustic effects: caused by the propagation of a shock wave (rise in pressure) originating in the discharge path; this effect is perceptible up to a range of around 10 km
Thermal effect: heat generated by the Joule effect in the ionised channel
Electrodynamics effects: these are the mechanical forces applied to the conductors placed in a magnetic field created by the high voltage circulation. They may result in deformations
Electrochemical effects: these relatively minor effects are consist in the form of electrolytic decomposition in accordance with Faraday’s law –– induction effects: in a varying electromagnetic field, each conductor becomes the seat of an induced current
Effects on a living being (human or animal): the passage of a transient current of a certain r.m.s value is sufficient to incur risks of electrocution by heart attack or respiratory failure, together with the risk of burns.
Health Effect of lightning strike Lightning has the potential to cause a number of injuries to include:
Eye injury Lung damage Heart damage Superficial burns Eardrum rupture Broken bones and dislocations Skull fractures and cervical spine injuries Keraunoparalysis - a temporary paralysis
Cardiac arrest. Lightning strike is mainly an injury to a person's nervous system, many times with
brain and nerve injury. Unconsciousness, paralysis, and shortness of breath, chest pain, noticeable burns, back or neck pain, or any indication of a possible broken bone.
Protection against lightning
Different types of protective devices are:-
Earthing screen
Overhead ground wires
Lightning arresters
(1)The Earthing screen
The power station & sub-station can be protected against direct lightning strokes by providing Earthing screens.
On occurrence of direct stroke on the station, screen provides a low resistance path by which lightning surges are conducted to ground. Limitation:
It does not provide protection against the travelling waves which may reach the equipment’s in the station.
(2) Overhead ground wires
It is the most effective way of providing protection to transmission lines against direct lightning strokes.
It provides damping effect on any disturbance travelling along the lines as it acts as a short-circuited secondary. Limitation:
It requires additional cost.
There is a possibility of its breaking and falling across the line conductors, thereby causing a short-circuit fault.
(3)Lightning Arresters
It is a protective device which conducts the high voltage surge on the power system to ground
The Earthing screen and ground wires fail to provide protection against travelling waves. The lightning arrester provides protection against surges.
Lightning arresters and their component? A lightning
arrester is
a
device
used
on electrical
power systems
and telecommunications systems to protect the insulation and conductors of the system from the damaging effects of lightning. The typical lightning arrester has a high-voltage terminal and a ground terminal. Component
1. A
lightning
arrester
may
be
a spark
gap or
may
have
a
block
of
a semiconducting material such as silicon carbide or zinc oxide. "Thyrite" was once a trade name for the silicon carbide used in arrester.
2. Some spark gaps are open to the air, but most modern varieties are filled with a precision gas mixture, and have a small amount of radioactive material to encourage the gas to ionize when the voltage across the gap reaches a specified level.
3. Other designs of lightning arresters use a glow-discharge tube (essentially like a neon glow lamp) connected between the protected conductor and ground, or voltageactivated solid-state switches called varistors.
4. Lightning arresters built for power substation use are immense devices, consisting of a porcelain tube several feet long and several inches in diameter, typically filled with discs of zinc oxide. Heat Stress Explain Thermal Comfort? 1. The term ‘thermal comfort’ describes a person’s state of mind in terms of whether they feel too hot or too cold. 2. The six factors affecting thermal comfort are both environmental and personal. These factors may be independent of each other, but together contribute to an employee’s thermal comfort. Environmental factors:
Air temperature Radiant temperature Air velocity Humidity
Personal Factors:
Clothing Insulation Metabolic heat 3. By managing thermal comfort you are likely to improve morale and productivity as well as improving health and safety. 4. People working in uncomfortably hot and cold environments are more likely to behave unsafely because their ability to make decisions and/or perform manual tasks deteriorates. For example: People may take short cuts to get out of cold environments Employees might not wear personal protective equipment properly in hot
environments increasing the risks An employee’s ability to concentrate on a given task may start to drop off, which increases the risk of errors occurring
What is Legal requirement of room temperature and air flow rate? As per Maharashtra factories rule 1963 22-A. Ventilation and temperature - (l) Limits of temperature and air movement - In any factory the maximum wet-bulb temperature of air in a work-room at a height of 1.5 metres above the floor level shall not exceed 30°C and adequate air movement of at least 30 meters per minute shall be provided; and in relation to dry-bulb temperature, the wet-bulb temperature in the work-room at the said height shall not exceed more than that shown in the Schedule hereto, or as regards a dry-bulb reading intermediate between the two dry-bulb readings, that specified in relation to the higher of these two dry bulb readings: Dry Bulb Temperature
Wet Bulb temperature
30°C to 34°C
29°C
35°C to 39°C
28.5°C
40°C to 44°C
28°C
45°C to 47°C
27.5°C
Hand Tool and portable Power Tool Causes of hand tool injury? (a) design failures forming failures / dimensioning wrong choice of material wrong working hardness (b) Defects in material
pores, shrink hole, cracks, strange inclusions distribution of carbides undue segregations
(c) Machining failures
bad surface quality (notch effect) damages on surface (grinding failures, erosion failures) welding defects (joint welding, deposit welding) nitriding failures v missing stress relieving distortion
(d) Heat treatment failures
quench stress crack ii decarburization retained austenite insufficient tempering stage v coarse grain/mixed grain superheating precipitations on grain boundary
(e) Handling failures
mechanical overstressing thermal overstressing corrosive overstressing
Common Causes of Accidents • • • • • • • • • • •
using the wrong tool for the job tools falling from overhead sharp tools carried in pockets using cheaters on tool handles excessive vibration using tools with mushroomed heads failure to support or clamp work in position carrying tools by hand up or down ladders using damaged electrical cords or end connectors Failure to use ground fault circuit interrupters (GFCIs), especially outdoors. Poor maintenance, Wrong tool, wrong use, carelessness, bad storage and
•
poor material. Inadequate knowledge of handling of tool.
Prevention and control of tool accident Basic hazard awareness and common sense can prevent serious injuries with hand and power tools. As a general rule follow the safe practices listed below. 1) Always wear eye protection. There is always the risk of flying particles and dust with hand and power tools. Appropriate eye protection is essential and must be worn by the user and others nearby. For eye protection see the Personal Protective equipment. 2) Use the right tool for the job. Using a screwdriver as a chisel, using a cheater on a wrench handle, or using pliers instead of a proper wrench are typical examples of the mistakes which commonly lead to accidents and injuries.
2)
Use tools as recommended by the manufacturer. For example, don’t use cheaters on handles. This will exert greater forces on the tool than it was designed for and is likely to cause breakage and possible injury.
3)
Damaged or broken tools should be removed from service. Chisels with mushroomed heads, hammers with cracked or loose handles, wrenches with worn jaws, damaged extension cords, and ungrounded tools are all unsafe and should be removed from service and be either repaired or destroyed.
4) Maintain tools in safe operating condition. Prevent mushrooming. Tools which are struck by hammers, such as chisels or punches, should have the head ground periodically to prevent mushrooming. Keep handles secure and safe. Don’t rely on friction tape to secure split handles or to prevent handles from splitting. Check wedges and handles frequently. Be sure heads are wedged tightly on handles. Keep handles smooth and free of rough or jagged surfaces. Replace handles that are split, chipped, or that cannot be refitted securely. Keep hand tool cutting edges sharp. Sharp tools make work easier, improve the accuracy of your work, save time, require less effort, and are safer than dull tools. 5) Never climb ladders with tools in your hand 6) Protect the cutting edges of tools when carrying them 7) Keep your hand tools clean. Protect them against damage caused by corrosion. Wipe off accumulated dirt and grease. 8) Good housekeeping orderly layout and cleanliness 9) Workers and supervisor should be trained • To wear safety goggle, face shield, helmet • To select right tool for each job • To guard, inspect, repair, and maintain tool in good condition • To us proper storage facilities when tool not in use • To replace the tool when worn Name the list of power tool •
Angle grinder
•
Lathe
•
Bandsaw
•
Miter saw
•
Ceramic tile cutter
•
Pneumatic torque wrench
•
Chainsaw
•
Powder-actuated tools
•
Circular saw
•
Table saw
•
Concrete saw
•
Disc cutter
•
Cold saw
•
Grinding machine
•
Crusher
•
Heat gun
•
Jackhammer
•
Jigsaw
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Jointer
Safety in all types of power presses Power tools can be hazardous when improperly used. There are several types of power tools, based on the power source they use: electric, pneumatic, liquid fuel, hydraulic, and powder-actuated. The following general precautions shall be observed by power tool users: 1. 2. 3. 4.
Never carry a tool by the cord or hose; Never remove prongs from any cords; Never stand in or near water when using tools; Always use a Ground Fault Circuit Interrupter (GFCI) with electrical tools if working in
5. 6. 7. 8.
a wet environment; Never “yank” the cord or the hose to disconnect it from the receptacle; Keep cords and hoses away from heat, oil and sharp edges; Replace all frayed and/or damaged extension cords. Do not try to tape cords; Disconnect tools when not in use, before servicing and when changing accessories
such as blades, bits and cutters; 9. All observers shall be kept at a safe distance away from the work area; 10. Maintain good footing and balance; 11. Avoid loose fitting clothes, ties or jewellery such as bracelets, watches or rings, which can become caught in moving parts; 12. Use tools that are either double-insulated or grounded (three-pronged); 13. Keep work area well-lit when operating electric tools; 14. Ensure that cords and hoses do not pose as a tripping hazard; and 15. All portable electric tools that are damaged shall be removed from use and tagged “Do Not Use”. This shall be done by supervisors and/or employees. Selection Criteria of power Tool 1. Use the right tool for the job, and the right tool for the user. If its small hole is to be drilled and if it is easily possible by hand drill then power drill is not necessary. 2. Tool supplier should give the complete information about the job for which a tool required so we can recommended appropriate tool for that job 3. Normally portable power tool are to be used on light or home work for continuous operation or production service or heavy work industrial duty toll are to be selected. 4. Avoid high contact forces and static loading.
5. 6. 7. 8.
Reduce excessive gripping force or pressure. Avoid extreme and awkward joint positions. Avoid twisting hand and wrist motion by using power tools rather than hand tools. Use two- or three-finger triggers for power tools; use four-finger triggers only when the
tool is balanced. 9. Maximum grip force for a trigger should not exceed 4 pounds (1.8 kg). 10. Choose tools with handles that have added friction such as compressible rubber or closed-cell foam, with slightly etched surfaces. 11. Handles should be 4.5 to 5.5 inches (11.4 to 14.0 cm) long; add .5 inches (1.3 cm) of length, minimum, if wearing gloves. 12. Select tools with 1.25- to 1.75-inch (3.2- to 4.4-cm) handle diameter, 1.5-inch (3.8-cm) recommended. For precision operations, use .3- to .6-inch handle diameter (.8- to 1.5cm). 13. Use torque reaction bars on tool balancers. 14. Use tools with auto-shutoff clutch 15. Use pulse tools. 16. Avoid or limit vibration; select impact tools that minimize vibration (e.g., impulse tools) rather than mechanical impact tools. 17. Select pneumatic tools that do not allow air exhaust to vent on the hand, wrist, face or other exposed skin areas. Plant Design/ Housekeeping/ Maintenance What are the accidents in “poor housekeeping”? 1. Men getting hit by failing from overhead 2. Men slipping as greasy, wet or dirty floor 3. Men failing in open tank without cover in level floor 4. Accidents due to poor lighting 5. Fire accidents due to faulty electrical wires What are some benefits of good housekeeping practices? Effective housekeeping results in:
reduced handling to ease the flow of materials
fewer tripping and slipping accidents in clutter-free and spill-free work areas
decreased fire hazards
lower worker exposures to hazardous substances (e.g. dusts, vapours)
better control of tools and materials, including inventory and supplies
more efficient equipment clean-up and maintenance
better hygienic conditions leading to improved health
more effective use of space
reduced property damage by improving preventive maintenance
less janitorial work
improved morale
improved productivity (tools and materials will be easy to find)
Describe the hazards and Precaution in sand and shot blasting method Health Hazards Abrasive blasting operations can create high levels of dust and noise. 1. Silica sand (crystalline) can cause silicosis, lung cancer, and breathing problems in exposed workers. 2. Coal slag and garnet sand may cause lung damage similar to silica sand (based on preliminary animal testing). 3. Copper slag, nickel slag, and glass (crushed or beads) also have the potential to cause lung damage. 4. Steel grit and shot have less potential to cause lung damage. 5. Slags can contain trace amounts of toxic metals such as arsenic, beryllium, and cadmium. Engineering Controls Substitution 1. Use a less toxic abrasive blasting material. 2. Use abrasives that can be delivered with water (slurry) to reduce dust. Isolation and Containment: 1. Use barriers and curtain walls to isolate the blasting operation from other workers. 2. Use blast rooms or blast cabinets for smaller operations. 3. Use restricted areas for non-enclosed blasting operations. 4. Keep co-workers away from the blaster. Ventilation 1. Use exhaust ventilation systems in containment structures to capture dust.
Administrative Control: 2. 3. 4. 5.
Do not use compressed air to clean as this will create dust in the air. Clean and decontaminate tarps and other equipment on the worksite. Schedule blasting when the least number of workers are at the site. Avoid blasting in windy conditions to prevent the spread of any hazardous materials.
Fire Safe Housekeeping Method for Engineering Industries 1. Keep combustible materials in the work area only in amounts needed for the job. When they are unneeded, move them to an assigned safe storage area. 2. Store quick-burning, flammable materials in designated locations away from ignition sources. 3. Avoid contaminating clothes with flammable liquids. Change clothes if contamination occurs. 4. Spillage of Toxic or reactive explosive and flammable chemical should be clean as soon as possible which can may be the reason for fire. 5. Reduce the accumulation Oil, cotton waste, paper, and packing material substance causing spontaneous ignition e.g. dust, solvent, jute, sparks welding cutting process in flammable area. 6. Hazards in electrical areas should be reported, and fixed the problem soon possible. 7. Dust May produce the significant explosive hazard when suspended in air. Hence the risk of explosion can be reduced by accumulation and disposal of dust. 8. Combustible waste should be segregated from combustible waste and keep away from source of ignition 9. good standards of housekeeping are essential to protect from fire hazards – keep workplaces tidy 10. Regularly remove combustible waste, including accumulations of dust 11. Keep ignition sources away from combustible material, flammable liquids/gases, etc. 12. keep use of flammable liquids to a minimum and close containers when not in use 13. Do not allow the smoking near to flammable area. 14. Provide training to workers and make to understand them the need of housekeeping to reduce fire hazards.
Safety precaution of scaffold? 1. Wooden board not be painted 2. Wooden board should not to any cracks 3. Check for rust in pipes / clamps 4. Clamps should fixed and good quality 5. Board’s thickness should be 3.4 cms and no bending
6. The construction must be rigid, properly based 7. Use of good and sound materials 8. The wooden bellies have not joints 9. Vertical poles should not be more than 6 feet 10. Chains, ropes used for the suspension of scaffoldings 11. Never throw any materials from height 12. Use safety harness while working at above 6 feet 13. Properly ties to be arrangement. Safety rules when using ladders? 1. The foot wear is not greasy, oily and muddy and has a good grip on the rungs. 2. When climbing or coming down a ladder should be face the ladder side and had on with both hand. 3. Carry light tools in pockets in a shoulder bag. 4. Hold on with at least new hand if use of both hands then, use safety belt 5. Never climb higher than the third rung from the top on straight or second tired from the top on extension ladder. 6. Step ladder must be fully open and the divider locked 7. Metal ladder shall not be used near electrical equipment’s. 8. Metal ladder shall not be place on firm footing and at angle of 75 9. Any ladder found defect in any way should be marked do not use 10. Ladder shall not be placed on a box or drum. 11. Rubber protection on head and heel of a ladder is necessary. MAINTENANCE Importance of Preventive maintenance Here are other important benefits of a properly operated preventive maintenance program: 1. Equipment downtime is decreased and the number of major repairs are reduced 2. Better conservation of assets and increased life expectancy of assets, thereby
eliminating premature replacement of machinery and equipment 3. Reduced overtime costs and more economical use of maintenance workers due to
working on a scheduled basis instead of a crash basis to repair breakdowns 4. Timely, routine repairs circumvent fewer large-scale repairs
5. Improved safety and quality conditions for everyone. 6. To improve the performance and safety of the equipment at your property. 7. Preventative maintenance assures the efficiency and speed of your equipment. 8. Regularly scheduled preventative maintenance can confirm that the machine is
working properly and avoid emergency situations and outages. 9. Preventive Maintenance Saves Money 10. Preventive Maintenance Saves Time 11. Preventive Maintenance Helps Safeguard Your Data 12. Preventive Maintenance Improves Performance.
Importance of Periodic maintenance
Provides increased component operational life and availability
Allows for pre-emptive corrective actions
Results in decrease in equipment and/or process downtime
Lowers costs for parts and labour
Provides better product quality
Improves worker and environmental safety
Raises worker morale
Increases energy savings
Role of preventive maintenance in health and safety 1. prevention of risks, 2. protection of safety and health, assessments of risks, 3. elimination of risks and accidents, 4. the informing, consultation, balanced participation in accordance with national laws
and / or practices 5. and training of workers and their representatives,
6. General guidelines for the implementation of the said principles. 7. Obligations of employers, employees and other groups. 8.
Help to avoiding risks;
9. evaluating the risks which cannot be avoided; 10. combating the risks at source; 11. adapting the work to the individual, especially as regards the design of work places,
the choice of work equipment and the choice of working and production methods, with a view, in particular, to alleviating monotonous work and work at a predetermined work rate and to reducing their effect on health; 12. adapting to technical progress; 13. replacing the dangerous by the non-dangerous or the less dangerous; 14. developing
a coherent overall prevention policy which covers technology,
organization of work, working conditions, social relationships and the influence of factors related to the working environment; 15. giving collective protective measures priority over individual protective measures; 16. Giving appropriate instructions to the workers.