Industrial Hazards & Safety Precautions

Pharmaceutical Industrial Management (Pharm 5211):

Section B

Introduction

Increased emphasis on process safety due to no. of serious accidents

Public awareness – a force for industry to improve its safety profile

Hazardous chemicals from combustion and runaway reactions – play leading role in chemical process accidents.

Process safetyIncludes…….

Inherent safer design: user friendly plant design, withstand human error & equipment failure, no serious effect on safety

Process safety analysis: consists of hazard analysis: risk analysis, estimating damage, and review of project and procedure.

Safety devices: pressure relief devices, flame arresters, method of handling effluent, etc.

Hazardous materials and conditions: reactive chemicals, combustion and flammability hazards, gas explosion, dust explosion, static electricity, hazards of vacuum, inert gases, punctured line and vessels.

Hazard analysis

Hazard – inherent potential of a material or activity to harm people, property, or the environment.

Risk – a measure of economic loss or injury in terms of both the incident likelihood and magnitude of loss or injury.

Hazard and operability study (HAZOP) – a set of formal hazard identification and elimination procedures designed to identify hazards to people, process plants and the environment.

Hazard analysis

Process Hazard Analysis (PHA): Highly toxic, flammable materials, other hazardous chemicals require an initial PHA and should be updated every 5 years. Documentation – important (everything documented)

Safety, health, environment and loss prevention review (SHEL): often desirable to improve efficiency of use of time.

Hazard analysis

Purpose of HAZOP is to identify, not analyze or quantify hazards in a process.

HAZOP study is incomplete until response to action is documented. This study can be both batch and continuous process.

Aims of the study are……

To identify as many deviations as possible To decide whether action is required and identify solutions To decide what information or action required To ensure that required actions are followed through

Safety devices: Fire

Fire exposure – thermal expansion, vaporization, decomposition – pressure rise and overheating of the wall: - protected by a pressure relief device.

Also, by insulation, water spray, shut off valves, etc.

Safety devices: Fire

Operation failure – due to overpressure conditions including blocked outlet, cooling water failure, power failure, instrument air failure, thermal expansion, vacuum, etc.

Equipment failure – due to overpressure situations including rupture or break of internal tubes – protected by safety relief valves.

Types of valves: balanced safety relief valves, pressure vacuum relief valves, rupture disks, etc.

Safety devices: Devices for effluent

Disposal of an effluent vent stream from emergency relief devices – consider these factors: single or multi-phase stream, flammable stream, toxic stream, corrosive stream to equipment or personnel.

Light hydrocarbons – discharged directly to atmosphere (sometimes)

Toxic vaours – sent to flare or scrubber to render them harmless

For handling, blow down drums, cyclone vapour-liquid seperators and quench tanks

Safety devices: Cyclones

To handle liquids with low to moderate viscosity and for fouling service

High efficiency of separation; pressure drop is higher than blow-down drums; frequently used in chemical industry

Safety devices: Quench tank

To remove condensable vapours from flammable or toxic mixtures

Often used in petroleum refiners.

Applications……….

o to handle liquids with low to high viscosity

o to handle liquids with moderate solid loading

o to handle high liquid loading

Safety devices: Flame arresters

Passive devices designed to prevent propagation of gas flames through pipelines

Work by a permeable barrier (metallic) with narrow channels, to remove heat and free radicals, to prevent re-ignition of hot gas.

Equipment choice depends on……….type of arrester needed, appropriate location, design, flow resistance, maintenance and cost.

2 types: end of line arrester & tank vents deflagration arrester

Storage and handling of hazardous materials

Good planning, design and management practices

Toxicity – ability to cause biological injury, property of all materials, depends on dose & degree of hazard

Toxic hazards – caused by chemical means, routes: eye, inhalation, ingestion, skin and ears.

Storage conditions, Dilution, refrigeration, pressure storage of liquefied gas – reduce hazards.

Flammability hazards

Fire – result of fuel and oxygen coming together in suitable proportion and with a source of heat

Net product of a fire is either heat producing or heat absorbing reactions

2 types of flames: Diffusion flame (occurs on ignition of a fuel jet)

Aerated or premixed flame ( fuel and air premixed)

Heat, light, smoke, toxic gases – product of fire

Combustible dusts

Hazardous, very high surface area to volume ratio

Explosive (when suspended in a cloud in air)

A spark is sufficient to ignite, flames spread rapidly, hot gases expand and produce pressure waves.

Should be stored under pressure.

Gas explosions

Flush points and flammable limit (in % by volume)

Control based on prevention or protection or both

Auto ignition temperature (AIT) is minimum temp. at which vapours ignite spontaneously from heat or environment.

Hazard triangle – fire triangle

Fire hazards

4 categories based on nature of combustible material:

• Class A fires – materials like wood, paper, cloths

• Class B fires – materials like petroleum products

• Class C fires – involves energized electrical equipments

• Class D fires – fire in combustible metals

Fire extinguishers

Water

Dry chemicals

Dry powders

Stream

Carbon dioxide

Halon 1301

Vaporising liquids

Work by removal of oxygen, removal of fuel or removal of heat by cooling

Fire extinguishers

Portable fire extinguishers with water, CaCl2, soda and acid solutions

Materials expelled by manually operated pump or CO2

When acid and NaHCO3 are inverted, they mix & CO2 produced

CaCl2 as anti-freeze and used down to -400F

Foam: chemical (filled with CO2) or mechanical (filled with air)

Dry chemicals (finely divided powdered material) – e.g., NaHCO3, KHCO3, (NH4)3PO4

Halon 1301- Bromotrifluromethane, a liquefied compressed gas extinguisher, act by cooling action and dilution of vapours

Fire safety policy

Maintaining proper fire exits

Placing fire extinguishers in easily accessible places

Prohibiting flammable material in certain areas

Periodic inspection of buildings for violations

Maintaining fire alarm systems for detection and warning

Maintaining high level of training and awareness to labors

Conduct fire drills at regular intervals

Combustible dust

Finely divided & suspended in air – explosive and leads to employee deaths, injuries and destruction of entire building.

Metals (Al, Mg), wood, coal, plastics, bio-solids, sugar, paper, soaps, dried blood and certain textiles.

Explosions are of two types

Primary explosions: ignited by dust concentration, when flame front reaches dust collector cause further explosion

Secondary explosions: to prevent, dust collectors with exhausts or vent. Shakers are very prone due to static charge. To control….

reduce oxygen in air

reduce fuel (dust particles) in air

By mixing inert air, etc.

Electrical hazards

Different sources: 240 VAC, DC supplies, EHT voltages.

Current over 10 mA is painful, in excess of 100 mA is lethal.

Skin resistance: 1000 ohms for wet skin, 500 ohms for dry skin

Death – by as little as 40 volts.

Don’t contact any live electric conductor.

*Good housekeeping and general tidiness.

Some important precautions

Don’t operate machine with wearing loose clothing, button shirt sleeves, wear protective caps.

Ensure machine guards (well-fitted, well-positioned)

Don’t use hand tools of wrong size

Ensure that hand cutting tools are sharp

Use safety glasses during drilling or grinding

Wear appropriate eye protection

Leave machine or equipments in safe conditions for next person

Mechanical hazards

Mechanical motion: linear, translational or rotational

Produce work, changes in temperature.

Proper selection and use of tools and guards

Hand tools and power tools – cause injury if improperly handled

Thank you

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