TOPIC 5 : WASTE TREATMENT AND DISPOSAL TECHNOLOGY

Outline of topic 5:

AIR CONTAINMENT

GENERAL VENTILATION AND LOCAL EXHAUST SYSTEMS

CONFINE SPACE SAFETY MEASURE

IntroductionWHAT IS YOUR UNDERSTANDING?

• Who are you ?• What is your role?• We have any ISSUES for these?• Are you important for this ISSUES…….?

INTRODUCTION

Air Containment

What is ventilation?

Ventilation is the process of supplying and removing air by natural or mechanical means to or from any space.

It is used for heating, cooling and controlling airborne contaminants which affect employees and the general environment.

Industrial ventilation emphasizes the control of toxic and/or flammable contaminants

What is Industrial Ventilation?

Industrial ventilation generally involves the use of supply and exhaust ventilation to control emissions, exposures, and chemical hazards in the workplace.

Traditionally, nonindustrial ventilation systems commonly known as heating, ventilating, and air-conditioning (HVAC) systems were built to control temperature, humidity, and odors.

Ventilation may be deficient in:

• confined spaces;• facilities failing to provide adequate maintenance of

ventilation equipment;• facilities operated to maximize energy conservation;• windowless areas; and• areas with high occupant densities.

Any ventilation deficiency must be verified by measurement.

What are confined spaces?

A confined space means any place in which, by virtue of its enclosed nature, there arises a reasonably:

foreseeable specified risk of fire or explosion loss of consciousness of any person due to an increase in body

temperature loss of consciousness or asphyxiation of any person due to gas, fume,

vapor or lack of oxygen drowning of any person due to an increase in the level of liquid asphyxiation of any person who is trapped by a flowing solid

Confined spaces include any chamber, tank, vat, pit, well, sewer, tunnel, pipe, flue, boiler, pressure receiver, hatch, caisson, shaft or silo.

HAZARDS IDENTIFICATION

1. Deficiency of oxygen in airAir generally comprises 21% oxygen. However, in the following conditions, the oxygen in the air may decrease, resulting in a menace with human life:

Chemical reactions caused by oxygen consumption- oxygen is consumed due to oxidation during such processes of

welding, rusting, naked flame operations, fermentation and moulding. Substitution

- oxygen is squeezed out by such inert gases as nitrogen, argon and carbon dioxide. Adsorption on surface

- oxygen is adsorbed by porous surfaces, such as activated carbon.

Changes of the oxygen content in air that is breathed in, can cause the adverse physical reactions to the human body.

2. Flammable spaces Flammable gas in a confined space can lead to explosion or fire.

A space becomes flammable when oxygen in the air mixes with flammable gases, vapors or dust.

These gases and vapors may be formed by residues mixed with flammable substances, the use of flammable substances, or chemical reactions (e.g. the formation of methane).

A space may also become flammable when combustible dust abounds or flows in the air when disturbed.

Dust may come from agricultural products e.g. flour, chemicals, plastic particles, medicine or metal powder.

Flammable spaces will explode when contact with igniting sources such as welding sparks or sparks from portable electrical appliances.

The explosive range of flammable gases or vapors (percentage in air)

CHEMICAL SUBSTANCES

The principal means of encountering chemical substances include: - respiration- skin absorption - eating.

The effects brought by chemical substances upon the human body may be chronic or acute, depending on: - the period of contact (how long get contact with chemical substances)- the intensity of the hazards during contact (how dangerous the chemical substances)- the impact of such hazards on health (example: corrosive,

toxic or harmful)

PHYSICAL HAZARDS1. Mechanical hazards

-some dangerous components such as belts, rotation shafts and gears in equipment may cause harm when used.

2. Electrical hazards- risks of death caused by electric shock or getting burn may arise when touching electric cables, electric wires and transformers in confined space.

3. Noise hazards-noise produced when working in confined spaces is generally higher than normal (leading to impairment in worker’s hearing and may even lead to deafness).

4. Radiation hazards- sparks produced when using radioactive equipment in confined space may cause harm (laser or welding sparks).

5. Environmental hazards- environmental conditions are more likely to pose danger in confined spaces(extremely high or low temperature, dampness, wet spaces)

6. Transportation hazards- sewer are situated on road, workers will have the risk of being knocked down by vehicles passing by.

7. Engulfment by liquid or flowing flow- flowing solids such as silt may pose the risk of engulfment.

Mechanical & Electrical hazards

Noise hazard Environmental hazard

Transportation hazard

Engulfment by liquid

Engulfment by flowing solids

OTHER HAZARDS1. Hazards from manual operations

- The working environment of confined spaces is generally narrow and workers inside need considerable effort when performing manual

operations.

2. Biological hazards - Workers may be infected with different varieties of bacteria and viruses and even threatened by biological hazards produced by insects and

snakes.

General Ventilation and Local Exhaust Systems

Thousands of workers contract occupational asthma and other lung diseases each year.

Many people die or are permanently disabled by these conditions and are unable to work.

People develop those diseases because they breathe in too much dust, fume or other airborne contaminants at work, often because control measures do not work well enough.

Most industries are affected, including woodworking, welding, paint-spraying, stonemasonry, engineering and foundry work.

INTRODUCTION

Employers are often unaware that their workers are being overexposed to these substances or the existing controls may be inadequate. The problems include:

Source of exposure are missed

Employers (and supplier) are over-optimistic about the effectiveness of the controls

Existing controls are deteriorated

The controls are not used correctly

General (dilution) ventilation systems supply clean air that mixes with the air in the workplace, diluting the concentration of the contaminant.

General ventilation is not suitable to control exposure to toxic substances because these systems actually spread the contaminant throughout the workplace before exhausting it.

General ventilation systems are used primarily to control temperature and humidity, to remove odors, and sometimes to remove traces of toxic substances and microorganisms emitted from carpeting, paneling, furniture, and people.

GENERAL VENTILATION

‘General exhaust ventilation, also called dilution ventilation, is different from local exhaust ventilation because instead of capturing emissions at their source and removing them from the air, general exhaust ventilation allows the contaminant to be emitted into the workplace air and then dilutes the concentration of the contaminant to an acceptable level (e.g., to the PEL or below). Dilution systems are often used to

control evaporated liquids. ’

A general ventilation system

General exhaust ventilation (dilution ventilation) is appropriate when:

Emission sources contain materials of relatively low hazard. (The degree of hazard is related to toxicity, dose rate, and individual susceptibility);

Emission sources are primarily vapors or gases, or small, respirable-size aerosols (those not likely to settle);

Emissions occur uniformly; Emissions are widely dispersed; Moderate climatic conditions prevail; Heat is to be removed from the space by flushing it with outside air; Concentrations of vapors are to be reduced in an enclosure; and Portable or mobile emission sources are to be controlled.

LOCAL EXHAUST SYSTEM Local exhaust ventilation is an engineering control system to reduce

exposures to airborne contaminants such as dust, mist, fume, vapor or gas in a workplace.

Local exhaust ventilation systems remove the contaminant before it spreads through the workplace.

The systems are designed to take advantage of the motion of the contaminant in order to capture it without drawing in large amounts of air as well.

They are most useful for controlling toxic materials when their airborne concentrations could exceed legislated standards.

‘A typical local exhaust ventilation system is composed of five parts: fans, hoods, ducts, air cleaners, and

stacks. Local exhaust ventilation is designed to capture an emitted contaminant at or near its source, before the contaminant has a chance to disperse into

the workplace air. ’

Local exhaust system

COMPONENTS OF A LOCAL EXHAUST SYSTEM

A local exhaust system consists of four (4) elements:

1. Hoods- a structure designed to enclose or partially enclose a contaminant-producing operation and to guide air flow in an efficient manner to capture a contaminant.-typical captured velocities required are:i) 100 feet per minute (fpm) for vapors and gasesii) 200 fpm or more for dusts

2. Ductwork- ductwork in an exhaust system is to provide a channel for flow of the

contaminated air exhausted from the hood to the point of discharge.

- typical velocities required are:i) 1000 fpm for vapors and gasesii) 4000 fpm for heavy dusts- the heavier the particle, the greater the velocity needed

3. Air cleaning device (cleaner)-to remove contaminants from the air stream before it is passed to the fan and expelled to the atmosphere or recycled to the work area.- two types of air cleaning devices:i) air filtersii) dust collecters

4. Air moving device (fan)-the device that draws the air through the entire system- It must be capable of generating enough of pressure drop to draw the

required volume of air through the hood, ducts, and collecting devices at the correct velocity, and of overcoming the resistance to air flow from hoods, ducts, and collecting devices.

It is vital to identify all components that may be part of the Local exhaust ventilation system, for example:

Parts of equipment such as the machine casing or guards if they have extraction to control emissions

Flues from hot processes, e.g: furnaces or ovens

Systems to replace extracted air (make-up-air), particularly where large ventilated booths extract large volumes of air from the workroom

Local exhaust ventilating is appropriate when:

Emission sources contain materials of relatively high hazard; Emitted materials are primarily larger-diameter particulates

(likely to settle); Emissions vary over time; Emission sources consist of point sources; Employees work in the immediate vicinity of the emission

source; The plant is located in a severe climate; and

PRINCIPLE OF LOCAL EXHAUST

Basic principles for applying local exhaust ventilation to a specific problem:

i. Enclose the source as completely as practicableii. Capture the contaminant with adequate velocitiesiii. Keep the contaminant out of worker’s breathing zoneiv. Supply adequate make-up airv. Discharge the exhausted air away from air inlet systems

What employers need to do before applying LEV?

LEV may not be practicable controls as there may be many sources or extensive contaminants clouds that are too large for LEV alone to control. The other control options include:

Eliminate the source Substitute the material being used by something safer Reduce the size of the source Modify the process to reduce the frequency or duration of

emission Reduce the number of employees involved with a process Apply simple controls, eg: fitting lids to equipment

What employers need to know when LEV is appropriate?

The key properties of airborne contaminants. How gases, vapors, dusts and mists arise. How contaminant clouds move with the surrounding air. The processes in the workplace which may be sources of

airborne contaminants. The needs of the operators working near those sources. How much control will be required. How to prepare a specification for the LEV designer.

Employers also need to be aware of:

the general principles of hood design and application; the need for airflow indicators and other instrumentation; capture zones, working zones and breathing zones; the general principles of ductwork, air movers and air

cleaners and how they interact; the principles of how to discharge contaminated air safely and

replace it with clean air; the process of installing and commissioning the LEV system; the need for a user manual and logbook; the requirement for thorough examination and test of LEV.

What employees need to know to carry out routine checks

The parts of an LEV system and their function.

How the LEV system should be used.

How to recognize a damaged part.

Simple checks that the LEV system is delivering its design performance and is effectively controlling emissions and exposure.

What maintenance and repair engineers need to know?

How to recognize and assess hazards. How to follow safe systems of work. To warn operators that maintenance is under way. How the LEV system works. What assessment methods to use to check the LEV system’s

performance is maintained. What routine maintenance is needed (following instructions

such as those in a ‘user manual’). What measures of performance to record and who to report

to if there are problems.

Prevention and Control

‘A well-designed system and a continuing preventive maintenance program are key elements in the prevention and control of ventilation system problems. ’

Confined Space Safety Measure

Oxygen Deficiency (Asphyxiation)

Fire/Explosion

Accumulation of Flammable Vapour

Overcome by Toxic Fumes

COMMON HAZARDS

Why people enter confined spaces?

Confined spaces are normally entered to perform necessary industrial tasks. The list below represents some typical reasons for entering confined spaces:

a) cleaning to remove waste or sludge b) physical inspection of plant or equipment c) installing pumps, motors or other equipment d) maintenance work such as painting, sand blasting or applying surface coatings e) reading of meters, gauges or dials f) repair work, such as welding or cutting g) installing, repairing or inspecting cables such as telephone, electrical or fibre

optic h) tapping, coating or testing of piping systems (e.g. steam, water or sewage) i) constructing a confined space such as an industrial boiler j) rescuing people who are injured or overcome by fumes.

VENTILATION IN CONFINED SPACES

Confined spaces contain atmospheres that are flammable, toxic or whose oxygen level has been depleted or enriched.

Natural ventilation is generally insufficient to remove contaminated air from the inside space and to exchange it for fresh air from the outside.

The lack of air exchange occurs particularly in confined spaces that have few openings for access and due to the configuration of the confined space itself.

They can be effectively ventilated with apparatuses that move the air and remove the contaminated air from the confined space introducing:

- clean, - breathable air, and - controlling the level of danger

BASIC REQUIREMENTS OF VENTILATION

Although a single rule or group of rules is unlikely to cover all of the ventilation requirements applicable to confined spaces, the objectives of ventilation in confined spaces are the following:

To remove contaminated air (flammable or toxic) from the space and maintain safe concentration levels in terms of permissible exposure level (PEL) or lower explosive limit (LEL), using the most convenient one.

To provide fresh and breathable air inside the space.

To create a more comfortable environment inside the space.

VENTILATION BEFORE ENTERING OR WORKING

Confined spaces must be ventilated before entering or working to the degree necessary to reduce flammable and toxic substances to acceptable levels and to provide adequate oxygen content inside the space.

VENTILATION TO ENTER AND WORK

Ventilation requirements to enter and work in confined spaces depend on the nature of the space, its content, and the operations that will be performed inside the same.

The operations that are performed inside a confined space may require the application of a single type of ventilation, such as general ventilation, or may require the application of two types, such as general ventilation combined with a local exhaust ventilation system.

1. General Ventilation -Refer to general ventilation as the action of exhausting or supplying air for breathing and for climate control inside the space, that is, ventilation to control the heat.

2. Local Exhaust Ventilation -To remove the contaminants that are generated in a single point, as in welding, or in localized clean-ups with solvents, local exhaust systems are more effective.

3. Dilution Ventilation - Occasionally, this ventilation mechanism must be used in circumstances

where the operation or the process performed prohibits the use of local exhaust ventilation.4. Dilution and Exhaust Ventilation (entry and exit / push/pull)

- Type of ventilation consists of incorporating uncontaminated air inside a space to dilute contaminants, combining them with an exhaust localized at the area of greatest generation of contaminants, utilizing flexible ducts.

VENTILATION OF FLAMMABLE ATMOSPHERES

The fans, exhausts, motors and other equipments that are use to ventilate atmospheres that contain vapors, emanations, fogs, dusts, etc., flammables or explosives, must be equipments that are essentially safe by design, such as fans with pressured air jets, eductors, or vapor ejectors, etc.

The equipment must be properly insulated and grounded, as appropriate, to control the accumulation of electricity and discharges.

VENTILATION SYSTEM ARRANGEMENTSVentilation systems must be arranged to provide the best possible air

distribution to all the space and the air must be of breathable quality so that it replaces the contaminated air that is removed from the space.

1. Air Circulation-The location of the exhaust and air intakes for the exchange is extremely important to achieve a proper distribution of air throughout the confined space.

2. Replacement Air-The replacement air that is fed to a space to replace the contaminated air must be clean and contain normal levels of oxygen that can be breathed.

3. Exhaust Air Outlets-Exhaust air containing flammable or toxic substances must be ventilated to the exterior atmosphere to a place where the contaminants can be diluted and dispersed.

4. Lighter or Heavier than Air Contaminants

-In a confined space, contaminants that are lighter or heavier than air tend to accumulate in greater concentration in higher or lower areas, respectively.

A RISK MANAGEMENT APPROACH FOR CONFINED SPACES

The Workplace Health and Safety Act 1995 (the Act) describes a five step risk management process by which hazards can be managed. The process entails:

Step 1: Identify hazards Step 2: Assess risks associated with the hazard Step 3: Decide on control measures to prevent or minimize the level of risk Step 4: Implement the control measures Step 5: Monitor and review the effectiveness of the control measures

Step 1: Identify the hazards analysing injury and incident records talking with workers about their experience or problems which may arise conducting a task analysis consultation with designers, manufacturers and suppliers of confined

spaces obtaining advice from occupational health and safety specialists,

engineers or occupational hygienists consultation with unions, employer associations, professional bodies or

government associations using scientific or technical information (e.g. atmospheric testing, reports,

safety alerts or journals).

Step 2: Assess the risks

Once the hazards have been identified, the associated risks for each hazard should be assessed. There are three major factors to consider when assessing the risk of hazards (the likelihood of an incident occurring and the consequences)

First – determine the likelihood Second – determine the consequences

Third – rate each risk

Step 3:Deciding on control measures

When the hazard cannot be eliminated measures must be taken to control the risk of death, injury or illness.

The hierarchy of control presents control measures in an order of

priority. The higher order controls provide a greater level of protection against a risk.

Step 4: Implement and review control measures

Providing training and instructions on what the control measures are, how they work, any changes to the controls (including why the changes need to be made)

Adequate supervision to ensure that the controls are being used correctly

Maintenance procedures – for example, releasing a pressure valve on a service line

Communication procedures between staff and supervisors – for example, monitoring controls or when new problems/situations arise

Measuring the effectiveness of controls

CONTROL MEASURES FOR CONFINED SPACES

1. Elimination – the ideal solution would be to eliminate the confined space hazard altogether, by eliminating the need to enter the space.

2. Substitution – involves replacing a hazard or work process with a less hazardous one.

3. Isolation and engineering – this involves modifying the workplace, plant or process to physically distance the worker from the hazard. Isolating the worker from the hazard can also be effective.

4. Atmospheric testing – shall be carried out consistent with the hazards identified and the risk assessment.

1. Gas Monitoring

TYPICAL CONTROL MEASURES

Gas monitoring by HSE personnel

Confined space status chart

2. Adequate Ventilation and Lighting

3. Permit-to-Work System

4. Personal Gas Meter

5. Access Control System

CONFINED SPACE-SAFE ENTRY POLICY

When requested to enter a confined space:

i) Only enter a confined space when a permit to enter has been issuedii) If you consider it is safe to do soiii) Only remain in the inside for as long as it is necessary to carry out the work

It is full responsibility of the owner of the confined space to ensure that the confined space is safe to enter:

i) The surveyor has the right to refuse to enter an unsafe or unknown spaceii) If he is not confident that a space is safe, he should report his concerns and

not to enter until all safety requirements are met.

CONFINED SPACE-SAFE ENTRY PROCEDURE

Prior to entry an enclosed space the following procedure should be applied:

a) A Safety meeting should be held prior to the survey to discuss all aspects of safety measures

b) Entry Permit should be obtained for the space to be enteredc) Identify the hazards and assess the risksd) Evaluate ventilation of the spacee) Evaluate need for isolation of the spacef) Ensure that a standby and rescue team is in placeg) Check and evaluate gas measurements takenh) Evaluate need for precaution against extreme temperaturei) Evaluate the lighting arrangementj) Evaluate if special clothing and equipment are required

PERMIT-TO-WORK and PERMIT-TO-ENTER

A permit-to-work will:

set out the work to be done, the location and the precautions to be taken predetermine safe methods of work provide a clear record that all foreseeable risks have been considered define the precautions to be taken and their sequence provide written authority for the confined space to be entered and the

work to start and the time when the work must cease.

Entry into a confined space should only be allowed when a separate permit-to-enter has been issued.

(this permit should only be issued after tests have taken place to ensure that the atmosphere is safe to breathe)

TESTING OF THE ATMOSPHERE

Initial testing should be carried out by a certified “Marine Chemist” or a “Competent person” or similar accredited person who will issue a certificate stating whether the space is ‘safe for man’ and/or work, and if any special conditions are to be observed.

Ventilation should be stopped about 10 minutes before tests are made and not restarted until the tests are completed.

The testing should be carried out in the following sequence - Oxygen-deficient or -enriched atmospheres - Flammable atmospheres - Toxic atmospheres when considered necessary

To evaluate the measurements taken, the following limit values should be used.

a) Testing for oxygenb) Testing for flammable atmospherec) Testing for toxic atmosphered) Testing instruments

PREPARATION FOR ENTERING CONFINED SPACES

Ventilation-Ventilation should be continuous where possible because in many confined spaces the hazardous atmosphere will form again when the flow of air is stopped.

Isolation of space-The surveyor should evaluate the need for isolation of the confined space from service before entering the space.

Standby / Rescue-A standby person should be assigned to remain on the outside of the confined space and be in constant contact.-Rescuers must be trained in and follow established emergency procedures and use appropriate equipment and techniques (such as lifelines, respiratory protection, standby persons).

PERSONAL PROTECTION EQUIPMENT (PPE)

PPE is traditionally regarded as the last line of protection with the emphasis being placed on avoidance and appropriate managerial control methods.

Basic surveyor PPE should include:-Body protection (hard wearing overalls with suitable pockets for notebook)-Foot protection (steel toecaps, steel midsoles, good grip, oil resistant)-Head protection (hard hat with chinstraps)-Hand protection (hard wearing gloves);-Eye protection (protective glasses, goggles);-Ear protection (ear defenders or ear plugs – worn subject to communication system);-Gas meter - multi-gas meter for measuring of HC, H2S, CO, O2 is recommended-Lighting (hand held with lanyard and appropriate beam width).

CONTINUE

Extent to which a person may be safely exposed to a hazardous substance (typically a gas or solvent vapor) without endangering his or her health. These limits are generally discretionary and every country defines its own limits, resulting in a lack of widely accepted standards.

EXPOSURE LIMITS