Designing of laboratory heating equipments

1. P.SAIKUMAR
1008-16-884-005
M.PHARMACY
PHARMACEUTICAL CHEMISTRY
UNIVERSITY COLLEGE OF TECHNOLOGY
OSMANIA UNIVERSITY
LABORATORY DESIGN, SAFETY AND MANAGEMENT
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2.  Designing laboratory – equipment
 Heating devices
 Ovens
 Hot plates
 Heating mantles
 Oil, salt, or sand baths
 Hot air baths and tube furnaces
 Heat guns
 Air conditioning systems
 Types of air conditioning
 Ventilation
 Laboratory fume hoods
 References
CONTENTS:
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3.  The process of constructing a new laboratory revolves around four general
activities: planning, design, construction, and moving.
 Specific activities vary within each phase of the process, and each stage.
Scope
 The primary objective in laboratory design is to provide a safe environment
for laboratory personnel to conduct their work.
 Therefore, all health and safety hazards must be identified and carefully
evaluated so that protective measures can be incorporated into the design.
Introduction
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4.  The most common type of electrical equipment
 Used to supply the heat needed to effect a reaction or separation.
 The use of steam-heated devices rather than electrically heated devices is
generally preferred whenever temperatures of 100 °C or less are required.
 Because they don’t present shock or spark risks, they can be left unattended with
assurance that their temperature will never exceed 100 °C.
General precautions:
 Enclose the actual heating element in any heating device in a glass,
ceramic, or insulated metal case to prevent laboratory personnel from
accidentally touching the wire carrying the electric current. This
construction minimizes the risk of electric shock.
 Resistance devices used to heat oil baths should not contain bare wires.
 If any heating device becomes so worn or damaged that its heating element
is exposed, either discard the device or repair it before it is used again.
 Be aware that dry and concentrated residues can ignite when overheated in
stills, ovens, dryers, and other heating devices.
Heating Devices
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5.  Electrically heated ovens to remove water or other solvents from
chemical samples and to dry laboratory glassware.
 Never use laboratory ovens to prepare food for human consumption.
 Purchase or construct laboratory ovens with their heating elements and their
temperature controls physically separated from their interior atmospheres.
 Small household ovens and similar heating devices should not be used in
laboratories.
 Vacuum drying ovens, discharge volatilized
substances inside the oven to form explosive
mixtures with the air.
 This hazard can be reduced by connecting
the oven vent directly to an exhaust system.
Ovens
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6.  Hot plates solutions are to be heated to 100 °C or higher and the
inherently safer steam baths cannot be used as the source of heat.
 Use only hot plates that have completely enclosed heating elements in
laboratories.
 Although almost all laboratory hot plates currently sold meet this criterion,
many older ones pose an electrical spark hazard arising from either the on/off
switch located on the hot plate, the bimetallic thermostat used to regulate the
temperature, or both.
 Normally, these two spark sources are located in the lower part of the hot
plate in a region where any heavier-than-air and possibly flammable vapors
evolving from a boiling liquid on the hot plate would tend to accumulate.
Hot Plates
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7.  Heating mantles heat round-bottom flasks, reaction kettles, and related
reaction vessels.
 These mantles enclose a heating element in layers of fiber glass cloth.
 As long as the fiberglass coating is not worn or broken and no water or other
chemicals are spilled into the mantle heating mantles pose minimal shock
hazard.
 Always use heating mantles with a variable autotransformer to control the
input voltage.
 Never plug them directly into a 110-V line. Higher voltages will cause a
mantle to overheat, melting the fiberglass insulation and exposing the bare
heating element.
Heating Mantles
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8.  Electrically heated oil baths small or irregularly shaped vessels or to
maintain a constant temperature.
 For ≤ 200 °C, a saturated paraffin oil is often used;
 For ≥ 300 °C, a silicone oil should be used.
 Care must be taken with hot oil baths not to generate smoke or have the oil
burst into flames from overheating.
 When using oil, salt, or sand baths, take care not to spill water and other
volatile substances into the baths. Such an accident can splatter hot material
over a wide area and cause serious injuries.
Oil, Salt,or SandBaths
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9.  Always monitor an oil bath by using a thermometer or other thermal sensing
device to ensure that its temperature does not exceed the flash point of the oil
being used.
 For the same reason, fit oil baths (left unattended ) with thermal-sensing
devices that turn off the electric power if the bath overheats.
 Molten salt baths, like hot oil baths, offer the advantages of good heat transfer,
commonly have a higher operating range (e.g., 200 to 425 °C), and may have a
high thermal stability (e.g., 540 °C).
 Care must be taken to keep salt baths dry, because they are hygroscopic, a
property that can cause hazardous popping and splattering if the absorbed water
vaporizes during heating.
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10.  Hot air baths:-
useful heating devices,
electrically heated,
frequently used to heat small or irregularly shaped vessels.
constructed from metal, ceramic, or, less desirably, glass vessels
low heat capacity
• Tube furnaces are often used for high-temperature reactions under reduced
pressure. The proper choice of glassware or metal tubes and joints is required,
and the procedures should conform to safe practice with electrical equipment
and evacuated apparatus.
Hot Air Baths and Tube Furnaces
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11. • Laboratory heat guns are constructed with a motor-driven fan that blows air
over an electrically heated filament.
• They are frequently used to dry glassware or to heat the upper parts of a
distillation apparatus during distillation of high-boiling point materials.
• Heat guns almost always pose a serious spark hazard.
• Never use them near open containers of flammable liquids, in environments
where appreciable concentrations of flammable vapors may be present, or in
laboratory chemical hoods used to remove flammable vapors.
HeatGuns
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12.  Air-conditioning is a process of controlling the air temperature, relative
humidity, ventilation, air movement and air cleanliness of a given space in
order to provide the occupants with a comfortable indoor temperature.
 One of the costliest items in a laboratory construction project is the air
conditioning system.
 Labs need more air than almost any other type of facility and supplying that
air can be expensive.
 Two Major Types of Systems:
1.Constant Volume (CV)
2.Variable Air Volume (VAV)
Air conditioning systems
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13. Constant Volume System
 It exhausts a constant amount (volume) of air through the lab fume hoods while
at the same time supplying a constant volume of air into the laboratory.
 The amount of air exhausted and supplied is constant.
Advantages:
 The constant volume system is simple (to design, install and maintain).
 The start-up and testing, installation, and maintenance can be performed by
conventional experienced HVAC contractors.
 Since all hoods will be in operation at all times and that they will be exhausting
at a constant rate it is likely that the equipment specified for a CV system is of
sufficient size to provide enough air for a safe, comfortable lab.
 The initial cost of a CV system is typically lower than a VAV system requires
more controls and more sophisticated equipment they tend to be more expensive.
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14. Variable Air Volume Systems
 Variable Air Volume (VAV) systems vary the amount of air being exhausted and
supplied to a lab based upon the usage of the fume hoods.
 Systems utilize a sensing device built into the side wall of the hood to measure
the air volume drawn into the hood.
 As the volume increases the sensor activates and increases the exhaust. A
decrease in the air volume results in a reduction of the exhaust.
Advantages:
 Cost savings resulting from reduced energy consumption. Since the system
exhausts less conditioned air it requires less conditioned air with resulting lower
energy costs.
 Reduction in size of the HVAC equipment. distinct advantage if space is at a
premium. A subsequent reduction in equipment cost is also achieved.
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15. When considering and selecting an air conditioning system, the designer must
evaluate the following factors:
 Building location, surrounding environment and external climate.
 Uses and functional requirements of the building
 Client’s budget, investment policy and expected quality of service
 System qualities– e.g. aesthetics, life, reliability and maintainability. However
for the present work unitary air conditioning system is selected.
 Energy consumption – for both economic and environment reasons
Air Conditioning System Selection
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16.  It is required to promote and maintain laboratory safety and protection to life
and property.
 Items such as fume containment, worker safety, proper cleanliness through
pressure relationships, filtration, air changes per hour (ACH), point of fume
capture, temperature, and Relative humidity requirements are elements
necessary to design the ventilation system depending on the laboratory type.
 When working in a required clean environment such as when mixing
medications (pharmacy) or working with infectious bacteria (research), airflow
direction and air cleanliness are requirements.
Ventilation
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17.  Laboratory fume hoods are a type of specialized local exhaust that is
designed to isolate and remove gases, vapours, and particles from laboratory
sources and limit exposure to the user.
 The location of the fume hood with respect to open windows, doorways, and
personnel traffic directly influences the containment ability of the hood.
 Fume hoods should not be located adjacent to a single means of access to an
exit.
 A fire hazard or chemical release incident, both of which may start in a fume
hood, can block an exit rendering it impassable.
 A fire or explosion in a fume hood located adjacent to a path of egress could
trap someone in the lab.
 Hoods should be located more than 10 feet from any door or doorway.
Laboratory Fume Hoods
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18.  Architectural features and their recommended distance from fume hoods.
 Drying ovens or drying cabinets shall not be installed underneath fume hoods.
 The heat from drying ovens increases the risk of volatilization of chemicals
inside the fume hood, particularly chemical solvents and may increase the risk
of explosions or fires.
 In addition, heat transfer to the fume hood may affect the functionality of the
fume hood
Architectural Feature Minimum Distance from
Hood (feet)
Pedestrian Walkways 4
Opposite Laboratory Bench 5
Opposite Laboratory Fume Hood 10
Adjoining Laboratory Fume
Hood
3
Opposing Wall 7
Adjoining Wall 1
Doorway 10
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19. • Laboratory Design Guidelines-University of North Carolina, USA
 Designing and planning of laboratories (2009)
 Laboratory Design and Construction Guidelines (2010)-University of South
Carolina, USA
 International Journal of Application or Innovation in Engineering &
Management (IJAIEM), Volume 2, Issue 9, September 2013 Page 287
 Forensic Laboratories: Handbook for Facility Planning, Design,
Construction, and Moving
References
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