Detection System

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Chapter 11
Engineering Controls

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Risk Evaluation
• Hazardous materials
• Chemical process
• Physical operations
• Equipment design
• Plant location and layout
• Operator practices and training

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Hazardous Materials
Evaluation
• A detailed analysis of all the properties
of the materials handled, stored, and
processed in the plant:
• Quantities
• Physical properties
• Toxicity
• Stability hazards
• Corrosiveness
• Impurities

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Chemical Process Evaluation
• Analyzes the hazardous properties of
reactants, which are products that might
be formed under certain conditions, and
the environmental effects of those
products.

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Physical Operations
Evaluations
• Dusting
• Heat transfer
• Pressure
• Vaporization
• Spaying
• Mixing
• Separation
• Generation

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Equipment Design Evaluation
• Equipment systems are designed so
that the failure of one or more devices
will not result in a disaster.

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Plant Location and Layout
Evaluation
Key elements include:
• Drainage and runoff control
• Climatic conditions
• Effects of uncontrolled release
• Community capability and emergency response
• Plant accessibility
• Available utilities
• Gate security
• Hazardous unit placement
• Spacing of equipment

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Operator Practices and
Training Evaluation
• Operational failures have been
identified as the most frequent cause of
industrial disasters.

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Design and Operation of
Plants for Safety
• There must be adequate spacing
between process equipment, specific
storage, and loading facilities.
• Evaluate and limit the storage of
hazardous material.
• Evaluate the use of open structures and
will recommend new designs for total
storage containment.

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Figure 11-1 Triangular Equipment Placement

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Alarms and Indicators
The most effective tool used by process
technicians in the operation of a large
chemical facility are alarms and
indicators.

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Fire Alarms and Detection
Systems
Automatic fire alarm systems come in
three types:
• Fixed-temperature type
• Rate-of-rise type
• Nuclear detector type

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Redundant Alarm and
Shutdown Devices
Operating a large chemical complex
requires the use of redundant systems
that provide emergency warning and
shutdown protection. Redundancy is a
process that uses two or more devices
to shut down a system.

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Interlocks and Automatic
Shutdown Devices
• An interlock is a device that will prevent
an operational action unless a specific
condition has been satisfied
• Software
• Hardwire
• A permissive is a special type of
interlock that contains a set of
conditions that must be satisfied before
a piece of equipment can be started.

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Process Containment and
Upset Control
• There are a number of elements in
controlling process containment and in
the design of upset control:
• Reduction in hazardous material storage
inventory
• Storage of liquefied gases and the conditions
under which these should be stored
• Plan for a design that provides total
containment

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Figure 11-3 Traditional and Nontraditional Diking Systems (Totally Self-Contained).

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Closed System/Closed-Loop
Sampling
Closed systems/closed-loop sampling is
a procedure where a bypass loop is
installed that allow a small part of the
system to be diverted from the main
flow.

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Figure 11-4 Closed-Loop Sampling System

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Floating Roof Tank and
Ventilation Systems
• Floating roof storage tanks are used for
storing materials at atmospheric
pressure.
• Ventilation systems are usually
designed to protect process technicians
from organic vapors, harmful additive
dusts, and fumes.

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Figure 11-5 Floating Tank Designs

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Effluent Control and waste
Water Treatment
New technicians are typically assigned
to this area in order to train on a variety
of complex systems.

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Figure 11-6 Clarifier

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Figure 11-7 Settling Basin

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Noise Abatement
• Noise abatement is an engineering
procedure designed to reduce or limit
noise through the use of modern
technology.

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Flares
• Flares are used to burn waste gases
and control pressure generated by
process upsets.

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Figure 11-8 Flare System

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Pressure Relief Devices
• Safety valves for gases
• Relief valves for liquids
• Rupture discs for both

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Figure 11-9 Pressure Relief Devices