The document discusses engineering controls for safety in chemical plants. It evaluates various hazards including hazardous materials, chemical processes, equipment, layout, and operator training. It also describes safety devices and systems such as alarms, shutdown systems, containment, sampling methods, storage tanks, effluent control, noise abatement, flares, and pressure relief valves that are used to control hazards and protect operators. The goal of engineering controls is to safely manage risks through the proper design, location and operation of equipment and facilities.

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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