© 2012 Delmar, Cengage Learning Chapter 11 Engineering Controls.

© 2012 Delmar, Cengage Learning

Chapter 11Engineering Controls


Risk Evaluation

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


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


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.


Physical Operations Evaluations

• Dusting• Heat transfer• Pressure• Vaporization• Spaying• Mixing• Separation• Generation


Equipment Design Evaluation

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


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


Operator Practices and Training Evaluation

• Operational failures have been identified as the most frequent cause of industrial disasters.


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.


Figure 11-1 Triangular Equipment Placement


Alarms and Indicators

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


Fire Alarms and Detection Systems

Automatic fire alarm systems come in three types:

• Fixed-temperature type• Rate-of-rise type• Nuclear detector type


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.


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.


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


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


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.


Figure 11-4 Closed-Loop Sampling System


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.


Figure 11-5 Floating Tank Designs


Effluent Control and waste Water Treatment

New technicians are typically assigned to this area in order to train on a variety of complex systems.


Figure 11-6 Clarifier


Figure 11-7 Settling Basin


Noise Abatement

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


Flares

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


Pressure Relief Devices

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


Figure 11-9 Pressure Relief Devices

© 2012 Delmar, Cengage Learning Chapter 11 Engineering Controls.

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Transcript of © 2012 Delmar, Cengage Learning Chapter 11 Engineering Controls.