Process Plant Equipment

Operation, Control, and Reliability

Michael D. Holloway, Chikezie Nwaoha, Oliver A. Onyewuenyi, Michael D. Holloway, Chikezie Nwaoha, Oliver A. Onyewuenyi

• Publisher: Wiley
• Year: 2012
• ISBN:
  9781118162545
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Chemical & Biochemical Engineering
• Index: Technology & Engineering

"Process Plant Equipment Book is another great publication from Wiley as a reference book for final year students as well as those who will work or are working in chemical production plants and refinery…" -Associate Prof. Dr. Ramli Mat, Deputy Dean (Academic), Faculty of Chemical Engineering, Universiti Teknologi Malaysia

"…give[s] readers access to both fundamental information on process plant equipment and to practical ideas, best practices and experiences of highly successful engineers from around the world… The book is illustrated throughout with numerous black & white photos and diagrams and also contains case studies demonstrating how actual process plants have implemented the tools and techniques discussed in the book. An extensive list of references enables readers to explore each individual topic in greater depth…" – Stainless Steel World and Valve World, November 2012

Discover how to optimize process plant equipment, from selection to operation to troubleshooting

From energy to pharmaceuticals to food, the world depends on processing plants to manufacture the products that enable people to survive and flourish. With this book as their guide, readers have the information and practical guidelines needed to select, operate, maintain, control, and troubleshoot process plant equipment so that it is efficient, cost-effective, and reliable throughout its lifetime. Following the authors' careful explanations and instructions, readers will find that they are better able to reduce downtime and unscheduled shutdowns, streamline operations, and maximize the service life of processing equipment.

Process Plant Equipment: Operation, Control, and Reliability is divided into three sections:

• Section One: Process Equipment Operations covers such key equipment as valves, pumps, cooling towers, conveyors, and storage tanks
• Section Two: Process Plant Reliability sets forth a variety of tested and proven tools and methods to assess and ensure the reliability and mechanical integrity of process equipment, including failure analysis, Fitness-for-Service assessment, engineering economics for chemical processes, and process component function and performance criteria
• Section Three: Process Measurement, Control, and Modeling examines flow meters, process control, and process modeling and simulation

Throughout the book, numerous photos and diagrams illustrate the operation and control of key process equipment. There are also case studies demonstrating how actual process plants have implemented the tools and techniques discussed in the book. At the end of each chapter, an extensive list of references enables readers to explore each individual topic in greater depth.

In summary, this text offers students, process engineers, and plant managers the expertise and technical support needed to streamline and optimize the operation of process plant equipment, from its initial selection to operations to troubleshooting.

Appendix I: Methods for Measuring Process Temperature

Chikezie Nwaoha

Control Engineering Asia, Ten Alps Communications Asia, Aladinma, Nigeria

Temperature measurement of a substance, regardless of its state, is a very critical aspect of process measurement in the oil and gas, water and wastewater, pharmaceutical, food and beverage, and power industries, and its accuracy is very pertinent to proper operation of a plant. Determining the temperature of a substance contained in equipment or passing via the equipment, temperature measurement devices usually form part of a control loop assembly: a closed system of selected instruments that have the objective of monitoring fluid flow, controlling fluid flow, and so on. In this case, their role is to monitor and control the temperature of the fluid within the design limits.

In most cases, a computer is included in the temperature measurement loop to handle functions such as data gathering and transmission, bulk data storage, display, alarms, and control. This has given rise to the manufacture of temperature measurement instruments that are computerized and intelligent.

I.1 Types of Instruments

A variety of industrial temperature measurement instruments are used to measure the temperature profile of a fluid, gas, or solid (see Table I.1). The most important of these are detailed and described below.

Table I.1 Comparison of Various Types of Sensors [1]

Sensor	Advantages	Limitations
Thermocouple	Self-powered	Nonlinear
	Simple	Low voltage
	Rugged	Reference required
	Inexpensive	Least stable
	Wide variety	Least sensitive
	Wide range
RTD	Most stable and accurate	Expensive
	Area sensing	Current source required
	More linear than thermocouple	Slow response time
	Most repeatable	Low sensitivity to small temperature change
	Contamination resistant	Self-heating
Infrared	No contact required	High initial cost
	Very fast response time	More complex support electronics
	Good stability over time	Spot size restricts application
	High repeatability	Emissivity variations affect readings
	No oxidation/corrosion to affect sensor	Accuracy affected by dust, smoke, and background radiation
Bimetallic	Simple, robust, and inexpensive	Not recommended for measurement of temperature above 550°C
	Has good accuracy
		The metals undergo permanent warp distortion
	Can measure temperature in the range −40 to 550°C
		Use limited to local mounting
	Can withstand 50% overage temperature measurement
Liquid-filled glass	More economical, versatile, widely used	Compensation necessary for ambient (surrounding) temperature changes and long capillary tube
	Rugged in construction, low maintenance
		For accuracy the pressure bulb should be large
	Can be used for remote indication
		In case of error the entire system has to be replaced
	Stable in operation
	System provides enough power to drive the control mechanism

I.1.1 Liquid-Filled Glass Thermometers

A reliable and low-cost device, the liquid-filled glass thermometer (Fig. I.1) is composed of a glass bulb with a capillary. When it expands, the liquid in the bulb forms a thin thread in the capillary, with the length of the thread forming a measure of the existing temperature. The space above the liquid contains only the saturated vapor of the fluid. The liquids used regularly are pentane, −200 to 20°C; alcohol, −110 to 50°C; toluene, −70 to 100°C; mercury (vacuum), −35 to 280°C; and mercury (gas-filled), −35 to 750°C [1]. Ocassionally, the liquid is pressurized to increase the measuring limit. The thickness of the material used in manufacturing a liquid-filled glass thermometer usually affects the time of response. To achieve high accuracy, requirements such as high thermal conductivity, high coefficient of thermal expansion for the fluids, and linear expansion must be considered.

I.1 Liquid-filled glass (capillary) thermometers offer low maintenance and enable remote indication.

I.1.2 Bimetallic Thermometers

A bimetallic thermometer consists of a strip of two dissimilar metals with different coefficients of heat expansion joined together and attached to an indicator. As a result of the metals' different rates of expansion, the bimetal is caused to warp, indicating a temperature change. One end of the metal strip is attached to the housing and the other end to an indicator. The metal strips can be riveted together but they are usually rolled or soldered jointly. To attain a high degree of deflection, a bimetallic strip is wound to form a spiral. Bimetalic thermometers can come in different designs: cone-shaped spiral, cylindrical spiral, flat spiral, and a combination of flat and cylindrical spiral. For high accuracy, bimetallic thermometers must be calibrated at or close to the conventional operating temperature being monitored. Although these devices are portable and do not require a power supply, they are usually not as accurate as thermocouples or resistance temperature devices. Bimetallic thermometers tend to be used where relative changes need to be monitored, and applications include use in oil refineries and in hot-work wire heaters, and they also work effectively in tempering tanks.

I.1.3 Thermocouples

Thermocouples represent a type of temperature measurement technique that allows direct electronic monitoring of temperature. A thermocouple consists of two different types of wires (dissimilar metals) joined together at one end. The wire metals can be an alloy or a very pure metal, and the measurement technique works on the principle of a thermo voltage being created when two different metals are brought into contact with one another.

A variety of temperature limits and materials of construction are available to measure temperature for different applications: copper/constantan; chromel/alumel; platinum/rhodium–platinum; and iron/constantan. To achieve high accuracy, thermocouples used for process measurement...

Table of contents

• Cover
• Copyright
• Dedication
• Title Page
• Contributors
• Preface
• Section I: Process Equipment Operation
• Section II: Process Plant Reliability
• Section III: Process Measurement, Control, and Modeling
• Appendix I: Methods for Measuring Process Temperature
• Appendix II: Airflow Troubleshooting
• Appendix III: MIG Shielding Gas Control and Optimization
• Appendix IV: Rupture Disk Selection
• Appendix V: Pressure Gauge Selection
• Appendix VI: Corrosion and Its Mitigation in the Oil and Gas Industries
• Appendix VII: Mixers
• Appendix VII: Glossary of Processing Terms
• Index