PROCESS TECHNOLOGY TROUBLESHOOTING

Instructor’s Manual with Test Bank

PROCESS TECHNOLOGY TROUBLESHOOTING

Charles E. Thomas 1 / 4

CHAPTER 1

INTRODUCTION TO PROCESS INSTRUMENTATION & TROUBLESHOOTING

OBJECTIVES

• Describe the basic instruments used in the process industry.• Describe key terms associated with process control and troubleshooting • List the various types of control loops.• Explain how symbols and diagrams are used by process technicians in the chemical processing industry.• Describe the various troubleshooting models.• Describe the methods used in troubleshooting process problems.

REVIEW QUESTIONS

• Describe the two different types of analyzers and explain how each is

designed to work.Analyzers can calculate both quantitative and qualitative variables.Quantitative variables are most closely associated with the amount or percentage present in a process. Qualitative analyzers simply determine whether a substance is present or not. Examples of this are analyzers that are designed to detect the presence of methane gas.

• List the primary elements and sensors associated with flow.

Examples of flow elements include; turbine flow meters, magnetic flow meters, ultrasonic flow meters, vortex flow meters, thermal flow meters, coriolis meters, and orifice plates.

• List the primary elements and sensors associated with temperature.

Examples of temperature elements include: thermometers, bimetallic

thermometer strip, filled thermal bulb, resistance bulb, thermocouple type J & K,

• List the primary elements and sensors associated with pressure.

Pressure Elements, shows several examples of these instruments.

Examples of process instruments include:

• Pressure elements—sense changes in pressure and convert to mechanical motion

• Bellows bourdon tube
• C type bourdon tube
• Diaphragm capsule pressure elements
• Helical bourdon tube 2 / 4

• Pressure transmitter
• Spiral bourdon tube

• Pressure gauges—psia, psig, psiv, psid, bar, pascal, kilopascal, etc.• Vacuum gauge expressed in inches of mercury (in Hg) • Manometers- A manometer is a device that can be used to measure pressure or vacuum. A manometer operates under hydrostatic pressure principles; a column of water always exerts a specific force.• Pressure Transmitter- A pressure transmitter uses a pressure element to sense pressure and sends a signal to a controller or recorder.

• List the primary elements and sensors associated with level.

Examples of level elements and instruments include:

• Displacer— buoyancy devices • Sight glass—transparent tube mounted on the side of a tank.• Float and tape—float rests on the surface of the fluid. Tape moves up and down depending on the level.• Conductivity probes—high and low level alarms. Use electricity to complete lower leg circuit. If liquid reaches the higher leg, the circuit is broken. This type of system is designed to keep the level between the high and low conductivity probes. Typically used on non- flammable material.• Capacitance probes—radiation devices, load cells.• D/P cell (Transmitter)—converts pressure difference to a level indication. Measures hydrostatic pressure difference between two points on a pressurized vessel.• Continuous level detector gauge—pressure sensitive. Measures hydrostatic pressure in open vessels.• Bubbler system—forces air through a tube that is positioned in the liquid. The liquid’s resistance to flow registers on a pressure sensitive level gauge. Measures hydrostatic pressure in open vessels.

• Explain why the skills required to be a jet fighter pilot are similar to those

skills required to be a process technician.A process technician’s role can be compared to that of a jet fighter pilot.The pilot not only needs to be familiar with his or her aircraft, but must also be able to use it in a variety of combat situations. The skills needed to make a good fighter pilot are the same skills required to make a good process technician.

• How do increases and decreases in pressure inside an enclosed vessel

impact the boiling point of a substance?When a liquid exceeds atmospheric pressure it will boil. Measurements of boiling point for individual substances takes place at a given temperature and at atmospheric pressures. When pressure is added to an enclosed 3 / 4

container the boiling point is artificially shifted to a higher point until it is hot enough to exceed the pressure.

• Why is it so difficult to develop for educators a pure “process

instrumentation” textbook?When the curriculum for the process technology program was originally designed, it was decided that an introductory course in “process” instrumentation should be included in the required core classes. The design of this course would be different from any that was presently being offered at community colleges or universities. During this time period instrumentation courses were taught from the aspect of an instrumentation technician, since several community colleges had well- developed instrumentation technician training programs. The founding members of the process technology program decided that the instrumentation class needed to be taught from a process technician’s point of view. This type of course did not exist at the time.

The transition to the development of a “process” instrumentation course has been difficult since old habits are hard to let go of. A number of texts have been developed, unfortunately, each still reads like required course work for an instrumentation program. The needs of a process technician are drastically different than those of an instrument and electrical “I & E” technician, since each approaches the job from a different perspective or point of view. It is important to point out, however, that instrumentation is the foundation upon which advanced troubleshooting is based. A basic knowledge of the process equipment and systems combined with modern process control provide the building blocks upon which these skills are developed.

Process technology and modern process instrumentation for process technicians should merge around the concepts of the control loop, equipment systems and the control room. Course work needs to resemble real time process simulations. It is important to point out that process technicians are uniquely different from other occupations. A process technician operates the equipment and processes using modern instrumentation and electronics. Maintenance technicians are important members of the team who specialize in the maintenance, repair, and installation of equipment, instruments, electrical and instrument systems.Developing a true process instrumentation course has proven to be very difficult since it would require a paradigm shift from the more traditional approach.

• What is temperature defined as?

Temperature is defined as the degree of hotness or coldness of an object or environment.

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