inst240_sec4

INST 240 (Pressure and Level Measurement), section 4

Lab

Level measurement loop: Questions 91 and 92, completed objectives due by the end of day 4Bulleted questions following lab objectives to be reviewed orally during lab time on day 4

Feedback questions

Questions 81 through 90, due at the end of day 4

Exam

Day 5Question 93 previews the mastery exam circuit-building activity

Recommended daily schedule

Day 1

Theory session topic: Ultrasonic, radar, and laser level measurement

Questions 1 through 20; answer questions 1-9 in preparation for discussion (remainder for practice)

Day 2

Theory session topic: Weight, capacitance, and radiation level measurement


Day 3

Theory session topic: Point-contact and nonlinear level measurement


Day 4

Theory session topic: Review for exam


Build and test mastery exam circuit (Question 93)

Feedback questions (81 through 90) due at the end of the day

Day 5

Exam

Mastery exam includes the circuit-building activity shown in question 93

Objectives for both “mastery” and “proportional” exams listed in the syllabus (beginning on the next page)

1

INST 240 (Pressure and Level Measurement)

Credits/hours: 6 credits = 108 clock hours

Prerequisite or corequisite: INST 200 (Introduction to Instrumentation)

Course description: In this course you will learn how to precisely measure both fluid pressure andfluid/solids level in a variety of applications, as well as accurately calibrate and efficiently troubleshootpressure and level measurement systems.

Program outcomes addressed:

(1) Communication; Communicates and expresses thoughts across a variety of mediums (verbal, written,visually) to effectively persuade, inform, and clarify ideas with colleagues.

(2) Time management; Arrives on time and prepared to work; budgets time and meets deadlines whenperforming technical tasks and projects.

(3) Safety; Complies with national, state, and local safety regulations when repairing, calibrating, andinstalling instruments.

(4) Diagnose and repair existing instruments; Assesses, diagnoses, and repairs faulty instruments inmeasurement and control systems using logical procedures and appropriate test equipment.

(5) Install and configure new instruments; Builds, configures and installs new instrument systemsaccording to plans, applying industry construction standards, and ensuring correct system operationwhen complete.

(7) Calibrate instruments; Assesses instrument accuracy and corrects inaccuracies using appropriatecalibration procedures and test equipment.

(8) Document instrument systems; Interprets and creates technical documents (electronic schematics,loop diagrams, and P&IDs) according to industry (EIA, ISA) standards.

(9) Self-directed learning; Selects and researches relevant information sources to learn newinstrumentation principles, technologies, and techniques.

Instructor contact information:

Tony Kuphaldt

Desmond P. McArdle Center

Bellingham Technical College

3028 Lindbergh Avenue

Bellingham, WA 98225-1599

(360)-752-8477 [office phone]

(360)-752-7277 [fax]

[email protected]

Required materials:

• Socratic worksheets: INST240 sec1.pdf, INST240 sec2.pdf, INST240 sec3.pdf, INST240 sec4.pdf

→ Download at: http://openbookproject.net/books/socratic/sinst

• Lessons in Industrial Instrumentation, By Tony R. Kuphaldt. Useful for all quarters of instruction.

→ Download at: http://openbookproject.net/books/socratic/sinst/book/liii.pdf

• Spiral-bound notebook for reading annotation, homework documentation, and note-taking. A separatenotebook for each course is recommended.

• Instrumentation reference CD-ROM (free, from instructor). This disk contains many tutorials anddatasheets in PDF format to supplement your textbook(s).

• Tool kit (see detailed list)

• Simple scientific calculator (non-programmable, non-graphing, no unit conversions, no numerationsystem conversions), TI-30Xa or TI-30XIIS recommended

2

Supplemental materials: (recommended, not required)

• “BTCInstrumentation” channel on YouTube (http://www.youtube.com/BTCInstrumentation), hostsa variety of short video tutorials and demonstrations on instrumentation.

• Instrumentation, by Franklyn W. Kirk, published by American Technical Publishers. ISBN-10:0826934234 ; ISBN-13: 978-0826934239. This text is light on detail and math, but does a good jobintroducing all the major principles and technologies in simple language. Excellent photographs andillustrations, too. Useful for all three quarters of instruction.

• Instrument Engineer’s Handbook, Volume 1: Process Measurement and Analysis, edited by Bela Liptak,published by CRC Press. 4th edition ISBN-10: 0849310830 ; ISBN-13: 978-0849310836.

• Purdy’s Instrument Handbook, by Ralph Dewey. ISBN-10: 1-880215-26-8. A pocket-sized field referenceon basic measurement and control.

• Cad Standard (CadStd) or similar AutoCAD-like drafting software (useful for sketching loop andwiring diagrams). Cad Standard is a simplified clone of AutoCAD, and is freely available at:http://www.cadstd.com

• Any good introductory physics textbook (Applied Physics by Tippens, or Conceptual Physics by Hewitt)

• CRC Handbook of Chemistry and Physics

Student performance objectives:

Assessment legend: [P] = Preparation, [L] = Lab, [F] = Feedback questions, [X] = Exam

• Mastery (must eventually be demonstrated without error)

• [L] Proper use of deadweight tester as a calibration standard

• [L] Proper use of U-tube manometer as a calibration standard

• [L] Calibration of an electronic pressure transmitter to specified range and accuracy

• [L] Calibration of a pneumatic liquid level transmitter to specified range and accuracy

• [L] Create accurate as-built loop diagrams

• [L] Correctly identify common pipe and instrument tube fittings

• [L] Troubleshoot a problem within an electronic (4-20 mA loop) pressure measurement system, given aspecified time to logically identify the location and nature of the problem

• [L] Troubleshoot a problem within a pneumatic (3-15 PSI loop) level measurement system, given aspecified time to logically identify the location and nature of the problem

• [L] Work safely and constructively within a team

• [X1] Build a circuit to energize an electromechanical relay

• [X1] Convert between gauge and absolute pressure measurements

• [X1] Convert between different pressure units – only a simple calculator may be used!

• [X1] Calculate force, pressure, or area given the other two variables

• [X1] Identify proper use of ∆P instrument for pressure/vacuum measurement

• [X1] Calculate instrument calibration points given ranges

• [X1] INST250 Review: identify globe valve components

• [X1] INST260 Review: count sequentially in binary

• [X2] Build a circuit to sense pressure or vacuum using a differential pressure transmitter

• [X2] Calculate weight, density, or volume given the other two variables

• [X2] Calculate ranges for hydrostatic level-measuring instruments (∆P)

• [X2] Calculate calibration tensions for displacer-style level transmitters

• [X2] Identify suitability of basic level-measuring instruments to different processes

• [X2] Calculate instrument calibration points given ranges

• [X2] INST250 Review: match different control valve names with their P&ID symbols

• [X2] INST260 Review: explain basic network arbitration methods (e.g. CSMA/CD. master/slave. tokenpassing, etc.)

3

• Proportional (graded on a percentage scale according to quality/quantity of fulfillment)• [P] Identify and use appropriate sources of information for independent learning• [L] Explain how to diagnose a hypothetical problem in a pressure measurement system• [L] Explain how to diagnose a hypothetical problem in a level measurement system• [L] Explain or demonstrate a principle relevant to a pressure measurement system• [L] Explain or demonstrate a principle relevant to a level measurement system• [L] Perform a basic math calculation relevant to a pressure measurmement system• [L] Perform a basic math calculation relevant to a level measurmement system• [L] Explain or demonstrate safety procedure or tool usage• [F] Convert between different pressure units• [F] Qualitative analysis of a deadweight tester• [F] Explain operation of manometer• [F] Explain operation of different pressure gauge types• [F] Determine response of Twin-T differential capacitance circuit to applied pressure• [F] Perform algebraic manipulation of the Ideal Gas Law equation• [F] Calculate voltages and currents in a series-parallel DC circuit• [F] Determine the consequence of a component fault in an opamp circuit• [F] Analyze a series-parallel DC circuit, both faulted and unfaulted• [F] Determine likelihood of different faults in a simple circuit• [F] Convert between different pressure units• [F] Analyze calibration adjustments in a force-balance pneumatic ∆P transmitter• [F] Determine pressures in a three-valve manifold during maintenance• [F] Calculate instrument inputs and outputs for various conditions• [F] Analyze simple strain gauge circuit• [F] Perform algebraic manipulation of a fractional equation• [F] Perform simple trigonometric calculations• [F] Calculate voltages between different sets of points among several sources• [F] Sketch a circuit diagram for a simple 4-20 mA instrument loop• [F] Diagnose a problem in a multi-element electric heater circuit• [F] Qualitatively determine gas pressure inside heated vessels• [F] Determine likelihood of potential faults in a DP level measurement system• [F] Calculate voltage drops in a loop-powered level transmitter circuit• [F] Calculate ranges for instruments with remote seals• [F] Explain operation of a dip-tube densitometer• [F] Perform algebraic manipulation of a non-linear equation (satellite orbit velocity)• [F] Identify proper oscilloscope control functions• [F] Analyze a simple one-transistor amplifier circuit• [F] Sketch a circuit diagram for a simple relay circuit• [F] Diagnose a problem in a time-delay motor control circuit• [F] Calculate parameters associated with a guided-wave radar instrument• [F] Determine effects of process vapors on a capacitive level probe• [F] Describe different methods for measuring liquid interfaces• [F] Describe the purpose of a stilling well• [F] Analyze a strain-gauge bridge circuit• [F] Perform algebraic manipulation of a the Hall effect equation• [F] Perform algebraic manipulation of a fractional equation• [F] Calculate voltages between different sets of points among several sources• [F] Sketch a circuit diagram for a simple 4-20 mA instrument loop• [F] Diagnose a problem in a time-delay motor control circuit• [X1] Identify how to calibrate mechanical pressure gauges (link and lever mechanisms)• [X1] Identify different types of pressure switches and their operation• [X1] Identify and explain force- and motion-balance pressure-measuring instruments• [X1] Calculate complex pressure transmitter ranges

4

• [X1] Calculate electronic circuit parameters related to pressure measurement• [X2] Identify different types of level switches and their operation• [X2] Calculate liquid interface level transmitter ranges• [X2] Calculate complex buoyancy problems• [X2] Identify suitability of various level-measuring instruments to different processes• [X2] Calculate electronic circuit parameters related to level measurement

file INST240syllabus

5

Sequence of second-year Instrumentation courses

(or equivalent)

INST 200 -- 1 wk INST 205 -- 1 wk

GRADUATION !

Job Prep IIntro. to InstrumentationINST 206 -- 1 wk

Job Prep II

1st quarter 2nd quarter 3rd quarter

Pressure and LevelMeasurement

Measurement

MeasurementAnalytical

Temperature and Flow

INST 240 -- 4 wks

INST 241 -- 4 wks

Fal

l qu

arte

r

INST 242 -- 3 wks

Final ControlElements

Process Optimizationand Control Strategies

PID Controllersand Tuning

INST 250 -- 4 wks

INST 251 -- 4 wks

Win

ter

qu

arte

r

INST 252 -- 3 wks

Data AcquisitionSystems

Programmable LogicControllers

DCS and Fieldbus

INST 261 -- 4 wks

INST 262 -- 4 wks

Sp

rin

g q

uar

ter

INST 260 -- 3 wks

continuing students

(after completing all three quarters)

Core Electronics -- 1 year

file sequence

6

General student expectations

(Punctuality) You are expected to arrive at school on time (by 8:00 AM) every day. One late arrivalis permitted during the timespan of each sequential course (e.g. INST240, INST241, etc.) with no gradededuction. The grade deduction rate for late arrivals is 1% per incident.

(Attendance) You are expected to attend all day, every day. Each student has 12 “sick hours” per quarterapplicable to absences not verifiably employment-related, school-related, or weather-related. The gradededuction rate is 1% per hour of absence in any course. Each student must confer with the instructor toapply “sick hours” to any missed time – this is not done automatically for the student. Students may donateunused “sick hours” to whomever they specifically choose. You should contact your instructor and teammembers immediately if you know you will be late or absent. Absence on an exam day will result in a failinggrade for that exam, unless due to a documented emergency. Exams may be taken in advance for full credit.

(Participation) You are expected to participate fully in all aspects of the learning process includingindependent study, lab project completion, and classroom activities. It is solely your responsibility to catchup on all information missed due to absence. Furthermore, you shall not interfere with the participation ofothers in the learning process.

(Teamwork) You will work in instructor-assigned teams to complete lab assignments. Team membershipis determined by accumulated attendance and punctuality scores: students with similar participatory trendsare teamed together. Any student compromising team performance through frequent absence, habitualtardiness, or other disruptive behavior(s) will be expelled from their team and required to complete alllabwork independently for the remainder of the quarter.

(Preparation for theory sessions) You must dedicate at least 2 hours each day for reading assignmentsand homework questions to prepare yourself for theory sessions, where you will actively contribute your newknowledge. Graded quizzes and/or work inspections during each theory session will gauge your independentlearning. If absent, you may receive credit by having your preparatory work thoroughly reviewed prior tothe absence, or passing a comparable quiz after the absence.

(Feedback questions) You must complete and submit feedback questions for each section by the specifieddeadline. These are graded for accuracy and recorded as a “feedback” score. Plagiarism (presenting anyoneelse’s work as you own) in your answers will result in a zero score. It is okay to help one another learn thematerial, and to learn from outside sources, but your explanations must be phrased in your own words andwith your own work shown.

(Disciplinary action and instructor authority) The Student Code of Conduct (WashingtonAdministrative Codes WAC 495B-120) explicitly authorizes disciplinary action against the following typesof misconduct: academic dishonesty (e.g. cheating, plagiarism), dangerous or lewd behavior, harassment,intoxication, destruction of property, and/or disruption of the learning environment. Furthermore, the Codestates “Instructors have the authority to take whatever summary actions may be necessary to maintain orderand proper conduct in the classroom and to maintain the effective cooperation of the class in fulfilling theobjectives of the course.” Distractive or disruptive behavior such as (but not limited to) unauthorizedtelephone or computer use, disrespectful comments, sleeping, and conversation that either impede yourparticipation or the participation of others may result in temporary dismissal from class with attendancehours deducted.

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General grading and evaluation standards

Assessment criteria

• Mastery (all must be mastered – constitutes first 50% of course grade)• Mastery section of each lab exercise (unlimited attempts)• Mastery section of each exam including the hands-on circuit building or troubleshooting activity (up to

two attempts per sitting; up to three sittings); or mastery capstone assessment (unlimited attempts)

• Proportional (grades based on quality of fulfillment, counts toward last 50% of course grade)• Labwork, consisting of questions answered in an oral and demonstrative format (10% of grade)• Proportional section of all exams (20% of grade)• Feedback questions for all sections (20% of grade)• Daily quizzes demonstrating preparation for theory sessions (-1% per failed quiz)• Daily punctuality (-1% per incident of tardiness)• Attendance (-1% per hour past allotted “sick time”)• Destroyed items (-10% per incident) or purchase and replacement of the damaged item – This regards

avoidable incidents due to personal carelessness. When in doubt, ask the instructor how to properlyuse a tool or piece of equipment!

• Repaired instruments (+5% per item) – Instrument identified in need of repair by the instructor

Negative weighting represent objectives where 100% passing is a basic expectation (passing every quiz,punctuality every day, no accidents, etc.). Perfectly meeting these expectations does not count toward yourgrade, but failing to meet these basic expectations will result in grade loss.

Grading scaleAll grades are criterion-referenced (i.e. no grading on a “curve”)

• 100% ≥ A ≥ 95% 95% > A- ≥ 90%• 90% > B+ ≥ 86% 86% > B ≥ 83% 83% > B- ≥ 80%• 80% > C+ ≥ 76% 76% > C ≥ 73% 73% > C- ≥ 70% (minimum passing course grade)• 70% > D+ ≥ 66% 66% > D ≥ 63% 63% > D- ≥ 60% 60% > F

The proportional section of an exam may be taken only after taking the mastery section. Failing themastery exam will result in a 50% deduction from the proportional exam score, and you get a maximum oftwo re-takes to pass the mastery which must occur within three school days of the first attempt. Failure topass the mastery within three sittings will result in a failing grade for the course. Absence on a scheduledexam day will result in a 0% score for the proportional exam unless you provide documented evidence of anunavoidable emergency. You may receive half-credit on missed proportional exam questions after grading byexplaining your original mistake(s) and providing completely corrected responses on the first attempt.

If any other “mastery” objectives are not completed by their specified deadlines, your overall gradefor the course will be capped at 70% (C- grade), and you will have one more course day to complete theunfinished objectives. Failure to complete those mastery objectives by the end of that extra day (except inthe case of documented, unavoidable emergencies) will result in a failing grade (F) for the course.

Answers to “feedback questions” are due at the end of each course section. Full credit is given foreach question correctly and thoroughly answered, half credit for each question either not fully answeredor containing minor errors, and zero credit for major conceptual errors. Late submissions will receive zerocredit, unless due to a documented emergency.

“Lab questions” are assessed in a group format where students take turns answering questions from thelist at the instructor’s prompting. Grading follows the same rubric as for feedback questions: full creditfor thorough, correct answers; half credit for partially correct answers, and zero credit for major conceptualerrors. If you are absent during this assessment, you must submit written answers to all of the lab questions,which will be graded by the instructor.

file grading

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General tool and supply list

Wrenches• Combination (box- and open-end) wrench set, 1/4” to 3/4” – the most important wrench sizes are 7/16”,

1/2”, 9/16”, and 5/8”; get these immediately!• Miniature combination wrench set, 3/32” to 1/4”• Adjustable wrench, 6” handle• Hex wrench (“Allen” wrench) set, fractional – 1/16” to 3/8”

Note: when turning a bolt, nut, or tube fitting with a hexagonal body, the preferred ranking of handtools to use (from first to last) is box-end wrench or socket, open-end wrench, and finally adjustable wrench.Pliers should never be used to turn the head of a fitting or fastener unless it is absolutely unavoidable!

Pliers• Needle-nose pliers• Slip-joint pliers• Diagonal wire cutters

Screwdrivers• Slotted, 1/8” and 1/4” shaft• Phillips, #1 and #2• Jeweler’s screwdriver set

Measurement tools• Tape measure. 12 feet minimum• Vernier calipers, plastic okay

Electrical• Multimeter, Fluke model 87-IV or better• Wire strippers/terminal crimpers with a range including 10 AWG to 18 AWG wire• Soldering iron, 10 to 25 watt• Rosin-core solder• Package of compression-style fork terminals (e.g. Thomas & Betts “Sta-Kon” part number 14RB-10F,

14 to 18 AWG wire size, #10 stud size)

Safety• Safety glasses or goggles (available at BTC bookstore)• Earplugs (available at BTC bookstore)

Miscellaneous• Teflon pipe tape• Utility knife

You are recommended to engrave your name or place some other form of identifying mark on your tools,as you will be doing a lot of your work in teams, and it is easy to get tools mixed up. Also, lost tools getreturned to their owners much faster when they are marked!

An inexpensive source of high-quality tools is your local pawn shop. Look for name-brand tools withunlimited lifetime guarantees (e.g. Sears “Craftsman” brand, Snap-On, etc.).

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Methods of instruction

This course develops self-instructional and diagnostic skills by placing students in situations where theyare required to research and think independently. In all portions of the curriculum, the goal is to avoid apassive learning environment, favoring instead active engagement of the learner through reading, reflection,problem-solving, and experimental activities. The curriculum may be roughly divided into two portions:theory and practical.

TheoryIn the theory portion of each course, students independently research subjects prior to entering the

classroom for discussion. At the start of the classroom session, the instructor will check each student’spreparation using one of several methods (direct inspection of work, a pop quiz, targeted questions, etc.).Students then spend some class time working in small groups coordinating their presentations. The rest ofthe class time is spent interacting Socratically with the instructor in a large-group dialogue. The instructorcalls students (or student groups) to present what they found in their research, questions that arose duringtheir study, their solutions to problems, and any problem-solving techniques applied. The instructor’s roleis to help students take the information gleaned from their research and convert this into understanding.

LabIn the lab portion of each course, students work in teams to install, configure, document, calibrate, and

troubleshoot working instrument loop systems. Each lab exercise focuses on a different type of instrument,with a eight-day period typically allotted for completion. An ordinary lab session might look like this:

(1) Start of practical (lab) session: announcements and planning(a) Instructor makes general announcements to all students(b) Instructor works with team to plan that day’s goals, making sure each team member has a clear

idea of what they should accomplish(2) Teams work on lab unit completion according to recommended schedule:

(First day) Select and bench-test instrument(s)(One day) Connect instrument(s) into a complete loop(One day) Each team member drafts their own loop documentation, inspection done as a team (withinstructor)(One or two days) Each team member calibrates/configures the instrument(s)(Remaining days, up to last) Each team member troubleshoots the instrument loop(Last day) All teams answer lab questions, one team at a time, with the instructor

(3) End of practical (lab) session: debriefing where each team reports on their work to the whole class

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Distance delivery methods

Sometimes the demands of life prevent students from attending college 6 hours per day. In such cases,there exist alternatives to the normal 8:00 AM to 3:00 PM class/lab schedule, allowing students to completecoursework in non-traditional ways, at a “distance” from the college campus proper.

For such “distance” students, the same worksheets, lab activities, exams, and academic standards stillapply. Instead of working in small groups and in teams to complete theory and lab sections, though, studentsparticipating in an alternative fashion must do all the work themselves. Participation via teleconferencing,video- or audio-recorded small-group sessions, and such is encouraged and supported.

There is no recording of hours attended or tardiness for students participating in this manner. The paceof the course is likewise determined by the “distance” student. Experience has shown that it is a benefit for“distance” students to maintain the same pace as their on-campus classmates whenever possible.

In lieu of small-group activities and class discussions, comprehension of the theory portion of each coursewill be ensured by completing and submitting detailed answers for all worksheet questions, not just passingdaily quizzes as is the standard for conventional students. The instructor will discuss any incomplete and/orincorrect worksheet answers with the student, and ask that those questions be re-answered by the studentto correct any misunderstandings before moving on.

Labwork is perhaps the most difficult portion of the curriculum for a “distance” student to complete,since the equipment used in Instrumentation is typically too large and expensive to leave the school labfacility. “Distance” students must find a way to complete the required lab activities, either by arrangingtime in the school lab facility and/or completing activities on equivalent equipment outside of school (e.g.at their place of employment, if applicable). Labwork completed outside of school must be validated by asupervisor and/or documented via photograph or videorecording.

Conventional students may opt to switch to “distance” mode at any time. This has proven to be abenefit to students whose lives are disrupted by catastrophic events. Likewise, “distance” students mayswitch back to conventional mode if and when their schedules permit. Although the existence of alternativemodes of student participation is a great benefit for students with challenging schedules, it requires a greaterinvestment of time and a greater level of self-discipline than the traditional mode where the student attendsschool for 6 hours every day. No student should consider the “distance” mode of learning a way to havemore free time to themselves, because they will actually spend more time engaged in the coursework thanif they attend school on a regular schedule. It exists merely for the sake of those who cannot attend duringregular school hours, as an alternative to course withdrawal.

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General advice for successful learning

Reserve a time and a place for study• Schedule a block of time every day for study and make it a priority!• Create or join a study group, and help each other commit to regular study time.• Keep the environment of your study place ideal: whatever music (or no music) helps you concentrate,

whatever time allows for the least number of distractions, etc.• Plan to arrive at school at least a half-hour early and use the time to study as opposed to studying late

at night. This also helps guard against tardiness in the event of unexpected delays, and ensures you abetter parking space!

Who to study with• Classmates with similar schedules.• Classmates who are serious about their education.• Note that the intelligence of your study partners is not a significant criterion!

How to make time for study• Rid yourself of unnecessary, time-wasting gadgets: televisions, video games, mobile phones, etc. I am

not kidding!• Avoid recreational use of the internet.• Bring a meal to school every day and use your one-hour lunch break for study instead of eating out.• Carefully plan your lab sessions with your teammates to reserve a portion of each day’s lab time for

study.• Cut off all unhealthy personal relationships.

Make efficient use of the time you have• Do not procrastinate, waiting until the last minute to do something.• Don’t let small chunks of time at home or at school go to waste. Work a little bit on assignments during

these times.• Identify menial chores you can do simultaneously (e.g. house cleaning and laundry), and plan your

chore time accordingly to free up more time at home.

Take responsibility for your learning and your life• Obtain all the required books, and any supplementary study materials available to you. If the books

cost too much, look on the internet for used texts (www.amazon.com, www.half.com, etc.) and use themoney from the sale of your television and video games to buy them!

• Make an honest attempt to solve problems before asking someone else to help you. Being able toproblem-solve is a skill that will improve only if you continue to do work at it.

• If you detect trouble understanding a basic concept, seek clarification on it immediately. Never ignorean area of confusion, believing you will pick up on it later. Later may be too late!

• Do not wait for others to do things for you. No one is going to make extra effort purely on your behalf.• Seek help for any addictions. Addictions won’t just destroy your chance at an education – they can

destroy your whole life!

. . . And the number one tip for success . . .• Realize that there are no shortcuts to learning. Every time you seek a shortcut, you are actually cheating

yourself out of a learning opportunity!!

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Creative Commons License

This worksheet is licensed under the Creative Commons Attribution License, version 1.0. To viewa copy of this license, visit http://creativecommons.org/licenses/by/1.0/ or send a letter to CreativeCommons, 559 Nathan Abbott Way, Stanford, California 94305, USA. The terms and conditions of thislicense allow for free copying, distribution, and/or modification of all licensed works by the general public.

Simple explanation of Attribution License:

The licensor (Tony Kuphaldt) permits others to copy, distribute, display, and otherwise use thiswork. In return, licensees must give the original author(s) credit. For the full license text, please visithttp://creativecommons.org/licenses/by/1.0/ on the internet.

More detailed explanation of Attribution License:

Under the terms and conditions of the Creative Commons Attribution License, you may make freelyuse, make copies, and even modify these worksheets (and the individual “source” files comprising them)without having to ask me (the author and licensor) for permission. The one thing you must do is properlycredit my original authorship. Basically, this protects my efforts against plagiarism without hindering theend-user as would normally be the case under full copyright protection. This gives educators a great dealof freedom in how they might adapt my learning materials to their unique needs, removing all financial andlegal barriers which would normally hinder if not prevent creative use.

Nothing in the License prohibits the sale of original or adapted materials by others. You are free tocopy what I have created, modify them if you please (or not), and then sell them at any price. Once again,the only catch is that you must give proper credit to myself as the original author and licensor. Given thatthese worksheets will be continually made available on the internet for free download, though, few peoplewill pay for what you are selling unless you have somehow added value.

Nothing in the License prohibits the application of a more restrictive license (or no license at all) toderivative works. This means you can add your own content to that which I have made, and then exercisefull copyright restriction over the new (derivative) work, choosing not to release your additions under thesame free and open terms. An example of where you might wish to do this is if you are a teacher who desiresto add a detailed “answer key” for your own benefit but not to make this answer key available to anyoneelse (e.g. students).

Note: the text on this page is not a license. It is simply a handy reference for understanding the LegalCode (the full license) - it is a human-readable expression of some of its key terms. Think of it as theuser-friendly interface to the Legal Code beneath. This simple explanation itself has no legal value, and itscontents do not appear in the actual license.

file license

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Metric prefixes and conversion constants

• Metric prefixes

• Yotta = 1024 Symbol: Y

• Zeta = 1021 Symbol: Z

• Exa = 1018 Symbol: E

• Peta = 1015 Symbol: P

• Tera = 1012 Symbol: T

• Giga = 109 Symbol: G

• Mega = 106 Symbol: M

• Kilo = 103 Symbol: k

• Hecto = 102 Symbol: h

• Deca = 101 Symbol: da

• Deci = 10−1 Symbol: d

• Centi = 10−2 Symbol: c

• Milli = 10−3 Symbol: m

• Micro = 10−6 Symbol: µ

• Nano = 10−9 Symbol: n

• Pico = 10−12 Symbol: p

• Femto = 10−15 Symbol: f

• Atto = 10−18 Symbol: a

• Zepto = 10−21 Symbol: z

• Yocto = 10−24 Symbol: y

1001031061091012 10-3 10-6 10-9 10-12(none)kilomegagigatera milli micro nano pico

kMGT m µ n p

10-210-1101102

deci centidecahectoh da d c

METRIC PREFIX SCALE

• Conversion formulae for temperature

• oF = (oC)(9/5) + 32

• oC = (oF - 32)(5/9)

• oR = oF + 459.67

• K = oC + 273.15

Conversion equivalencies for distance

1 inch (in) = 2.540000 centimeter (cm)

1 foot (ft) = 12 inches (in)

1 yard (yd) = 3 feet (ft)

1 mile (mi) = 5280 feet (ft)

14

Conversion equivalencies for volume

1 gallon (gal) = 231.0 cubic inches (in3) = 4 quarts (qt) = 8 pints (pt) = 128 fluid ounces (fl. oz.)= 3.7854 liters (l)

1 milliliter (ml) = 1 cubic centimeter (cm3)

Conversion equivalencies for velocity

1 mile per hour (mi/h) = 88 feet per minute (ft/m) = 1.46667 feet per second (ft/s) = 1.60934kilometer per hour (km/h) = 0.44704 meter per second (m/s) = 0.868976 knot (knot – international)

Conversion equivalencies for mass

1 pound (lbm) = 0.45359 kilogram (kg) = 0.031081 slugs

Conversion equivalencies for force

1 pound-force (lbf) = 4.44822 newton (N)

Conversion equivalencies for area

1 acre = 43560 square feet (ft2) = 4840 square yards (yd2) = 4046.86 square meters (m2)

Conversion equivalencies for common pressure units (either all gauge or all absolute)

1 pound per square inch (PSI) = 2.03602 inches of mercury (in. Hg) = 27.6799 inches of water (in.W.C.) = 6.894757 kilo-pascals (kPa) = 0.06894757 bar

1 bar = 100 kilo-pascals (kPa)

Conversion equivalencies for absolute pressure units (only)

1 atmosphere (Atm) = 14.7 pounds per square inch absolute (PSIA) = 101.325 kilo-pascals absolute(kPaA) = 1.01325 bar (bar) = 760 millimeters of mercury absolute (mmHgA) = 760 torr (torr)

Conversion equivalencies for energy or work

1 british thermal unit (Btu – “International Table”) = 251.996 calories (cal – “International Table”)= 1055.06 joules (J) = 1055.06 watt-seconds (W-s) = 0.293071 watt-hour (W-hr) = 1.05506 x 1010

ergs (erg) = 778.169 foot-pound-force (ft-lbf)

Conversion equivalencies for power

1 horsepower (hp – 550 ft-lbf/s) = 745.7 watts (W) = 2544.43 british thermal units per hour(Btu/hr) = 0.0760181 boiler horsepower (hp – boiler)

Acceleration of gravity (free fall), Earth standard

9.806650 meters per second per second (m/s2) = 32.1740 feet per second per second (ft/s2)

15

Physical constants

Speed of light in a vacuum (c) = 2.9979 × 108 meters per second (m/s) = 186,281 miles per second(mi/s)

Avogadro’s number (NA) = 6.022 × 1023 per mole (mol−1)

Electronic charge (e) = 1.602 × 10−19 Coulomb (C)

Boltzmann’s constant (k) = 1.38 × 10−23 Joules per Kelvin (J/K)

Stefan-Boltzmann constant (σ) = 5.67 × 10−8 Watts per square meter-Kelvin4 (W/m2·K4)

Molar gas constant (R) = 8.314 Joules per mole-Kelvin (J/mol-K)

Properties of Water

Freezing point at sea level = 32oF = 0oC

Boiling point at sea level = 212oF = 100oC

Density of water at 4oC = 1000 kg/m3 = 1 g/cm3 = 1 kg/liter = 62.428 lb/ft3 = 1.94 slugs/ft3

Specific heat of water at 14oC = 1.00002 calories/g·oC = 1 BTU/lb·oF = 4.1869 Joules/g·oC

Specific heat of ice ≈ 0.5 calories/g·oC

Specific heat of steam ≈ 0.48 calories/g·oC

Absolute viscosity of water at 20oC = 1.0019 centipoise (cp) = 0.0010019 Pascal-seconds (Pa·s)

Surface tension of water (in contact with air) at 18oC = 73.05 dynes/cm

pH of pure water at 25o C = 7.0 (pH scale = 0 to 14)

Properties of Dry Air at sea level

Density of dry air at 20oC and 760 torr = 1.204 mg/cm3 = 1.204 kg/m3 = 0.075 lb/ft3 = 0.00235slugs/ft3

Absolute viscosity of dry air at 20oC and 760 torr = 0.018 centipoise (cp) = 1.8 × 10−5 Pascal-seconds (Pa·s)

file conversion constants

16

Question 0

How to read actively:

• Make notes in a notebook while reading – if you’re not “reading with a pencil,” you’re not activelyreading! “Shorthand” notation, diagrams, and other notes jotted in a notebook are more effective atprompting active reading than underlining, highlighting, or otherwise marking up the original text.

• Mentally summarize each new concept or application you encounter in your own words before movingon to the next. If you cannot do this, you know you need to re-read the relevant sections until you can!

• Try to link new concepts to previously-learned concepts, and imagine how new concepts might apply toapplications not mentioned in the text. Make notes on these points so you may raise them as questionsduring class time.

• Note page numbers where important concepts, equations, images, tables, and problem-solving techniquesare introduced This will help you locate these important references during class time when you willcontribute in the dicsussion (“On page 572 it shows . . .”).

• Note page numbers of any sections in the reading that confound you, so you may call attention to it atthe start of class time to get help from classmates and/or the instructor.

• If the text demonstrates a mathematical calculation, such as how to apply a new equation to solving aproblem, pick up your calculator and work through the example as you read! Applications of math arean ideal opportunity to actively read a technical book, actually engaging in the material rather thanpassively observing what it says.

• Reserve the front pages of your notebook (or keep a separate notebook) for all mathematical formulaeyou come across in your reading. Briefly explain in your own words what each formula does and whatits terms mean.

Problem-solving techniques

• Clearly identify all “given” information, and also what the question is asking you to determine or solve.

• Sketch a diagram or graph to organize all the “given” information and show where the answer will fit.

• Performing “thought experiments” to visualize the effects of different conditions.

• Working “backward” from a hypothetical solution to a new set of given conditions.

• Changing the problem to make it simpler, and then solving the simplified problem (e.g. changingquantitative to qualitative, or visa-versa; substituting different numerical values to make them easierto work with; eliminating confusing details; adding details to eliminate unknowns; considering limitingcases that are easier to grasp).

• Identify any “first principles” of science, electronics, and/or instrumentation (e.g. Conservation laws,Feedback, Zero and Span, Ohm’s Law, etc.) that might apply to the question.

• Specifically identify which portion(s) of the question you find most confusing and need help with. Themore specific you are able to be, the better.

file question0

17

Questions

Question 1

Read and outline the “Ultrasonic Level Measurement” subsection of the “Echo” section of the“Continuous Level Measurement” chapter in your Lessons In Industrial Instrumentation textbook. Notethe page numbers where important illustrations, photographs, equations, tables, and other relevant detailsare found. Prepare to thoughtfully discuss with your instructor and classmates the concepts and examplesexplored in this reading.

file i03960

Question 2

Read and outline the “Radar Level Measurement” subsection of the “Echo” section of the “ContinuousLevel Measurement” chapter in your Lessons In Industrial Instrumentation textbook. Note the page numberswhere important illustrations, photographs, equations, tables, and other relevant details are found. Prepareto thoughtfully discuss with your instructor and classmates the concepts and examples explored in thisreading.

file i03961

Question 3

Read and outline the “Magnetostrictive Level Measurement” subsection of the “Echo” section of the“Continuous Level Measurement” chapter in your Lessons In Industrial Instrumentation textbook. Notethe page numbers where important illustrations, photographs, equations, tables, and other relevant detailsare found. Prepare to thoughtfully discuss with your instructor and classmates the concepts and examplesexplored in this reading.

file i03962

18

Question 4

The following graph shows the signal strength received by a guided-wave radar (GWR) level instrumentover time:

Am

plitu

de (

mV

)

Distance (inches)0

UNZ

Reference (fiducial)

pulse

Echo pulse

End-of-probepulse

Explain how the graph will change if:

• The liquid level increases• The dielectric constant (ǫ) of the liquid decreases

Also, explain what UNZ refers to (the Upper Null Zone).file i00289

19

Question 5

Guided-wave radar (GWR) level transmitters have the unique ability to measure not only total liquidlevel but also liquid-liquid interface levels at the same time. Explain how this technology works, and alsowhat properties of the liquids are necessary to achieve good detection.

Also, explain what the echo diagram (time-domain reflectogram) would look like for a radar instrumentdetecting a liquid-liquid interface. Shown here is an echo diagram for a radar instrument detecting a singleliquid (i.e. gas and liquid only, no liquid-liquid interfaces):

Am

plitu

de (

mV

)

Distance (inches)0

UNZ


pulse

Echo pulse

End-of-probepulse

file i03610

20

Question 6

Ultrasonic, radar, and magnetostrictive level measuring instruments use the principle of time-of-flightto determine the level of a process substance in a vessel.

A critical factor for the accuracy of any time-of-flight measurement technology is the velocity ofpropagation for the wave in question, through the substance(s) that wave must travel. Examine each ofthese illustrations and then determine which of the velocities of propagation (v) matter (and which do not)to level measurement accuracy. Be prepared to explain why, in each case!

Ultrasoniclevel

instrument

Echo

vair

vwater

Ultrasoniclevel

instrument

Echo

vair

vwater

vair

vwater

vmetal

Magnetostrictivelevel instrument

Float

(rod)

instrument

Echo

vair

vwater

instrument

vair

vwater

vair

vwater

Guided-waveradar level

Guided-wave

voil

Echo Echoes

radar interfacelevel instrument

Non-contactradar level

file i03625

21

Question 7

Suppose an instrument salesperson comes to your shop and tells you his company’s radar leveltransmitter product is superior to all hydrostatic and displacer level transmitters because those instruments’accuracy depends on a fixed process liquid density, whereas radar transmitters do not. Thus, he tells you,his radar transmitters will give accurate level measurements even when process pressures and temperatureschange.

What do you think of this claim? Is the salesperson’s claim true, or not? Explain.file i03626

Question 8

Calculate the percentage of incident power reflected back to the transmitter, and the percentage ofincident power transmitted (forward) through the liquid in this radar level measurement application:

Pincident

Pforward

Preflected

(Air)

(Water)

Radar level transmitter

ε = 1

ε = 78

Also, calculate the ullage for this vessel in both units of meters and units of feet/inches, given areflected pulse (“echo”) time of 11.176 nanoseconds. Note: the propagation velocity of radio waves inair is approximately 3 × 108 meters per second, the same as the speed of light in a vacuum.

file i04216

22

Question 9

Examine the different configuration parameter fields for a guided-wave radar transmitter shown in thisscreenshot (taken on a personal computer running Emerson AMS software, interrogating a Rosemount model3300 level transmitter), and explain the importance of each one:

file i00292

23

Question 10


Pincident

Pforward

Preflected


ε = 1.15

ε = 11

Also, calculate the ullage and fillage for this vessel, given a reflected pulse (“echo”) time of 18.3nanoseconds and a total vessel height of 30 feet.

file i04217

24

Question 11

Calculate the echo times for both the total level (air/oil interface) and oil/water interface in this radarlevel measurement application:


Referencepulse

Timing diagram

t1

t2

air/oil oil/water

4 m

3.6 m

2 mε = 1

ε = 5

ε = 80

Air

Oil

Water

Also, calculate the power reflection factors for both interfaces (air/oil and oil/water).file i04218

25

Question 12

Calculate the two distances (x1 and x2) in this radar level measurement application given echo times of9.7 ns and 85.3 ns, respectively:


Referencepulse

Timing diagram

t1

t2

x1

x2

Vaporε = 1.2

ε = 6.0Liquid

Liquidε = 35

vapor/liquid liquid/liquid

t1 = 9.7 ns

t2 = 85.3 nsfile i04219

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18

Question 19

Question 20

26

Question 21

Read and outline the “Weight” section of the “Continuous Level Measurement” chapter in your LessonsIn Industrial Instrumentation textbook. Note the page numbers where important illustrations, photographs,equations, tables, and other relevant details are found. Prepare to thoughtfully discuss with your instructorand classmates the concepts and examples explored in this reading.

file i03963

Question 22

Read and outline the “Capacitive” section of the “Continuous Level Measurement” chapter in yourLessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03964

Question 23

Read and outline the “Radiation” section of the “Continuous Level Measurement” chapter in yourLessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03965

Question 24

One way to measure the quantity of liquid or solid inside a vessel is to simply weigh the vessel usingdevices called load cells:

WT Output signal

Vessel

Explain what a load cell is, how it works, and what advantages this concept of vessel weighing enjoysover other level-measurement technologies. Also, identify how such a level-measurement system would becalibrated.

file i00325

27

Question 25

When using load cells to measure vessel level, certain precautions must be taken to ensure accuratemeasurements:

Vessel

Pipe

Flexiblecoupling

Pipe

FlexiblecouplingLoad

cellLoadcell

One important precaution to take is installing flexible couplings on all pipes leading into and out of thevessel. Rigid pipes will cause measurement errors – explain why this is.

Another important precaution to take is in regard to electric arc welding done on the vessel. If there isany arc welding to be done, the “ground” clamp must be connected above the load cells, not below:

Wrong!Right

Vessel

Loadcell

Loadcell

28

Failure to heed this precaution will likely destroy the load cells – explain why.file i00326

Question 26

Hobbyists building their own Tesla Coils often need to fabricate their own high-voltage capacitors forbuilding the LC resonant circuit which is the heart of the coil:

Basic resonant stage of a Tesla Coil

To oscillatorcircuit

One ingenious way to build such capacitors is to use old glass beer or soda bottles filled with salt water,with a metal rod or chain dipped into the water and aluminum foil wrapped tightly around the outside:

Terminals

Beer-bottle capacitor

To obtain enough capacitance, one must usually group several of these beer-bottle capacitors togetherin parallel. I mean, what’s the point of having beer-bottle capacitors unless you can make a six-pack withthem?

As odd as it may seem, this actually has something to do with industrial instrumentation! Identifywhich parts of the “beer-bottle capacitor” form the conductive plates of the capacitor and which part formsthe dielectric. Then identify how capacitance would be affected if we were to change the level of salt waterin the beer bottle. Finally, identify how this principle could be applied to the measurement of liquid levelinside a vessel.

file i00317

29

Question 27

Capacitive level probes come in two general varieties: those operating on conductive liquids and thoseoperating on non-conductive liquids. Capacitance level probes designed to work with non-conductive liquidsare nothing more than metal rods, and the liquid itself forms the dielectric:

Liquid

Probe

Metal vessel

Terminals

(dielectric)

Vapor

How are conductive-liquid capacitance probes different? If the liquid cannot be used as a dielectricbecause of its conductivity, what does form the dielectric?

file i00318

30

Question 28

Nuclear radiation may be blocked by dense substances such as lead. In fact, radioactive substances usedin instruments are often enclosed in lead-lined boxes, allowing radiation to be emitted in one direction only:

lead

source Radiation

What do you suppose might happen to the radiation if some solid substance less dense than lead wereto be placed in front of a radioactive source?

lead

source ???

What if the source were placed on one side of a storage vessel, and a radiation detector placed onthe opposite side? How would the level of liquid or solid in that vessel affect the radiation received at thedetector?

lead

source

???

DetectorSolid material

Explain what “radioactivity” is, identify alternative arrangements of source and detector for measuringlevel, and identify some safety precautions one must take when working with nuclear radiation instrumentsystems.

file i00320

31

Question 29

Draw the symbols for the following types of liquid level indicating instruments, each one mounted tothe top of a process vessel:

• Tape and float• Radar gauge• Ultrasonic (sound) gauge• Laser (light) gauge• Resistive tape• Capacitive probe• Nuclear radiation

file i00323

Question 30

Some level measurements are more critical than others, demanding greater instrument accuracy. Onesuch category is called custody transfer. Explain what “custody transfer” means, and give an example of acustody transfer level measurement application.

file i00324

Question 31

Explain how a resistive tape level sensor works, and why care must be taken to prevent vapor pressureinside the liquid-holding vessel from affecting it.

file i00319

Question 32

Question 33

Question 34

Question 35

Question 36

Question 37

Question 38

Question 39

Question 40

Question 41

Read and outline the “Level Switches” section of the “Discrete Process Measurement” chapter in yourLessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03966

32

Question 42

An oil sump for a hydraulic system is equipped with a float-type level switch for sensing low oil leveland providing automatic shut-down capability for the hydraulic system:

Flow Flow

"choppy" liquid surfaceLS

float

Turbulence will impose alateral force on the float,

possibly causing a false trip

The flow rate of oil through the sump is quite high, and this presents a problem. With the oil being soturbulent, the float does not rest gently on the oil’s surface. Instead, it is tossed to and fro on the choppysurface, which can make the level switch “think” the float has gone down further than it actually has, thuscausing needless shutdowns.

One solution to this problem is a stilling well. Describe what a “stilling well” is, how you might makeone for this application, and why it works to prevent the problem.

file i00298

33

Question 43

A form of liquid level switch called a tilt switch is often used for detecting sewage level in “lift stations”where sewage collected from homes via gravity is pumped out of the collection sump to the wastewatertreatment plant (usually located miles away):

Empty Full

Pump Pump

LSL

LSH LSH

LSL

To WWTP To WWTP

From homes From homes

Tilt switches often use a small glass vial containing liquid mercury as the tilt sensor. Explain how aglass tube partially filled with mercury works as an electrical tilt switch, and explain how these switcheswould function in the following lift station pump control circuit:

L1 L2

LSH LSL

M1

M1 OL

motor

OL

To 3-phaseAC power

M1

file i00303

34

Question 44

A very interesting form of liquid level switch exploits an optical principle known as Snell’s Law, whichrelates the angle of a light beam as it passes from one transparent medium to another to the velocities oflight in both media:

Incidentlight beam

Refractedlight beam

θ1

θ2

v1 = Speed of light in first material

v2 = Speed of light in second material

sin θ1

v1

=sin θ2

v2

In this example, which material has the faster velocity of light? How can you tell?

Something interesting happens when we increase the angle of θ1. At some point, θ2 increases to equal90o, at which point the light never leaves the first medium, but experiences total internal reflection:

Incidentlight beam

light beam

θ1

v1 = Speed of light in first material

v2 = Speed of light in second material

Reflected

θ2 = 90o

Total internal reflection

Use algebra and trigonometry to solve for the minimum angle θ1 at which total internal reflection occurs,in terms of v1 and v2.

We exploit this principle in a refractive-type level switch by aiming a light beam at the inside surfaceof a quartz prism at such an angle that the light will internally reflect when the prism is surrounded by air,but refract (and escape) when the prism is surrounded by water. This works because the velocities of lightin air and water are not equal, and both these velocities are greater than the velocity of light in quartz:

35

Quartzprism

Light source

(air)

Quartzprism

Light source

(water)

Identify what else is needed in this optical system to make a complete, working switch, and identifyprocess fluids that would work well with this form of switch.

file i00305

36

Question 45

Explain how the following electronic level switch works:

Probes

Liquid

+V

Relay

R1

Q1

Identify what kinds of process liquids this level switch would be applicable to, and why. Also, identifywhich ladder-logic switch symbol would be appropriate for this particular level switch:

Normally-open

(N.O.)

Normally-closed

(N.C.)

file i00306

37

Question 46

Switches, whether they be hand-actuated or actuated by a physical process, come in two varieties:normally-open (NO) and normally-closed (NC). You are probably accustomed to seeing both types of switchrepresented in pushbutton form on schematic diagrams:

Normally-openpushbutton switch pushbutton switch

Normally-closed

Normally-open pushbutton switches close (pass current) when actuated (pressed). When un-actuated,they return to their “normal” (open) state.

Normally-closed pushbutton switches are just the opposite: they open (stop current) when actuated(pressed) and return to their “normal” (closed, passing current) state when un-actuated.

This is simple enough to comprehend: the “normal” status of a momentary-contact pushbutton switchis the state it is in when no one is touching it. When pressed, the pushbutton switch goes to the other(opposite) state.

Things get more confusing, though, when we examine process switches, such as pressure switches, levelswitches, temperature switches, and flow switches:

Normally-open Normally-closedpressure switch pressure switch

Normally-open Normally-closedlevel switch level switch

Normally-open Normally-closed

Normally-open Normally-closed

temperature switch temperature switch

flow switch flow switch

Define “normal” in the context of one of these process switches. In other words, explain what condition(s)each process switch must be in to ensure it is in the “normal” state; and conversely, what condition(s) needto be applied to each switch to force it into its other state.

file i02966

38

Question 47

Read selected sections of the National Transportation Safety Board’s report (NTSB/PAR-04/02,PB2004-916502 Notation 7666) of the 2003 storage tank explosion and fire in Glenpool, Oklahoma, andanswer the following questions.

Describe in your own words how the situation progressed from the initial tank filling to the explosion.What was the most likely cause of this accident, and how could it have been avoided?

Read pages 9-13, and also page 20, of the report, and identify the following:

• Explain what a floating roof is, and the purpose it serves in a fuel storage tank.• Describe what a datum plate is, and how the stored fuel quantity may be determined by manual tape

measurement of liquid level and reference to a strapping table.• At what volume and height (level) values did the original strapping table give for liquid contact with

the floating roof, and for the point at which the roof would actually float? How does this compare withthe values determines for liquid contact by investigators after the accident?

• Describe what a bonding system is inside a floating-roof fuel storage tank, and explain the purpose ofthis system.

• Explain what the filling rate of a floating-roof fuel storage tank has to do with safety, especially at apoint when there is not enough fuel in the tank to float the roof.

file i03968

Question 48

Read and outline the “Liquid Volume Measurement” section of the “Signal Characterization” chapter inyour Lessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

Note: feel free to skip the calculus derivations in this section, concentrating on the end-results: formulaethat predict volume given height measurement in vessels of different geometry.

file i03969

Question 49

Some level switches use a vibrating rod or paddle to sense the presence of liquids or solids at a specificpoint. Explain how such vibrating level switches work, in as much detail as you can. Hint: sometimes theseswitches are known as tuning fork switches if they use two balanced paddles to sense the presence of liquidor solid material.

Also identify potential problems with this type of “point-level” detector caused by improper installation.file i00301

Question 50

Some level switches use a motor-rotated paddle to sense the presence of solids at a specific point. Explainhow such “rotating paddle” level switches work, in as much detail as you can.

Also identify potential problems with this type of “point-level” detector caused by improper installation.file i00302

Question 51

One form of non-contact level switch utilizes nuclear radiation to sense the absence or presence of levelwithin a vessel, either liquid or solid. Briefly explain how these level switches work.

file i00304

39

Question 52

Explain how the following electronic level switch works:

Liquid

+V

Relay

R1Q1

Probe

Grounded metal vessel

Identify what kinds of process liquids this level switch would be applicable to, and why. Also, identifywhich ladder-logic switch symbol would be appropriate for this particular level switch:

Normally-open

(N.O.)

Normally-closed

(N.C.)

file i00513

Question 53

Question 54

Question 55

Question 56

Question 57

Question 58

Question 59

40

Question 60

Question 61

Determine a basic 5-point (0%, 25%, 50%, 75%, and 100%) calibration table for the displacer leveltransmitter in this scenario:

Blockvalves

disp

lace

r

0%

100%

Measurementspan = 24 in

Water 0%

100%

Measurementspan = 24 in

5 in

The displacer weighs 10 pounds (dry) and has a diameter of 2 inches. The process liquid is water(density = 62.428 lb/ft3). The 0% process liquid level (LRV) begins when the displacer is submerged 5inches. Assume a pneumatic transmitter mechanism with an output range of 3 to 15 PSI, and a calibrationtolerance of +/- 1% (of span).

Percent of Buoyant Output signal Output signal Output signalspan (%) force (lb) ideal (PSI) min. (PSI) max. (PSI)

0255075100

file i02958

41

Question 62

A rain gauge is nothing more than a vertical tube designed to capture rain water, and indicate theaccumulated rainfall on a scale alongside the tube:

Rain

scale

Tube

The diameter of the tube used for the rain gauge is irrelevant. Although a larger tube will of courserequire more water to fill to the same height, it will also capture proportionally more rain, so any diametertube measures rainfall just the same.

However, if we equip our rain gauge with a funnel to capture more rain, the measurement will beaffected:

Rain

scale

Tube

Funnel

Supposing the diameter of the funnel is 5 inches, and the diameter of the tube is 1 inch, how much rainwater level will be indicated by the scale after one-quarter inch of actual rainfall? Does this represent a shift

42

in zero, a shift in span, or a shift in both for the rain gauge compared to its performance without the funnel?file i02959

Question 63

Calculate values for the following calibration table, for a transmitter measuring liquid level interface(densities = 50 lb/ft3 and 70 lb/ft3), with a calibration tolerance of +/- 1% and a 4-20 mA output range:

DP cell with

Interfacemeasurement

100%

0%

Flow in

Flow out

H L

4-20 mA output

"dry" leg

D = 70 lb/ft3

D = 50 lb/ft3

span = 11 in

4 in

15 in

Span = 11 in

Interface Percent of ∆ pressure Output signal Output signal Output signallevel (in) span (%) sensed (”W.C) ideal (mA) min. (mA) max. (mA)

01025507590100

file i00686

43

Question 64

Calculate values for the following calibration table, for a displacer-type level transmitter measuringliquid level interface (densities = 50 lb/ft3 and 70 lb/ft3), with a calibration tolerance of +/- 1%:

Vessel

Blockvalves

disp

lace

r

Transmitter

3-15 PSI output

Span =

D = 50 lb/ft3

D = 70 lb/ft3

11 inches

Interface Percent of Buoyant Output signal Output signal Output signallevel (in) span (%) force (lbs) ideal (PSI) min. (PSI) max. (PSI)

01025507590100

Assume the following displacer characteristics:

• Shape: cylindrical• Length = 11 inches• Diameter = 1.5 inches• Dry weight = 2.7 lbs

file i00687

44

Question 65

This P&ID shows how two pressure transmitters may be linked with a radar level transmitter to providedata necessary to calculate not only liquid level, but also liquid density and total liquid mass stored in thevessel:

14LT

Radar

PT14a

PT14b

UY14

UIR14

This is sometimes referred to as a hybrid level measurement system. Explain what the word “hybrid”means in this context, and how these three transmitters accomplish the measurement objectives of liquidlevel, density, and total mass. Also, explain what all the symbols mean in the P&ID.

file i00295

45

Question 66

Determine the following voltage drops in this level-sensing circuit when the process level is at a height of12 feet. Note that this is not a loop-powered transmitter, but receives its electrical power through separatepower conductors (120 volts AC). Assume negligible (0) voltage drop along the signal conductor lengths:

250ΩL1

L2

G

ES 120VAC60 Hz

Fieldpanel

Field process area

Tag number Description Manufacturer Model Calibration Notes

Loop Diagram: Revised by: Date:

TB27

250 Ω resistor +/- 0.1 %

1-5 VDC

Control roomP5 Fieldpanel

1414

14

P30

3

4

TB40

Feed tank level

LT

CBL 1TB12

M. Tech

2

3

CBL 30 CBL 11

LY

LI

20

21

LT-14 Radar level transmitter 0-30 ft ; 4-20 mA

Red LionPanel indicator

Enraf

LY-14

LI-14

Dec 32, 1997

Radar

L1

L2

G

TB13

1

2

3

ES

120

VA

C60

Hz

• Voltage drop across transmitter terminals =• Voltage drop between TB40-3 and TB27-21 =• Voltage drop across 250 Ω resistor =• Voltage drop between TB12-3 and TB27-21 =

file i00293

46

Question 67

An ultrasonic level transmitter has a calibrated range of 40 to 75 inches and its output signal range is4 to 20 mA. Complete the following table of values for this transmitter, assuming perfect calibration (zeroerror). Be sure to show your work!

Measured level Percent of span Output signal(inches) (%) (mA)

476

7560

15.134

file i00098

Question 68

Qualitatively sketch the height/volume relationship for a stepped cylindrical vessel:

h

h

0FullEmpty V

Liquid

H

H

file i02926

Question 69

Qualitatively sketch the height/volume relationship for a spherical vessel, such as the type used to storeliquefied butane under pressure:

h

D

Liquid

h

0

D

FullEmpty V

file i02925

47

Question 70

When measuring the volume of liquid stored in a vertical cylinder, the function relating liquid height(h) to stored liquid volume (V ) is quite simple:

h

r

V = πr2h

The term πr2 defines the cross-sectional area of the cylindrical tank, which when multiplied by theliquid height (h) gives an answer for volume (V ) in cubic units.

Calculating stored liquid volume in a horizontal cylinder is not nearly as simple. The effective cross-sectional area of the cylinder varies with liquid height, and this variation is not linearly proportional toheight. As a result, the function relating liquid height to stored liquid volume is quite complex:

rh

L

V = L

[

(h − r)√

2hr − h2 + r2 sin−1(h − r)

r+

πr2

2

]

Using this formula, calculate the amount of liquid volume stored in a horizontal cylinder with thefollowing dimensions, assuming a liquid height of 3 feet:

r = 5 feetL = 25 feet

Express your answer in units of gallons.file i02957

48

Question 71

The lever transmitter (LT) in this level control system is hydrostatic; i.e. it senses liquid level in thevessel based on the hydrostatic pressure exerted by the liquid’s height in the vessel:

Vessel

LTLIC

LV

Suppose the density of the liquid within the vessel decreases. What effect will this have on the controlledliquid level? In other words, what will the liquid level inside the vessel do over time in response to this changein density?

file i02960

49

Question 72

A level indicator is registering a liquid level that is falsely high. The operator has hand-gauged thestorage vessel with a tape measure and determined the actual level to be 8.2 feet, but the level indicator(LI) registers 10.1 feet. The calibrated range of the 3-15 PSI pneumatic transmitter is 0 feet to 12 feet. Youmeasure the pneumatic pressure signal with a test gauge and find that it is 13.1 PSI. Which instrument isat fault in this system? How do you know?

LT

Vessel 0-12 feet0-12 feet

LI

Level transmitter Level indicator

Measured signal:Actual level:

Indication:

3-15 PSI3-15 PSI

8.2 feet

10.1 feet

13.1 PSI

file i02961

Question 73

A potable (drinking) water storage tank requires a high-level alarm to warn operations personnel ofimpending overflow conditions. A high-level switch is on order, but until this switch arrives for installation,you are asked to devise a very simple yet effective high-level indicator device that will function in the interim.

Explain how you would build such a device. Bonus points for devising a method that uses very simpleparts (easily found in a maintenance shop).

file i03592

Question 74

Question 75

Question 76

Question 77

Question 78

Question 79

Question 80

50

Question 81


Pincident

Pforward

Preflected


Oil

Airεr = 1

εr = 7

Also, calculate the ullage for this vessel in units of feet, given a reflected pulse (“echo”) time of 17.0nanoseconds. Assume a speed of light in vacuum to be 3 × 108 meters per second. For all your answers, besure to show your work!

Preflected = %

Pforward = %

Ullage = ft

file i00034

51

Question 82

Suppose a capacitive level instrument using a bare metal probe is used to measure the level of oil ina tank. Further suppose that this oil heats up and emits vapors that displace the air normally above theliquid surface. Determine the effect of these vapors on the instrument’s level measurement: will the vapors’displacement of air cause the instrument to register an increase in liquid level, a decrease in liquid level, orcause no change at all? Explain your answer.

This is a graded question: you will be graded on accuracy and originality (no plagiarized answers!).file i00035

52

Question 83

The level of a liquid-to-liquid interface can be difficult to measure. Describe one practical example of aliquid-liquid interface level measurement scenario, and describe in detail at least two different level-sensingtechnologies appropriate for continuously measuring the level of that interface.


53

Question 84

A common accessory device for measuring liquid level in a vessel is a stilling pipe, sometimes called astilling well. Describe what this device is, how it works in conjunction with a level measurement instrument(e.g. radar gauge, ultrasonic transmitter, float, capacitance probe, resistive tape, etc.), and why one wouldbe needed in an actual process.


54

Question 85

Strain gauges may be used to measure the weight of a process vessel, and therefore infer the level offluid or solids in that vessel. Strain gauge circuits almost always take the form of a Wheatstone bridge, thebridge circuit producing an output voltage that varies with the amount of strain sensed by the gauge:

R1 R2

RstrainR3

+−Vexcitation

Measuringinstrument

Assume that the bridge is balanced when the vessel is empty (zero level), and that the resistance of thestrain gauge increases with increasing vessel weight (increasing level). Identify:

• The polarity of the voltage across all bridge resistors.• The polarity of the voltage sensed by the measuring instrument as level increases.• Which variable resistance (R1 or R2) adjusts zero.• Which variable resistance (R1 or R2) adjusts span.• One electrical fault resulting in a positive over-range (> 100 % level) reading.• One electrical fault resulting in a negative over-range (< 0 % level) reading.

file i00038

55

Question 86

The Hall Effect describes the voltage generated across the width of a conductive strip (VHall) with acertain thickness (x), given a perpendicular magnetic field (B) and electric current (I):

VHall = KIB

x

I

B

B

I

x

VHall

Manipulate the Hall Effect equation to solve for magnetic flux density B in terms of the other variables.Be sure to show all your work!

B =

file i03295

56

Question 87

The following equation relates torque (τ , which is the twisting force) and radius (r) of two meshinggears:

τ1

r1

=τ2

r2

A student attempts to manipulate this equation to solve for r1, and gets this incorrect result:

r1 =τ2

τ1r2

Explain exactly where the student went wrong in solving for r1, then properly solve for r1. Be sure toshow all your work!

file i03520

57

Question 88

Determine the voltages registered by a voltmeter between the following points in this circuit. Be sureto note whether the voltmeter’s indication will be a positive value or a negative value in each case:

A

B

C

D

21 V

12 V4 V

9 V

VA = (red lead on A, black lead on ground)

VB = (red lead on B, black lead on ground)

VC = (red lead on C, black lead on ground)

VD = (red lead on D, black lead on ground)

VAC = (red lead on A, black lead on C)

VDB = (red lead on D, black lead on B)

VBA = (red lead on B, black lead on A)

VBC = (red lead on B, black lead on C)

VCD = (red lead on C, black lead on D)

file i02523

58

Question 89

Sketch a circuit whereby this loop-powered pressure transmitter sends a signal to an analog voltage meter(acting as a remote pressure gauge). Include any necessary power sources and other electronic componentsin your completed circuit:

H L

4-20 mA loop-poweredpressure transmitter

1-5 V voltmeter

file i02671

59

Question 90

In this time-delay relay circuit, the motor will immediately start when the pushbutton is pressed, andcontinue to run for about 5 seconds after the pushbutton is released. The green light-emitting diode (LED)is supposed to be on whenever the motor is stopped, and off whenever the motor is running:

C1

Pushbutton switchRelay R1

R2

Mtr LED24 V

TP1

TP2

TP3

TP4

TP5

TP6

TP7TP8TP9

However, a problem has developed with this circuit. The green LED always remains on and the motornever starts, no matter what is done with the pushbutton switch. Based on this information, determine thefollowing:

• Two components or wires in the circuit that you know cannot be failed either open or shorted, besidesthe 24 volt source.

• Two components or wires in the circuit you think could possibly be bad (either one independentlycapable of causing the problem), and the type of failure each would be (either open or shorted).

file i03169

60

Question 91

Lab Exercise

Your team’s task is to set up a liquid level measurement loop using a pneumatic ∆P transmitter (Foxboromodel 13A d/p cell is recommended). Each instrument in the loop should be labeled with a proper tag name(e.g. “LT-82” for a level transmitter), with all instruments in each loop sharing the same loop number.Write on pieces of masking tape to make simple labels for all the instruments and signal lines.

Part of this lab exercise is using a liquid manometer as a standard pressure-verification instrument.Another part is the correct identification of common pipe and tube fittings. A 3-valve or a 5-valve manifoldmust be attached to your transmitter for isolation and testing purposes.

Each student must calibrate their transmitter for a unique level measurement range, the LRV and URVpoints determined by the instructor. It is strongly recommended that you carefully measure the span of thelevel measurement range with a tape measure and calibrate your transmitter’s span on the calibration benchas accurately as you can with a zero-based range (e.g. if the span is 35.1 inches, calibrate for a range of 0 to35.1 inches), then field-set the transmitter’s zero adjustment so that its output matches the actual level inthe vessel (e.g. with an offset of 3.25 inches, that transmitter’s range will now be 3.25 to 38.35 inches). Thisprocedure avoids the problem of trying to accurately measure the transmitter’s zero offset (suppression) witha tape measure and wasting time on the bench adjusting the calibration pressure back and forth betweentwo non-zero values as you repeat zero and span adjustments. It also teaches the very practical concept offield-setting the zero of a transmitter.

Caution: the zero-adjust screw on the Foxboro pneumatic transmitter is quite delicate,and may easily be ruined if overtorqued. Be especially careful not to turn the screw too farcounter-clockwise and back it out of the nut, because it often cross-threads when subsequentlyturned the other way.

Each student must diagnose a fault in the system within a 3-minute time limit, correctly identifying boththe general location and nature of the fault, and logically justifying all diagnostic steps taken. Additionaltime will be given to precisely locate and rectify the fault following successful diagnosis within the allottedtime. Failure to identify both the general location and nature of the fault within the allotted time, and/orfailing to demonstrate rational diagnostic procedure will disqualify the effort, in which case the student mustre-try with a different fault. Multiple re-tries are permitted with no reduction in grade.

Objective completion table:

Performance objective Grading 1 2 3 4 TeamComponent selection and testing mastery – – – –

Loop diagram and inspection mastery – – – –Loop calibration (± 1% of span) mastery – – – –

Manometer usage mastery – – – –Troubleshooting (3 minute limit) mastery – – – –

Pipe and tube fitting identification mastery – – – –Lab question: Diagnosis proportional – – – –

Lab question: Instruments proportional – – – –Lab question: Math proportional – – – –

Lab question: Tools/safety proportional – – – –

61

Lab questions (reviewed between instructor and student team in a private session)

• Diagnosis• Explain what will happen (and why) if the nozzle in your pneumatic transmitter plugs• Explain what will happen (and why) if the restrictor (orifice) in your pneumatic transmitter plugs• Explain what will happen (and why) if the diaphragm inside the amplifying relay tears (develops a leak)• Identify some of the symptoms of “dirty” instrument air manifest in pneumatic instruments• Identify and explain how large signal tube volumes degrade the performance of pneumatic instruments• Identify what things may be determined about a malfunctioning pneumatic transmitter simply by forcing

the baffle (flapper) toward the nozzle and observing the results• Explain what will happen (and why) in a liquid level control loop if the equalizing valve on the DP

transmitter’s three-valve manifold is left open. Assume the controller is in automatic mode when thishappens, and that the transmitter infers liquid level by hydrostatic pressure of the process liquid appliedto its “high” port (direct-acting).

• Explain what will happen (and why) in a liquid level control loop if the equalizing valve on the DPtransmitter’s three-valve manifold is left open. Assume the controller is in automatic mode when thishappens, and that the transmitter infers liquid level by hydrostatic pressure of the process liquid appliedto its “low” port (reverse-acting).

• Instruments• Explain how a tube fitting seals against fluid leaks• Explain how a tapered-thread pipe fitting seals against fluid leaks• Identify the “high” and “low” pressure ports on your pressure transmitter, and explain their significance• Identify the process “bleed” (“vent”) fittings on your pressure transmitter, and explain the significance

of locating them in either a high or a low elevation on the flange of your transmitter• Identify and explain range turndown on your transmitter (also called rangedown)• Explain how a 3-15 PSI pneumatic signal conveys information• Identify and explain the purpose of the relay on your pneumatic transmitter• Identify and explain the purpose of the restrictor on your pneumatic transmitter• Identify and explain the purpose of the baffle/nozzle assembly on your pneumatic transmitter• Identify and explain “elevation” and “suppression” as these terms apply to liquid level measurement

using a ∆P gauge or transmitter• Identify how to equip your level measurement process with a bubble tube or dip tube• Identify alternative techniques for measuring the same liquid level (other than inference by hydrostatic

pressure)• Explain the operating principle of the pressure transmitter (as detailed as possible)• Identify and explain zero and span adjustments on your transmitter• Explain how to use a ∆P gauge or transmitter to measure positive pressure versus measuring a vacuum• Demonstrate three-valve manifold operating procedures (with a real manifold)

• Math (no calculator allowed!)• Calculate the correct pneumatic signal pressure (PSI) given a pressure transmitter calibration range

and an applied pressure• Calculate the pressure applied to a transmitter given a calibration range and the measured pneumatic

signal pressure value• Calculate the percentage of span error for a transmitter given a calibration range and an As-Found

calibration table• Calculate the allowable process pressure error for a transmitter given an allowable percentage of span

error• Calculate the range of a hydrostatic level transmitter given the desired process liquid range and the

liquid density• Convert between different pressure units, without relying on the use of a reference for conversion factors

(i.e. you must commit the major conversion factors to memory)

62

• Tools/Safety• Demonstrate how to properly use a manometer as a standard pressure instrument• Explain why a manometer works as a standard pressure gauge• Explain why it is important to keep the manometer in a perfectly vertical orientation• Explain how an inclined manometer works• Explain how a “well” or “cistern” manometer works• Explain how to interpret the pressure indicated by a U-tube manometer filled with oil instead of water• Demonstrate how to properly use an air pump as pressure source• Identify the preferred tools (in order) to use when connecting tube fitting components: open-end wrench,

box-end wrench, pliers, adjustable wrench• Explain how to create precise, low pressures of compressed air using simple equipment• Explain importance of deadweight tester fluids when calibrating pressure instruments for different

processes (pure oxygen, food processing, medical, etc.)• Explain how to safely check the calibration of a DP transmitter in a liquid level control loop without

causing the controller to over-react to the pressures you apply to the transmitter as part of yourcalibration check.

63

It is relatively easy to construct a “process vessel” for measuring water level in, by using inexpensivePVC plastic piping and fittings:

PV

C p

ipe

H L

Drain valve

Tee fitting

Tee fitting90o elbow

tube fitting

"Run" teetube fitting

Clear plastic tube(sightglass)

Tape marking LRV

Tape marking URV

suppression

Water is poured in the top, through the open tee fitting, and is drained through a valve at the bottom(preferably a 1/4 turn ball valve).

Even with an instrument valve manifold on the ∆P transmitter, a shutoff valve is advisable between theprocess vessel connection and the transmitter to facilitate removal of the transmitter and manifold withouthaving to drain the vessel.

Note: The Foxboro model 13 and 15 pneumatic transmitters cannot handle large suppression valueswithout the addition of a special “suppression kit” spring and screw adjustment to the transmittermechanism. When using the stock zero-adjust screw to account for suppression (the degree to which thetransmitter’s tube connection is below the LRV height on the vessel), be sure to position the transmitter sothat the suppression is a small percentage of the measurement span.

64

Part of this lab exercise is to properly identify the following types of pipe and instrument tube fittingsfrom memory (without the aid of a pictorial reference). Note that synonyms are separated by slash marks(e.g. “street/run”):

Pipe fittings

• Thread sizes: 1/8 inch NPT, 1/4 inch NPT, 3/8 inch NPT, and 1/2 inch NPT• Fitting type: tee (female, branch, and street/run)• Fitting type: elbow (female 45o, female 90o, and street)• Fitting type: cross• Fitting type: nipple• Fitting type: coupling• Fitting type: reducing coupling• Fitting type: reducing bushing• Fitting type: reducing adapter/expander• Fitting type: union• Fitting type: cap• Fitting type: plug• Fitting type: flange

Instrument tube fittings

• Tube sizes: 1/8 inch, 1/4 inch, 3/8 inch, and 1/2 inch• Fitting components: nut and ferrule(s)• Fitting type: straight connector (male and female)• Fitting type: elbow connector (male and female)• Fitting type: union (straight and reducing)• Fitting type: tee (union, branch, run)• Fitting type: union elbow• Fitting type: union cross• Fitting type: bulkhead union• Fitting type: cap• Fitting type: plug

In order to make this a practical as well as educational exercise, your team will identifydifferent tube and pipe fittings while cleaning up and re-organizing the tube and pipe fittingcollections in the lab.

file i00123

65

Question

92

Loop

dia

gra

mte

mpla

te

Description Manufacturer Model Notes


Tag # Input range Output range

66

Loop diagram requirements

• Instrument “bubbles”• Proper symbols and designations used for all instruments.• All instrument “bubbles” properly labeled (letter codes and loop numbers).• All instrument “bubbles” marked with the proper lines (solid line, dashed line, single line, double lines,

no lines).• Optional: Calibration ranges and action arrows written next to each bubble.

• Text descriptions• Each instrument documented below (tag number, description, etc.).• Calibration (input and output ranges) given for each instrument, as applicable.

• Connection points• All terminals and tube junctions properly labeled.• All terminal blocks properly labeled.• All junction (“field”) boxes shown as distinct sections of the loop diagram, and properly labeled.• All control panels shown as distinct sections of the loop diagram, and properly labeled.• All wire colors shown next to each terminal.• All terminals on instruments labeled as they appear on the instrument (so that anyone reading the

diagram will know which instrument terminal each wire goes to).

• Cables and tubes• Single-pair cables or pneumatic tubes going to individual instruments should be labeled with the field

instrument tag number (e.g. “TT-8” or “TY-12”)• Multi-pair cables or pneumatic tube bundles going between junction boxes and/or panels need to have

unique numbers (e.g. “Cable 10”) as well as numbers for each pair (e.g. “Pair 1,” “Pair 2,” etc.).

• Energy sources• All power source intensities labeled (e.g. “24 VDC,” “120 VAC,” “20 PSI”)• All shutoff points labeled (e.g. “Breaker #5,” “Valve #7”)

67

Sam

ple

Loop

Dia

gra

m(u

sing

asin

gle

-loop

contro

ller)

Process areaField panel Control room panel

Controller

Resistor

I/P transducer

Control valve

I/P

ES 120 VAC

AS 20 PSI

Loop Diagram: Furnace temperature control

TT205

JB-12

TB-15

TB-15

3

4

1

2

Temperature transmitterTT-205 Rosemount 444

TE205

CP-1

TB-11

TB-11

1

2

7

Vishay 250 ΩTY-205a

TIC-205 Siemens PAC 353

TY-205b

TV-205 Fisher Easy-E 3-15 PSI

Fisher

H

N

3

4

22

21

19

18

TY205b

TY

205a

Breaker #4Panel L2

5

6Cable TY-205b

Cable TT-205 Cable TT-205

Cable TY-205b

TIC205

Revised by: Mason Neilan

TV205

Tube TV-205

Column #8Valve #15

546

0-1500oF 0-1500oF

Fail-closed

Reverse-acting control

TE-205 Thermocouple Omega Type K Ungrounded tip

Red

BlkRed

Yel Red

Blk

Red

Blk

Red

Blk

Wht/Blu

Blu Blu

Wht/Blu

Cable 3, Pr 1

Cable 3, Pr 2

Wht/Org

Org Org

Wht/Org

Blk

Red

Blk

Red

Blk

Wht

Red

Blk

Red

Blk

Upscale burnout


Date:


0-1500o F 4-20 mA

4-20 mA 3-15 PSI

0-100%

1-5 V 0-1500o F

April 1, 2007

68

Sam

ple

Loop

Dia

gra

m(u

sing

DC

Scontro

ller)

Field process area



DCS cabinet

Red

Blk

Red

Blk

Red

Blk

Fisher

Fisher


Blue team pressure loop April 1, 2009

Card 4

Card 6Channel 6

Channel 611

12

29

30

Red

Blk

TB-80

TB-80

Field panel JB-25

TB-52

TB-52

PT-6 Pressure transmitter Rosemount 3051CD 0-50 PSI 4-20 mA

PIC6

PT6

Cable 4, Pr 1

Cable 4, Pr 8

1

2

15

16

Cable PT-6

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Cable PV-6

11

12

11

12PY6

AS 20 PSI

PV6

0-50 PSI

I/P

0-50 PSI

846

Emerson DeltaV 4-20 mA 4-20 mA HART-enabled inputPIC-6

PY-6

PV-6

I/P transducer

Controller

Control valve Vee-ball

4-20 mA 3-15 PSI

3-15 PSI 0-100% Fail-open

Duncan D.V.

Tube PV-6

Cable PT-6

Cable PV-6

Analog input

Analogoutput

Direct-acting control

H

L

69

Sam

ple

Loop

Dia

gra

m(u

sing

pneum

atic

contro

ller)




LT24

In

H

LOut

C

D

A.S. 21 PSI

Tube LT-24a Tube LT-24b

A.S. 21 PSI

Process areaBulkhead panel

14

B-104Control panel CP-11

Tube LV-24

LV24

Tube LV-24

Supply

LIC

24

Tube LV-24

(vent)

Sludge tank level control I. Leaky April 1, 2008

LT-24 Level transmitter Foxboro 13A 25-150 "H2O 3-15 PSI

3-15 PSI 3-15 PSIFoxboroLIC-24 130

LV-24 Fisher Easy-E / 667 3-15 PSI 0-100% Fail closedControl valve

Controller

file

i00654

70

Question 93

Circuit-building performance exerciseConnect a loop-powered differential pressure transmitter (4-20 mA output) to a DC voltage source

and a meter such that the meter will indicate a increasing signal when a certain stimulus is applied to thetransmitter. All electrical connections must be made using a terminal strip (no twisted wires, crimp splices,wire nuts, spring clips, or “alligator” clips permitted).

This exercise tests your ability to properly connect power to a loop-powered differential pressuretransmitter, connect multiple batteries together to achieve the required total supply voltage, choose theappropriate sensing port (“high” or “low” pressure) to apply the specified stimulus, condition the electricalsignal (if necessary) so the meter can properly register it, properly connect an analog meter into the circuit,and use a terminal strip to organize all electrical connections.

H L- +

+ -

MeterDifferentialpressure

transmitter

Terminal strip

Resistor+ -

Batteries

The following components and materials will be available to you during the exam: assorted 2-wire4-20 mA differential pressure transmitters calibrated to ranges 0-30 PSI or less, equipped with Swagelokcompression tube connectors at the “high” and “low” ports ; lengths of plastic tube with ferrules pre-swaged ; terminal strips ; lengths of hook-up wire ; 250 Ω (or approximate) resistors ; analog meters; battery clips (holders).

You will be expected to supply your own screwdrivers and multimeter for assembling and testing thecircuit at your desk. The instructor will supply the battery(ies) to power your circuit when you are readyto see if it works. Until that time, your circuit will remain unpowered.

Meter options (instructor chooses): Voltmeter (1-5 VDC) Ammeter (4-20 mA)

Signal increases with... (instructor chooses): Positive pressure Vacuum (suction)

Study reference: the “Analog Electronic Instrumentation” chapter of Lessons In IndustrialInstrumentation, particularly the sections on loop-powered transmitters and current loop troubleshooting.

file i03771

71

Answers

Answer 1

Answer 2

Answer 3

Answer 4

Answer 5

The echo diagram would contain a second pulse, like this:

Am

plitu

de (

mV

)

Distance (inches)0

UNZ


pulse

Echo pulse

End-of-probepulse

Echo pulse(liquid/liquid interface)

Answer 6

Partial answer:

• Ultrasonic level, bottom-mounted: vwater matters, vair does not• GWR level: vair matters, vwater does not

Answer 7

Answer 8

Partial answer:

Preflected = 63.45%

Ullage = 1.676 meters

72

Answer 9

Answer 10

Preflected = 26.15%

Pforward = 73.85%

Ullage = 8 feet 4.78 inches

Fillage = 21 feet 7.22 inches

Answer 11

t1 = 13.33 ns

t2 = 67.00 ns

Rair−oil = 14.59%

Roil−water = 36.00%

Answer 12

x1 = 1.328 m

x2 = 4.630 m

Answer 13

Answer 14

Answer 15

Answer 16

Answer 17

Answer 18

Answer 19

Answer 20

Answer 21

Answer 22

Answer 23

Answer 24

Answer 25

Answer 26

73

Answer 27

Answer 28

74

Answer 29

LI

Tape and Float

LI

RADAR

Radar

LI

US

Ultrasonic

LI

LASER

LI LI

CAR TAPE

Laser Resistive tape Capacitive probe

75

LX LIR

Nuclear radiation

Answer 30

Answer 31

I’ll let you research how a resistive tape works! Once you grasp its basic operating principle (hydrostaticpressure from the liquid “squeezing” the tape up to a certain level), it will become obvious why high vesselpressure could cause erroneous level readings.

Follow-up question: how can we prevent pressure inside the vessel from causing false tape measurements?

Answer 32

Answer 33

Answer 34

Answer 35

Answer 36

Answer 37

Answer 38

Answer 39

Answer 40

Answer 41

Answer 42

I’ll let you figure out the solution to this!

Answer 43

Be sure to review the operation of this simple motor start-stop circuit in your answer!

Answer 44

Answer 45

76

Answer 46

The “normal” condition for a process switch is the condition of least stimulus. For example:

• A pressure switch will be in its “normal” state when there is minimum pressure applied

• A level switch will be in its “normal” state when there is no level detected by the switch

• A temperature switch will be in its “normal” state when it is cold

• A flow switch will be in its “normal” state when there is no flow detected by the switch

Answer 47

Answer 48

Answer 49

These switches use an electronic circuit to vibrate the rod or paddle, then trigger their output signalupon sensing the dampening of that vibration caused by the presence of liquid or solid immersion.

Potential problems include:

LS

LS

angle of repose

dead stock

Answer 50

Level is detected when the paddle (or motor) torque exceeds a pre-set limit.

Potential problems include paddle fouling and seized paddle shaft bearings.

Answer 51

Some nuclear level switches work by sensing the blockage of radiation due to process level, others bythe “backscattering” (reflection) of radiation by the process level. Delayed coker drum level detection (inthe oil refining industry) is one notable application of the latter technique, where hydrocarbons’ property ofreflecting neutron radiation more than other substances is the primary detection characteristic.

Answer 52

This switch works on the principle of electrical conductivity through the liquid. I’ll let you explain indetail how the circuit works.

The action of this switch is best described as a normally-closed (N.C.).

77

Answer 53

Answer 54

Answer 55

Answer 56

Answer 57

Answer 58

Answer 59

Answer 60

Answer 61

Partial answer:

Percent of Buoyant Output signal Output signal Output signalspan (%) force (lb) ideal (PSI) min. (PSI) max. (PSI)

0 0.5675 325 5.8850 1.929 8.8875 12.12100 3.291 15.12

Answer 62

Partial answer:

The scale will indicate 6.25 inches of water for one-quarter inch of rainfall.

Answer 63

Interface Percent of ∆ pressure Output signal Output signal Output signallevel (in) span (%) sensed (”W.C) ideal (mA) min. (mA) max. (mA)

0 0 28.83 4 3.84 4.161.1 10 29.19 5.6 5.44 5.762.75 25 29.71 8 7.84 8.165.5 50 30.60 12 11.84 12.168.25 75 31.48 16 15.84 16.169.9 90 32.00 18.4 18.24 18.5611 100 32.36 20 19.84 20.16

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Answer 64

Partial answer:

Interface Percent of Buoyant Output signal Output signal Output signallevel (in) span (%) force (lbs) ideal (PSI) min. (PSI) max. (PSI)

0 310 4.08

2.75 2550 0.675075 12.12

9.9 90100 0.7874

Answer 65

The use of two pressure transmitters, one at the bottom and one at the top, is reminiscent of a hydrostatictank expert system (using three pressure sensors). If this vessel were vented, we could get away with onlyusing one pressure transmitter along with the radar gauge to calculate liquid level, density, and total mass.

Answer 66

Partial answer:

• Voltage drop across transmitter terminals =• Voltage drop between TB40-3 and TB27-21 =• Voltage drop across 250 Ω resistor = 2.6 volts• Voltage drop between TB12-3 and TB27-21 =

Answer 67

Partial answer:

Measured level Percent of span Output signal(inches) (%) (mA)

476

7560

64.28 69.38 15.151.9 34 9.44

Answer 68

Answer 69

Answer 70

V = 495.4 ft3 = 3706 gallons

Note: if your answer is wildly in error, you might want to check to see that your calculator is set to dotrigonometric functions in units of radians instead of degrees!

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Answer 71

The controlled liquid level will rise.

Answer 72

The transmitter is at fault, not the indicator.

Answer 73

Did you really think I would reveal possible solutions to the problem this easily?

Answer 74

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Answer 82

This is a graded question – no answers or hints given!

Answer 83


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Answer 91

Answer 92

Your loop diagram will be validated when the instructor inspects the loop with you and the rest of yourteam.

Answer 93

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