Abstract submitted to Escape 12 for

Trouble shooting is an application of well-known problem solving techniques to plant problems. This paper proposes that trouble shooting be included in the undergraduate program and that CAPE educators play a leading role in shaping the education. First, the six-step problem solving method is tailored to trouble shooting. Then, the tailored method is applied to a process example, which demonstrates the need for mastery of both process principles and CAPE technology. Guidance is given to instructors on how they can manage the teaching and learning to maximize benefit to the students. 1.0 Trouble shooting in CAPE Education Trouble shooting involves continuously monitoring, diagnosing and improving process systems. It is a fundamental task performed by engineers. In this paper, we will describe how trouble shooting can be integrated into the undergraduate program in a manner that will reinforce previous education, build lifelong learning skills, and be enjoyable for the students. But first, why should CAPE educators address trouble shooting? Let’s consider some of the aspects of trouble shooting chemical processes that militate for a systems approach to trouble shooting: (1) sensors supply nearly all information about current behavior, (2) many corrective actions are implemented by final elements, (3) all processes are automated which affects the symptoms and introduces possible sources for faults, (4) historical data can be used as a basis for identifying and diagnosing faults, and (5) often, a fault in one unit exhibits symptoms in another unit. A second related question is whether students need education in trouble shooting. Those instructors who have addressed the topic will certainly answer with a resounding “yes”. Most students enjoy the challenge of trouble shooting but initially apply an undisciplined approach. An important goal of education is to provide a systematic method that can be adapted and applied to many professional activities. Finally, a third question is how do we link trouble shooting to key educational goals. The trouble-shooting educational objectives can be presented using the three categories developed by Rugarcia, Felder, Woods, Stice (2000); examples of trouble shooting goals for each category are given in the following. • Attitudes: Students must learn how to solve problems when equipment never functions exactly as designed, measurements always have errors, and feed material properties are never known exactly. • Skills: Students need a firm fundamental understanding of the six-step trouble shooting method along with a recognition of the emotional factors in good problem solving. • Knowledge: Students need deep knowledge of engineering systems – especially control principles and equipment– to be successful troubleshooters. 2.0 A Problem-Solving Method We agree that trouble shooting is an important CAPE topic, but can we teach it? Over the past decade, we have seen great progress in teaching engineering problem solving. Excellent documentation of approaches is available in, for example, Woods (1994) and Fogler and LeBlanc (1995), and evidence for the value of a methodology is given in Woods (2000). This paper will show how to apply the general, six-step problem-solving method to trouble shooting process systems, which helps students link process fundamentals to equipment operation. 2.1 Tailoring Problem Solving for Trouble Shooting Problem solving can be applied to many aspects of life, and it is often introduced in first or second year of university education through simple problems like baking a cake or determining why a lamp is not working. However, higher-year students need to learn how to problem solve by applying process fundamentals (e.g., material and energy balances), equipment behavior (e.g., tray flooding), instrumentation basics (e.g., sensor accuracy), and process safety (e.g., pressure relief). Using realistic process examples have several advantages. First, realistic process examples will reinforce prior learning. Students have typically approached chemical engineering systems as a design problem. In trouble shooting, they encounter the same systems and process fundamentals from the operations viewpoint. Second, students will learn the importance equipment behavior. The second effect is especially valuable for today’s students who have received an engineering-science-based education in the transport topics. Third, students will begin to encounter unique challenges involved with being successful in a process plant, where we need to work with people and communicate clearly. We will retain the six-step problem-solving method because it is appropriate for trouble shooting. However, students require considerable assistance in taking the big step from baking a cake to plant safety and profitability. This guidance can be provided by key questions that students should be asking at every stage of the method. A full listing of these questions is too long to include in this paper, but it is available via the WWW (Marlin, 2001). To demonstrate how to tailor the method for process trouble shooting, we present example questions for each of Steps 1 to 6. In this example, we focus on the task of identifying the cause of the “problem”. The same general strategy is used to prioritize, to identify the cause, to correct the fault, and to prevent reoccurrence of the problem. Trouble shooters should cycle back and forth among the steps, not apply them serially. • Step 1, Engage: Patiently read the problem statement, or listen to the operator describe the problem. Manage stress. Yes, you are expected to solve the problem and you can. • Step 2, Define: Sort the evidence. What is the situation? Is this startup after a shutdown? Is this the first time the process has been run? What are the facts? What is opinion? What is the source of the information? What are symptoms or initial evidence? Who are the people in the problem and affected by the problem? • Step 3, Explore: Create a rich understanding of the situation. In this we specify: Who/when/where/what is and is not in the problem? We patiently gather these data, and we brainstorm numerous hypotheses about what could be the cause. Make many “what if?” assumptions and test these out. We are willing to take a risk, make mistakes and explore to understand what really is involved in this problem. What is the short term and long term desired state? In a plant, we often identify two desired states. One is a short-term state that quickly regains safe operation and if possible, achieves acceptable product quality. The second is a longer-term state that might require equipment changes or a process shutdown to achieve. We learn the key skill of checking information before using it in trouble shooting. For example, we know material balances, so we can check flow rates and component balances, and the student must consider the accuracy of the specific measurement devices in deciding whether the data is reliable. We look for hints in the historical data? We will explore different possible root causes if the plant (1) is being started up, (2) experiencing slow changes in performance or (3) has been in essentially unchanged operation for an extended time. We recall practical experience about the equipment in the system. We use existing checklists linking typical symptoms and faults with possible causes to prioritize and assess the list of hypotheses. Next, we use the hypotheses and evidence to develop a truth table to compare the data with the hypotheses. Since the data are seldom complete, the troubleshooter selects a sequence of diagnostics actions to be implemented in the plant. The sequence of the actions should provide inexpensive, rapid feedback first. • Step 4, Plan: Evolve a plan to test the hypotheses and identify the root cause or perhaps to correct the fault without discovering the fault. • Step 5, Implement the plan. The action must be appropriate for an operating plant. “Shutdown the plant and repair the tray” is only acceptable when other less expensive solutions are not possible. In some cases, “Lower the production rate until the next turnaround” is a better short-term solution. • Step 6, Evaluate: How can I continue to test/verify my hypothesis as I implement the solution? –We look back after each step to ensure that the goal is correct and achievable. In this final step, we should monitor the response to the solution to ensure that the root cause has been identified. If not, then repeat the above process. If we think we have identified the cause, then we repeat the strategy to correct the root cause. Then we repeat the strategy to avoid this problem in the future. We should establish a program that would prevent a reoccurrence of the problem, if possible. This program might include new sensors or laboratory analyses, or it could involve equipment enhancements. 3.0 Trouble Shooting Case Studies Students need considerable practice to understand and master the trouble-shooting method. These should begin with relatively simple cases when the students are becoming familiar with the method. The instructor should be aware of the students’ knowledge of common equipment, such as heat exchangers and pumps, so that the cases are within the students’ capabilities. Subsequent cases build complexity of knowledge base and analysis. To reduce pressure on individuals, the first few cases can be performed as group exercises. After each of the six steps, a member of the group can explain their results to the class. The instructor can offer guidance and ensure that all groups are progressing well before moving to the next step. After some practice, groups can progress to trouble shooting a case without intermediate assistance. 3.1