The mere formulation of a problem is far more often essential …kntu.ac.ir/DorsaPax/userfiles/file/Mechanical/OstadFile/... · 2013-10-05 · The engineering design team then began

The mere formulation of a problem is far more often essential than its solution, which may be merely a matter of mathematical or experimental skill. Albert Einstein

Be sure you are right, then go ahead. Davy Crockett

O B J E C T I V E S

Upon completion of this chapter and all other assigned work, the reader should be able to

Explain why formulation of a problem statement is a critical step in the engineering design process. Generate problem statements that focus upon the function to be achieved by any viable design solution. Identify the hazards associated with misdefining a problem.

A p p l y a number of techniques and strategies to define the "real" problem to be solved, including the statement-restatement technique, the source/cause approach, the revision method, present state-desired state (PS-DS) strategy, and Duncker diagrams. Perform Kepner-Tregoe situation analysis to evaluate various aspects of a situation in terms of three criteria (timing, trend, and impact), thereby determining what is known, which task(s) should be performed, and in what order these tasks should be completed. Perform Kepner-Tregoe problem analysis to determine possible causes of a problem.

O U T L I N E

3.1 Focus on Function Lawn Mowers and Yo-Yos

3.2 Formulating the Real Problem

3.2.1 The Dangers of Misdirected Search Re-entry of Space Capsules

3.2.2 The Statement-Restatement Technique

3.2.3 Determine the Source and the Cause

3.2.4 The Revision Method

3.2.5 Present State and Desired State via Duncker Diagrams

3.2.6 Other Heuristics

3.3 Kepner-Tregoe Situation Analysis

3.3.1 Situation Analysis The Water Tank Disaster

3.3.2 Problem Analysis The Airplane Rash

Summary

Problems

ADDITIONAL CASE HISTORIES

Case History 3.1 The Tylenol Case

Case History 3.2 Blowing in the Wind: Boston's John Hancock Tower

Case History 3.3 Apollo 13: Preventing a 7iagedy

Focus on Function Recognizing that a specific problem should be formulated if one is to develop a specific solution is important. Unfortunately, a problem statement sometimes becomes too specific; that is, the engineer describes the problem in terms of a particular solution, limiting creativity and often leading to simple modifications in an existing solution rather than a breakthrough design. Instead a problem statement should focus upon the function(s) to be performed by any viable solution.

Lawn Mowers and Yo-Yos

The following anecdote emphasizes the importance of the problem statement in engineering design and the need to maintain one's focus on function.'

1. Although undocumented, this anecdote was provided by a reliable source.

78 Chapter 3 Structuring the Search for the Problem

During the mid-1960s, an engineering meeting was held at a gardening equipment firm. The engineers were informed that the lawn mowers manufactured by the company were losing market share due to increased competition from other manufac- turers. In order to overcome this loss, the engineers were told to solve the following problem: Design a new lawn mower that will be the most popular product in the field.

The design engineers commenced work on this problem. After considerable time and effort, they generated a number of "new lawn mower" designs (e.g., a lawn mower with additional safety features (guards, automatic shut-off switches, etc.), one with mul- tiple blades for more effective cutting, and another that could be folded into a compact shape for easy storage). Unfortunately, none of these designs were so revolutionary that it would take over the market and become the resounding success sought by the company's management.

At this point, one of the senior engineers suggested that they return to the original problem statement and rewrite it with a focus on function, as follows: Design an effective means of maintaining lawns.

The engineering design team then began to brainstorm2 new ideas for achieving this modified objective. In brainstorming, one seeks to generate as many ideas as possible in a relatively short time, without stopping to evaluate any of these ideas during the brainstorming session. The assumption is that if one can generate 50 ideas in two hours (for example), at least some of those ideas will be worth pursuing. A number of new approaches for maintaining lawns were suggested, including a chemical additive for lawns that would prevent grass from growing to heights greater than two inches.

One engineer then commented that he had been watching his three-year-old son playing with a yo-yo on the lawn. The child was joyful as he swung the yo-yo in a circu- lar horizontal arc above his head. The engineer suggested that perhaps a high-speed spinning cord could be used to cut grass. This idea led to the design of a breakthrough product that did indeed become extremely popular in the marketplace.

Can you guess what type of garden-care product was developed? Do not define the problem in terms of an existing product; otherwise, you may

simply generate variations of this product and fail to recognize a valuable new approach. Instead, focus upon those functions that are desired in a solution to the problem and formulate the problem statement in terms of these functions.

%

Formulating the Real Problem Engineering is an iterative process: One should be prepared to reconsider assumptions, decisions, and conclusions reached during the earlier stages of the design process if any new results indicate the need to do so. For example, the initial problem statement may be too vague, ill-conceived, or simply incorrect. One must determine the object of a search before beginning to search; an incorrect problem statement is very unlikely to lead to the opti- mal solution of a problem.

2. Brainstorming is a creative technique that is reviewed in Chapter 7.

Formulating the Real Problem 79

The Dangers of Misdirected Search A problem statement can be incorrect, leading to a misdirected search for solutions (as opposed to defining the problem in terms of a specific solution instead of a functional objective, thereby unwittingly limiting the search for solutions). For example, consider the following design anecdote.

Re-entry of Space Capsules

During the early days of the space program, it was understood that upon re-entry into the earth's atmosphere and due to frictional heating, the outside of a space capsule would rise to a temperature much higher than any known material could withstand. Thus, a research directive (i.e., a problem statement) was issued: Develop a material that is able to withstand the extremely high temperatures of re-entry.

When the Apollo moon landings occurred during the late 1960s and early 1970s, such heat-resistant materials had still not been developed. Yet our astronauts returned safely to earth! How could this be?

The answer is that the problem formulation eventually had been redirected towards the true objective, which was to protect the astronauts, not to develop a heat- resistant material.

This reformulation of the problem statement was the breakthrough step that led to the final solution. Researchers noted that some meteors reach the earth's surface without completely disintegrating. These meteors are not completely destroyed because their surfaces vaporize when they become molten, so that only some of their material is lost. Vaporization acts to cool a surface: This process is known as ablative cooling. Space capsules were then protected with heat-shielding material that vaporizes at high temperatures. The heat due to friction is thereby dissipated in the form of vapors.

Case History 3.1 The Tylenol Case also illustrates the hazards of misdirected search.

The problem statement is the most critical step in the engineering design process. Clearly, if you begin to journey to an incorrect site, you are very unlikely to correct your travel plans until you have arrived at the site and discovered your error.

We must strive to determine the real problem to be solved. In real-life engineering-as opposed to textbook problem solving-you may be asked to solve ill or incorrectly defined problems, you may be provided with insufficient or incorrect information, and you will be given a deadline for developing the "best" solution.

3 . Fogler and LeBlanc (1995).


How, then, does one determine the real problem to be solved? Numerous heuristics have been proposed for properly formulating a problem. (A heuristic is often described as a rule of thumb, which simply means that it is a systematic approach that seems promising because it led to success in the past. However, unlike a law of physics, it does not guarantee success because it has not been verified through numerous problem-solving efforts and trials.4) The engineering design process shown in Figure 1.1 is, in fact, a heuristic.

Some heuristics for accurate problem formulation are as follows.

The Statement-Restatement Technique The statement-restatement techniques has four objectives, as discussed below.6 One seeks to achieve these objectives by stating and restating the problem in different and innovative ways. The assumption is that by restating the problem in different forms, one will develop a deeper and more accurate understanding of the actual problem that needs to be solved.

1. Determine the real problem (in contrast to the stated problem). How would this be achieved? Fogler and LeBlanc (1995) recommend the use of various restatement triggers, such as:

Varying the emphasis placed on certain words and phrases in the problem statement. Next ask yourself if the focus of the problem itself has changed. If so, in what way? Is this a better focus? Substituting explicit definitions of certain terms in the problem statement for these terms. Does this result in a different and more precise statement? If so, in what way? Why? Changing positive terms to negatives and vice versa; for example, try to identify ways in which energy is being wasted in a plant rather than seeking ways to save energy. Has the focus of the problem statement changed? How? Why? Replacing persuasive and/or implied words in the problem statement (such as "obviously" and "clearly") with the reasoning behind the use of such words. Is this reasoning valid? What is the evidence for such reasoning? If the reasoning is invalid, should the problem statement be modified? In what way?

4. An example of a heuristic is the guideline used by Conrad Pile, a merchant in Tennessee's Wolf River Valley during the early 1800s. Pile reasoned that a customer was probably indus- trious-and thus a good credit risk-if he had patches on the front of his trousers, in contrast to someone with patches on the back of trousers (the assumption being that anyone with patches on the rear must be lying down much of the time). This simple rule of thumb helped Pile to become a successful merchant and trader (Lee 1985). 5. See Parnes (1967) and Fogler and LeBlanc (1995). - 6. We have modified the terminology used in the statement-restatement technique to be more consistent with engineering design problem solving.


Expressing words in graphical or mathematical form7 and vice versa. Has this improved your understanding of the problem to be solved? How? Why?

Table 3.1 illustrates the use of such triggers to generate seven solution paths that could be investigated.

2. Determine the actual constraints or boundaries (in contrast to the given or inferred boundaries). One way to achieve this objective is to relax any constraints that are contained within the problem statement. Design constraints usually should be quantitative rather than qualitative (e.g., "less than 100 lbs" as opposed to "lightweight"); however, both quantitative and qualitative boundaries can be relaxed. One can relax a quantitative boundary by simply adjusting the numbers (e.g, using "less than 200 lbs" in place of "less than 100 lbs"). Similarly, a qualitative boundary can be relaxed by simply replacing certain key words, (e.g., replacing the word "lightweight" with "not burdensome to move or lift").

After relaxing a constraint, ask yourself if the problem itself has been modified in a significant way. If not, then work within the more relaxed constraints. Sometimes engineers work within perceived problem boundaries that are imaginary, thereby limiting the solutions that can be considered and making the problem-solving task more difficult. If the problem has changed, determine the cause for this change. One relaxed constraint may have altered the entire problem focus.

3. Identify meaningful goals (in contrast to a set of given or inferred goals). Sometimes one defines a problem in terms of particular goals that must be achieved by any viable solution. In engineering design, these goals are qualitative (e.g., "minimum cost", "safety") as opposed to constraints that are usually quantitative ( e g , "less than $10,000"). (Design goals will be discussed more fully in Chapter 4.1 Are all the stated goals equally important? Usually, the answer to this question is no. Try to prioritize the goals and then focus upon the most critical ones as you rewrite the problem statement.

4. Identify relationships between inputs, outputs, and any unknowns. What is the desired output(s) or benefit(s) of the design? What are the inputs to the design (e.g., raw materials, people, equipment, money)? How will the inputs be transformed into the desired output(s)? What is unpredictable in the process? Why? What additional data needs to be collected?

Restate the problem after answering these questions. The problem statement should then include what is known, what is unknown, and what is sought in a solution.

7. Graphical and mathematical models are more fully discussed in Chapter 6.

1 82 Chapter 3 Structuring the Search for the Problem

T A B L E 3 . 1 Reformulating the problem via the statement-restatement technique.

Initial problem statement: Increase the number of commuters who use public transportation.

Varying the emphasis upon certain words and phrases Increase the number of commuters who use public transportation.

Possible solution path 1: Increase the number of customers by decreasing the price (sell monthly passes at reduced price?). Increase the number of commuters who use public transportation.

Possible solution path 2: Advertise the benefits (savings, safety, etc.) of public transportation Increase the number of commuters who use public transportation.

Possible solution path 3: Provide or reserve highway lanes for buses.

Substituting explicit definitions for key words Increase the number of people travelling to work each day who use trainshuses.

Possible solution path 4: Encourage employers to reward employees who use public transportation.

Possible solution path 5: Provide office areas (desks, computers, etc.) in trainslbuses for those who would like to work while commuting.

Changing positive terms to negatives and vice versa Reduce the number of commuters who use public transportation.

Possible solution path 6: Investigate the reasons for people failing to use public transportation (e.g., high costs, discomfort, inconvenience) and try to eliminate these negative factors or minimize their impact.

Replacing persuasive and/or implied words and investigating the underlying reasoning; expressing words in graphical or mathematical forming

The initial statement, Increase the number of commuters who use public transportation, assumes that such an increase obviously will be benefi- cial because the number of people using private transportation then will be reduced (i.e., this is the underlying reasoning for the problem statement). We might describe this situation in mathematical form as follows:

Public commuters + private commuters = constant (total) Thus, if we increase the number of people in one category, the num-

ber in the other group must also decrease. Possible solution path 7: The above reasoning may be faulty. For

example, new commuters may be entering the system each day, thereby adding to the total number. Perhaps instead we should try to reduce the total number of commuters (those who use both private and public modes of transportation), for example, by increasing the number of people who telecommute from home.


The statement-restatement technique assumes that one begins with a fuzzy or ambiguous formulation of the problem, which is very often the case. By focusing on the above objectives and activities, the initial problem statement can often be refined and corrected until one has a correctly formulated expression of the problem to be solved.

3.2.3 5% Determine the Source and the Cause This heuristic simply states that one should consider the source of the problem statement.8 Does or can that source (a person, a journal article, data) explain how the problem statement was developed? Furthermore, does the problem statement focus upon the cause of the problem or merely its symptoms? The engineer needs to focus upon the source or cause of the problem, just as a physician needs to treat the cause of an infection and not simply its symptoms.

Case History 3.2 Blowing in the Wind: Boston's Hancock Tower emphasizes the need to determine the true cause of an undesirable situation.

3.2.4 8k2 The Revision Method Often the engineer is not confronted with a totally new problem, but instead must improve an existing product. The manufacturer may have invested substantial amounts of human resources, money, and equipment to design, develop, manufacture, distribute, and promote this product. The product cannot be abandoned without losing all of this investment. In addition, the product may be a current marketing success but it is expected to face increased competition from similar products in the near future. (This is par- ticularly true if patent protection on the design is about to expire; see Chapter 5.) Hence, improvements in the design must be made. The revision method can be used when one is searching for a fresh perspective on this task or as a creativity technique for generating new ideas (see Chapter 7).

The method simply assumes that the focus of the design effort occasion- ally should revert to the product or solution (rather than the specific function to be achieved by the solution) i f one has exhausted all efforts in reformulating the problem or i f one needs to stimulate creative thinking in order to generate new design concepts. For example, the benefits of focusing upon function were discussed in the lawn mower design anecdote. However, if we were seeking specific ways to improve an existing lawn mower design, it might be wise to change the problem statement from Design an effective means of maintaining lawns to Design an effective means of maintaining lawn mowers, in which case we would now be searching for ways to minimize the lawn mower's maintenance and increase its durability. Such a focus might then lead us to identify the sources of damage to a lawn mower. For

8. See Fogler and LeBlanc (1995).


example, stones and rocks can cause damage to the blades and undercarriage of a mower. In order to overcome these hazards, an improved design might use a set of strategically placed rollers that would allow the mower to move vertically when traversing a rock, thereby limiting damage to the machine. By changing to a focus upon the product, additional needs of the customer (i.e., ease of use, minimum maintenance and repair costs, ease of storage) can be recognized and a revision of the existing design can be developed.

3.2.5 2% Present State and Desired State via Duncker Diagrams

Another strategy9 for properly formulating a problem is to specify the present or problem state (PS), and the desired state (DS) or the solution state of the process or system under development. The engineer then modifies either the PS statement, the DS statement, or both until there is a satisfactory correlation between the two. For example, a student currently enrolled in both an engineering design and a physics course might begin with the following statements:

PS: I need to study physics. DS: I want to earn an A in engineering design.

Unfortunately, the PS does not seem to have anything in common with the DS, in this example; that is, the PS appears to be irrelevant to the DS. However, upon reflection and reformulation, the student might rephrase these statements as follows:

PS: I need to study physics because I have an exam next week. DS: I want to earn an A in engineering design.

A gap remains between the two statements, so further revision is needed:

PS: I need to study physics because I have an exam next week, but the only extra time that I can devote to physics is already scheduled for my term project in engineering design.

DS: I want to earn acceptable grades in both engineering design and physics.

We now begin to see the relationship between the PS and the DS, but further refinement is still needed:

PS: I am not sufficiently prepared for my upcoming physics exam and I also need to work on my term project in engineering design.

DS: I want to earn acceptable grades on both my engineering design term project and my physics exam.

9. See Higgins, Maitland, Perkins, Richardson, and Piper (1989) and Fogler and LeBlanc (1995).


Finally, a direct and obvious correlation between the PS and the DS exists. The student may now decide to investigate possible solution paths leading from the PS to the DS, such as I must become more efficient; I will speak with m y professors, and seek tutoring help; I will decrease the number of hours each week that I spend watching television and devote this time to m y academic work; I will reformulate m y term project so that less time is needed to complete it. The student might also investigate some combination of these actions. (Of course, not all of these solution paths may be valid.)

Also notice that the final versions of the PS and DS statements match in terms of specificity (project, exam) and explicit requirements (acceptable grades).

Duncker Diagrams: General, Functional, and Specific Solutions Duncker dia- grams10 are a graphical tool that can be used to develop a set of matching PS and DS statements. These diagrams focus on developing solutions at three levels: general, functional, and specific.

General solutions are of two types: (1) those that require some action be taken in order to achieve the desired state, and (2) those that transform the DS until it matches the PS, thereby eliminating the need to achieve the original DS but perhaps necessitating some change in the PS in order to make it acceptable. Sometimes NO action whatsoever is taken because we discover that the present state is actually preferable to all alternative states: This is sometimes called the null solution.

Functional solutions are then generated without consideration given to feasibility; one simply considers any and all possibilities for solving the problem (i.e., these are "what if" solutions). Finally, these functional solutions are transformed (if possible) into specific solutions that are indeed fea- sible. Figure 3.1 presents an example of a Duncker diagram for the problem of public transportation used earlier in Table 3.1. (This type of diagram is similar to idea diagrams used to stimulate creative thinking and which we review in Chapter 7).

Consider another fictional situation in which Duncker diagramming might be he1pful:ll

When first marketed, Family-Comp computers were very popular for home use. Although admittedly offering only limited capabilities in such tasks as word processing and computation, these machines were very inexpensive.

However, sales began to decline and it was determined that the computers were becoming less popular as people realized that they had limited need

10. Duncker (1945). 11. This example is totally fictional; however, its structure is similar to one given by Fogler and LeBlanc (1995), which involves a breakfast cereal product.


Present state Desired state 1 Too many commuters use - - - - - - - - + Less traffic

private transportation t

Eliminate

commute access to times 0,

number of

ourage muters tagger

F l G U R E 3 . 1 Duncker diagram for public transportation problem.

for such a machine when performing most household chores. Management then decided that a new strategy needed to be devised if their Family-Comp computers were to regain their former popularity in the marketplace.

We might then ask: What are some strategies that could be considered? For every benefit there is usually a cost. For example, perhaps the computers would become more desirable if additional capabilities were added to each machine; however, this strategy would necessitate additional company investments in design and development, and it would increase the retail price of each computer. A second alternative would be to (once again) per- suade the customers that they need a Family-Comp computer for household tasks, perhaps through a massive promotional campaign emphasizing various unusual or new applications of the computer in the home. However, such an effort-even if imaginative-might not succeed. What, then, can be done to resolve this dilemma?


A Duncker diagram for this situation can be used to generate possible solution paths (Figure 3.2). Notice how this diagram links the three levels of solutions, together with the transformation from the present state to the desired state. It allows us to organize our thoughts and refine various solution paths. Each of the resulting specific solutions should then be carefully refined and evaluated.

3.2.6 Other Heuristics Some other heuristics or guidelines for problem formulation include:

Restate the problem and explain it to another person (not someone on the design team); this may lead to a deeper understanding or another perspective of the task(s) to be performed. Are there similar problems that have been solved? If so, how does your problem differ (if at all) from these other problems? Why? Could some other existing solution be used or adapted to solve your problem?

1 Present state 1 Desired state Income is dropping as I computer becomes 1 Increase income I

[ p q p k caoabilities hour

increasingly unpopular

I to machines 1 1 apph for rn:

'

tions capabilities is @ I advantageous 1

markets for unsold machines

F l G U R E 3 . 2 Duncker Diagram for fictional case study of Family-Comp computers.


The heuristics for problem formulation are similar to those used for model- ing (see Chapter 6). In both cases, we seek to clarify both the problem itself and our search for its possible solution(s).

Kepner-Tregoe Situation Analysis Charles Kepner and Benjamin Tregoe (1981) have developed a four-step problem-solving method that can be very effective for engineering design.12 These steps are as follows:

Situation analysis (SA) The most urgent or critical aspects of a situation are identified first. Kepner-Tregoe situation analysis allows us to view the problem from different perspectives and at varying levels of detail. It is useful in focusing our efforts to determine what we know, which task(s) should be performed, and in what order these tasks should be completed. Problem analysis (PA) The cause of the problem or subproblem must be determined (corresponding to a focus upon the past since we seek the preexisting cause of a current subproblem). Decision analysis (DA) The action(s) needed to correct the subproblem andlor eliminate its cause must be determined (a focus upon developing a correction to the subproblem in the present time). Potential problem analysis (PPA) The action(s) needed to prevent recurrences of the subproblem-andlor the development of new problems-must be determined (corresponding to a focus on the future).l?

In other words, we should seek the cause(s) of the subproblems, decide on the steps to follow in developing viable solutions, and anticipate any negative impact that may result from implementation of the final solution(s). In this chapter we will review Kepner-Tregoe situation analysis and problem analysis; in Chapter 10 we will examine decision analysis and potential problem analysis

See Case History 3.3 Apollo 13: Preventing a Tragedy for an example of how effective the Kepner-Tregoe method can be when it must be applied in an abbreviated form because of time constraints.

Situation Analysis In Kepner-Tregoe analysis, the various aspects of a situation are first evaluated through the use of three criteria: timing, trend, and impact. Timing simply means that one should determine the relative urgency of each aspect of a problem (i.e., which subproblem is most urgent and requires our immedi-

12. See Kepner and Tregoe (1981) and Fogler and LeBlanc (1995). 13. We discuss new problems that can result from a design solution in Chapter 9.

Kepner-Tregoe Situation Analysis 89

ate attention? Which are less urgent?). Trend is used to indicate the expected growth pattern of the subproblem: does the difficulty seem to be increasing or decreasing, and at what rate? Finally, impact refers to the expected negative consequences of the subproblem: How severe is the problem?

One of three values or rankings are then assigned to each subproblem for each of the above criteria; these rankings are H (high), M (moderate), and L (low).

The following multidimensional problem illustrates this first step in Kepner-Tregoe analysis.

The Water Tank Disaster

The following news story is based on the Nassau edition of Newsday, the Long Island, N.Y., newspaper (April 24, 1981) and OPLOW, American Water Works Association, vol. 7, no. 6, June 1981, p. 3.

Inadequate safety precautions and an accident inside an empty water tank caused the deaths of two workmen in New Jersey on April 23. At 4 P.M., a scaffold inside the tank collapsed and caused the two men painting the tank to fall to the bottom. Stranded there, they were overcome by paint fumes and eventually lost consciousness. John Bakalopoulos, 34, of Brooklyn, N.Y., and Leslie Salomon, 31, also of Brooklyn, were not wearing oxygen masks. The Suffolk County Water Authority's contract for the painting job specified that workmen wear "air hoods," masks connected to air compressors. The masks were available, but Bakalopoulos and Salomon had decided not to wear them because they were unwieldy. Instead, Bakalopoulos wore a thin gause mask designed to filter out dust and paint particles. Salomon wore no mask.

Peter Koustas, the safety man who was handling the compressor and paint feed outside the tank, asked a nearby resident to call firemen [sic] as soon as he realized the scaffold had collapsed. Then he rushed into the tank with no oxygen mask, and he, too, was overcome by the fumes and lost consciousness.

The men lay unconscious for hours as rescue efforts of more than 100 policemen, firemen, and volunteers were hampered by bad weather. Intense fog, rain, and high winds made climbing the tank difficult and restricted the use of machinery. Several men collapsed from fatigue.

Inside the tank, conditions were worse. Because of the heavy fumes, rescuers used only hand-held, battery-powered lights, fearing that sparks from electric lights might cause an explosion. Lt. Larry Viverito, 38, a Centereach, N.Y,. volunteer fireman, was overcome by fumes 65 ft (20 m) above the floor of the tank. Fellow rescuers had to pull him out.

Rescuer John Flynn, a veteran mountain climber, said he hoped he would never have to go through anything like that night again. For five hours he set up block-and- tackle pulleys, tied knots, adjusted straps on stretchers, and attached safety lines and double safety lines. The interior of the tank was as blindingly white as an Alpine blizzard--completely and nauseatingly disorienting. Fans that had been set up to pull fresh air into the tank caused deafening noise.


When Flynn first reached the tank floor, he stepped into the wet paint and began to slide toward the uncovered 4-ft (1.2 m) opening to the feeder pipe in the center of the floor. Flynn was able to stop sliding, but John Bakalopoulos wasn't as fortunate.

As rescuers watched helplessly, Bakalopoulos, still out of reach, stirred, rolled over, and in the slippery paint slid into the feeder pipe. He plunged 110 f i (34 m) to the bottom.

Bakalopoulos was dead on arrival at the University Hospital in Stony Brook, N.Y., Peter Koustas, rescued at 1 :45 A.M. and suffering from hypothermia, died the following morning when his heart failed and he could not be revived. Only Leslie Salomon survived. (Source: The above anecdote is reprinted with permission from M. Martin and R. Schinzinger, Ethics in Engineering 2nd. ed., New York: McGraw-Hill, 1989, pp. 11 6-1 18.)

There are many aspects of this problem that could be considered in a design evaluation if one seeks to prevent similar accidents. In fact, there are so many dimen- sions to this situation that it may be difficult to determine the most important subproblems on which to focus-or even to determine the "real" problem that needs to be solved. Kepner-Tregoe situation analysis may help, as shown in Table 3.2.

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 l 1 l l l l l l l l i

T A B L E 3 . 2 Kepner-Tregoe situation analysis of the water tank problem.

- - - -

Concerns Subconcerns Priorities Timina Trend lmoact

Painters 1. 2. 3. 4. 5. 6. 1. 2.

Rescuers

Scaifolding collapse Paint fumes Open feedpipe Air hoods not worn Lack of communication Inadequate training Limited access to tank Weather conditions a. Climbing hazardous b. Machinery limited c. Fatigue Paint Fumes a. Limited lighting b. Unconsciousness Other tank conditions a. Blinding b. Noise (fans) c. Open feeder pipe d. Slippery paint Traininglpreparedness

H = High level of concernlurgency; M = Moderate level of concernlurgency;


Although there may be additional concerns that could be identified (such as rescue expenses and the subsequent use of the water tank), let us assume that Table 3.2 includes the major elements of the problem. A review of the priorities given to each subconcern indicates that "paint fumes" received high levels of concern in all three categories (timing, trend, and impact) for both paint crew members and their rescuers. Therefore, we should initially focus on this most urgent aspect of the situation.

This first step in Kepner-Tregoe analysis further requires that we classify each aspect of a situation into one of three categories, corresponding to the next step (problem analysis, decision analysis, or potential problem analysis) to be performed in resolving the problem. In the case of the water tank problem, since we already know the cause of the paint fumes (the paint itself), Kepner-Tregoe problem analysis is unnecessary; we would move directly to decision analysis (see Chapter 10) and strive to eliminate the need for painting the tank.

E

3.3.2 2: Problem Analysis Kepner-Tregoe problem analysis seeks to distinguish between the following elements:

What is the problem (and what is it not?) When did the problem occur (and when did it not occur)? Where did the problem occur (and where did it not occur)? What is the extent of the problem (number, degree, etc.)?

T A B L E 3 . 3 Principal elements of Kepner-Tregoe problem analysis.

Cause Consideration Is Is not Distinction of distinction

identity What is the problem?

Location Where is problem found?

Timing When did problem occur?

Magnitude Not much? How many? How extensive?

What is NOT the problem?

Where is problem NOT found?

When did problem NOT occur?

How little? How localized?

What is different Why? between "is" and "is not"?

What is the Why? difference in locations?

What is different Why? in timings?

What distinguishes the Why? affected and nonaffected elements?


This approach seeks to ask the right questions in order to determine the cause of the problem or subproblem. It focuses upon identifying a problem's characteristics, timing, location, and magnitude. One is also expected to consider the negatives (e.g., what is not the problem, when did it not occur) since this may lead to the cause of the problem. Table 3.3 summarizes Kepner-Tregoe problem analysis.

Specific forms of the questions (What? Where? When? Who? How? Why?) can be asked during Kepner-Tregoe problem analysis and are sum- marized in Table 3.4.

T A B L E 3 . 4 Questions to ask during Kepner-Tregoe problem analysis. Source: Adapted and modifed from Fogler and LeBlanc, 1995.

Is Is not

What

When

Who

Where

Why

How

What is known? What was observed? What are the constraints? What is important? What are the goals/objectives? What can be expected?

When did the problem occur? When must solution be implemented? When did changes occur? When were instruments calibrated?

Who can provide more information? Who is the customer? Who performed (each) task? Who is source of information? Who is affected by problem?

Where did problem occur? Where are input sources located? Where is equipment located? Where are products shipped? Where is customer located?

Why is problem important? Why does solution work? Why is there a problem?

How is problem related to other problems?

How can a task be performed? How did problem develop?

What is NOT known? What was NOT observed? What are NOT constraints? What is NOT important? What are NOT goals? What is NOT expected?

When did the problem NOT occur? When is solution NOT needed? When did changes NOT occur? When were instruments NOT calibrated?

Who can NOT provide information? Who is NOT the customer? Who did NOT perform (each) task? Who is NOT source of information? Who is NOT affected by problem?

Where did problem NOT occur? Where are input sources NOT located? Where is equipment NOT located? Where are products NOT shipped? Where is customer NOT located?

Why is problem NOT important? Why does solution NOT work? Why is there NOT a problem?

How is problem NOT related to other problems?

How can a task NOT be performed? How did problem NOT develop?


As an example of Kepner-Tregoe problem analysis, consider the following anecdote.

The Airplane Rash

In 1980 some Eastern Airlines flight attendants aboard a new type of airplane began to develop a red rash that lasted for about 24 hours.14 The rash was limited to the attendants' arms, faces, and hands. Furthermore, it only appeared on routes that traveled over large bodies of water. In addition, only some--not all-attendants were affected on any given flight, but the same number of attendants contracted the rash on every flight.

When those flight attendants who had contracted the rash recovered and then flew on other (older) planes over the same water routes, no rashes appeared.

The attendents became anxious about this mysterious illness, and numerous physicians were asked to determine the cause of the problem-to no avail. In addition, the airplane cabins were examined by industrial hygienists, but again nothing was found to be amiss.

Given the above information, let's use Kepner-Tregoe problem analysis to determine the cause of the rash, constructing Table 3.5.

Based upon the above analysis, we conclude

that the source of the rash must be related to materials found only on the newer planes, that these new materials come in contact with the hands, arms, and face of some (but not all) flight attendants, and that such selective contact is related to crew procedures that only occur during flights over large bodies of water.

Such an analysis leads us to the actual cause of the rash: life vests or preservers. These water safety devices were made of new materials, were found only on the newer planes and were demonstrated by selected flight attendants on routes over bodies of water.

Kepner-Tregoe problem analysis can be useful in our efforts to determine the cause(s) of a problem. As noted earlier, we will return to Kepner-Tregoe analysis in Chapter 10. ia!

14. Fogler and LeBlanc (1995) and Chemtech, vol. 13, no. 11, (1983), p. 655.


I I I I I I I I I I I I I I I I I I I 1 1 1 1 1 1 1 1 1 1 1

T A B L E 3 . 5 Kepner-Tregoe problem analysis of the airplane rash.

Is not Distinction Possible cause

Other symptoms

Skin External contact

When Flights over water

Where New planes

Extent Some attendants

Face, arms, hands

Flights over land

Old planes

Other attendants

Other areas of body

Different crew Materials procedures

Materials, Materials, design design

Different crew Materials procedures

Exposed skin External contact

Formulation of a problem statement is a most critical step in an engineering design project since it will determine the direction in which the effort proceeds; the misformulation of a problem may result in a final design that is of little value or that may even be hazardous. Problem statements should focus upon the function(s) to be achieved by the desired design solutions. A number of techniques and strategies can be used to define the real problem to be solved; these include the statement-restatement technique, the source/cause approach, the revision method, and the present state-desired state (PS-DS) strategy via Duncker diagrams. Kepner-Tregoe situation analysis can be performed to evaluate various aspects of a situation in terms of three important criteria (timing, trend, and impact), thereby helping one to identify those issues that are most critical.

Problems 95

3.1 Apply one of the techniques for correctly defining a problem discussed in Section 3.2 to a problem of your choice. Present your results with clarity and identify any significant breakthroughs or corrections that were made as the result of applying the technique.

3.2 Apply one technique for correctly defining a problem to the following design problems: a. Space capsule b. Lawn mower c. Boston's John Hancock Tower (see Case History 3.2) (Do not use the same technique that was applied to the anecdotal problems in this chapter.)

3.3 Perform a literature search (books, journals, magazines, articles) and describe an example of engineering design in which a problem was initially defined incorrectly. (Hint: Investigate such references as When Technology Fails (edited by N. Schlager, 1994) and technical journals such as Chemtech.) What were the consequences of this misdefined problem statement?

3.4 Apply one or more of the techniques discussed in this chapter to correctly define the problem discovered in Problem 3.3. Show all work.

3.5 Apply Kepner-Tregoe situation analysis and problem analysis to a design case study selected by your instructor.

3.6 Select a problem (technical or nontechnical) of your choice and use the Kepner-Tregoe methods to analyze it. Present your results in tabular for- mats. (Include the source of the problem if it is taken from the literature.)

3.7 Toll booths on automotive turnpikes can result in a number of difficul- ties, such as unexpected delays, stress, unexpected lane changing and merging, accidents, and so forth. Apply Kepner-Tregoe situation analysis to determine the most critical issues associated with toll booths and their underlying causes. Present your results in tabular form.


C A S E H I S T O R Y 3.1 The Tylenol Case

Seven people were fatally poisoned in 1982 when they swallowed Tylenol cold remedy capsules that had been laced with ~~anide.15 This tragedy led to the widespread use of tamper-evident (TE) packaging for many products. Tamper-evident packaging allows the consumer to recognize if any tampering to the product has occurred. This packaging includes:

PVC shrink neckbands [plastic seals around the lip or cap of a container) 1 blister cards (plastic-coated cards that seal and display the product), and

drop rings (plastic rings around the neck of a bottle from which a strip is torn, leaving a ring that must be slide upward to unlock the cap. The drop ring design is an example of a child-resistant closure that is relatively easy for adults to open.)

Johnson & Johnson (the manufacturer of Tylenol) sought to develop pro- tective packaging that would make any tampering immediately evident to the consumer and thereby eliminate the potentially deadly consequences of such tampering. Their final package design included three different tamper- evident features. Johnson & Johnson felt confident that these features would protect their customers if every customer remained alert to any telltale signs of danger provided by the packaging.

In 1986 Johnson & Johnson discovered that they were wrong. A woman in New York died from cyanide poisoning after swallowing a Tylenol capsule. The company then realized that TE packaging was insufficient protection; the capsules themselves would need to become tamper-proof!

Note that the original problem-tampering with the packaging is not clearly evident to the consumer-was misformulated. The actual problem to be solved was prevent tampering with capsules. This failure to formulate the problem correctly then misdirected the search for a solution towards product packaging rather than the product itself.

However, there did not seem to be any way in which to completely prevent tampering with capsules. Confronted with this dilemma, Johnson & Johnson acted admirably in order to protect the public: They stopped man- ufacturing encapsulated products! Solid caplets, shaped like capsules but presumably tamper-proof, became the preferred form for such products.

15. Refer to such articles as "Tylenol Case Raises Questions About Capsules" (1986) and "T-E Packaging: Watchful Consumers Make It Work" (1993).

Additional Case Histories 97

Sadly, not all capsule products throughout the pharmaceutical industry were removed from the marketplace. In 1991 poisoned Sudafed capsules took the lives of two people in Washington.

C A S E H I ' S T O R Y 3.2 Blowing in the Wind: Boston's John HancockTower

Completed in 1972, the John Hancock Tower in Boston is 60 stories in height (790Afeet) with a steel-frame and covered with 4.5' x 11' floor-to-ceiling reflective panels of double-glazed glass. Although its architectural design was aesthetically pleasing, its structural design contained hidden flaws.16

Beginning in November 1972, the glass panels began to fall from the building's facade. Eventually so many of these nearly 500-pound panels had to be replaced with plywood sheets that the structure became known as the "Plywood Palace." The building remained unoccupied for four years until the source of the problem could be identified and corrected.

Wind tunnels tests were conducted on a model of the building and its environment while additional tests were run on the building itself. The tests indicated that the wind loads were higher near the lower portion of the structure than near the upper floors-exactly the opposite of the designers' expectations (the glass panels were thinner at the lower floors, reflecting these expectations).

Finally, the source of the failure was determined. Laboratory tests and inspection of some damaged panels at the tower revealed that the outer glass sheet or light usually cracked before the inner light (see Figure 3.3). Since the wind loading on any single panel should have been evenly distributed to the inner and outer lights, it seemed surprising that the outer sheets exhibited a greater tendency to crack first. Chips of glass in the lead solder provided the clue to the mystery: The solder connecting the reflective coating to the inside of the outer light and to the lead spacer was too rigid. As a result, the outer light in a panel received the brunt of the loads, causing it to crack. Eventually, all 10,344 panes of glass were replaced with single sheets of tempered glass.

16. See Ross (1984) and Levy and Salvadori (1992).


?m- Clear inner glass light ]I 11 llll- Clear outer glass light

Silver reflective coating

Solder connection

Continuous lead spacer

Continuous metal edge clip

A Kepner-Tregoe problem analysis

F l G U R E 3 . 3 Epoxy between the spacers and the outer window sheet was too strong, failing to allow distribution and damping of wind- induced vibrations. Source: Why Buildings Fall Down by Matthys Levy and Mario Salvadori, copyright O 1992 by Mathys Levy and Mario Salvadori. Reprinted by permission of W. W. Norton & Company, Inc.

might have generated Table 3.6, which would then have directed attention to the reflective coating and solder used on the outer lights.

I 1 1 1 1 l l r l l l l l l l l l l l l l l l l l l l 1 l l

T A B L E 3 . 6 Kepner-Tregoe problem analysis of the Hancock Tower's windows.

Is Is not Distinction Possible cause

What Shattered Other windows damage

When Outer lights All lights shatter first shatter

simultaneously

Where Lower floors Upper floors (mostly) (fewer instances)

Extent Complete loss Frame and other

Glass

Reflective coating on outer lights

Height, thinner lights at lower levels Glass

Materials, design Loading, materials (coating, solder, etc.) Distribution of wind loads

Materials


(a) Bending forward (b) Bending backward (c) Twisting clockwise (d) Twisting counterclockwise

Tuned dynamic dampers

F I G U R E 3 . 4 Mass damping system used in the John Hancock building. Source: From Ross (1 992)

The wind tests had uncovered another potentially more significant flaw in the building: Apparently it was too flexible along its longer edge.17 Two tuned dynamic dampers had been installed to offset the building's motions along its shorter dimension. Each damper consisted of a 300-ton lead mass connected with springs to the structure and riding on a thin layer of oil on the 58th floor of the building. As the tower moved in one direction or the other, the inertia of these huge masses resisted this motion, effectively damping the movement as shown in Figure 3.4. Unfortunately, the buidling's potential movement along its longer dimension had been under- estimated because the designers had failed to consider the P-delta effect in which the structure's weight adds to the effect of the wind, effectively increasing the bending motion in a given direction. Diagonal steel bracing weighing 1650 tons was added to the building in order to offset this possi- bly hazardous condition.

Although very costly and potentially hazardous, the building's flawed glass facade led to the discovery of a potentially more dangerous shortcoming. Sometimes the symptoms of one problem in a design will provide us with the opportunity to discover far more critical flaws.

17. Some structuralists felt that this additional concern was insignificant and unwarranted.


C A S E H I S T O R Y 3.3 Apollo 13: Preventing a Tragedy

Apollo 13 was 205,000 miles from the earth when the crew noticed a sud- den drop in the electrical voltage of Main B Buss, one of their two power- generating systems. They also heard a loud banging sound. The voltage then rose to normal. Even as Duty Commander John L. Swigert, Jr., reported these observations to NASA control in Houston, the voltage in the Main B system dropped to zero and the voltage in Main A began to fall.18

The astronauts were in deadly danger. Without power, Apollo 13 would become their tomb in space. The engineers in Houston, realizing that action would need to be taken immediately in order to prevent a tragedy, began to evaluate what was known (e.g., voltage drops, a loud noise) as they collected further information from the crew.

Then, only thirteen minutes after the first voltage drop, Commander Swigert reported that their number 2 cryogenic oxygen tank was reading empty and that the ship appeared to be venting gas into space. Moreover, the ship's other tank also was losing oxygen.

Using an abbreviated version of Kepner-Tregoe problem analysis, the Houston engineers quickly deduced that a rupture in the number 2 oxygen tank would explain all of the observed phenomena. A loud noise, such as that first heard by the astronauts, would accompany a rupture in the tank. Furthermore, the gas being vented into space could be the lost oxygen from the tank (as well as that from the damaged number 1 tank). Finally, since Apollo 13's power-generating systems depended upon oxygen in order to operate, a decrease in the oxygen supply would explain the observed loss of electrical power.

Once the situation was understood, appropriate actions could be taken to preserve the remaining oxygen and conserve electrical power, thereby allowing the crew of Apollo 13 to return safely to earth.

Eventually, the reason that the oxygen tank ruptured also was discovered. Prior to launch, a ground crew had connected a heater inside the number 2 oxygen tank to a 65-volt power supply (instead of Apollo 13's 28-volt supply), thereby fusing the heater's automatic cutoff switch to the ON posi- tion. When the astronauts then activated the heater, it remained on, eventually overheating the oxygen until the tank exploded into space.

Kepner-Tregoe analysis allows one to quickly evaluate a set of observations and identify the most likely underlying cause for a problem. As such, it is a trouble-shooting or diagnositc tool of significant value.

18. Refer to Kepner and Tregoe (1981).


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