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Akhilesh Gulati

Quality Insider

TRIZ for Product Improvement

Using functional analysis to create a better design

Published: Sunday, December 8, 2013 - 13:27

Editor’s note: This article continues the series exploring structured innovation using the TRIZ methodology, a problem-solving, analysis, and forecasting tool derived from studying patterns of invention found in global patent data.


Members of My Executive Council (MEC) had been learning about and working on applying TRIZ for almost a year. Although not proficient enough to classify themselves as experts, some were interested in learning advanced concepts, especially Josh. He had been active not only in looking for TRIZ opportunities but also in sharing examples with his customers and suppliers.

Recently, Josh visited one of his old sailing buddies and shared with the council the example of how TRIZ could be used to attach a company logo to a ship’s funnel. Although his buddy had kidded him at first when he heard the idea, he also challenged Josh to see if the same methodology could be used on a different problem. He reminded Josh of an earlier conversation they’d had. “Remember how we always wished the preheaters [heat exchangers] we had on ships could have been simpler?” he asked.

Josh had to test his memory muscles to recall:
• Temperature changes caused pipes to expand, which lead to leaks, especially at the cover-plate interface gasket.
• The pipe baffles, which were required to prevent pipe vibration and sagging, made it difficult to clean the pipe surfaces. The baffles were, however, useful for directing the flow of oil.

Could TRIZ be used to improve on that design?

Josh decided to share this issue at the council meeting. To help everyone understand what he was talking about, he passed out a couple of diagrams of heat exchangers (figures 1 and 2). He explained that a heat exchanger allows heat from a fluid (such as a liquid or a gas) to pass to a second fluid without the two fluids having to mix together or come into direct contact. On ships, this type of heat exchanger is used to preheat engine cooling water; heating steam flows through the set of metal tubes while water passes through the sealed shell that surrounds them.

Figure 1: Heat exchanger

Figure 2: Straight-tube heat exchanger

Heat exchangers are not unique to the marine industry, so if TRIZ methods could help redesign these preheaters, other industries could also benefit from the improvement.

Josh posed the challenge to the MEC group by stating the following contradictions:
• I want the hangars/baffles, and I don’t want the baffles.
• The endplate helps compensate for pipe length variation with temperature changes, but it creates additional complexity.

“Isn’t there something else within TRIZ that we could apply to improve this product?” Josh asked Henrietta. She thought this would be a good opportunity to introduce a more advanced TRIZ concept called “functional analysis” to them. Reviewing this example with the group would give them an overview of the concept.

“For any product or process to work, it typically requires many functions,” said Henrietta, adding that a product or process can be described in terms of its parts and respective functions. “An automobile, for example, is something that satisfies the function to transport people.

“A functional description of a process has three parts: a subject, a verb, and an object,” Henrietta continued. For the automobile, this is expressed as:

Car

Transports

People

(subject)

(action verb)

(object)

 

“To begin the process, start by completing the following three steps,” she explained, writing them on a whiteboard:
1. Identify the system components.
2. Provide descriptions of the relationships between each component and the complete system.
3. Collect information about the positive and negative aspects of these relationships using the form of what (subject) does what (verb) to what (object).

 

Using the heat exchanger as an example, she listed the main components of the system:
• Shell
• Tube sheet
• Pipes (to carry steam)
• End cover
• Incoming fluid to be heated (water, in this case)
• Baffles
• Outgoing fluid (hot water)

To describe the relationships and outcomes, she said that the basic functions could include the following: Pipes heat the water as it flows through the shell. The water comes out hot at the other end. Because the pipes expand with heat, they also tend to move the tube sheet, which is an undesirable function.

Describing another functional relationship within the heat exchanger system, you could also say: The shell transmits the water and also supports the compensator and holds the tube sheet. The pipes heat the water by carrying steam through them.

Additionally, there are some auxiliary functions of a heat exchanger that are useful to know to get the big picture of the system. These functions have been listed as subject performs some action on the object.

The MEC group listened to Henrietta politely but obviously perplexed.“You can see why I was hesitant to cover advanced tools at this meeting,” she said. However, the group insisted that she continue.

“People new to functional analysis find this part of the problem formulation quite unnatural and difficult,” she said. “The language is different from our everyday communications. However, the concept requires that we define the action appropriately to ensure that the subject either changes or preserves something about the object. It’s a time-consuming process because we need to ensure that all relevant inter-component relationships are systematically considered. Furthermore, we must determine whether these actions are beneficial or harmful so we can formulate a distinct problem to be solved. Effectively identifying all the negative functional relationships within a system will allow us to use TRIZ functional analysis successfully.”

Using a graphical representation sometimes makes it a bit easier to understand. When improving a product or system, the undesirable (i.e., harmful) effects must be determined. Henrietta asked the council members to recall the definition of an ideal final result, which is:

Benefit / (Cost + Harm)

She then stated it a bit differently: “A does something to B. If it is harmful, let’s get rid of it. If it is useful, determine whether it is OK as is, or whether it needs to be improved. This helps us understand a complicated situation and focus on exactly what needs to be improved.”

Recognizing that the user of the product (in this case, the marine engineer) is generally more interested in the product’s function (heating the water) than the product itself (the heat exchanger), it follows that if it is possible to achieve this function without certain components of the system, the overall system will benefit. This benefit usually takes the form of a lower cost of production or operation.

This idea of improving the system by preserving the function while removing components is one of the product evolution trends known as “trimming.” In TRIZ terms, this means that the ideal final result would be that the system performs the function without the presence of the product or component with the harmful effect.

After conducting a complete functional analysis and identifying individual problems in terms of their effect on the overall system, the problems would need to be ranked and prioritized. This is an iterative process that continues until all combinations are evaluated. In the heat exchanger example, analysis might indicate that trimming first the end cover and then the baffles would be most beneficial to the overall system. Then you could look at how to prevent the tube-sheet motion inside the shell if the end cover is eliminated, and then, how to prevent the pipe vibration if the baffles are eliminated.

One solution is shown by a u-tube heat-exchanger (figure 3). Josh passed around another diagram to illustrate this. This type of heat exchanger uses u- shaped tubes instead of straight tubes, and the shell is formed as a closed-end cylinder. This gives tubes the freedom to expand freely at the curved end. The complete tube assembly can be pulled out for ease of cleaning. This trimming of the end cover has thus eliminated a couple of the harmful effects while retaining the benefits of the original design. And because the whole tube assembly is removed for cleaning, the baffles are not much of a hindrance during that process.

Figure 3: U-tube heat exchanger

This was an example of how functional analysis was used to understand the beneficial and harmful interactions of a heat-exchange system, and how trimming was used to find a better solution. Henrietta concluded the session by thanking Josh for creating a situation that forced the group to learn a new tool of TRIZ.

Discuss

About The Author

Akhilesh Gulati’s picture

Akhilesh Gulati

Akhilesh Gulati has 25 years of experience in operational excellence, process redesign, lean, Six Sigma, strategic planning, and TRIZ (structured innovation) training and consulting in a variety of industries. Gulati is the Principal consultant at PIVOT Management Consultants and the CEO of the analytics firm Pivot Adapt Inc. in S. California. Akhilesh holds an MS from the University of Michigan, Ann Arbor, and MBA from UCLA, is a Six Sigma Master Black Belt and a Balanced Scorecard Professional.