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Revision as of 20:38, 8 October 2009

Client Comments on Report 1

We received your report, and we have some comments and questions. It seems like the most prominent identified opportunity for improvement for both consumer satisfaction and environmental implications is to reduce foam production. Please respond point by point to the items below. We are looking forward to seeing your ideas in Report 2.

• Executive Summary: Thank you for the clear summary. What are the “alternative processes” to which you are referring? Is all turbulence bad, or is a certain amount good? Many beers are supposed to have a certain about of head – would that happen under pure laminar flow? In my experience, once the initial foam in a keg is removed, the beer typically comes out well if not overpumped – should we be reducing all turbulence or just some?
• Stakeholder Needs: Good list – there may be some missing such as intuitive and mistake-proof. For example, I remember the first time I tapped a keg – the people who purchased the keg didn’t tap it because they couldn’t figure out how. I tried it and ended up spraying a little bit of beer because the tap was not fully tightened before actuating the arm. Also, users want fast service, ease of storage and carrying without loss or damage, etc. Cheap and durable are two different needs of the retailer/distributor, regardless of material, and they may also want standardization and the ability to identify when a tap needs maintenance or replacement. Try to be more comprehensive.
• Use: Good observations and documentation. Can you explain why beer sprays up when the tap is screwed in with the lever already down?
  • Sure, no problem, check our changes in this section.
• Assembly: Thank you for the clear diagram. Can you show how part 8/9 seals against the keg and how the air and beer orifices open into different chambers? A diagram would help.
• Mechanical Function: Good description. Use of part numbers will help identify parts with diagram – for example o-ring.
• Mechanical Analysis: You ask two interesting questions, but we are not sure that your analysis answers them.
  • You mention that your two analyses relate to the amount of foam dispensed. How do they relate to that? Is that statement based on some research and/or experiments? Or is that just intuition?
  • In your first analysis about the pressure increase in the keg, we think you have missed some of your assumptions, such as about imcompressibility. Also, your diagram is not a complete free body diagram and the labels don't seem to correspond to your notation. Please define all of your notation and check that it is consistent, especially the subscripts. Do state 1 and state 2 refer to different times? Please draw your control volume(s) in your free body diagram(s). Are you following the same mass of air through the system as it changes pressure and/or volume, or are you comparing the same volume which may contain different masses of air at different times?
  • You say that it takes "many pumps" to have enough pressure to pour beer, but in your presentation you mentioned that it was easy to accidentally pump too much. This seems contradictory so please explain.
  • In your second analysis regarding the Reynold's number, please provide a diagram of the location where you are calculating it and explain why you chose to calculate it at that location. Also, check whether you are calculating volume flow rates or mass flow rates, and check that the units match on both sides of your equations. Where did you get the equation that you use to relate flow rate to velocity?
• Bill of Materials: Good list. Why is the plunger disk labeled 2.1 – is it a separate part? Is there any reason why any of these components could not be made out of plastic to support inexpensive high volume manufacturing? Maybe there is an opportunity to sell under market prices and make the existing product obsolete? Any idea what production volume is like for these?
• DFMA: Good observations. Any further insight on why brass might be used for some components?
  • Extra research was done and the best reason we could think of was brass's ability to clean itself of bacteria.
• FMEA: Nice list. Since the tap sticks out of the keg somewhat awkwardly, what is likely to break first if someone leans against the tab or tries to force the keg into a vehicle without removing the tap? Do these ever fail in a way that causes beer to be lost?
• DFE: Interesting assessment and an interesting angle on the foam focus – there could be a marketing angle here. You say the product is recyclable, but what do you think actually happens to it at the end of its life? Could any design considerations make it more likely to actually get recycled? At what point(s) in the life cycle of the beer in the keg do you think the most foam might be created and discarded? Is the keg tap a significant factor with respect to overall beer foam issues, or perhaps the equipment that fills the kegs is more important?
• If any of your images, figures, or text were taken from another source, please be certain to provide proper attribution.