Talk:Keg tap

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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?
    • The alternative manufacturing processes include metal injection molding (high volume production), and casting. While all turbulence is not bad (like you mentioned, certain beers do require some head), we intend to make the flow as laminar as possible. The reasoning behind this is the amount of foam can be adjusted by the pouring method; if a beer is supposed to have some foam, the user can hold the nozzle away from the cup instead of letting the beer flow down its side. A further explanation has been added to the Executive Summary.
  • 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.
    • After performing market research, the stakeholder needs became much clearer. The survey results in particular demonstrate that many issues arise from misuse or not knowing how to tap the keg. We have updated the lists to include more specific consumer desires.
  • Use: Good observations and documentation. Can you explain why beer sprays up when the tap is screwed in with the lever already down?
    • An explanation has been added to the usage 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.
    • A cross sectional illustration of the center cylinder has been added for clarification.
  • Mechanical Function: Good description. Use of part numbers will help identify parts with diagram – for example o-ring.
    • Part numbers have been added to the description.
  • 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?
      • See section for further explanation.
    • 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?
      • Issues fixed.
    • 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.
      • See section for clarification.
    • 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?
      • Reynold's number was calculated halfway through the tube. This location was chosen because this tells us if the flow is turbulent immediately before it is dispensed. See section for revisions to calculations.
  • 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?
    • The plunger disk is labeled as 2.1 because we could not separate it from the plunger without breaking the tap, so we are treating the parts as a sub-assembly. Some of the components could be made of plastic, but this would significantly decrease the durability of the product, which would be an issue for beer distributors who rent taps with kegs and need them to be returned in one piece. However, if a plastic tap was significantly cheaper, distributors might opt to buy them in bulk, then charge the consumer a flat price and not require them to be returned. Further discussion has been added in the DFMA section
  • DFMA: Good observations. Any further insight on why brass might be used for some components?
    • With some additional research, we found that brass may be used for certain parts because of its antimicrobial properties.
  • 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?
    • Failure Mode of plunger added to chart (will not cause loss of beer).
  • 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?
    • Recycling issues have been added to End of Life section.
    • To answer your question directly regarding foam creation, the main source of foam is the movement during transportation. A lot of foam is also created by over-pumping the tap, so the tap itself does play a role in overall foam issues. Foam is mostly discarded during use.
  • If any of your images, figures, or text were taken from another source, please be certain to provide proper attribution.
    • References added.
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