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  • the acid shower
  • The packaging foam
  • The mixing blunder (a)
  • The mixing blunder (b)
  • thermo-flow control dilemma
  • pollution delusion -- security reality
  • kodak's disinterest
  • the dirt of site cleanup
  • mounting a compressor
  • the swelling ring
  • chemical signature

  • The Acid Shower
    A diluted nitric acid tank was positioned to feed a reactor through gravity flow. The fluid level was monitored through a float sensor. During routine operation the night shift manager was alerted by the technician to the fact that the acid tank is empty -- per the board indicator. The manager, a junior chemist, initiated an instrumentation test, which came out clear. He then concluded that the tank must indeed be empty, and went out to the plant to check it out. The tank was placed on a third floor of a steel structure, and it was equipped with a draining outlet close to its bottom. Mindlessly the chemist turned open the drainage, and instantly recoiled as a gush of acid flushed him. The acid poured all the way down the second and first floor. Since it was the night shift there were no people on the path of the acid, but the expensive instrumentation there was seriously damaged. The careless chemist was briefly hospitalized.

    It turned out that the old floater sprank a hole, was filled with fluid, and sank to the bottom of the tank, sending the erronous signal of an empty tank. The shift manager failed to conjecture this possibility. He also failed to regard the fact that the acid could not evaporate. If the tank has emptied, the acid must be somewhere! Lastly, the manager was not trained in basic precautions of how to position oneself when opening a drain valve.

    Design lesson: critical storage tanks should be equipped with two independent volume-meters, or with a visual lens for inspection.

    The Mixing Blunder (a)
    A veterinary pill was to be a mixture of seven ingredients. The chemist and the vet who developed the formula administered the ingredients separtely, and assumed it would be a simple engineering challenge to premix the components. Alas, it turned out that for the ingredient mix to be fluid it had to be heated to about 200F. However two of the ingredients were mutually reactive at that temperature. The engineers tried for several weeks to tinker with the mixing challenge, and failed. When they lowered the temperature to prevent a reaction, the viscosity climbed up, and the mixing became ineffective. The chemist tried to solve the difficulty his way by searching for a de-catalytic ingredient that would hinder the reaction. The working solution was not mentioned because it was too expensive... The only way to insure proper mixing was to mix the first six ingredients with the 7th one in a powder form.

    The Mixing Blunder (b)
    Mixtures of large organic molecules (especially those with polymeric tendencies) tend to be much more viscous then the premix fluids. Viscosity affects mixing efficiency and determines the shape of blender blades. This fact creates a big difference when a large number of such molecules must be mixed to a rigorous tolerance. It makes a huge difference which order to apply. The design of the mixing phase was anticipated as a 1 week work, it lasted six months...

    Lesson: mind your degrees of freedom when estimating design work!

    The Packaging Foam
    A group of chemists developed a nifty idea. Two organic chemicals sprayed together created a foam, which quickly dried out, and hardened. They reasoned that their invention would be useful in packaging of fragile cargo. The container box would be filled with that foam, and secure the fragile cargo against rough road handling. When the chemistry was perfected they deemed themselves to be done with the needed R&D. It turned out that to build an industrial grade device to insure the right proportions of the mixture, consistently is an expensive proposition. Also, for large boxes it took too long for the light ingredient to evaporate, and industrial shipper were too impatient. On the receiving end, the foam was washed away with warm water. Shippers were reluctant to apply. Over 2 million dollars in just the chemistry R&D were wasted because the R&D team did not attack first the expected "cost mines".

    Thermo-flow control dilemma
    Two feeding fluids had to be kept in relatively high temperature to facilitate their smooth flow. The mixture had to be cooled off to hinder an undesired side reaction. Alas, the desired reaction was exothermic and the mixture was easily tipping off to the unwanted side reaction. In a too low temperature the desired reaction was slowing down. Accordingly raising the reactor temperature created an escalated temperature increase, and reducing the reactor's temperature created a non-linear de-escalation of the temperature. In addition, when the side-reaction took over the feeding streams were cut down. The slower flow increased the temperature of the feed (the heat exchanger was unchanged), which in turn kept the side reaction cooking.

    The design team decided to engineer the control strategy over the production facility, and ended up wasting large amounts of the expensive materials on trying various strategies. It was extremely difficult to avoid unstable and oscilating control situation. They spent another small fortune contracting out the modeling of the system. Having never wrestled with trying to solve Navier-Stokes equations in a non-adiabatic situation, did not realize how impractical this is, even with numeric approximation. If the team had invested in a pilot they could have developed a working strategy without wasting large amounts of material. Control strategy scales up very well! In cases like the above where a strategy is a matter of trial and error, pilot is a must!

    pollution delusion -- security reality
    A chemistry research team has developed a pollution-reduction idea: placing an adsorption unit behind the radiator of vehicles. The sucked in air would deposit air-pollution particles on the specially engineered adsorption walls, and the air would come out cleaner. When the adsoprtion surface is saturated, it is replaced with a fresh one. According to compuation, if the unit was changed each time the car stops for gas, the adsorption would continue uninterrupted. It worked fine in the lab. When they went out with their idea, the engineers in the automotive firm have quickly calculated that even if all the cars in America were equipped with this gizmo, the effect on air pollution would have been negligible. In retrospect it looked so incredibly naive on the part of the chemists. The quantitative calculation was easy to make before the invested effort in engineering the adsoprtion surface. The chemists argued that they had no reliable data regarding miles-per-car per day, at which speed, and times how many cars are on the road in a particular time of the day. Alas, even a rough guess of these figures would have sifficed to indicate the futility of the idea. Lesson: perform a critical calculation even if you have pitiful little data to work from!

    But the story does not end here. Years after having shelving this pollution-delusion idea, it was resurrected. This time for a completely different application: Security. Selected cars are equipped with a classified version of this invention to adsorp air particles. If the car rides in a suspected neighborhood, and adsorps explosive particles, it becomes an important security asset. Lesson: don't kill your old ideas, however much embarrasmment they have earned you. Their day might come!

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