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  • Users: MartinLe
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  1. MartinLe

    Frequency inverters and interference on the power supply side, sizing alternators

    I'm not an electrical engineer. Recently I learned that gas powered cogeneration plants (common on wastewater treatment sites) are poor replacement for a Diesel engine for an emergency power supply, and about another problem: Frequency inverters produce high frequency signals on the side of the...
  2. MartinLe

    Tesla "autopilot" disengages shortly before impact

    https://fortune.com/2022/06/10/elon-musk-tesla-nhtsa-investigation-traffic-safety-autonomous-fsd-fatal-probe/ "On Thursday, NHTSA said it had discovered in 16 separate instances when this occurred that Autopilot “aborted vehicle control less than one second prior to the first impact,”...
  3. MartinLe

    Primary sludge thickener - how big is the risk that the rabble rake gets stuck? Mitigation?

    The manufacturer of rabble rakes for static primary sludge thickeners has concerns that the rake might get stuck if it's not moving for a longer time (ay power failure). How likely is this actually? How thick does primary sludge get, when thickened statically? The circular thickeners in...
  4. MartinLe

    Large Fire at residential building in Essen Germany

    This week a residential building in Essen, Germany, caught fire: https://www.dw.com/en/germany-fire-rips-through-apartment-complex-in-essen/a-60852478 3 lightly injured, ~100 residents made it out unharmed. Fire broke out on a balcony, spread over whole facade The building was from 2016 or...
  5. MartinLe

    Are there problems with gap corrosion when using pipe couplings (Straub or other suppliers)

    I'm talking about pipe couplings like this: My concern is the gap between the pipe ends - 5m at small diameters, 5-10 at larger (starting at 57 mm). The general wisdom is that gabs and cracks in pipelines are at risk of corrosion. I'm concerend about this 5mm gap (not the coupling). As far as...
  6. MartinLe

    accounting for thermal expansion in this shape

    There's decent formulas and rules of the thumb about for using 90° bends to absorb thermal expansion in pipelines. How to account for this shape: The pipeline follows the parapet on the top of a series of vessels. the pipe is stainless steel, DN 250, to the left it's ~7m to a fixed point...
  7. MartinLe

    Shift from craftsmanshift towards engineering in manufacturing?

    I have a hunch: Until a few decades ago, engineers would do their design, then in many cases the foremen or other skilled crafts persons on the shop floor would figure out what jigs to build etc. to manufacture something efficiently. Anecdotally this is confirmed by stories from one of my...
  8. MartinLe

    Rubber or steel expansion joints in a sludge pipeline

    We will need expansion joints, to account for thermal expansion, in a pipeline DN150 carrying sewage sludge (between digester and HX). Looking at different expansion joints, I prefer rubber ones like these: https://elaflex.de/en/products-catalogue/section-4-rubber-expansion-joints#H*file~1562...
  9. MartinLe

    Degassing of high points in in sludge lines

    In a current project we will have high points in sludge pipelines from the anaerobic digester to the sludge HX. There's the question on how to get residual gas from these high points. There's space where we can safely vent this gas, the question is how to get the gas from the pipeline How much...
  10. MartinLe

    Question on microfluidic systems for mRNA Vaccine production

    I hope this is the right forum for this question! https://blogs.sciencemag.org/pipeline/archives/2021/02/02/myths-of-vaccine-manufacturing Apparently, in the production of mRNA vaccines the microfluidic components play a major part in encapsulating the mRNA in a stable lipid coat (the...
  11. MartinLe

    2 dead in Tesla accident "Noone wasdrivingthe car"

    https://www.click2houston.com/news/local/2021/04/18/2-men-dead-after-fiery-tesla-crash-in-spring-officials-say/ “no one was driving” the fully-electric 2019 Tesla when the accident happened. There was a person in the passenger seat of the front of the car and in the rear passenger seat of the...
  12. MartinLe

    Spargers for air lift anaerobic sludge digestion

    An anaerobic digester for PS and WAS in a WWTP, air-lift with sewage gas injection below the draft tube - are there better sparger designs than just an open pipe end? AFAIK air lift pumps are more efficient with smaller bubble sizes (to a point the higher pressure loss is offset by better...
  13. MartinLe

    Can you draw and export control functions in AutoCAD plant P&ID?

    This is a picture from the DIN ISO 62424 (equivalent to the IEC 62424): Now it would be really cool to be able to draw something like this, then export the data in way that you can copy into your control narrative (for each hexagon/control task), to add a bit of text and setpoints so the...
  14. MartinLe

    Cooling air for blower station on WWTP?

    At a wwtp, we will be installing a new cogeneration plant and adsorption chiller. Because adsorption chillers don't com in abritrary sizes, we may have 10 or 20 extra kW cooling power (in the form of cold water, ~ 5°C/15°C). Now the plant operator has the idea to cool the air inflow into the...
  15. MartinLe

    What should be in a reading list on failures, disasters and their prevention

    Beyond the specific codes etc. I work with in my field, what are essential readings on the above? I'm interested in the social aspects as well as in how to systematically think about the technical aspects. Reports of investigations into specific accidents may also be interesting. My own field...
  16. MartinLe

    I don't understand the position and function of this three-way mixer

    This is the situation: For clarity, this is a P&ID sketch of part of the same manifold: I don't understand the position of the three way mixer, as this would mix hot water into the return and serves no function to control the heat of the flow to the HX - it could limit flow to the HX but...
  17. MartinLe

    Is there an elegant way to satisfy two different air demands with one set of compressor?

    I need air for two applications. Application one is flushing filters: ~ 500 Nl/min 4 bar, dew point +3°C The other is operating small valves and the like: ~ 3 or 4 Nl/min 6.5 bar dew point -20°C Both need quality class 1 re. particulates and oil. Since the client does not want to deal with...
  18. MartinLe

    Emptying pressure pipe

    Three submersible pipes in paralell will feed a pipeline, lifting wastewater by about 7m and feeing into a tank (near the bottom). Sveveral instruments will be installed along the pipe, including a static mixer, flow meter, etc. I think it would be a good idea to be able to empty the pipe. The...
  19. MartinLe

    Why do forward osmosis membranes face less scaling?

    "Forward osmosis (FO) is an osmotic process that, like reverse osmosis (RO), uses a semi-permeable membrane to effect separation of water from dissolved solutes. The driving force for this separation is an osmotic pressure gradient, such that a "draw" solution of high concentration (relative to...
  20. MartinLe

    Time management when juggling several projects & planning

    I have two problems: I find it hard to make realisitc estimates how long something wil take me and I find it difficult to be productive when juggling several projects. I'm consultant engineer. Typically I have one or two construction sites and one project in a planning/design phase...

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