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  1. mrev23

    Head loss through air intake duct piping

    Include entrance/exit losses as the air speeds up / slows down to enter/exit your rectangular flow path. Hints here: https://www.engineeringtoolbox.com/minor-loss-air-ducts-fittings-d_208.html Suggest doing some searches related to entrance and exit losses.
  2. mrev23

    Questions regarding Fan Performance Curve

    AMCA knows what a fan curve that incorporates velocity pressure looks like: https://www.amca.org/educate/articles-and-technical-papers/amca-inmotion-articles/straightening-out-fan-curves.html Also from AMCA...
  3. mrev23

    Questions regarding Fan Performance Curve

    "fan curves are no good if they account for velocity pressure." No good for whom? It benefits the vendor to sell the higher number. Then a shortfall in performance can be blamed on the engineer because they didn't account for what the vendor actually advertised. Pump vendors routinely sell...
  4. mrev23

    Questions regarding Fan Performance Curve

    The OP was correct: the discharge velocity pressure matters in a technically correct reading of a fan curve. But the distinction is often ignored. There is a large amount of sloppiness in HVAC “engineering.” We get away with it because there are large uncertainties and safety factors. It is...
  5. mrev23

    Cooling tower bypass into the basin VS completely bypassing the tower

    What 'pros' are you claiming while trying "to convince someone that is unnecessary to bypass to the tower Basin?" Two 'cons' to completely bypassing the basin: 1. Water treatment chemicals in the basin will not be refreshed while it is bypassed. Depleted chemicals will be less effective in...
  6. mrev23

    Dry in Wyoming, need waterline help to water cattle

    What is the cost of this system? What would be the cost of hiring a professional to design it? Would the cost of having it designed for the particular situation be less than the cost of a few cattle dying if a design gleaned from 30+ posts on a free internet forum fails?
  7. mrev23

    Bell mouth inlets in return air plenums

    ...illustration in the link by Capliard shows a bell with constant radius of not less than 0.2 times the duct diameter for a round duct. For r = 0.2 * D, the inlet area is nearly twice the duct area. To achieve an area ratio of 2:1, the radius of the bell would be r = (sqrt(2) - 1) / 2 * D...
  8. mrev23

    Power equation vs Joule-Thompson effect vs Ideal gas law

    I am not sure this is true: "the Ideal gas law states that there should be a temperature drop after the obstruction." As I recall: Throttling (without heat transfer) is a constant-enthalpy process The enthalpy of an ideal gas is a function only of temperature. So I wouldn't expect any...
  9. mrev23

    Venting floor drains connected to sump

    Thank you, PEDARRIN2. I was skeptical of the engineer's recommendation. Taken to an extreme, one might claim that (with a large enough drain line) a single vent could suffice for a building of any size because the IPC places no limit on the length of a combination waste and vent. And even...
  10. mrev23

    Requirement of Insulation on Drainage piping Due to Condensate Drain

    Insulation isn't needed if you can count on the given values: Dew point temperature = 52.25 F Condensate drain temperature is 53.6 F But, as cautioned by EnergyProfessional, the dew point temperature in the ceiling void is not controlled and might climb above the condensate drain temperature...
  11. mrev23

    Venting floor drains connected to sump

    Hello, Please help regarding advice from someone with more venting experience than I have. I think a vent is needed for the most remote floor drain in the image below. The EOR says the vent on the sump pump is sufficient. This may be accurate if: 1) it can be treated as a "combination waste...
  12. mrev23

    Using 'minimum static deflection' to choose a vibration isolator from a manufacturer's catalog

    Which vibration isolator complies with a specification that requires a "minimum static deflection of 1 inch" (where the load imposed on the isolator is 300 pounds): Proposed by the contractor: An isolator with a rated deflection of 1 inch at a rated load of 500 pounds in the manufacturer’s...
  13. mrev23

    Determining the load on a pump vibration isolator

    Gregory: The supplier wants to include the weight of the pipe. I think that is a mistake. The pump supplier wants no pipe weight on their connections. No pipe weight can be transmitted to the connections if the flex connectors are doing their jobs. Artisi: The thrust force was my concern in...
  14. mrev23

    Determining the load on a pump vibration isolator

    ...So the water weight (due to only the discharge pipe) on the vibration isolators seems to be: (59.75 lb/ft) * (8 feet) = 478 lbs Is this correct? Or are the vibration isolators not subjected to the water-weight in the drop for some reason?
  15. mrev23

    Force on a suction diffuser support

    ...balanced everywhere except at the inlet, where the flex connection doesn’t transmit any vertical force. The inside area of the inlet is ~ pi / 4 * (10-in)^2 = 78 square inches. This suggests to me that the leg of the suction diffuser, and the spring isolators, are subjected to a load of 26...
  16. mrev23

    Tangential or coalescing air separator for hydronic system?

    ...40% of the free air --- 60% of the free air would remain. But that is after one pass. After the second pass, the remaining air would be (1 - 0.4) * (1 - 0.4) = 36% of what it was when the system was started. After the 10th pass, the remaining air would be (1 - 0.4) ^ 10 = 0.6% of what it...
  17. mrev23

    Lead-free chrome-plated brass ball valve

    Is the industry moving away from lead-free chrome-plated brass ball valves for domestic water systems? As there was some confusion during a conversation with one supplier, I am referring to the ball being chrome-plated, not the valve body. A Brand-X supplier said they stopped making them...
  18. mrev23

    Max length of vent from drip pan elbow

    The flow rate through the vent pipe is used to calculate value of V/V* for Chart II-1 in Appendix II of ASME B31.1. But Chart II-1 doesn't plot values of V/V* for values of f(L_max/D) greater than 1.0. The implication seems to be that if the value of f(L_max/D) is greater than 1.0, then the...
  19. mrev23

    Max length of vent from drip pan elbow

    ...steam. Ignoring the difference between nominal and actual pipe size, the maximum vent length for a 6” pipe and f(L_max/D) = 1 is: L_max = 1 / f * D = 1 / 0.013 * (6 / 12) = 38 feet. This suggests that if a 6” vent is longer than 38 feet, then we can’t use Chart II-1 to even begin a check...
  20. mrev23

    Centrifugal pumps: whether to use flange taps for pressure gauge connections

    When is it recommended, or not, to use the flange taps provided by a pump manufacturer for connecting pressure gauges? The detail at the link below shows one gauge connection to the flange tap on the suction side of the pump; the other is downstream of the flex connector on the discharge side...

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