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  • Users: packdad
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  1. packdad

    Valve design question re: Pressure on bonnet

    Let's say you have a valve with a bonnet that bolts to the body. It's a gasketed connection with the gasket located within the bolt circle. When the pressure force on the bonnet is considered during valve design, do you assume design pressure only within the diameter of the gasket, or do you...
  2. packdad

    Is "heavy gauge" defined?

    Is there a definition for "heavy gauge" sheet steel? In other words, does a sheet need to be greater than some minimum thickness to be called heavy gauge? Or, as I now suspect, is this more of a subjective term?
  3. packdad

    Requirements for an N-Stamp?

    In order to have a Section III component N-stamped, does it require that both the design and fabrication be done by an N certificate holder (as opposed to just the fabrication)? That's been my understanding, but I've forgotten the basis. I'm off to go flip through the Code, but I thought I'd...
  4. packdad

    Relocating a chilled water expansion tank

    We have a chilled water system with a closed, pressurized expansion tank located near the mid-elevation of the system. We want to relocate the tank above the topmost elevation of the system so that it may be vented to atmosphere and not require air overpressure. The current tank ties into the...
  5. packdad

    Cross-Ref. Between Numbering Systems and Grades?

    Just curious if there exists some form of a cross-reference between the ASTM standard designations (eg, A693) and the UNS designations (eg, S174000)? Also, is there a cross-reference between the ASTM numbers and the various types of stainless steels (for example, a listing of all the ASTM...
  6. packdad

    National Board registration req'ts in N.C.

    I work at a nuclear plant in North Carolina. I am ordering some ASME Section III Class 3 check valves for a system that sprays cold water into the containment building under emergency conditions. The question has come up: Do these valves have to be registered with the National Board? I am...
  7. packdad

    Sulfur vs Peroxide-Cured EPDM

    I'm supposed to order new EPDM seats for some butterfly valves that are used for isolation in an HVAC system, and I'm told that peroxide-curing is preferrable to sulfur-curing. Why? It should be noted that we would like to minimize compression set in this application, and from what little...
  8. packdad

    Aluminum beer bottles

    According to our local newspaper, a brewery is marketing aluminum beer bottles. The following quote is from the original article: "The brewery has partnered with Alcoa, the world's largest aluminum maker, to produce aluminum bottles that keep beer colder for as much as 50 minutes longer than a...
  9. packdad

    Thermal (radial) expansion of a ring

    How do you calculate the radial thermal expansion (or contraction) of a ring? For example, if you had a spool piece that was not constrained in any way, and you applied heat, how would you calculate the new ID and OD? Is it as simple as the original ID or OD times the thermal coefficient times...
  10. packdad

    Use of Belzona inside pump casing

    We have a horizontal centrifual pump in a raw (lake) water system. We are apparently considering the use of a Belzona product to coat the inside of the pump casing to protect it from erosion/corrosion. Since this is a critical-application pump, should I be concerned about the Belzona coating...
  11. packdad

    Air entrainment / Vortice formation

    Imagine you have a pipe tee with the branch oriented vertically downward. The tee (which is connected to a piping network) is partially full of water, so that there is a water/gas interface directly above the branch connection. Now, imagine that you are drawing water down through the branch...
  12. packdad

    Condensation Resulting From Mixed Air Flows?

    Help! I haven't touched a psychrometric chart since college. Here's the question: If you have two air streams coming together and mixing such that condensation is produced, what does this look like on a psych chart? I remember that, when you have two air streams mixing (say, Stream 1 and...
  13. packdad

    Roughness value for rubber hose

    I see this question come up from time to time, but I don't think I've ever seen a definitive answer. I didn't find a good answer using the keyword search function. Anyone know what range of roughness values (or friction factors) to apply to rubber hose for the purpose of calculating flow...
  14. packdad

    Tolerances & Relief Valve Testing

    When you test a relief valve to verify its setpoint, do you count instrument accuracy and setpoint tolerance simultaneously? For example, if you (or the OEM) have relief valve with a rated setpoint tolerance of +/- 3%, and you measure inlet pressure with a gauge that is accurate to +/- 0.5%, do...
  15. packdad

    Question about saturated fluids...

    Say you have a container that holds saturated water at some pressure and temperature (the specific values don't matter). The bottom half of the container holds saturated liquid and the top half holds saturated vapor. If you punch a hole in the container, does the mass flow rate out of the...
  16. packdad

    Isolation valves allowed upstream of relief valves?

    ASME B&BVC, Section VIII, Appendix M (I think) allows full-area stop valves to be placed upstream of pressure vessel relief valves, provided that certain provisions are met, such as keeping the stop valve locked open and keeping a person at the valve at all times whenever it is shut. While...
  17. packdad

    Pressure vs. Time for air tank with a slow leak

    Is there a "standard" equation for pressure versus time for a vessel pressurized with air which has a slow leak? I'm sure it's exponential in nature, or, at least, "exponentialish". I've tried some basic stuff using ideal gas law, conservation of mass, and Bernoulli, and I...
  18. packdad

    Age Effects On Performance Curve

    In general, how would you expect age to affect the performance curve of a centrifugal pump? In order to perform bounding calculations which encompass future wear on a pump, I have typically assumed the curve to degrade a certain percent by head. In other words, for a given GPM value, I...
  19. packdad

    Speed Humps

    I was curious if there are standard design criteria for speed humps? If so, where can they be found? I ask the question because they recently installed speed humps in a neighborhood adjacent to ours, and I am convinced that they were constructed with too much of a peak. They are clearly more...
  20. packdad

    Looking for Nusselt relationship

    I was flipping through my old heat transfer text in search of a Nusselt relationship for forced flow along (ie, parallel to) the outside of a tube or cylinder. Most equations are for flow across (ie, perpendicular to) a tube. It occurs to me that the relationships for forced flow across a flat...

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