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  1. jistre

    central air on residential flat roof

    Mini-split. No ductwork and no roof penetrations.
  2. jistre

    Discharge Piping Diameter Reduction

    Also, that section applies to single devices.
  3. jistre

    Discharge Piping Diameter Reduction

    API 521, 7.2.2 ... "Each pressure-relief device that vents directly to the atmosphere should normally have an individual vent pipe sized for a relatively high exit velocity; however, the outlet piping should not be smaller than the pressure-relief-device outlet." ... From the language, it...
  4. jistre

    PSV Service Tags

    Good point, XL83NL. I did not consider that the vessel might be outside of the US. Star for you.
  5. jistre

    PSV Service Tags

    To be fair, those are the general requirements for marking, not specifically requirements for marking after service.
  6. jistre

    PSV Service Tags

    Sec VIII, Div. 1 of the ASME BPVC. Paragraph UG-129.
  7. jistre

    2012 October PE Exam

    I opened my letter standing right in the middle of the street because that's where I was when I saw that it had arrived. It didn't matter what was coming down the street, I wasn't going to wait any longer to find out the results. That whole process is pretty terrible, but it's all worth it when...
  8. jistre

    PSV Sizing for Fire Case - Relief Temp above Design Temp

    I believe it's because typical insulation is not a fire protective material. A plant fire can be very intense and the insulation isn't designed to protect against the heat and forces imparted by the fire. In addition, high pressure water or foam streams used to fight the fire may physically...
  9. jistre

    What are pipe "loops"?

    I used to work in the petrochem process industry. Those loops are definitely to allow the pipe to expand and contract thermally. By adding the loops at strategic locations, you can reduce the stress on the pipe and its supports/structure/etc. to prevent breakage.
  10. jistre

    PE Exam- Question about bringing Reference books

    About the only thing for the PE that they're going to check is the calculator. They WILL check to make sure that you have one of the approved models, and they WILL NOT allow you to take the exam if yours is verboten. Other than that, the rules for the PE are largely geared toward preventing...
  11. jistre

    low temp. psychrometric questions

    Thanks, guys. I'm checking out the Akron software. Only thing is that the enthalpy of the air at the summer design temperature reported by the Akron software is about 33% higher than the enthalpies reported by two other software packages, which agree with each other closely.
  12. jistre

    low temp. psychrometric questions

    Okay, the statistical nature of thermo makes the RH question make sense to me. Temperature is an average measure, so there have to be some molecules above freezing, even though the bulk temperature is below 32. Now that I have the nugget of information that lets my head accept dewpoints and...
  13. jistre

    low temp. psychrometric questions

    Clarification. My chart does not show RH lines below 0F, not 32F. Still, RH below the freezing point of water is confusing me.
  14. jistre

    low temp. psychrometric questions

    I'm trying to figure out what happens to psychrometry when air gets really cold. I'm trying to get a handle on the TR required to bring air down to -65, but I have two problems. One, the ASHRAE charts only go down to -40. Two, it makes no sense to me to talk of relative humidity once air gets...
  15. jistre

    Steam losses in process industry

    For what it's worth, I worked with an old salty engineer who had lots of fun phrases. One was, "You show me a plant with old steam traps, and I'll show you a plant that is leaking money." Again, FWIW, just the sayings of a very experienced engineer I used to work with.
  16. jistre

    Need suggestions for load calculations for ultra cold rooms

    Ahh, I hit 'post' too soon. I wanted to mention that I've looked around and found various "cold room" applications. However, these just calculate loads for product holding rooms (think large frozen food freezers), aren't suitable for my application, and really won't calculate down to -65F...
  17. jistre

    Need suggestions for load calculations for ultra cold rooms

    Hey guys, let's see if I can pick your brains. I have a project in a research facility that will have an ultra cold room serving as a research area that will be held at -65F. Yeah. I have various options in terms of refrigerants and heat sinks, and I'm trying evaluate them better, so I'm...
  18. jistre

    Expansion tank on glycol chiller system

    Ziggypump, Just wanted to note that in a steam boiler system, the boiler feedwater pumps must go upstream of the boilers and deliver water at system pressure. Downstream doesn't work because the boilers are producing vapor, not hot water. I think you were probably talking specifically about...
  19. jistre

    Design Process

    Can I plagarize my project specifications from The Bard himself? I. General A. Project Personnel 1. The first thing we do, let's kill all the lawyers. I know, I know what the meaning of that line really is, but taken out of context, it makes me fell all kinds of better.
  20. jistre

    what is best application for heating and cooling for resorts?

    Hmm. If you've never heard of a boiler or hydronic heating, my advice to you is to suggest to your employer that they bring someone on who knows what they're doing. If this is a large resort, misquoting the project can be extremely expensive for your company. Worse, if the job is let and...

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