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  • Users: PagoMitch
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  1. PagoMitch

    White Rust in HVAC Ductwork, again

    All, So last year I posted a question re: how to resolve white rust on interior sheet metal duct wall. That thread has been closed, but here is the link: https://www.eng-tips.com/threads/how-to-resolve-white-rust-issues-inside-ductwork.521755/#post-9014179 I recommended to the owner that the...
  2. PagoMitch

    NFPA 99 - Dedicated Exhaust for Med Gas Storage Room

    I am designing a couple small Med Gas Storage Rooms in a Hospital; (4) K cylinders each of N2 and CO2 (about 300 ft^3 each tank, 1200 ft^ 3 each room, 2400 ft^3 on this floor). These will be in separate rooms, although it is technically not required. NFPA 99 2018 requires 1-hr walls, with...
  3. PagoMitch

    Non- Refrigerated Body Storage Temperatures?

    All, Have an interesting HVAC project that is Morgue related. I have done a few full Morgues, with the required viewing areas, autopsy tables and body reefers. This is different. A facility on a remote island I am temporarily working at wants to increase their deceased body storage holding...
  4. PagoMitch

    Removal of rust inside improperly stored 6" steel piping

    Did a search and could not get an apropos result. I'm assisting a US based facility on an island, and a Contractor has had a half dozen nominal 20' sticks of S40 A53B 6" grooved piping sitting outside in his storage yard. For years. It is to be used in a chilled water distribution system (40F...
  5. PagoMitch

    How to resolve white rust issues inside ductwork?

    I am helping a client commission some medium sized (34,000 CFM) chilled water AHU's that were installed several years ago, but never started. This is in a hospital, on an island with lots of rain and high humidity. In cutting into a large (10 ft x 3ft) vertical SA plenum in order to get to some...
  6. PagoMitch

    CHW Closed Loop Piping Corrosion - How much is too much?

    All, We are designing some new construction projects at hospital which has had poor - if any, CHW closed loop piping treatment for the last 15 years. Long story. On a related note, we have been told that at some time in the past 10 years they hired a local Contractor to "acid flush" the loop...
  7. PagoMitch

    Sensible and Latent People Loads

    Doing some Hospital HVAC in the Tropics, on an island where much of the population are persons of size. ASHRAE lists values from 245S/105L for sitting, to 250S/250L for standing and walking. However, I cannot find any references - anywhere - of how these values are affected by persons of...
  8. PagoMitch

    Piping pressure ratings vs source tank pressures

    I have been designing hospital med gas and lab/commercial gases for decades. In few cases has the pressure rating of the gas piping (O2, N20, He, N2, Ar, etc) downstream of the tank(s) regulator been equal to or greater than the unregulated tank pressures. For instance, for Medical Grade O2, a...
  9. PagoMitch

    Installer credentials for medium+ pressure gases piping installations?

    Could anyone point me to a standard or certification for installers for specialized gases? NFPA 55 does a great job of calling out what needs to happen; but nothing even hinted at for qualifications of installers. NFPA 99 (covering Health Care Med Gases) specifies ASSE 6000 series installers...
  10. PagoMitch

    Simplified calculation for pressure drop for isothermal compressible gas flow

    Does such a thing exist for O2 at high pressure? Searched this site, and cannot find anything similar. I have tried several online calculators for same, with results that vary by an order of magnitude... from 22 psi to 322 psi. On the TLV website calculator (pretty detailed, and the unit...
  11. PagoMitch

    We have a hospital project where th

    We have a hospital project where the architect has changed our tanks from (2) 15,000 gallon tanks (22'H) to (1) 30,000 gallon tank (36'H). Due to other reasons, the available area has shrunk. The change has generated (2) problems which have me between a rock and a hard place. #2 diesel, in a...
  12. PagoMitch

    1000 psi O2 piping material

    Been awhile since I have been on the site... I have a client with a research related need for piped O2 at 1000 psi. Source is (16) 2000 psi O2 H series tanks. My usual domain is Hospitals, and this is way outside of that. I've researched some ASME docs - but cannot seem to find the applicable...
  13. PagoMitch

    Medical Air for outside air?

    Have an interesting problem and trying to think outside the box. Working in a hospital doing a replacement of about 100 old chilled water fan coils with new, but with the addition of hot water heat. These serve medical offices only, no patient rooms. They were installed 20-40 years ago and...
  14. PagoMitch

    Plant steam for direct humidification in Hospitals

    This has been covered in a couple other threads, but could not find what I was looking for. Carryover of amines and other boiler chemicals into the steam piping has pretty much (with some holdouts...) been acknowledged; that's by intent to protect equipment and piping. I assume this is a...
  15. PagoMitch

    Efficient chilled water piping insulation

    Hopefully someone from a tropical area can help here; have a real goofy problem. Currently doing some work in a hospital in the tropics. Chilled water supply temps are 42F, return is 57F. Needed the large delta t in order to use existing piping and still meet load requirements of 480 tons...
  16. PagoMitch

    HDPE or FRP jacket for pre-insulated buried steam piping

    Just designed a project with a couple thousand feet of small (2" through 6") buried steam and CD piping. I have specified pre-insulated FRP cased 10g steel piping for the buried lines. Considered using HDPE with all other pipe/insulation characteristics the same, (there is a lot of it out...
  17. PagoMitch

    UL Class 1 or 2 Filters?

    Doing some air handling unit work in a hospital. I am suggesting that the contractor use UL Class 1 filters, which (when clean) do NOT support combustion. Class 2 filters WILL support combustion. The contractor is of the opinion that once the filter loads up with lint, that it has lost the...
  18. PagoMitch

    HVAC corrosion in an air marine environment

    I originally posted this over in HVAC. but it was suggested that this might be a more applicapable forum. Corrosion between Cu tubes and Al fins is accellorated in coastal areas. Military HVAC units (on buildings) are usually specified with Cu/Cu tubes/fins for that reason. While I can find...
  19. PagoMitch

    quantifiable coastal atmosphere

    Corrosion between Cu tubes and Al fins is accellorated in coastal areas. Military HVAC units (on buildings) are usually specified with Cu/Cu tubes/fins for that reason. While I can find a reference (sort of) to air salinity (http://www.arl.noaa.gov/faq_ac18.php), I cannot find a reference...
  20. PagoMitch

    ultra low temp annealing?

    Have a friend building a motorcycle swingarm out of mild steel. Several welds, hammering into final shape, final fitment, then powdercoated and baked for 4 minutes at about 225C. The part comes out looking great... but deformed. See pic. How can this happen at such a low temp? I was taught...

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