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  1. SDTH

    Cement Lining for Ductile Iron Pipes vs Carbon Steel Pipes

    Thank you, I would like to know if the reason is stated in any white paper, guide or similar publications.. The standards also don't provide any basis for the thickness. Probably derived from practice. I didn't see any details mentioned in DIPRA publications also. SDTH
  2. SDTH

    Cement Lining for Ductile Iron Pipes vs Carbon Steel Pipes

    Hello All, In AWWA Standards, the cement lining thickness specified for Carbon Steel Pipes is more than that specified for Ductile Iron Pipes (almost double). Can anyone explain why?.. Is it because the resistance to corrosion for Ductile Iron material is more than that of Carbon Steel ? SDTH
  3. SDTH

    CLTD Method Again

    Thank you all.. HAP is indeed good..i use the latest version too.. But how many of us know the calculations that go behind it...TRANSFER FUNCTIONS to be precise... Ofcourse why would we know?..it simply works perfect with the software.. Im just curious about the calculations. I found CLTD more...
  4. SDTH

    CLTD Method Again

    Thanks Kyrous, cdxx139 I have no idea why I'm obsessed behind CLTD - probably bcz I cant 'SEE' all those calculations behind HAP. I understand that CLTD table differ with type of wall and orientation and its tedious to develop all those tables. Let me share a thought. Feel free to correct me...
  5. SDTH

    CLTD Method Again

    thread403-426357 Dear All, I use HAP software for cooling load calculation. This is good for detailed design submissions. I was thinking to develop a simpler excel based cooling load calculation using CLTD method so that i can use it for Concept design stage. Has anyone scratched their brain...
  6. SDTH

    Heat Load Calculation CLTD method

    Hello All, I'm trying to develop and excel sheet for CLTD/CLF based heat load calculation.. I read an article which directed me to ASHRAE page for free software named CLTDTAB which would help obtain CLTD/CLF values for various types of walls..Temperature differences... Unfortunately I coudnt...
  7. SDTH

    Redundancy aspects for District Cooling system

    Hello all, Is there any international standard (ASHRAE/IDEA) OR any local regulatory authority which specifies to have redundancy for Chillers of District cooling plants? If so, how much is the % redundancy? If not, what is the standard industrial practice? Thanks in advance, SDTH
  8. SDTH

    Low Delta T

    Hello LowdeltaTsolver, Thanks for your response. I wasn't discussing about a running scenario. Just curious about how the Chiller responds when it receives chilled water at lower than the tuned temperature. Lets take the example of variable secondary, constant flow primary. The secondary keeps...
  9. SDTH

    Low Delta T

    Thanks moideen.. Little inch, I remember 2 C was a result of low delta T syndrome. When the air handler's and FCU's coil and 2 way valve doesn't extract heat as intended and 2 way valves are still open due to demand on air side being not met, the option is to keep running chiller and pump...
  10. SDTH

    Low Delta T

    Thanks Little inch and IRstuff, I think I got it. Ive seen chillers receiving water at 8 degree celcius and still delivering at the set 6 degree celcius. the compressor must have ramped down (VFD operated chillers) or the pre rotation vain on compressor suction must have closed as a part of part...
  11. SDTH

    Low Delta T

    Dear All, Can anyone explain to me what physically happens within a chiller when it receives water at a temperature lower than it is sized for. I have read many articles which explains the drop in efficiency with formulas. the chiller doesn't know formulas..Can anyone explain how the chiller...
  12. SDTH

    Lifting Station

    Hi little inch... Things have taken a new turn.. Client checked the proposal for providing an additional float switch(for pump dry run protection redundancy) along with the level transmitter; and guess what, Client omitted the level transmitter an has asked to use four independent float...
  13. SDTH

    Lifting Station

    Thanks little inch.. Redundancy for transmitter is a weak point.. But somehow the engineers who did the FEED design did not look into it. We are onboard as Detail Engineering consultant assigned by the Contractor who bid the project keeping one transmitter in mind. One transmitter costs USD...
  14. SDTH

    Lifting Station

    Thanks Littile inch.. We will workout the hydraulics. Meanwhile, I'm listing down few points. Please check if my understanding is correct... We kept 20 cm from high high alarm level to the lowest inlet pipe invert level– to allow some time for the alarm to sound and operator to come and take...
  15. SDTH

    Lifting Station

    Ok.. I may sound dumb.. We got the discharge line route surveyed... the pump infact pumps down hill with peaks in between... liquid level at pump suction centerline 126.83m...highest point level 131.58m... discharge point level..126.3m Shoudnt I consider static head as 131.58m - 126.83m. The...
  16. SDTH

    Lifting Station

    Thank you Littleinch, Well explained. I will work it out and share the final sketch... Regards, SDTH
  17. SDTH

    Lifting Station

    Thanks Ashtree.... We have limitations as it is a retrofit project.. the invert level of incoming pipe and sump base level is fixed as it is an existing lifting station. Will share a sketch once done.. Regards, SDTH
  18. SDTH

    Lifting Station

    Thank you Ashtree, The calculations wee done as what you suggested - 10 start/stop per hour, minimum submergence from pump vendor etc. The grey area is whether we have a specific standard or rule of thumb to follow while we set the levels (volume and there by heights) between pump stop and pump...
  19. SDTH

    Lifting Station

    Hi, I am involved in the design of a sewage lifting station. Could any one help me with the level setting? We have considered four levels (as per existing lifting stations) to be sensed by a level transmitter. The following are the levels - highest to lowest. 1. high level alarm (set below the...

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