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Water, Water Everywhere....

Water, Water Everywhere. Colorado Boxed Beef Corporation Auburndale, Florida. Wednesday, October 17, 2000. THE FIRST FOOLS OF FOOD IRRADIATION. Tell Colorado Boxed Beef that they should stay out of the irradiated meat business……. Water, Water Everywhere.

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Water, Water Everywhere....

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  1. Water, Water Everywhere.... Colorado Boxed Beef Corporation Auburndale, Florida Wednesday, October 17, 2000 THE FIRST FOOLS OF FOOD IRRADIATION Tell Colorado Boxed Beef that they should stay out of the irradiated meat business……

  2. Water, Water Everywhere.... Fire sprinkler water distribution system, installed by Brown Automatic Sprinklers, failed on 8/6/98, about a year after installation

  3. failure site corresponds to: Water, Water Everywhere.... • maximum bending moment for coupled pipe • first exposed thread root

  4. rust pattern Water, Water Everywhere.... Photograph of fractured end showing a helical rust pattern on inside pipe wall which coincides with thread root on pipe exterior

  5. Water, Water Everywhere.... Photograph showing cross-section of fractured 1.5” pipe.

  6. note wall thickness beneath thread root Water, Water Everywhere.... Photograph showing fracture surface of pipe section which separated from coupling. Note that fracture follows path of a single continuous thread root.

  7. Water, Water Everywhere.... Vertical perspective of 1.5” pipe section showing features used in ANSI standard pipe thread analysis. OD h DE2

  8. Water, Water Everywhere.... Pipe supplied by Allied Tube and Conduit Harvey, Illinois http://www.alliedtube.com/html/fire.htm

  9. Water, Water Everywhere.... per Wiley Engineer’s Desk Reference • 12 foot on center standard hanger spacing [per NFPA] • W[H2O filled] = 2.71 #/ft • Mmax = 2.71*(122)*12/12 = 390 in-lbs

  10. http://www.alliedtube.com/html/fire.htm From specifications for Dyna-Flow pipe, NPS 1.5”, wall thickness = [OD-ID]/2 = 0.0810”

  11. Water, Water Everywhere.... …and now, the “moment” of truth…… • for tubular cross section, I moment of inertia= p(ro4-ri4)/4, • I/ym = section modulus = p(ro4-ri4)/4ro • for thin wall tubing, • ro ~ ri = r, (ro4-ri4) = (ro-ri)(ro+ri)(ro2-ri2) = t(2r)(2r2) = 4r3t • I/ym ~ pr2t = p(0.950)2(0.081) = 0.230 in3 for our Dyna-Flow pipe • a tensile stress of 390/0.230 = 1700 lbs/in2 is introduced into the top surfaces of the pipe at the support points

  12. Why Dyna-Flow???

  13. Designation: A795-90

  14. Standard Specification for Black and Hot-Dipped Zinc-Coated (Galvanized) Welded and Seamless Steel Pipe for Fire Protection Use According to ASTM A795-90…. • Composition similar to that for A36 steel – st = 58,000 lbs/in2 • Appears to be about a safety factor of about 34 [36000/1700], when comparing applied tensile stress to material strength

  15. another factor to consider: With a 15 foot suspended length, Mmax goes to ~619 in-lbs and the safety factor drops to about 21.5. Dyna-Flow, properly installed, should not have failed.

  16. Standard Specification for Black and Hot-Dipped Zinc-Coated (Galvanized) Welded and Seamless Steel Pipe for Fire Protection Use consequences of threading the pipe sections for joining

  17. ANSI/ASME B.1.20.1 – Pipe Threads, General Purpose E2 = pitch diameter [distance between pitch lines] at full engagement [wrench tight] of coupling

  18. ANSI/ASME B.1.20.1 – Pipe Threads, General Purpose • height of thread, h, = vertical distance from root to crest of thread • for 1.5” NPS, h = 0.06957”

  19. ANSI/ASME B.1.20.1 – Pipe Threads, General Purpose • for 1.5” NPS, distance across pitch diameter [E2] = 1.84130” • diameter at first exposed thread root [DE2] = E2 – h • DE2 = 1.84130 – 0.06957 = 1.77173”

  20. Water, Water Everywhere.... a few more calculations….. • Taking manufacturer’s ID specification, ID = 1.728” • Wall thickness, t*, at first exposed thread = [DE2 – ID]/2 • t* = 0.022 in • I/ym = pd2t/4 = p(1.77173)2(0.022)/4 = 0.054 in3 • s = 390/0.054 = 7200 lbs/in2 • Safety Factor, S, = st/sappl = 58000/7200 = 8.0 • Safety Factor down [from 21.5], but pipe should not have failed

  21. Water, Water Everywhere.... sL One more thing – the water pressure inside the pipe… • For an internal water pressure of p = 100 lbs/in2: • sL = pr/2t* = [100*(1.728/2)]/[2*0.022] • sL = 1960 lbs/in2 • our Safety Factor has taken yet another hit • sappl = 7200+1960 = 9160 lbs/in2 • Safety Factor = 35,000/9160 = 3.9 • pipe should not have failed [and it didn’t, not immediately, that is…..

  22. Water, Water Everywhere.... Stress Concentration Factor, K • Effect of cut pipe threads: • d = h = 0.06957, r ~ 0.05 • b = DE2 = 1.77 • a K of 2-3 would not be unusual • Would only contribute to failure under rapid load conditions… • Safety Factor would probably still cover it, but we’re getting close….

  23. Steel Sprinkler Pipe, Subject 852 and then there is UL’s CRR [Corrosion Resistance Ratio] • Compares thicknesses of any scheduled pipe to the thickness of a schedule 40 pipe…. well, thickness3, that is • CRR = tsch-x3/t403 • CRR of plain Dyna-Flow = 0.0813/0.1453 = 0.174 • CRR of threaded Dyna-Flow = 0.0223/0.1453 = 0.0035 • a decrease of 98%!!! You might want to consider whether CRR is a proper basis for comparison between CPRs for materials having different wall thicknesses. We do have a quiz coming up…..

  24. Standard Specification for Black and Hot-Dipped Zinc-Coated (Galvanized) Welded and Seamless Steel Pipe for Fire Protection Use Then there’s the question of why Dyna-Flow should never have been threaded taking the worst possible case,… • ODmax = ODnom + 1/64” • tmin = 0.875*tnom

  25. Recalculating the wall thickness at the first exposed thread using worst case scenario….. • ODmax = 1.900 + 1/64 = 1.915625” • tmin = 0.875*0.081 = 0.070875” • IDmax = ODmax – 2*tmin = 1.773875” • DE2 = 1.77173” • t* = [DE2-ID]/2 = [1.77173-1.773875]/2 = -0.0011”!!!

  26. Published on July 10, 2001, Bradenton Herald, The (FL) BLAKE HOSPITAL SUES OVER DAMAGE The parent company of Blake Medical Center is suing to recover nearly $4 million allegedly lost as a result of a construction-related incident in 1998 that left parts of the Bradenton hospital soaking wet. Crews with R.W. Construction Co. and Riverview-based Brown Automatic Sprinklers Inc. were at the hospital Dec. 28 to remodel an existing waiting room into a cardiac treatment room. In the course of their work, workers failed to check a water pressure gauge on a fire sprinkler line before

  27. and so this story ends…….

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