Insta-Plug New low-pressure Feedwater heater and condenser tube plug Not to leak or fall out for the...

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Transcript of Insta-Plug New low-pressure Feedwater heater and condenser tube plug Not to leak or fall out for the...

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Insta-Plug New low-pressure Feedwater heater and condenser tube plug Not to leak or fall out for the life of the exchanger American Power Systems Dan Bina Hollaender Enterprises, Inc. Roger Adelman Slide 2 Plugging tubes: A problem with many solutions Metallurgical Plugs Metallurgical bonding mechanisms: Welded, brazed, soldered Explosive (kinetic) Mechanical Plugs Friction/interference mechanisms: Tapered cylinders Tapered cylinder in mating sleeve Taper around a cylinder (Screws/Compressors) Slide 3 Mechanical Plugs Primary Advantages: Quick to install Simple to install Relatively low cost Effective for lower pressures Primary Disadvantages: Failure, particularly with cycling Slide 4 Why Plugs Fail (1) Forces on a stuck mechanical plug F f1 = N 1 N1N1 2 F f = N 2 N2N2 Blowout Alternative Blowout Slide 5 Why Plugs Fail (2) Friction and normal force competition F f1 = N 1 N1N1 2 F f = N 2 N2N2 Blowout Alternative Blowout Slide 6 Why Plugs Fail (3) Friction and normal force competition F f1 = N 1 N1N1 N1N1 1. As installed2. Possible In use Slide 7 Why Plugs Fail (4) Friction loses the competition F f = N N N x >F fx, even the slightest amount and plug slips F fx NxNx NyNy F fy Slide 8 Why Plugs Fail (4) How can that happen? Differential behavior of tube and plug Changes in coefficient of friction Mechanical dynamics Infiltration of intermediate material Other (micro cracking, etc.) IT IS A FAIL UNSAFE CONDITION: Once it begins it tends to continue to loosen Slide 9 A different mechanical approach: InstaPlug Slide 10 InstaPlug A non-wedge based plug unique one-piece shape + a material with very special properties Slide 11 NiTiNol or Memory Metal Nickel/Titanium alloy Exists in two allotropic forms (atomic structures) Martensite (at lower temperatures) Austenite (at higher temperatures) Special processing gives two important properties Ability to remember a first shape after being in second Superelasticity almost six times normal metals Inert enough to be widely used in medical implants Retains large elastic energy when press-fit Slide 12 Simple positive process (1) Create the plug and shrink it As machined d+~0.004 Reduced diameter for installation Heat treatment Slide 13 Simple positive process (2) Install into well prepared tube/tubesheet a.Place in clean tube end b.Heat to restore memorized interference fit Slide 14 Insta-Plug common sizes Slide 15 Engineering and Design NOT the simple analysis used for exposition here Sophisticated Finite Element Analysis for Deflection Force Stress/strain distribution Thermal analysis Slide 16 Conclusion We believe that we now have cost effective, and reliable means in the Insta-Plug that will : not fail in service regardless of the cycling conditions provide for installation that is fast, safe and simple be cost competitive with other mechanical plugs account for real world service demands e.g. thermal cycling We intend that Insta-Plug, like our experience with explosive welded plugs for high pressure feedwater heaters, will last the lifetime of the heat exchanger.