Notes
Slide Show
Outline
1
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
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)
3
Mechanical Plugs
  • Primary Advantages:
      • Quick to install
      • Simple to install
      • Relatively low cost
      • Effective for lower pressures
  • Primary Disadvantages:
      • Failure, particularly with cycling
4
Why Plugs Fail (1)
Forces on a stuck mechanical plug
5
Why Plugs Fail (2)
Friction and normal force competition
6
Why Plugs Fail (3)
Friction and normal force competition
7
Why Plugs Fail (4)
Friction loses the competition
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.)
9
A different mechanical approach:
InstaPlug™
10
InstaPlug™
A non-wedge based plug
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
12
Simple positive process (1)
Create the plug and shrink it
13
Simple positive process (2)
Install into well prepared tube/tubesheet
14
Engineering and Design
  • NOT the simple analysis used for exposition here
  • Sophisticated Finite Element Analysis for
    • Deflection
    • Force
    • Stress/strain distribution
    • Thermal analysis
15
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 plugs for high pressures “lasts the lifetime”of the heat exchanger