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B Question about pressure cooker "jiggler weights"

  1. Jun 4, 2016 #1
    Old style pressure cookers regulated pressure by having a vent tube in the lid with a weighted stopper that sits atop it, known as a jiggle or jiggler weight. The jiggler weight seals the vent tube until enough pressure builds to move the weight, which releases pressure until the weight falls back into a sealing position. Some of them included multiple jiggler weights, such as one for 5, 10, and 15 PSI regulation. The lighter the weight, the lower the PSI regulation.

    My question is: what is the relationship between weight and pressure? Is it a simple linear relationship, i.e., twice the weight = twice the pressure required to move the weight? For example, if a 1.5 oz. jiggler weight regulates the pressure at 5 PSI, how heavy would it have to be to regulate the pressure at 10 and 15 PSI?
     
  2. jcsd
  3. Jun 4, 2016 #2

    CWatters

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    Yes. Pressure = Force / area

    Force is provided by the weight and area is the area of the vent tube.

    1.5oz = 5 PSI
    3oz = 10 PSI
    4.5oz = 15 PSI

    However there should be a safety valve somewhere in case too much weigh is applied or the weight becomes jammed in the vent tube. If there isn't a safety valve don't use it!
     
  4. Jun 4, 2016 #3
    If you are thinking about pressure and what steam temperature you might have, don't forget that you are talking gauge pressure, not absolute pressure. With no weight the pressure is atmospheric (14.69 psi at sea level) and if you double the weight from 1.5 to 3, the pressure increases from 19.69 psia to 24.69 psia. For safety, gauge pressure is the right stuff. For cooking and temperature control, absolute pressure is the right stuff.
     
  5. Jun 4, 2016 #4
    Thanks for the helpful replies and the advice.
     
  6. Aug 23, 2017 #5
    Do things take longer to cook if you use a 1.5 oz jiggler compared to using a 3 oz one?, same size pot.
     
  7. Aug 24, 2017 #6

    jbriggs444

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    Yes. The temperature of boiling water at the lower pressure is lower and that at the higher pressure is higher.
     
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