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Blowdown effect

  • This arrangement has another advantage , when the valve is closing , the final steam blowing across the force setup high frictional resistance to closure of valve , this cause boiler pressure to fall below the blow off pressure before the valve closes.This is Blow down effect.
  • This causes considerable wastage of steam , the shaped valve seat causes the valve lid to pulsate and this drilling action enables the valve to close properly and sharply with very little blow down effect
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