Hood and Pocket Ventilation System

Hood and Pocket Ventilation SYstemHood and Pocket Ventilation System

A well designed high efficiency closed hood is in fact much more than an enclosure over the dryer section. Together with the pocket ventilation system and heat recovery unit, it provides the papermaker with all the tools necessary to ensure full control over drying performance and energy consumption in the dryer section.

Hood and PV system mainly consists of four modules viz.

  1.      Insulated Enclosure and PV boxes
  2.      Supply and Exhaust fans
  3.      Heat Recovery Unit (HRU) and PV heaters
  4.      Control Circuit


Hot dry air through supply fans enters the PV boxes installed in the cylinder pockets whereas the hot moist air is exhausted out of the enclosure to maintain desired humidity inside the hood. HRU facilitates heat transfer between hot moist air going out and dry ambient air coming inside the hood. Further air is heated with condensate, flash and live steam in PV heaters. Insulated hood maintains uniform drying conditions inside the hood. All these processes are coordinated with the help of logic in control circuit.

Pocket Hood SketchFeatures and benefits

  •   Improves the production rates (around 5%) through pocket ventilation system
  •   Energy conservation through heat recovery unit (around 8%)
  •   Control circuit-      a)  PV air temperature control       b)  Dew point temperature control     c)   Zero point control
  •   Create a controlled and favorable environment for paper drying process
  •   Maintains good working conditions in the paper machine room in terms of noise. Substantial improvement in paper quality.