For valves that have a stem that emerges from body of the valve, the place where this happens is called the bonnet of the valve. The bonnet also contains the valve packing. The internals of some valves are installed into the valve through the bonnet and are referred to as top-entry. Here are the important features and types:

  • Mounting Pad: This is for the attachment of an actuator to the valve for automation or control purposes.
  • Bellows Seal Bonnet: A bellows seal is used on globe valves to reduce fugitive emissions.
  • Extension Bonnet: This is used in the case of extreme temperatures hot or cold. Although the valves internals can be made to withstand extreme temperatures, the actuators will not. An extension bonnet is used to insulate the actuator from the process the valve is controlling.

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