when to select an open bonnet vs enclosed bonnet design?

SlurryFlo control valve with an enclosed bonnet design.

Enclosed Bonnet Design

The SlurryFlo Control Valve bonneted gate design uses a simple stem packing arrangement; this delivers several benefits to the client, such as minimal thrust requirements, lower packing friction, reduced packing leakage, and more precise gate modulation. The enclosed bonnet design is field proven with significant success in mining applications around the world.
SlurryFlo control valve with an open bonnet design.

Open Bonnet Design

The SlurryFlo Control Valve open bonnet design eliminates the bonnet cavity. A longer gate section replaces the stem, which retracts past the valve’s body. As a result, the packing material seals around the gate’s perimeter (similar to a traditional knife gate valve). 

SAF will specify an open bonnet when certain conditions are expected (e.g. vertical pipe with horizontally mounted valve, fluids with high viscosity, high % solids, unique fluid characteristics, etc). The design decision is application dependent. In rare cases, where the flow conditions have changed significantly, an enclosed bonnet design can be converted to open bonnet with a field retrofit kit.
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