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Materials - Design - Bonnet
- Aug 18, 2018 -

Balls are usually made of several metallics, while the seats are from soft materials like Teflon®, Neoprene, and combinations of these materials. The use of soft-seat materials imparts excellent sealing ability. The disadvantage of soft-seat materials (elastomeric materials) is, that they are not can be used in high temperatures processes.

For example, fluorinated polymer seats can be used for service temperatures from −200° (and larger) to 230°C and higher, while graphite seats may be used for temperatures from ?° to 500°C and higher.


The stem in a Ball valve is not attached to the ball. Usually it has a rectangular portion at the ball, and that fits into a slot cut into the ball. The enlargement permits rotation of the ball as the valve is opened or closed.


The Bonnet of a Ball valve is fastens to the body, which holds the stem assembly and ball in place. Adjustment of the Bonnet permits compression of the packing, which supplies the stem seal. Packing material for Ball valve stems is usually Teflon® or Teflon-filled or O-rings instead of packing.