Butterfly Valve Types
Concentric butterfly valves this type of valve has a resilient
rubber seat with a metal disc.
Doubly-eccentric butterfly valves (high-performance butterfly
valves or double-offset butterfly valves) different type of
materials is used for seat and disc.
Triply-eccentric butterfly valves (triple-offset butterfly valves)
the seats are either laminated or solid metal seat design.
Wafer-style butterfly valves
The wafer style butterfly valve is designed to maintain a seal
against bi-directional pressure differential to prevent any
backflow in systems designed for unidirectional flow. It
accomplishes this with a tightly fitting seal; i.e., gasket,
o-ring, precision machined, and a flat valve face on the upstream
and downstream sides of the valve.
Lug-style butterfly valve
Lug-style valves have threaded inserts at both sides of the valve
body. This allows them to be installed into a system using two sets
of bolts and no nuts. The valve is installed between two flanges
using a separate set of bolts for each flange. This setup permits
either side of the piping system to be disconnected without
disturbing the other side.
A lug-style butterfly valve used in dead end service generally has
a reduced pressure rating. For example, a lug-style butterfly valve
mounted between two flanges has a 1,000 kPa (150 psi) pressure
rating. The same valve mounted with one flange, in dead end
service, has a 520 kPa (75 psi) rating. Lugged valves are extremely
resistant to chemicals and solvents and can handle temperatures up
to 200 °C, which makes it a versatile solution.
Usage in industry
In the pharmaceutical, chemical and food industry a butterfly valve
is used to interrupt product flow (solid, liquid, gas) within the
process. The valves used in these industries are usually
manufactured according cGMP guidelines (current good manufacturing
practise). Butterfly valves generally replaced ball valves in many
industries particularly petroleum due to lower cost and ease of
installation, but pipelines containing butterfly valves cannot be
'pigged' for cleaning.
Flange Butterfly Valve
1.Main Parts and Materials
DI with rubber