For fats and oils deodorization and physical refining plants0 pages

For fats and oils deodorization and physical refining plants
FDV Valve
Application
The Alfa Laval FDV valve is designed for internal installation at
the bottom of deodorization column trays. The valve is actuated
by steam and is specially designed to allow rapid draining
during stock changes and shutdowns. The contents of a
single tray can be drained in 1-3 minutes.
The FDV valve is a part of the Alfa Laval SoftColumn™ deodorizing
concept, but is also available as a retrofit component for
other deodorizers - irrespective of make.
Working principle
The FDV Valve consists of a valve body with a large opening
and integrated seat, a horizontal disc that seals against the
valve seat and an actuator installed vertically under the valve
body and directly connected to the valve disc by a vertical shaft.
The actuator is a double action type, using steam to move
the disc up and down, i.e. to open or close the valve. The
steam is injected in one side of the actuator while the other
side is connected to the vacuum. Two pipes leading through
welded connections in the deodorizer wall provide the steam
and vacuum supply.
A control box with automatically actuated ball valves for steam
and vacuum is located outside the deodorizer and is connected
to the FDV valve pipes.
To open the valve, the lower chamber of the actuator is pressurized
by steam, and the upper chamber is connected to the vacuum.
The resulting pressure differential causes the valve disc to
move rapidly upwards, thus exposing the large opening and
allowing for rapid draining of the tray.
To close the valve, the steam is applied to the top chamber of the
actuator, while the lower chamber is evacuated. The valve disc
then quickly moves downwards and seals against the valve seat.
Design features
The FDV Valve is designed for installation inside the deodorizer,
and is assembled directly on the bottom of the tray. This mounting
permits the fastest possible draining of the trays during
stock change and shutdown. The wide, unrestricted opening of
the disc allows for a high liquid flow rate.
Sealing is ensured by a metallic E seal, assembled in the flat
disc and acting against the valve seat. When the valve is closed,
the liquid level exerts pressure on the disc, creating a hydrostatic
seal against the valve seat.
The valve seal consists of a resilient metal convolution in a “floating”
mount (pat. pending) that keeps it free from tension. The
surfaces are ground and lapped. This seal can withstand high
temperatures and exerts a high sealing pressure. It can also
withstand many cycles due to the low-strain elastic deformation.
The valve seat is flat and aligned to the bottom of the tray to
allow full draining with no liquid pocket.
The valve is attached to the bottom of the tray by a flange, so
it is easy to install. It is also easy to service and maintain, with
access only necessary from above.
An important feature of the Alfa Laval FDV Valve is the internal
actuator, which uses steam as the pressure medium. This
means that there are no external actuators, shafts or sealing
glands, all of which can cause air leakage to the inside of a
deodorizer.
The valve is designed for heavy-duty operation in continuously
running process environments.
It requires little maintenance attention because there are few
wearing parts. A complete overhaul therefore only involves
replacing few wear rings and seals. Recommended overhaul
is at 100.000 cycles, or 3 years of operation, whichever
comes first.
A full set of seals and wearing parts, with tools included, is
available as a complete service kit.
FDV Valve model 303 in open position