Volume Control
and Modulating Dampers
Typical Application
These dampers have been designed to meet the
Volume Control Damper: The blade linkage is manu-
requirements of the offshore Oil and Gas and
ally operated by a robust adjusting handle which
Nuclear Markets where corrosion resistance and
moves across a quadrant plate. The plate is labelled
mechanical integrity are of prime importance. They
to identify the open and closed positions. A locking
are used to control airflow through ventilation sys-
device is provided to secure the handle in the
tems, and are not intended for isolation purposes.*
desired position which may be anywhere between
The following design features have been included:
open and closed. Volume control dampers are not
Continuously welded construction
designed to shut off the airflow in the closed posi-
Opposed blade motion
tion.
Low airflow resistance
Options
Low noise generation
Manual, pneumatic or electric operation
Wide range of materials
The following options can be incorporated if
Excellent corrosion resistance
required: Oil impregnated bronze sintered bearings
in place of acetal resin bushes. Reduced cost rivet-
Casing
ed/welded/sealed casing construction. Spring side
seals and top/bottom angle stops. Modifications to
The damper frame is formed into rigid channel sec-
meet the requirements of specific client specifica-
tions that are welded or riveted together. The con-
tions, eg BNF Plc NF specifications.
struction is available in a range of materials and
thicknesses. Typically: stainless steel (1.5 mm to
3.0 mm thick), grade 316L or 304, pre-galvanised
mild steel sheet or galvanised after manufacture
(3.0 mm or 5.0 mm thick).
Blades
These are of marine stainless steel grade 316L or
304. They are of double skin aerofoil section and are
riveted on to continuous tubular spindles. The spin-
dles rotate in acetal resin bearings and are linked
outside the casing to provide opposed blade motion.
Adjusting Mechanism
Modulating Damper: The blade link-
age is operated by a pneumatic or
electric actuator. The supply to the
actuator is controlled by a positioner
unit which is provided with an elec-
tric (420 mA, 010 V dc), or pneu-
matic (315 psi) control signal. The
positioner unit can be supplied to
provide a feedback signal at the
HVAC control panel or management
system. Electrical units can be sup-
plied suitable for safe or hazardous
areas. This system varies the airflow
through the damper, by adjusting the
position of the blades, in relation to
an external parameter, such as air
temperature or room pressurisation.
Microswitches for remote indication
of blades fully open and fully closed
positions can also be installed. The
actuator, positioner unit and
microswitches can be housed within
an enclosure mounted on one side
of the damper casing.