Non Return/Pressure Relief Dampers
Typical Application
Options
The following options can be incorporated if
A range of high integrity dampers has been designed
required.
to meet the requirements of the offshore oil & gas
Oilite bearings. Reduced cost riveted/welded/
and nuclear markets where corrosion resistance,
sealed casing construction. Weight kits or spring bal-
mechanical integrity and performance are primary
ancing mechanisms. Modifications to meet the
factors. They are used to prevent backflow and
requirements of specific client specifications, eg
relieve pressure through ventilation duct systems.
BNF Plc NF Specifications. Low leakage style
The following design features have been included:
damper.
Continuously welded construction
Ordering
Parallel blade motion
Low airflow resistance
Low noise generation
Quantities, surface finish and other special require-
Excellent corrosion resistance
ments to be stated separately.
Duct Width 500W
Type NRD
Description
Duct Height 300H
Material 316L
Casing
Case Depth 200D
Case Thickness 1.5
The damper frame is formed into rigid channel sec-
Type Wozair:
Non Return Damper
tions that are welded or riveted together from stain-
less steel grade 304 or 316L, pre-galvanised mild
steel sheet or galvanised after manufacture (3.0 mm
Damper Types:
or 5.0 mm thick).
NRD = Non Return Damper
PRD = Pressure Relief Damper
Angles with closed cell gaskets are provided at the
Case Material:
top and bottom in order to achieve an effective seal
Stainless Steel
1.4301
= 304
between the casing and the blades.
(SS304)
Low Carbon
1.4307
(SS304L) = 304L
Blades
(SS316L) = 316L
Low Carbon
1.4404
These are of stainless steel grade 316L or 304, they
Mild Steel Sheet
are of double skin aerofoil section and are riveted to
Pre-Galvanised
FeP02 nac = GSS
continuous tubular spindles. The spindles rotate in
oil impregnated acetal resin bearings and are linked
Galvanised after Manufacture = GAM
externally to provide parallel motion. An effective
Case Thickness: 1.5mm upwards
seal is achieved by strips of closed cell gasket along
Nominal
Clear inside duct dimensions
the blade edges. Galvanised material option avail-
Duct Size:
`Quote' (Width x Height)
able.
Order Code Example:
Blade Linkage
NRD/316L/1.5/500W/300H/200D
This is of stainless steel grade 316 and is designed
to prevent chatter or blade damage.
Balancing
This is achieved by either hanging weights from the
holes provided in the blade linkage or by adjusting
the tension of a spring balancing mechanism. This
must be carried out on site after installation. Weight
kits and spring balancing mechanisms are optional
and if required must be stated at the time of order-
ing.
Pressure Relief Damper: At full airflow the position
of the linkage is such that the blades hang at
between 5° and 20° to the vertical.
Non-Return Dampers: At the `no flow' condition the
blades hang at 30° and 45° to the vertical.