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High Efficiency Weather Louvres
Introduction
Wozair offer a range of austentic stainless steel high efficiency weather louvres designed primarily for offshore and petro-chemical industries. The louvres are well suited to ventilation and power generation air intake and exhaust applications as well as louvre cladding systems.
The function of the weather louvre is to prohibit the ingress of wind driven rain into the ventilation system. Three configurations of louvre are available with a range of efficiency performance to suit particular applications. Each configuration has been subject to a performance test by a third party independent test authority (BSRIA).
The type SB is best suited to installation on exhaust ducts although it can be used on intake systems where some ingress of water is acceptable.
The type SBG is best suited to installation on intake systems requiring a high level of separation efficiency.
The type DBG is best suited to installation on intake systems where a very high level of separation efficiency is required resulting in no or negligible water ingress.
Wozair high efficiency weather louvres offer the following features:
All stainless steel construction from grade 304L or 316L
Welded construction Integral water drain system via front face or drain boss
Integral weathergrid on types SBG and DBG to improve water removal
Channel frame construction for all types with an angle frame option available on the SB
Optional bird mesh guard (fixed or removable) on type SB
Description
Frame
This is typically fabricated from 2.0 mm or 3.0 mm stainless steel grade 304L or 316L although alternative grades can be considered. It is a continuously welded channel or angle section construction with the flange drilled for mounting the louvre on to the ductwork.
The casings for types SBG and DBG have integral water drain channels within the side frame members.
All types of louvre can be configured for water drainage via the front face or alternatively, for channel frame sections only, be fitted with a collection trough in the base of the frame for drainage via a boss.
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Blades
All blades are fabricated from 1.2 mm stainless steel grade 304L or 316L.
Single Bank (type SB) The blades are mounted horizontally and stitch welded to the frame at each end. Each blade incorporates a weatherlip at the top edge which arrests wind driven rain at this crucial position.
Single Bank with Weathergrid (type SBG) The blades are as detailed for the type SB louvre but with the following additional features to improve efficiency:
Each blade incorporates an upturned drain lip on the lower edge. Extensive research has shown that the cascading effect of water down the front of the louvre makes a considerable contribution to water penetration since falling droplets can be carried through the louvre by wind force or system operating conditions. The drain lip reduces this cascading effect by diverting the water to the drain channels within the side frame members leading to a significant increase in efficiency.
Double Bank with Weathergrid (type DBG) The blades are as detailed for the type SBG louvre but with the following additional features to improve efficiency:
A second row of blades mounted vertically immediately behind the first row being stitch welded to the frame at each end. These blades have a lip on their trailing edge to arrest moisture carried over from the first bank of blades and drain to the bottom of the frame.
Weathergrid/Mesh Guard
Single Bank (type SB) As an option this louvre can be fitted with a stainless steel wire mesh guard to prevent birds and debris entering the system. The mesh may be specified with apertures 25 mm x 25 mm or 50 mm x 50 mm. Other options can be considered upon request. The mesh can be permanently fixed (welded) to the frame or bolted so as to be removable.
Single Bank (type SBG) or Double Bank (type DBG) These louvres are fitted withed with a weathergrid between adjacent blades. The grid acts as an air equalising screen to assist aerodynamic performance and disperse any wind driven rain that may penetrate upwards.
The apertures in the weathergrids are sized to prevent birds and debris from entering the system and therefore eliminate the necessity for a separate mesh guard.
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Dimensional Limits
The minimum louvre size is 200 mm wide x 200 mm high and the maximum is 2000 mm wide x 2000 mm high. For larger duct or airway sizes the louvre can comprise a number of modules with fixing details designed to suit the installation. The maximum recommended face velocity is 2.5 m/s for an intake system and 3.0 m/s for an exhaust system.
Performance Data
The aerodynamic performance and water ingress efficiency, based on an intake application, for each louvre type is given in the graphs that follow.
All performance testing on these products was conducted by the Building Services Research and Information (BSRIA) in accordance with the Heating, Ventilating and Air Conditioning Manufacturers Association (HEVAC) standard for weather louvre tests.
BSRIA test reports for the products are available on request.
Efficiency
The efficiency of each louvre type against airflow rate for an intake application is presented on the graphs. With a fan drawing air through the louvre wind driven rainfall was simulated using:
An incident wind of 13 m/s (29.08 mph) incident to the louvre face
A nominal rainfall rate of 75 mm/hr An increase in efficiency will result if either of these criteria is reduced or the louvre is used for an exhaust application.
The efficiency is a measure of the ability of the louvre to prevent water droplets from entering the system. For example at an efficiency of 99% only 1% of the rainfall will pass through the louvre.
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Frame Nominal Duct Size
Type Material Thickness Width Height
DBG / SS316 / 3.0 / 1000 / 500
Legend Louvre Type: SB = Single Bank SBG = Single Bank with Grid DBG = Double Bank with Grid
Material: SS316 = Stainless Steel (with grade)
Frame Thickness: 2.0 mm or 3.0 mm (refer to ‘Description’)
Nominal Duct Size: Clear inside duct dimensions – quote Width/Height
Ordering
Quantities, surface finish and other special requirements are to be stated separately.
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Filter Coalescers and Moisture Eliminators
Introduction
Wozair offer a range of filter coalescers which are typically installed in ducted systems near to the air intake and downstream of a weather louvre. Alternatively they can be installed at the intake end of an Air Handling Unit. Typically a filter coalescer comprises two stages: the first a panel filter that coalesces droplets and provides effective filtration of salt and dust particles; the second a vane eliminator to remove the coalesced droplets from the airstream.
Wozair filter coalescers offer the following features:
All stainless steel construction from grade 304L or 316L
Welded construction Integral water drain tray in the vane eliminator section
Reduction in salt concentration to less than 0.05 ppm
Easy access to maintain filters Optional drain trap Optional trace heating of drain trap Optional instrumentation to monitor
pressure drop locally or remotely
Description
Frame
This is typically fabricated from 2.0 mm or 3.0 mm stainless steel grade 304L or 316L although alternative grades can be considered. It is a continuously welded channel section construction with the flange drilled for mounting the louvre on to the ductwork.
The frame is provided with a hinged access door to allow for side withdrawal of the filters as required for maintenance and replacement. Where necessary or within an Air Handling Unit the filters can be arranged for front withdrawal.
Filter Coalescer
Wozair select filter coalescers from reputable manufacturers having an extensive track record of supply for offshore and marine applications. Filters can be of the panel type, prefilter bag type or high efficiency bag type. Combinations of a primary prefilter (panel or bag) and secondary high efficiency bag filter can be provided offering an increased dust holding capacity and to extend the life of the high efficiency bag filter.
The primary pre-filter (panel or bag) is cleanable but will need replacement eventually whereas the secondary high efficiency bag filter is disposable.
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Vane Eliminator
For most applications a vane eliminator is recommended to remove coalesced water droplets. The vane eliminator blades are formed from stainless steel grade 316L as standard. Alternatively marine grade aluminium or polymer eliminator blades can be provided. The vane eliminator section has an integral drain tray with a boss connection for the drain pipe. Drain traps can be included where required. Where water is liable to freeze in the trap self limiting parallel trace heating tape is provided suitable for a non-hazardous or hazardous areas, this being terminated at a locally mounted junction box.
Options
Pressure tappings can be provided across the filter or across individual filter sections where multi-stage filtration is required, to which differential pressure monitoring instrumentation can be connected. The following can be supplied:
Differential pressure gauge for local indication complete with a flag to indicate the allowable dirty pressure drop
Differential pressure switch, transmitter or indicating transmitter for non-hazardous or hazardous area applications to provide remote indication or alarm at a control panel
Block and bleed manifold with a transmitter
Dimensional Limits
The minimum recommended filter size is 300 mm wide x 300 mm high although the duct size may be reduced with the addition of transition pieces. No maximum duct size limit need apply although there is a limiting size for individual filter coalescer panels and bags. The maximum recommended face velocity is 5 m/s.
Maintenance
Filter coalescers remove unwanted particles from the airstream. They therefore require cleaning or replacement on a regular basis.
Ordering
Quantities, surface finish and other special requirements are to be stated separately.
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Laundry Lint Filters
Introduction
Wozair offer laundry lint filters to remove airborne lint particles. The filter comprises a fine mesh screen to remove such particles. They would typically be installed in the extract duct upstream of the fan.
Wozair laundry lint filters offer the following features:
All stainless steel construction from grade 304L or 316L
Welded construction Easy access to maintain filter screen
Optional instrumentation to monitor pressure drop locally or remotely
Description
Frame
This is typically fabricated from 2.0 mm or 3.0 mm stainless steel grade 304L or 316L although alternative grades can be considered. It is a continuously welded channel section construction with the flange drilled for mounting the louvre on to the ductwork.
The frame is provided with a hinged or removable access door to allow for side withdrawal of the filter screen as required for maintenance and replacement.
Filter
Wozair employ a fine stainless steel mesh screen held in a rigid frame.
Options
Pressure tappings can be provided across the filter to which differential pressure monitoring instrumentation can be connected. The following can be supplied:
Differential pressure gauge for local indication complete with a flag to indicate the allowable dirty pressure drop
Differential pressure switch, transmitter or indicating transmitter for non-hazardous or hazardous area applications to provide remote indication or alarm at a control panel
Block and bleed manifold with a transmitter
Dimensional Limits
The minimum recommended filter size is 150 mm wide x 150 mm high. No maximum duct size limit need apply although there is a limiting size for individual filter screens.
Maintenance
Filter screens remove unwanted particles from the airstream. They therefore require cleaning on a regular basis.
Ordering
Quantities, surface finish and other special requirements are to be stated separately.
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Woz-X Separators
Introduction
The Woz-X Separator is designed to remove oil and vapour mist drawn through extract ventilation ducts serving shale shakers and mud tank/ mud pit areas thus protecting operators, equipment and the environment.
The unit employs the unique X-Zyklon ® separator panel which is fabricated in stainless steel grade 304. The blade arrangement has an optimised profile for laminar airflow.
A single stage separator can be installed into existing extract systems or designed for new applications. Where very high levels of oil and mist separation are required a three stage separator is available. If required the Woz-X Separator can be packaged with extract fans.
Benefits
Traditional practice on North Sea platforms has been to employ a scrubber system that relies upon the removal of contaminants by reverse water spray. These are expensive, large and inefficient systems requiring pumps, valves and pipe work systems. Due to their size they are often not practical to retro-fit. They also generate a slurry waste that has to be collected and treated prior to disposal or removal.
The Woz-X Separator can be installed into existing extract systems at significantly less cost as it is a static device. Separated oil and vapour mist can be returned to the shale shaker or mud tank. The only operational cost is associated with periodic cleaning of the separator panel(s).
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Description
The Woz-X Separator consists of stainless steel 304 X-Zyklon® elements contained within a flanged stainless steel grade 304L or 316L duct section. Depending on duct size and airflow the elements shall be either mounted in ‘V’ formation or perpendicular to the airflow. The patented system consists of pairs of specially designed profiles and frame. The contaminants are separated by cyclone effects. The elements separate completely into two pieces and are washable, non-disposable filters and comply with UL 1046 – flame exposure test (TÜV tested).
Elements are arranged for side withdrawal through a hinged and sealed stainless steel cover plate. It is possible to consider a top withdrawal arrangement.
Where the separator panels are mounted in a ‘V’ arrangement or where the unit is mounted in a horizontal duct captured liquid and mud drains down through the XZyklon® elements themselves and into a drainage channel for removal and disposal or, as is recommended, piped to return the liquid to the shale shaker or mud tank.
Pressure tappings can be provided on either side of the element to measure pressure drop. These can be connected to a differential gauge for local indication or a pressure switch or transmitter for remote indication or alarm.
Dimensional Limits
The minimum separator size is 400 mm wide x 400 mm high although the duct size may be reduced with the addition of transition pieces. No maximum duct size limit need apply although there is a limiting size for individual separator elements.
Maintenance
Woz-X Separators remove unwanted particles from the airstream. They therefore require cleaning on a regular basis which is typically determined by the operational environment.
Separator Pressure Drop Data
The graph below gives pressure vs. velocity where velocity is that on the nett face area of the separator panel. The recommended optimum maximum face velocity is 2 m/s giving a pressure drop of 320 Pa. The separator can be run at up to 3 m/s but the pressure drop will be 600 Pa.
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Separation Performance Data
The capture efficiency for the separator has been tested to the requirements of VDI 2052.
This “serves as a guideline for the assessment of separator performance of aerosol capture systems. Test procedures are set out to enable a comparative study to be made of aerosol separator features that determine functional quality.
Aerosol separators are fitted to minimise contamination of the exhaust system and reduce malodorous emissions linked with particles. Particle separation occurs as a rule through so-called inertial separation and eventually by
sedimentation. Possible effects from condensation processes are not quantified in this test method.
Airborne fat and oil aerosols are formed on the one hand by micro droplets being directly given off from hot reservoirs, and on the other by recondensation of vaporised substances. The size range for 80% of the droplet mass extends from 0.05 to over 10ìm. This is shown by measurements of the aerosol size distribution in various aerosols sources.”
Separator performance is detailed on the graph below.
The fig. below shows the Separator efficiency of a basic module comparing face velocity and particle size.
To reach the relevant concentrations and limits of oil particles in the exhaust air (mg of oil per m3 exhaust air), you need to pay attention to the proportion of the particle – mass (weight).
particle size in um 10 5 3 1 0,8 0,5
mass proportion* 8000 1000 216 8 6,4 1
*a 10 micron size particle weighs 8000 times more than a 0,5 micron particle!
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