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Air Handling Equipment
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2 Section
2.1 Packaged Supply Air Handling Units
Introduction
Wozair specialize in the manufacture of bespoke stainless steel Air Handling Units. Both draw through and blow through units are available. Units are designed primarily for use on Offshore Oil and Gas facilities but are also suited to marine applications, exposed coastal site locations and operational applications demanding use of stainless steel. Units are manufactured to comply with customer requirements making most units unique. In addition to designing the packaged Air Handling Unit as the main supply plant, it can also perform the function of a pressurisation unit.
Units incorporating centrifugal fans are designed with the fans contained within a panelled crate, whereas those incorporating mixed flow or axial fans are generally designed with fans duct mounted.
Units are generally designed to be lifted and positioned as one complete assembly, so as to minimise installation time. However, if required they can be supplied in modular format for re-assembly on site.
The main features and components of an Air Handling Unit are presented herein.
Standards
Wozair design and manufacture its Air Handling Units to comply with EC directives.
Units comply with Directives and any amending Directives:
Machinery Directive 98/37/EC
Low Voltage Directive 73/23/EEC
ATEX Directive 94/9/EC
EMC Directive 89/336/EEC
Pressure Equipment 97/23/EC Directive
Skid
The Air Handling Unit is supplied as a skid mounted assembly with the skid fabricated from hot rolled structural steel sections. The skid can be designed to BS 449 and with consideration for transportation forces and any seismic conditions. Skids are welded by coded welders and hot dip galvanized to EN 1461 after manufacture or painted to customer’s requirements. If required, main welds can be subject to NDT. Lifting lugs and earthing points are provided.
Casing
The casing consists of a rigid construction framework with lagged infill panels for thermal insulation and noise attenuation.
The frame work is continuously welded and manufactured from stainless steel grade 1.4404 (316L) or 1.4307 (304L). The frame work is 1.5mm, 2.0mm or 3.0mm dependant upon the size and application. If required the frame work can be insulated with a closed cell elastomeric material or mineral wool to eliminate a heat bridge.
Infill panels are double skinned and flush mounted. Infill can be 25mm or 50mm thick and is used to provide thermal insulation and noise attenuation. Infill material can be extruded polystyrene rigid board bonded to the panel skin or mineral wool. Panel skins are manufactured from the same material as the frame work with a range of sheet thicknesses available from 0.9mm to 2.0mm. Hinged access panels are provided for inspection and maintenance of equipment.
A base plate manufactured from the same material as the frame work is sandwiched between the frame work and the skid and is insulated if required.
Externally mounted units can be provided with a pitched roof to shed rain.
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Fans
Fans are typically of the DIDW centrifugal type with non-stalling and non-overloading characteristics. However, units can be designed with SISW centrifugal, mixed flow or axial fans. Fans are generally belt driven although direct drive fans can be provided for operation with variable speed drives.
The fan casing can be galvanized steel, hot dip galvanized mild steel or stainless steel. Centrifugal and mixed flow fan impellers can be mild steel painted, mild steel galvanized or stainless steel. Axial fan impellers can be painted aluminium, GRP or stainless steel
Fans are driven by LV motors which can be rated suitable for use in a Zone 1 or Zone 2 hazardous area. Where belt drive is employed, belts are an anti-static, vee design. The motor is mounted on a frame integral to the fan set. The fan is isolated from the Air Handling Unit by anti-vibration mounts and flexible connections.
Fans operating with Zone 1 or Zone 2 motors shall incorporate anti-spark features.
Fans can be provided with the following accessories: speed sensor, bearing monitoring, extended lubricators, automatic grease lubricators, drain plug, access door, inlet and discharge guards and belt guards.
Air Handling Units can be designed with 100% run and standby fan sets or 2 x 50% fan sets or run and standby motors on a single fan. With dual fan arrangements, fans are installed in separate chambers to enable maintenance on one fan to be carried out whilst the other is in operation. These chambers can be configured side-by-side or one above the other, subject to practical transportation limits. Inlet guide vane, manual or automatic isolation and non-return dampers can be provided to control the airflow and isolate the fan chamber.
Motors
These are generally painted cast iron or steel totally enclosed ventilated type (TEFC) and can be supplied to operate on all common 3 phase low voltage supplies of 50 Hz and 60 Hz. They can be rated suitable for use in a Zone 1 or Zone 2 hazardous area as required and compliant with project specifications and standards where stipulated.
Cooling Coils
Cooling coils can be selected to operate with refrigerant, sea water or chilled water. Material selection matches the application but is typically seamless copper for refrigerant or chilled water and titanium for sea water. The tubes are expanded on to copper fins although aluminium fins are available. Copper fins may be pretinned or copper tube and fin coils electro-tinned after manufacture. Alternatively, with copper tube and fin coils or copper tube and aluminium fins a PolyAl anti-corrosion treatment can be provided.
As a general rule, where the face velocity on the cooling coil exceeds 2.5 m/s a vane eliminator should be installed to prevent moisture carryover. Vane eliminators can be supplied in stainless steel 316, marine grade aluminium or plastic.
The cooling coil section of the Air Handling Unit is provided with a drain tray to drain to the edge of the skid.
Temperature control valves for chilled water and sea water by-pass control can be supplied as required.
Heating Coils
These shall generally be as described above but suitable for operation with steam, hot water or a heating medium. Titanium tube is not used but some applications may demand the use of stainless steel tube.
Electric Heaters
Electric heaters are designed for thyristor or step control. Generally elements are 80/20 nickel/chrome resistance wire insulated with compacted magnesium oxide and ceramic beads in Incoloy 800 sheaths. Thermocouples, RTD’s or thermostats are installed to detect element and air over temperature. Element temperature is normally restricted to 150 - 200ºC. If required, heaters can be supplied suitable for operation in a Zone 1 or Zone 2 hazardous area, but any manual or auto reset device operated in conjunction with the over temperature sensor should be located in a control panel in a non-hazardous area. The elements are terminated in a stainless steel enclosure.
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Filters
A wide selection of panel and bag filters is available to suit a range of application such as removal of dust or coalescing filters for the removal of particulate salt to reduce the concentration to less than 0.05 ppm. They are arranged on mounting frames within the unit to suit side withdrawal. Instrumentation can be provided to monitor the filter condition during operation such as a differential pressure gauge, switch or transmitter. With coalescing filters, vane eliminators can also be provided to prevent moisture carry-over. Vane eliminators can be supplied in stainless steel 316 or marine grade aluminium.
Humidification
Electrically operated fresh steam humidifiers may be installed if required. Alternative humidifier types can be considered upon request. The humidifier, including its water tank and steaming chamber form part of the unit package, space permitting. A matrix of injection tubes is installed within the unit case as they provide the best solution for achieving the minimum absorption distance. The humidifiers are supplied with a control panel and can be suitable for thyristor or step control. It is preferable to locate humidifiers within a non-hazardous area.
Weather Louvres
For an exposed fresh air intake, a weather louvre can be provided to prevent the ingress of rain water into the Air Handling Unit inlet.
Control Dampers
In addition to the dampers previously described in the fan section, we can include for control dampers at the Air Handling Unit inlet or discharge. Dampers can be used to isolate the unit, regulate the airflow or, in the case of a unit drawing in a mixture of fresh and re-circulated air, modulating control dampers to vary the mix ratio. Modulating dampers can be provided with pneumatic, electro-pneumatic or electric positioners suitable for a hazardous or non-hazardous area.
Controls/Wiring
Control panels can be provided installed on the unit skid or supplied loose. The design and features of each panel is dependant upon the application and requirements. Control panels can be provided for installation in a hazardous area though it is recommended that wherever possible they are located in a non-hazardous area.
Wozair can provide heater thyristor control panels, variable speed drives and HVAC control panels to suit customer requirements.
Electrical components on the Air Handling Unit shall generally be cabled to a terminal box mounted external to the unit.
Cabling shall as a minimum be flame retardant PVC with options to provide low smoke, zero halogen cable both unarmoured and armoured. Cabling can be run in cable tray as required. Earthing continuity is achieved by cabling equipment to a common earthing point on the unit skid base. Cable penetrations into the unit are by way of gland plates or transit frames.
Safety Features
The units are provided with an EC Declaration of Incorporation. Where personnel can gain internal access to maintain filters, dampers, fan sets or
other equipment, lights of the filament or fluorescent type are provided, operated from a common switch. For the fan motor a push button emergency stop can be fitted. If required, any electrical components shall be suitable for use in a Zone 1 or Zone 2 hazardous area.
Ancillary Components
We can provide any of the following features:
Temperature, pressure and humidity instrumentation
Test points Interface junction boxes Maintenance beams to lift and move motors, typically 15kW
and above
Spreader beams with shackles for lifting and positioning the units on site
Access platforms and ladders for equipment at high level
Drain traps and pipes Trace heating of drains Testing
Various testing options are available on the completed Air Handling Unit including:
Running motors on project specified voltage and frequency 50Hz/60Hz
Volume/pressure testing based on BS 6583
Case deflection and leakage based on EN 1886
Case leakage testing up to 3000Pa Indicative noise breakout testing Measurement of the fan running speed
Recording motor running current Leakage performance of Wozair Air Handling Units meets DW143 Class B where the leakage from the casing is
calculated as:
Leakage (l/s/m²) = 0.009 x test pressure0.65
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2.2 Chiller Units, Air Conditioning and Condenser Units
Introduction
To compliment our range of Air Handling Units Wozair supplies Chiller Units, Packaged Air Conditioning Units and Condenser
Units. These units are selected suitable for the operating conditions in which they are to be located. In particular, for our core market on Offshore Oil and Gas facilities, units of bespoke design are available manufactured in stainless steel and with Zone 1 or Zone 2 hazardous area electrical and instrumentation equipment.
Water/seawater cooled and air cooled Chiller Units are available with duties up to 1000kW and condenser units with duties up to 200kW. Compressors can be screw, semi-hermetic or reciprocating with open drive.
Packaged Air Conditioning Units are generally of the cabinet type configured for vertical upward or downward airflow. For harsh operating environments, the units can be manufactured in stainless steel but otherwise shall be painted or coated steel. Such units are fitted with panel filters and a direct expansion or chilled water cooling coil. In addition, heating and humidification requirements can be incorporated into the unit design. Units are generally of the split type. Also small “through the wall” units can be supplied which are ideally suited to applications where a non-hazardous environment exists inside the room with a hazardous environment external to the room.
Units operate with zero ozone depletion potential refrigerants: R134A and R407C.
Units are generally designed to be lifted and positioned as one complete assembly so as to minimise installation time.
Standards
For the European market Wozair will ensure that Chiller Units, Packaged Air Conditioning Units and Air Cooled Condenser Units supplied comply with EC directives.
Units comply with Directives and any amending Directives:
Machinery Directive 98/37/EC
Low Voltage Directive 73/23/EEC
ATEX Directive 94/9/EC
EMC Directive 89/336/EEC
Pressure Equipment 97/23/EC Directive
Condenser Fans
Direct drive axial fans are used. Fans are driven by 3 phase LV motors which on bespoke units can be rated suitable for use in a Zone 1 or Zone 2 hazardous area. Fans operating with Zone 1 or Zone 2 motors shall incorporate anti-spark features.
Evaporating and Condenser Coils
Coils use seamless copper tube expanded on to copper fins although aluminium fins are available. Copper fins may be pre-tinned or copper tube and fin coils electro-tinned after manufacture. Alternatively, with copper tube and aluminium fins an anticorrosion treatment can be provided.
Water Cooled Condensers
Water cooled condensers are of the multi-pass shell and tube type with mechanically serviceable tubes and removable headers.
Controls/Wiring
Control panels and wiring form an integral part of the package. Alternatively, it is possible to consider a separate panel or incorporate the control functions into an HVAC system control panel. The design and features of each panel are dependant upon the application and requirements. Control panels can be provided for installation in a hazardous area though it is recommended that wherever possible they are located in a non-hazardous area.
Cabling shall as a minimum be flame retardant PVC with options to provide low smoke, zero halogen cable both unarmoured and armoured. Cabling on bespoke packages can be run in cable tray as required. Earthing continuity is achieved by cabling equipment to a common earthing point on the unit skid base.
Testing
All equipment is subjected to manufacturers routine test procedures. Pipe work, evaporators and coils shall be pressure tested. Chiller units can be supplied complete with the refrigerant charge. Packaged split units shall be supplied with refrigerant pipe work dehydrated and filled with a nitrogen holding charge.
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2.3 Extract Fan Skids
Introduction
Wozair specialize in the manufacture of bespoke Extract Fan Skids. Units are designed primarily for use on Offshore Oil and Gas facilities but are also suited to marine applications, exposed coastal site locations and industrial applications. Fan Skids are manufactured to comply with customer requirements.
Fan Skids Units are designed with centrifugal, mixed flow or axial fans. Units can be designed with: a single fan, 100% run and standby fan sets, 2 x 50% fan sets or run and standby motors on a single fan.
With DIDW dual fan arrangements the fans are contained within a panelled crate and are installed in separate chambers to enable maintenance on one fan to be carried out whilst the other is in operation.
With SISW, mixed flow or axial dual fan arrangements the fans are duct mounted with each fan installed in a separate duct branch and a manifold duct connection piece at the inlet to connect to the extract ductwork.
Units are generally designed to be lifted and positioned as one complete assembly so as to minimise installation time.
The main features and components of an Extract Fan Skid are presented herein.
Standards
Wozair design and manufacture its Fan Extract Skids to comply with EC directives.
Units comply with Directives and any amending Directives:
Machinery Directive 98/37/EC
Low Voltage Directive 73/23/EECATEX Directive 94/9/EC
EMC Directive 89/336/EEC
Skid
The Extract Fan Skid is supplied as a skid mounted assembly with the skid fabricated from hot rolled structural steel sections. The skid can be designed to BS 449 and with consideration for transportation forces and any seismic conditions. Skids are welded by coded welders and hot dip galvanized to EN 1461 after manufacture or painted to customer’s requirements. If required, main welds can be subject to NDT. Lifting lugs and earthing points are provided.
Casing
A crated unit is provided when using DIDW centrifugal fans.The casing consists of a rigid construction framework with lagged infill panels for thermal insulation and noise attenuation.
The frame work is continuously welded and manufactured from stainless steel grade 1.4404 (316L) or 1.4307 (304L). The frame work is 1.5mm, 2.0mm or 3.0mm dependant upon the size and application. If required, the frame work can be insulated with a closed cell elastomeric material or mineral wool to eliminate a heat bridge.
Infill panels are double skinned and flush mounted. Infill can be 25mm or 50mm thick and is used to provide thermal insulation and noise attenuation. Infill material can be extruded polystyrene rigid board bonded to the panel skin or mineral wool. Panel skins are manufactured from the same material as the frame work with a range of sheet thicknesses available from 0.9mm to 2.0mm. Hinged access panels are provided for inspection and maintenance of equipment.A base plate manufactured from the same material as the frame work is sandwiched between the frame work and the skid and is insulated if required.
Externally mounted units can be provided with a pitched roof to shed rain.
Fans
Fans are DIDW or SISW centrifugal, mixed flow or axial with non-stalling and non-overloading characteristics. Fans are generally belt driven although direct drive fans can be provided for on-off operation or operation with variable speed drives.
The fan casing can be galvanized steel, hot dip galvanized mild steel or stainless steel. Centrifugal and mixed flow fan impellers can be mild steel painted, mild steel galvanized or stainless steel. Axial fan impellers can be painted aluminium, GRP or stainless steel.
Fans are driven by LV motors which can be rated suitable for use in a Zone 1 or Zone 2 hazardous area. Where belt drive is employed, belts are an anti-static, vee design. The motor is mounted on a frame integral to the fan set. The fan is isolated from the ductwork by anti-vibration mounts and flexible connections.
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Fans operating with Zone 1 or Zone 2 motors shall incorporate anti-spark features.
Fans can be provided with the following accessories: speed sensor, bearing monitoring, extended lubricators, automatic grease lubricators, drain plug, access door, inlet and discharge guards and belt guards.
Extract Fan Skids can be designed with 100% run and standby fan sets or 2 x 50% fan sets or run and standby motors on a single fan. With DIDW dual fan arrangements fans are installed in separate chambers to enable maintenance on one fan to be carried out whilst the other is in operation. With SISW mixed flow or axial dual fan arrangements, fans are installed in separate duct branches complete with shut-off damper to enable maintenance on one fan to be carried out whilst the other is in operation. Dual fans can be configured side-by-side or one above the other subject to practical transportation limits.
Inlet guide vane, manual or automatic isolation and non-return dampers can be provided to control the airflow and isolate the fan.
Motors
These are generally painted cast iron or steel totally enclosed ventilated type (TEFC) and can be supplied to operate on all common 3 phase low voltage supplies of 50 Hz and 60 Hz. They can be rated suitable for use in a Zone 1 or Zone 2 hazardous area as required and compliant with project specifications and standards where stipulated.
Weather Louvres
For an exposed discharge, a weather louvre can be provided to prevent the ingress of rain water into the fan extract duct. Refer to catalogue section 5.
Controls/Wiring
Control panels can be provided installed on the unit skid or supplied loose. The design and features of each panel is dependant upon the application and requirements. Control panels can be provided for installation in a hazardous area though it is recommended that wherever possible they are located in a non-hazardous area.
Wozair can provide variable speed drives and HVAC control panels to suit customer requirements.
Electrical components on the Extract Fan Skid shall be cabled to accessible terminal boxes.
Cabling shall as a minimum be flame retardant PVC with options to provide low smoke, zero halogen cable both unarmoured and armoured. Cabling can be run in cable tray as required. Earthing continuity is achieved by cabling equipment to a common earthing point on the unit skid base. Cable penetrations into panelled units are by way of gland plates or transit frames.
Safety Features
The units are provided with an EC Declaration of Incorporation. Where personnel can gain internal access to maintain dampers or fan sets, lights of the filament or fluorescent type are provided, operated from a common switch. For the fan motor, a push button emergency stop can be fitted. If required, any electrical components shall be suitable for use in a Zone 1 or Zone 2 hazardous area.
Ancillary Components
The following features can be provided:
Interface junction boxes Maintenance beams to lift and move motors, typically 15kW and above
Spreader beams with shackles for lifting and positioning the units on site
Access platforms and ladders for equipment at high level
Testing
Various testing options are available on the completed Fan Skid including:
Running motors on project specified voltage and frequency 50Hz/60Hz
Volume/pressure testing based on BS 6583
Case deflection and leakage based on EN 1886 (panelled units only)
Case leakage testing up to 3000Pa (panelled units only)
Indicative noise breakout testing Measurement of the fan running speed
Recording motor running current
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