Air cleanliness in residential and work premises is essential. Agree, the musty atmosphere in the house is very unpleasant. However, the change in the air volume is achieved not only by the inflow of air, but also by its removal beyond the walls of the building. And exhaust ventilation systems often fail to cope with the last task.
Modern buildings, be they multi-level office complexes, residential buildings, sports complexes or industrial halls, consist of spacious, high-ceilinged premises. For regular air replacement in them, forced extraction by several roof-type ventilation devices is required.
We will tell you how the ventilation equipment is chosen, how the fans are installed on the roof and why it is impossible to do without a glass here.
The content of the article:
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Features of roof fans
- Types of ventilation structures
- Nodes of the passage of a flat reinforced concrete roof
- Installation of reinforced concrete glass
- Installation of a roof fan in a reinforced concrete glass
- Sequence of installation work
- Universal nodes of the roof passage
- The specifics of using a metal glass
- Conclusions and useful video on the topic
Features of roof fans
These appliances are for rooftop use only. They are most effective in systems forced ventilation objects of a large area. By installing roof fans on a building with or without integration into the air duct system (for example, above the airport hall), it will be possible to solve the problem of removing polluted air.
Ventilation units are capable of removing smoky, waste (with impurities, unpleasant odors), gaseous and moisture-laden air from the large-sized rooms being serviced. Roof fans can be used for any aboveground and some underground facilities.
Ventilation devices placed on buildings are divided into axial, radial and diagonal depending on the method of air intake and discharge.
Types of ventilation structures
Axial fans. Combines simplicity of design, reliable operation and easy maintenance. Structural endurance allows them to be used equally effectively both for air exchange and when creating smoke ventilation, as well as for air pressurization in case of fire (operate at an air flow temperature above 400OWITH).
Due to their simple design, axial (axial) ventilation units easily cope with the removal of high-temperature and aggressive air media
The devices are highly resistant to chemical compounds in the composition of the exhaust air, which allows mount axial fans on the roof of industrial facilities in the pharmaceutical and chemical industries activities.
Most household fans belong to this group: channel devices, devices installed in wall inlets and exhaust valves, bathroom fans, combined and separate bathrooms.
Radial fans. These ventilation devices are characterized by a volute casing that directs air at right angles to the impeller with centrifugal rotation. They can pump air volumes containing mechanical pollutants up to a concentration of 100 mg / m3, remove air regularly even in strong winds.
The characteristic structure of the blades provides the device with a high performance, but also a high noise level. Therefore, radial roof fans are mainly used in industrial facilities. The temperature of the air pumped out by the radial device must be less than 80OWITH.
Although these ventilation devices can be operated in rather mild conditions, this compensates for their high power.
Diagonal fans. These ventilation units are a combination between axial and radial models. Their suction impeller draws in air in the axial direction, and before exhausting the air flow, it deflects it by 45O. This results in an increase in power due to the centrifugal force typical of radial fans.
The combination of the qualities of axial and radial roof ventilation units provides diagonal models with an efficiency of up to 80%. With sufficient power, radial roof fans are relatively compact and quiet.
Nodes of the passage of a flat reinforced concrete roof
The outlet of the ventilation channels through the layers of the roofing "pie" of flat roofs is possible only when using a special technical unit for the roof passage.
This structural element compensates for the dynamic and static loads exerted by the ventilation unit in operation. Also, the ready-made passage assembly simplifies waterproofing work in the ventilation outlet sector.
Convenience of a brick building as a glass - the possibility of masonry at the installation site of the ventilation device. However, in terms of the quality of waterproofing, the convenience of installing a fan, a brick glass loses to both steel and reinforced concrete
On reinforced concrete top ceilings, assembled from slabs or poured into formwork along the corrugated board, the nodes of the passage can be laid out of bricks, formed by a strip foundation or concrete casting. Outwardly, it looks like a ventilation shaft raised above the roof level, on the headband of which a fan is mounted.
However, such a design of the passage assembly is ineffective, since it creates difficulties with attaching fans and a lot of difficulties with waterproofing adjacent areas.
A reinforced concrete passage assembly, which is an improved version of the Soviet ST series, will allow the exhaust ventilation system to be mounted on a reinforced concrete floor. This product consists of two reinforced concrete shells (glasses) - a cylindrical inner and four- or hexagonal outer parallelepiped.
The outer glass is used as a reference. Thanks to the edges, it is easy to waterproof it along the perimeter of the joint with the main roof covered with a roll carpet. The inner sleeve, shaped like a round tube, is insulated on the outside. The outer glass of the roof passage unit is equipped with monolithic anchor elements of fasteners with a reinforced concrete slab base of the roof and with a roof fan.
Reinforced concrete double-shell glasses can be installed on ceilings and gentle slopes with a high bearing capacity with a slope of up to 12O. It is required to choose a model corresponding not only to the parameters of the roof fan, but also with a bottom slope equal to the actual roof slope. The weight of the double-hull reinforced concrete roof passage is over 300 kg.
Installation of reinforced concrete glass
Before lifting the glass passage assembly to the roof, visible metal elements and welds on a reinforced concrete product needs to be prepared - cleaned, covered with soil, then painted in two layers anti-corrosion compound. The outer surface of the outer shell should be putty, weather-resistant paint should be applied.
To lift a massive glass (about 300 kg) to the roof, slings and a crane are needed. Exposing the outer shell of the nozzle to the mounting place should be carried out on M200 cement-sand mortar.
The obvious advantages of reinforced concrete glass are the relative cheapness and resistance to vibration loads. And its disadvantage is a significant mass, which limits the scope of use.
Anchoring of reinforced concrete glass to the floor slab is carried out with the installation of embedded parts. If the fastening is carried out to the load-bearing roofing layer made of reinforced concrete slabs, then it is better to carry out a through installation of the glass, installing tie rod reinforcing bolts into the seams between the slabs.
Near the walls of the base of the installed glass, an inclined screed is made with M150 mortar. To insulate the perimeter, a mineral wool slab is placed near the roof passage under the screed. A layer of waterproofing roll materials is fused over the screed.
Along the line of the joint between the waterproofing materials and the glass, their edges overlap on its walls, closed with a galvanized apron and fixed with galvanized dowels. The seam along the line of abutment of the apron to the walls of the reinforced concrete glass is filled with a sealant (polyurethane, thiokol).
Installation of a roof fan in a reinforced concrete glass
Integration of roof fans into monolithic and slab reinforced concrete floors of industrial facilities is performed with using standard double-hull reinforced concrete glasses with an inner diameter of 700 to 1450 mm, a height of 400 mm.
Let us remind you that before installing the fan, the glass must become a structural part of the reinforced concrete roof slab.
In the upper and lower ends of the reinforced concrete unit for the roof passage there are wooden mortgages for fastening to the roof, for fixing the ventilation unit
To fix the fan in the upper part of the reinforced concrete glass, they are monolized with a cement-sand mortar embedded anchor bolts, in the lower one - tubes through which bolts are passed for fastening the fan pallet. After preparing the anchoring, a slope is created along the top of the glass from the M150 solution.
Before installation work, a revision check of the fan design and its electric motor is carried out. The clearance between the shell (or inlet pipe) and the impeller is checked.
Then a check valve is attached to the roof fan branch pipe, which automatically opens during the operation of the ventilation unit and closes the section of the branch pipe when it is turned off.
If, according to the project, a duct network is connected to the fan, the branch pipe (first link) must be connected to the ventilation unit before it is installed in a reinforced concrete glass. Air ducts are fixed to building structures, their weight should not affect the ventilation device.
Sequence of installation work
Given the massiveness of the ventilation device, it must be handled very carefully.
The installation procedure is as follows:
- The fan is manually set over the glass using a crane or jacks. The vibration isolation part of the fan (if the device is equipped with it) is fixed with standard bushings and locking bolts;
- The fan is installed on a glass, on the head of which a rubber gasket is placed. Anchor bolts are inserted into the holes of the mounting flange;
- The horizontal position of the device is verified with a level. The visor is mounted. Nuts and locknuts are screwed onto the anchor bolts;
- The gap between the top of the glass and the shell (or branch pipe) of the ventilation device is filled with construction sealant.
At the end of the installation, the stroke of the self-opening valve is adjusted by the counterweight. From the vibration isolators (if any) on the roof fan, the bushings and locking bolts are removed, which previously fixed the vibration isolating elements during the transportation of the device.
The power supply is connected, the strength of the connection and the free rotation of the impeller are evaluated, then the correctness of its rotation at start-up (according to the arrow).
Modern reinforced concrete nozzles for mounting fans have a convenient installation section - round on the inside, square on the outside
We emphasize that the placement of the condensate tray is mandatory during the colder months. The drain of the collected moisture is provided by a drainage pipeline with a diameter of 15-20 mm, connected to a sleeve at the bottom of the pallet.
Universal nodes of the roof passage
These bowls are prefabricated steel structures with a welded square body and faceplates from 400 mm in height. These nodes of the passage can be used on both hard and soft roofs, and with any type of roofing.
Ventilation systems can be equipped with universal metal glasses when they are placed on roofs with a slope of up to 30O.
It is important to equip the ventilation device with a glass that lifts it at least half a meter from the roof level. Otherwise, moisture from the accumulation of snow masses can penetrate into the ventilation duct.
The base plates at the top and bottom of the glass are made from 10 mm steel sheet. Additional reinforcement is provided by stiffeners made on the base plates. The structural elements of the product are connected by electric welding, the seam thickness is at least 6 mm.
The body of the steel roofing unit of the passage is mounted on a base made of channels, fixed to the load-bearing elements of the roof. There are welded studs on the top of the casing whose positions match the mounting holes on the fan base.
The double walls of the glass with a thickness of 10 and 12 mm contain thermal and noise insulating material. Models are also available without insulation inside the walls. By the way, when equipping a building with a smoke exhaust fan, a metal glass, in addition to increased fire resistance, may require additional external thermal insulation.
A petal valve or a heat-insulated valve equipped with an electric drive can be installed in the body of the steel glass. A condensate tray and a grate, or the outlet part of the air duct, are connected to the duct of the lower part of the roof passage unit.
The specifics of using a metal glass
The principle of installation of the steel unit for the roof passage on a rigid roof is almost identical to the procedure for installing a reinforced concrete glass. Consider the features of the assembly of a metal glass on a soft roof.
If the metal glass is equipped with check valve, then the latter must be mounted before installing the passage assembly in place. The valve may have shipping bolts that need to be removed. Note that when you try to set the valve on the installed glass, most likely, it will be skewed.
The advantage of the insulation protected by lining on the body of the steel glass is minimization of condensate deposits
The installation of the product is carried out on an opening prepared in the roof, corresponding to the dimensions of the inner section of the glass. It is fixed with anchor bolts on the load-bearing part of the roof, or on another load-bearing support capable of holding and fixing it in position. The passage unit is always positioned strictly vertically!
Final sealing, namely, a cement-sand screed of the mounting base of the glass, laying out thermal and waterproofing layers, placing skirts and aprons on the contour from galvanized steel and crimping clamps, is produced according to the actual conditions at the place of installation of the metal passageway assembly (roof structure, location and material of the support and etc.).
The own weight of the glass plus the weight of the fan mounted on it does not allow fixing the structure to the roofing cake. For them, mounting on a bearing support is mandatory.
Before mounting the fan on the glass, it is necessary to fix the pallet by preparing 14 mm holes for bolt connections on its side walls.
Installation of the roof fan to the metal glass is carried out with the fixation of the device on the studs using nuts and washers. After completing the installation, it remains to seal the contour of the gap between the fan and the glass with construction sealant.
The horizontality of the fan is verified by level, this is a must. Distortions allowed during installation work will damage the operation of the ventilation unit and reduce its service life.
Conclusions and useful video on the topic
Installation sequence on rigid roof and radial fan principle:
In what order is the roof fan installed on a soft roof:
Rooftop ventilation systems are designed for a long service life with minimal maintenance. However, they still need some maintenance: checking the strength of the joints (riveted, bolted, welded), inspection of the condition of the paint-and-lacquer coating of the fan flow area and blades on the impeller, cleaning from dust and pollution.
Therefore, it is necessary to provide free access to the equipment on the roof in the form of protected paths, so as not to damage the “pie” of the roof, especially the soft one. For this purpose, roll-up mats made of plastic or rubber are suitable.
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