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USE
Chimney caps should be used as the finishing item on gravitational ducts and fume chimneys. Chimney caps
perfectly protects against rain, intrusive objects and down draught´s. Allowing the ventilation and chimney ducts to
operate properly in all conditions.
CAUTION
Polluted air is removed through ventilation ducts/chimneys in buildings where there is natural ventilation. The efficiency
of gravitational chimney´s operation depends on the thrust that is created in them thanks to the gravitational buoyant
force.Gravitational, or the so called natural chimney draught is created because of the difference of the air density
between the surrounding atmosphere and the building interior. The air´s density depends mostly on its temperature.
When the temperature in the building is higher than outside, the density of the internal air is lower than the external and
the draught is positive. However, when the temperature outside is higher than in rooms (e.g. in summer), the air wants to
get into building through ventilation ducts instead of getting out. This effect is called back-draught.We deal with back-
draught when there is the lack of air inflow in to rooms for proper ventilation purposes. It happens in insulated houses and
the ones with hermetic windows, where there is either gas or oil heating, or fireplaces that take the air from the room for
combustion.The disturbance of the draft can be also caused by nature itself in the case of poor or bad location of the
building i.e. in regions of strong winds, close to other buildings, close to high trees, or on the hilly areas, in that case, the
direction of the airflow will be reverse - outside to inside i.e. back-draught.You should take precautions to avoid reverse
gas flow - back-draught - into rooms from an open chimney duct or other devices such as open fire. In case of the reverse
air flow, fumes can be forced back inside the building and this can be a health hazzard and even lead to death as the
fumes can be poisonous.
How to efficiently improve the function of a gravitational ventilation system?
DORN chimney caps are used to improve/increase the chimney up-draught. Our chimney caps use wind and its energy
to create lower pressure in the ventilation duct. The difference in pressure causes the fumes to be rise up the
chimney/duct and exit the building.
INSTALLATION
Our caps can be installed on ventilation chimneys having standard dimensions from 100 mm and to 315 mm.
The installation should be carried out according to the following points:
The upper part of the cap with the head should be removed by slackening of screws placed in the cap´s shank.
The ventilation ducts/chimney should be checked where the cap is to be fitted and should be cleaned if
necessary before installation.
Mark the cap´s installation holes where you want to place the cap and drill them to place.
Place the bottom part of the cap by means of screws.
Put the upper part of the cap onto the lower one.
Assemble both parts of the cap screwing tight the bolts placed in the cap´s shank.
Check if the cap is well assembled.
CONSTRUCTION
The head of the DORN chimney cap is made of aluminium, while the base of the cap is made of tin plate. The cap has the
thermal endurance to 180 °C (temporary to 300 °C).
MAINTENANCE
The survey should be carried out at last once a year. In order to remove dirt from inside the cap, or to examine the
ventilation ducts you should:
1.Remove the upper part of the cap by slackening of screws placed in the cap´s shank.
2.Clean all dirty parts with slightly warm water, a small amount of detergent and a cloth.
3.Wipe out all the parts dry.
4.Check the condition of the grease in the lubricating-turning set and fill the shortage with the grease that can
tollerate temperatures upto 1000 °C.
5.Install back all the parts.
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