Checking The Distance Between The Impeller And Nozzle (Air Gap) - CBI CH Series Translation Of The Original Instructions

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Checking the distance between the impeller and nozzle
(air gap)
Complying with the distance between the impeller and the nozzle is one of the
most important parameters for a fan that works in ATEX environments.
These fans are thoroughly checked but you cannot exclude a shift between the
impeller and nozzle during the transport, commissioning or special maintenance.
Proceed as follows for this inspection:
- Turn off and disconnect the fan from the power supply and from all sources of
energy interacting with it; also interrupt the flow of fluid although inactive.
If necessary, sanitise the environment if gas or dust that may
be toxic or harmful for the operator are present.
- Remove the protection on the intake of the fan and/or any ducts.
- Obtain the specific key K (supplied) or use a similar shim of appropriate dimen-
sions, according to distance S or the required air gap, according to diameter D
of the fan nozzle.
Indicatively shim S or the required air gap varies from 2 to 20 mm.
- Measure diameter D of the opening of the nozzle (contact side with the impeller).
Depending on diameter D, distance S or the required air gap should be:
For diameter D up to 200 mm S = 2 mm
For diameter D from 200 to 2000 mm
For diameter D greater than 2000 mm
- Insert key K (supplied) or a similar shim S on the entire circumference of the
impeller, making sure to double check the shortest distance between the impeller
and nozzle. Perform this operation at least 4 times, rotating the impeller manu-
ally 90° each time.
N.B. Shim S or the key must simply be inserted, even in the presence of
slight friction, for the measurement to be complied with.
- Where necessary, depending on the conformation of the blades, also check
distance S or the air gap in the orthogonal direction, between the blades and the
inner profile of the nozzle (contact side with the blades).
In case of non-compliance with the minimum distance between the impeller and
nozzle, check that the latter is assembled and centres correctly and verify the
possible presence of deformations due to an improper installation. If the problem
persists, contact the Manufacturer.
- Fit the protection on the intake of the fan and/or any ducts and restore the
correct operating conditions.
S = 1% of D
(e.g. D = 480 mm S = 4.8 mm)
S = 20 mm
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