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SUPPLY AND SERVICES

- specific weight: 0,475 kg/m3 The installation of a new rotor
- Velocity: 890 RPM has made necessary to change
- Velocity: 940 RPM “also the bearings, prime
- Temperature: 430 °C
- Temperature: 380 °C movers and finally also a
- Absorbed power: 1121 kW casing modifications has been
- Absorbed power: 1.980 kW
- Dust: 30 g/m3 necessary
- Dust: 30 g/m3

Due to the high increase in the flow value, required The new shaft has been sized in order to have a
by the new conditions of the plant, in this revam- first critical lateral speed equal to 1,35 the nomi-
ping it has been necessary the complete substi- nal speed, which is a good margin for this ope-
tution of the rotor and some modifications to the ration.
static parts of the Fan. The increase of the installed The new bearings are roller type, oil lubricated.
power has been done by adding, on the other shaft
end of the fan, an identical motor already available
at site. The new fan arrangement is a double driven
fan with a new double end shaft. Boldrocchi has Fan Casing
supplied a new complete metallic baseframe plus The increased diameter of the new impeller invol-
anchor bolts in order to support and fix the new ves a modification to the existing casing to have
motor; a new foundation plinth has been enginee- the proper clearance between the new wheel and
red and manufactured by the customer. the outlet cut-off: a shaped portion of the casing,
fabricated in Boldrocchi workshop, have been sup-
plied and then installed at site after having removed
Impeller and inlet bells partially the actual casing scroll as per our detailed
instructions.

To reach the new performance, a new impeller our For the modification of the existing casing due to
type 45L-355/1800M DWDI has been selected, the increased diameter of the impeller, we have
having special backward curved blades (single cut an arch length about 3.600 mm from the
thickness) with a diameter of about 3.600 mm. discharge cut-off, by taking care of the division
To protect the blades and part of the centre plate flange of the casing (for the dismounting of the
from the abrasive dust, wear plates on the 50% of casing in two pieces for the rotor removal). The
blades area and corners have been provided. new complete piece manufactured in our wor-
The material of the impeller, working at a tempera- kshop has been delivered in two pieces in order
ture of 400 °C: is ASTM A387. to facilitate the welding at site.
Since the new impeller has different width compa-
red to the existing one a new couple of inlet bells
has been included in our scope of supply.
E-motor and couplings
The new absorbed power of the fan and the in-
Shaft stallation of the second motor at the free end of
the Fan shaft, has involved a new transmission
The weight of the new bigger impeller has been coupling with elastic elements (due to the pre-
supported by a new shaft very similar to the exi- sence of the inverter) suitable to absorb an axial
sting one, but with increased diameter under the displacement at nominal conditions of about 21
impeller’s hub and in the bearing area. The new de- mm
sign has involved also the complete substitution of
the bearings.

82 Impiantistica Italiana - Gennaio-Febbraio 2023