Howden ENF User manual

Service Manual
Howden 24-07.030r04E 1/25
Installation and Maintenance
E-series Axial Flow Cooling Fans
Warning
Failure to comply with these instructions
could cause serious bodily harm or
property damage and will void the
warranty.

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E-series Axial Flow Cooling Fans
Service Manual
INDEX
I. General Information........................................................................................................................3
Introduction........................................................................................................................................3
Description.........................................................................................................................................3
Options / Accessories (at extra cost).................................................................................................3
Field Service......................................................................................................................................3
II. Receiving / Handling / Storage / Disposal ....................................................................................4
Fan identification ...............................................................................................................................4
Receiving and unloading...................................................................................................................5
Handling.............................................................................................................................................5
Storage..............................................................................................................................................5
De-commissioning.............................................................................................................................6
Exploded view and part list................................................................................................................7
III. Installation .....................................................................................................................................8
Required Tools ..................................................................................................................................8
Rotation and flow direction................................................................................................................8
Preparation........................................................................................................................................8
Coupling flange with parallel bore .....................................................................................................9
Coupling flange with tapered bushing ...............................................................................................9
Hub-plate installation.......................................................................................................................10
Blades installation..........................................................................................................................12
Minimum tip-clearance ....................................................................................................................14
Impeller diameter reduction.............................................................................................................15
Retaining plate.................................................................................................................................15
Balancing.........................................................................................................................................16
IV. Commissioning............................................................................................................................16
V. Preventive Maintenance..............................................................................................................18
VI. Contact Howden .........................................................................................................................19
VII. Trouble Shooting.......................................................................................................................20
VIII. Overview Tightening Torques.................................................................................................23
IX. Hardware Overview ....................................................................................................................24
X. Guideline for acceptable vibration levels of cooling fans in application category BV-3
(according ISO 14694) ......................................................................................................................25
XI. Document Version Control........................................................................................................25

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E-series Axial Flow Cooling Fans
Service Manual
I. GENERAL INFORMATION
Introduction
This manual provides information necessary to
install, operate and maintain E-series axial
flow cooling fans. Maintenance guidelines and
procedures are given so that your equipment
will operate efficiently, with a minimum of re-
pair or replacement requirements.
Description
Howden E-series fans are most widely used
and are available in three different blade pro-
files, ENF, ELF & ELFA. Whether you are
looking for a highly efficient impeller and/or a
low noise solution, the E-series offers you a
choice. The fibreglass reinforced polyester
blades have an integral shaft, which eliminates
concentration of stress at mechanical joints.
The FRP blade material offers superior damp-
ing of mechanical vibrations and of structure
borne noise compared with metal blades, pro-
longing the fan‟s lifetime. The fan blades are
connected to a polyurethane coated steel hub
with aluminium clamping pieces and A2
stainless steel or ST8.8 galvanised steel U-
bolts, nuts and washers for an easy installation
and manual blade pitch variation. The
impellers are connected to the drive shaft by
means of a polyurethane coated cast iron cou-
pling flange, with a cylindrical bore and electro-
galvanised hardware.
Howden E-series impellers are in compliance
with EC directive 94/9EC (ATEX 100) for the
equipment of level group II, Category 2, poten-
tially explosive environment class 01. Also re-
spect the instructions in paragraph IV commis-
sioning.
Note: The nomenclature is ‘cooling fans’,
however Howden supplies impellers only. Im-
pellers are components in the sense of Euro-
pean Machinery Directive 98/37/EC.
Allowable operating temperature
Min.
Max.
All diameters
- 20°C
+ 65°C
- 4°F
+ 149°F
Allowable incidental upset temp. (<12 h)
Max.
Max.
All diameters
+ 80°C
+ 176°F
Maximum tip speed
(As well depends on duty point)
m/s
ft/min
ENF
70
13780
ELF
60
11811
ELFA
46
9055
Table 1: Description table E-series
Options / Accessories (at extra cost)
Coupling flange with tapered bushing
connection, instead of standard cylindrical
bore connection.
Epoxy coating.
A4 stainless steel hardware.
Baked epoxy coating on aluminium
clamping pieces.
Polyurethane leading edge protection for
wet applications or stainless steel leading
edge protection for severe erosion.
Retaining plates to secure the impeller to
the drive shaft.
Bolted clamping piece fastening instead
of location pins, for horizontal drive shaft
applications.
Special impellers for fan selections out-
side the standard design range.
Tools (torque wrench or an inclinometer
for blade pitch adjustment).
Field Service
Howden Service maintains a staff of experi-
enced field service personnel. Their expert
knowledge may be of great assistance at in-
spection, installation, or to get your fan unit
back in service with a minimum of delay.

Service Manual
Howden 24-07.030r04E 4/25
II. RECEIVING / HANDLING / STORAGE / DISPOSAL
Fan identification
The fan identification code allows identification of the main characteristics of the fan. You can find
this code on the order acknowledgement and packing list included with the shipment.
FAN 30ENF6 EP
Another example:
FAN 8910ELF8
Identifies an ELF fan with a diameter of 8910 mm, 8 blades and without leading edge protection (EP)
The impellers are provided with a product identification plate fixed to the hub plate according the
example below. The unique order number permits future identification of the fan supplied.
Leading edge protection for wet cooling tower applications
Number of blades: 3,4,5,6,7,8,9
Impeller type: ENF, ELF, ELFA
Fan diameter: metric or imperial (>100 = mm, <100 = feet)
HOWDEN COOLING FANS
Hengelo, The Netherlands
Phone [phone]
Fax[phone]
Order No. 103459
Fan type 30ENF6 EP

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Service Manual
Receiving and unloading
Upon unloading this equipment, inspect it for
damage. If damage occurred, file a claim im-
mediately against the carrier and mark the bill
of lading accordingly.
Superficial transport damages like scratches
or small holes may be repaired with touch-up
material (PU filler, e.g. Sikaflex 252).
All consignments are accompanied by a
packing list with the following data:
Order number of the Customer and of
Howden.
Impeller type (fan identification code)
Parts supplied by Howden.
The delivered goods shall be checked upon
arrival for full compliance with the order
and/or the parts count and description stated
on the packing list.
Shortages should be reported to your How-
den Contract Engineer within 2 weeks from
receipt of shipment at destination.
Handling
Fan blades of E-series impellers larger than
26 ft. are packed in so-called “bunk beds” or
specially developed transport frames.
Figure 1
The width of these crates suits standard con-
tainer dimensions. Fan blades that will be
transported by container sea-freight, are
equipped with and hoist eyes (see figure 2),
to allow easy container loading / unloading.
Through these hoist eyes, one can pull the
bunk beds from the container without dam-
aging the fan blades or the crates.
Figure 2
The fan blades can be lifted from the packing
by placing a single sling around the blade.
Position the sling as such that the blade tip is
somewhat hanging down which makes it
easier to move the blades around.
Fan blades of impellers smaller than 26 ft.,
are packed in strong wooden cases or crates.
Storage
If not installed immediately, it is recom-
mended to store the impeller in a dry and
shaded area.
For long-term storage (in excess of 6 months)
it is necessary to check the condition of the
corrosion protection agent on all machined
surfaces.
Reapply or repair where necessary, using an
acid-free corrosion protection agent (e.g.
Esso Rust ban 397 or equivalent).
You may stack the “bunk beds” to a maximum
of 3 high. Do not allow any heavy materials of
any kind to be stored on top of the blades.

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Service Manual
De-commissioning
In accordance with our ISO14001 certified
environmental management system, our
cooling fans can easily be disassembled after
de-commissioning. Their metal components
and polyethylene fan casings are highly
suitable for recycling. Since no viable
recycling procedure for reinforced plastics
exists, fan blades need to be shredded and
incinerated or used as land-fill. The inert
nature of the materials used will prevent
chemical pollution of soil and ground water in
case of in land-fill.

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E-series Axial Flow Cooling Fans
Service Manual
Exploded view and part list
Figure 3 Figure 4
Item
Description
Material (standard construction)
Quantity
1
U-bolt
Stainless steel A2/ steel 8.8
2 / blade
2
Upper clamping piece
Aluminium
2 / blade
3
Lower clamping piece
Aluminium
1 / blade
4
Washer
Stainless steel A2/ steel 8
4 / blade
5
Nut
Stainless steel A2/ steel 8
4 / blade
6
Blade
Fibreglass reinforced polyester
-
7
Hub plate
Polyurethane coated mild Steel
1
8
Coupling flange bolt
Steel class 8.8 electro-galvanised
8
9
Washer
Electro-galvanised
16
10
Nut
Electro-galvanised
8
11
Coupling flange
Nodular cast iron polyurethane coated
1
12
Split tapered bushing
Manufacturers standard
1 (optional)
13
Bolt
Manufacturers standard
3 (optional)
14
Retaining plate
Polyurethane coated steel
1 (optional)
15
Central bolt M16 or M20 or M24
Steel class 8.8 electro-galvanised
1 (optional)
16
Washer
Electro-galvanised
1 (optional)
17
Gasket
Rubber
1 (optional)
18
Key
-
1 (optional)
19
Key
Not supplied by Howden
Table 2
1
2
16
3
4
5
6
15
14
9
8
12
10
9
11
13
7
18
19
17

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E-series Axial Flow Cooling Fans
Service Manual
III. INSTALLATION
Required Tools
Torque wrench (check tightening torques
for the correct model)
Socket and wrench
Inclinometer
Straight edge:
Minimum length > blade width
Rotation and flow direction
Standard rotation is clockwise when viewed
into the air-stream. See figure 5.
Figure 5
Preparation
Clean all mating surfaces between shaft, ta-
pered bushing (if applicable) and fan hub. All
corrosion preventive coatings should be re-
moved.
Check the following before parts shall be as-
sembled:
Drainage hole at the blade tip and blade
shoulder shall be open
Make sure the drive shaft is properly cen-
tred with respect to the fan casing. Also
check if the shaft is vertical within the pre-
scribed tolerance.
Check the concentricity of the driver shaft
end before mounting the impeller. The im-
peller should not be mounted if the con-
centricity error exceeds 0.02 mm (0.0008”)
see figure 6.
Figure 6
Flow

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Service Manual
Coupling flange with parallel bore
a) Check if the shaft and bore diameters are
according to specification. The standard
execution has a H7 fit.
b) Slightly lubricate the shaft, the key, and
the bore of the hub with grease.
c) Locate the key (19) into the drive shaft
(figure 7).
d) To slip the coupling flange over the shaft
we advise you to uniformly heat up the
coupling flange up to maximum 120 °C
(248 °F) by means of a hot plate, electric
induction or oil bath, until a 0.15mm dif-
ference in diameter is reached. Wear
protective gloves during this operation.
e) Slip the coupling flange (11) onto the
drive shaft and check the key for proper
fit. Be sure the coupling flange is com-
pletely through the shaft against the shaft
shoulder.
f) For reverse coupling flange configuration:
(e.g. impeller hanging below the driver)
Install the retaining plate (14) with gasket
(17) and secure it to the shaft with the
lock washer (16) and the central bolt
(15). Supply of retaining plate items 14,
15, 16 and 17 by Howden is optional.
Item 19 (key) is not supplied by Howden.
For torque values of the retaining plate
bolts see table 7 on page 22.
Figure 7
Coupling flange with tapered bushing
(Supply of coupling flange with tapered
bushing is optional).
a) Do not lubricate bushing, coupling flange
bore or hardware. Use of lubricants can
cause coupling flange damage.
b) Slip the bushing onto the drive shaft and
check the key (19) for proper fit (figure 8
on page 10). Be sure the shaft is com-
pletely through the bushing. Keep a bolt
length as minimum distance X between
bolts (13) and flange of the drive (figure 9
on page 10).
c) Lock the bushing on the shaft by tighten-
ing the setscrew in the flange. Support
the bushing with a sleeve to prevent it
from sliding down during assembly.
d) Install the coupling flange onto the bush-
ing. Start bolts (13) by hand turning just
enough to engage threads.
e) Keep tightening them as equally as
possible, in several steps, while drawing
the hub onto the bushing until the bush-
ing tightly grips the shaft.
f) Tighten the bolts to the torque shown in
table 3. Do not over-torque. Excessive
torque can cause coupling flange or
bushing damage. Some gap must remain
between the flange of the bushing and
coupling flange in properly tightened as-
sembly.
Torque value for bolts
tapered bushing to coupling flange
Class 8.8 (A3B)
Bolt size
(bushing type)
Torque
(Nm)
Torque
(lb.ft)
5/16” (P2)
22
16
3/8” (Q2, R2)
39
29
½” (S1)
95
70
5/8” (U1)
190
140
3/4” (W1, W2)
339
250
Table 3
14
19
11
15
16
17

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Service Manual
g) For reverse coupling flange configuration:
(e.g. impeller hanging below the driver)
Install the retaining plate (14) with seal
ring (17) and secure it to the shaft with
the lock washer (16) and the central bolt
(15). Supply of retaining plate items 14,
15 and 16 by Howden is optional. For
torque values of the retaining plate bolts
see table 7 on page 22.
Figure 8
Figure 9
Hub-plate installation
a. Mount the hub-plate (7) onto the machined
surface of the coupling flange (11) (fig. 10).
Figure 10
b. Place the bolts (8) with washers (9) and
tighten the nuts (10) alternating, keep tight-
ening on all of them as nearly equal as pos-
sible.
c. Tighten the nuts (10) to the torque shown in
figure 11 on the next page. (For the correct
thread size refer to table 8 on page 23).
Use original Howden hardware exclusively
(the nuts are treated with special “low fric-
tion” coating).
18
19
13
12
11
14
16
15
17
9
11
7
9
8
10

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E-series Axial Flow Cooling Fans
Service Manual
Figure 11
Tip: You may also choose to install the fan
blades onto the hub-plate before bolting the
complete impeller onto the coupling flange.
Figure 12
Tip: The hub-plate may be installed with the
clamping pieces either at the flow inlet or flow
outlet side. This may help to correctly position
the fan blades in the fan casing (see figure 12).
This configuration is only possible when the
coupling flange is fitted on the opposite side
from the lower clamping pieces or in a configu-
ration like figure 12, for impellers with a diame-
ter 9‟ (2743 mm).
If you prefer to use a configuration with the
coupling flange fitted in between the lower
clamping pieces, for impellers smaller than 9 ft.,
than please ask Howden at order placement.
Standard bolts (8.8, A3B)
Stainless steel (A4)
Nm lb.ft
75 55
185 136
360 266
625 461
1260 929
2600 1918
5500 4057
Thread
size
M12
M16
M20
M24
M30
M42
M48
Important
Impellers with a diameter smaller than
4455 mm or 14 feet are balanced
according to a certain hub-plate
configuration. Check the sticker on the
hub-plate to make sure the installation
corresponds to the applied balancing
method (refer to balancing section on
page 15).

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E-series Axial Flow Cooling Fans
Service Manual
Blades Installation
Impellers 4455 mm / 14 feet
Impellers up to and including a diameter of
4455 mm or 14 feet are balanced in assembly
and have a unique balancing code.
Check if the blades share the same project
number.
The blades must be positioned in the lower
clamping pieces with corresponding bal-
ancing code.
(For position of these numbers see figure 13).
Impellers > 4455 mm / 14 feet, and odd
number of blades
Impellers with an odd number of blades -
require the blades to be installed as sets.
Check if the blades share the same project
number.
The blades must be installed on a hub-
plate as sets. A blade-set share the same
2- or 3-digit figure in the balancing code
(e.g. 11A, 11B, 11C, 11D, 11E in case of a
5-bladed impeller).
(For position of these numbers see figure 13).
Impellers > 4455 mm / 14 feet, and even
number of blades
Impellers with an even number of blades re-
quire the blades to be installed in pairs.
Check if the blades share the same project
number.
The blades must be installed on the hub-
plate in pairs, with the paired blades posi-
tioned opposite each other. Always position
blade “A” facing blade “B”. Pairs share the
same 2- or 3-digit figure in the balancing
code (e.g. 31A facing 31B, 32A facing 32B,
33A facing 33B in case of a 6-bladed im-
peller).
(For position of these numbers see figure 13).
Note: For impellers > 4455 mm / 14 feet the
blade sets can be installed on any position of
a fan hub, provided that the blade sets will be
installed in the sequences spelled out in this
paragraph.
The blades are marked with a unique blade
number, a project number and a balancing
code (see figure 13).
Figure 13
Procedure:
a. Place a blade in a suitable lower clamping
piece of the hub plate, considering the in-
stallation rules as described in this para-
graph.
b. Place the upper clamping pieces over the
blade stem and insert the U-bolts through
the holes of the hub-plate. Place the
washers and hand-tighten the nuts just
enough to keep the blade in place. For the
standard configuration (blades on top of
hub plate) we recommend to insert and
tighten the inner U-bolt first (next to the
collar). When the blades are hanging un-
derneath the hub-plate we recommend in-
Balancing code
Blade nr
Project nr.

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E-series Axial Flow Cooling Fans
Service Manual
serting the outer U-bolt first. Check if the
upper clamping piece is mounted
horizontally by measuring the gap A an B
between the lower and upper clamping
piece (see figure 14).
Figure 14
c. Tighten the nuts alternating such that the
blade can still be somewhat turned in the
clamping piece.
d. Make sure that the blade stem collar is flush
against the lower clamping piece, which can
be achieved by pulling the blade outwards.
e. Place a straight edge or a sufficiently stiff
strip (at least as long as the profile width) on
top of the blade (discharge side) at about 50
mm (2 inches) from the blade profile end.
Place an inclinometer on top of the straight
edge (figure 15).
Figure 15
f. Lift the blade at the tip and rotate the blade
around its axis until the desired angle is set,
within a maximum tolerance of ± 0.5 de-
grees.
g. Re-check if the blade stem collar is flush
against the lower clamping piece.
Tighten the U-bolt nuts evenly to full torque
as shown in figure 16, starting with the U-
bolt at the collar side. Both the torque
values of our standard stainless steel (A2)
or galvanised steel (ST8.8) hardware as
well as our optional A4 stainless steel
hardware are shown. The material code A2,
St8.8 or A4 is stated on the nut. Make sure
that the blade angle does not change during
this operation (for the correct thread size
refer to table 8 on page 23).
After tightening of the nuts, the threaded
bolt ends out of the nuts shall have equal
length. The U-bolt is damaged if this is not
the case and don't fit for purpose anymore.

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E-series Axial Flow Cooling Fans
Service Manual
Note: the polyester stem will be com-
pressed during this operation and may pro-
duce a cracking sound.
Figure 16
h. Repeat the above operation for all blades.
i. Re-tighten the U-bolts after 50-75 hours in
operation, or 120-150 hours stand still. Do
not loosen the nuts first, but start to tighten
immediately.
j. When the blade angle has changed, the U-
bolts need to be tightened again to full
torque and also re-tightened after 120-150
hours.
Minimum tip-clearance
Tip clearance “s” is the distance between the
blade tip and the impeller casing (figure 17).
Due to normal impeller casing tolerances the
tip clearance is not constant around the im-
peller casing.
Figure 17
Howden recommends a tip clearance of 0.5% of
the impeller diameter. Fan selections using
Howden CF-P20 software use this default stan-
dard, unless otherwise specified. Tip clearance
shall never be less than 0.25%.
WARNING
DO NOT forget to re-tighten the U-
bolts as they may loosen due to creep
of the FRP material of the blade stem.
ONLY use original Howden hardware.
The nuts are treated with special “low
friction” coating.
DO NOT re-tighten location bolts of
the lower clamping pieces (location
bolts are used in special applications
only).
After loosening and disassembling of
a U-bolt, the legs of the U-bolt have
lost the parallel shape due to
relaxation effects. That is why it is not
allowed to re-use those U-bolts.
Thread
size
M12
M16
M20
M24
M30
M36
M42
(A2, St8.8)
= Standard
Nm lb.ft
60 44
140 103
250 184
425 313
650 479
1100 811
1300 959
( A4)
= Optional
Nm lb.ft
Idem
380 280
500 369
970 715
- -

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Service Manual
To make sure that the tip clearance is not less
than 0.25% in any location we recommend the
following steps:
a. Determine the longest blade by measuring
the tip-clearance of all blades at a fixed
point in the fan casing.
b. Now measure the tip clearance of the long-
est blade at a number of measuring points
(see table 4 for the number of recom-
mended measuring points). Slowly rotate
the impeller by hand to the different meas-
uring points.
c. Centre the impeller in the casing, or the
casing around the impeller, in case the tip
clearance is too small and repeat the previ-
ous steps.
Diameter
Metric (mm)
Diameter
Imperial (ft.)
Number of meas-
uring points
700-2000
3-6
4
2001-4000
7-13
6
4001-6000
14-18
8
6001-12500
22-40
12
12501-16000
44-48
16
Table 4
Impeller diameter reduction
In case the tip clearance is smaller than the
above described minimum tip clearance, and
centring the impeller does not help, one has the
possibility to reduce the impeller diameter by
placing one or more 5 mm thick nylon spacer
rings between the blade stem collars and the
lower clamping pieces. The same number of
spacer rings shall be installed on all blades of
an assembly. This method allows the impeller
diameter to be reduced by 40-50 mm.
After installing the nylon rings, torque the nuts
again according to the blade installation proce-
dure as described previously.
Retaining plate
(Supply of retaining plate is optional).
Install retaining plate with gasket, washers and
bolts after the coupling flange or after the im-
peller has been installed. For torque values of
electro-galvanised retaining plate bolts see
table 7 on page 22 of this manual.
Important
Howden strongly recommends the
installation of a retaining plate for all
vertical shaft applications with impeller
hanging below the driver or whenever
the airflow is directed towards the
driver.

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E-series Axial Flow Cooling Fans
Service Manual
Balancing
The impellers are balanced according to ISO
1940, balancing quality grade G6,3.
Impellers with a diameter smaller than 4455
mm or 14 feet are balanced in assembly ac-
cording to a certain hub-plate configuration:
A. Clamping pieces installed at flow inlet side
B. Clamping pieces installed at flow outlet side
A sticker on the hub-plate marks the applied
balancing method. See figure 18.
Figure 18 Sticker as attached on the hub-plate
If not agreed otherwise, the impeller is bal-
anced according method B by default.
IV. COMMISSIONING
a. Check all bolts and nuts for proper tighten-
ing (including the fan casing hardware).
b. Make sure that the metal bearing support
structure is electrically earthed in order to
avoid sparkling by electrical static dis-
charge.
c. Turn the impeller by hand to check that it
runs freely and does not rub or strike the
impeller housing.
d. Impellers driven by a two-speed e-motor:
Only switch from “high speed” to “low
speed” after the impeller speed has
slowed down to less than the “low speed”.
To be sure you may choose to switch the
e-motor only after the impeller has come
to a complete standstill. Neglecting this
rule may lead to irreparable impeller
damage!
e. Make sure that all tools and assembly aids
like beams, supports, ladders…etc. have
been removed. All the required protec-
tions, mechanical and electrical must be
installed before starting the fan. Make sure
that all applicable local safety require-
ments have been met to ensure safe op-
erating conditions.
f. „Bump” the motor to check for clockwise
rotation of the impeller, when viewed into
the air stream (also see figure 6).
Important
If the impeller is installed in a different hub-
plate configuration than it was balanced,
e.g. configuration B for an installation with
the clamping pieces at flow inlet side, you
run the risk of an unquiet operation.

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Service Manual
g. Immediately after first start up check for
smooth operation of the fan assembly.
Check for irregular noise / vibrations.
Howden adopts the guideline given in
standard ISO-14694 describing the
acceptable vibration levels. The “in situ”
vibration level of any fan is not solely
dependent on the balancing grade.
Installation factors, the mass and stiffness
of the supporting system, will influence the
in situ vibration level. Therefore, fan
vibration level “in situ” is not the
responsibility of the fan manufacturer
unless specified in the purchase contract.
ISO-14694 classifies fans according to
their application and drive power. Howden
cooling fans are in general used for
industrial processes, power generation
and HVAC with a drive power level up to
300 kW. According ISO-14694 Howden
cooling fans are classified in the so-called
fan application category BV-3.
For fans in application category BV-3
balancing grade G6.3 is recommended
(ISO-14694) and therefore Howden
cooling fans are balanced according to
this balancing grade. The vibration levels
given in table X are a guideline for
acceptable operation of Howden cooling
fans.
Immediately after commissioning the
vibration level has to be below or at the
given start-up value. When the vibration
level increases to alarm level investigation
to the cause of this level has to be initiated
and action taken to correct it. When the
vibration level increases to shutdown level
corrective action should be taken
immediately or the fan should be shut
down.
The vibration limits shown in table X apply
to assembled fan units. The values shown
are velocity, in millimetres per second
(mm/s). Filter-In, at fan rotational
frequency and are to be taken at the fan
bearings or at gearbox sides as per figure
19, in case the fan is mounted directly on
the gearbox shaft.
Figure 19 Vibration Measuring Points measured at Fan
Units of Air Cooled Condensers
Possible Measuring Points
1
Gearbox - lateral flange - horizontal
2
Gearbox - front end - horizontal
3
Gearbox - bearing cover of output shaft - vertical

Howden 24-07.030r0418/25
E-series Axial Flow Cooling Fans
Service Manual
h. Measure the power. In case the fan power
(after correction for temperature) is different
than required, adjust the pitch angle
accordingly (3 degrees tolerance from de-
sign blade angle). Note: the absorbed
power is inversely proportional to the air
temperature. If a larger adjustment is re-
quired, after temperature correction, verify
with a new fan selection or contact
Howden.
i. Re-tighten the U-bolts after 50-75 hours in
operation, or 120-150 hours stand still.
Check the tightening torque of the bolts of
the tapered bushing and the coupling
flange bolts.
V. PREVENTIVE MAINTENANCE
Though the impeller requires little
maintenance, it is recommended to conduct
inspections at regular intervals, to check
damage due to vibrations, fouling or wear
and tear.
Actual recommended maintenance intervals
will depend on the use and operation of the
complete system and shall be determined by
the operator.
Check for smooth operation of the fan
and listen for irregular noise or vibrations.
De-energise the fan and make a visual
inspection for deposits, and or damages.
Visually inspect the blades surface and
blade stems for cracks. Hairline cracks
could appear in resin rich areas around
the edges of the fan blade and will nor-
mally stop progressing. Hairline cracks in
itself are harmless, however we advise
you to fill these cracks with a touch-up
material (PU filler, e.g. Sikaflex 252) to
prevent moisture penetration affecting
the blades. Howden Cooling Fans can
provide you a repair kit complete with in-
structions.
For all other cracks we suggest to send
photographs to Howden Cooling Fans for
evaluation.
Important
De-energise the fan and use lock out and
tag out procedures prior to performing
adjustments, service, inspections or
lubrication.
WARNING
Contact with rotating fan blades can cause
severe injury or death. Never insert items
into the fan to determine movement or
direction of rotation. Install fan guards or
screens on arrangements with exposed
fans. Always use lockout and tag out
procedures before performing fan
adjustments, maintenance, service or
inspection.
Important
Following measures must be emphatically
respected for potentially explosive
environments and to comply with Directive
94/9/EC (ATEX 100):
Electrically earthed metal bearing
support to avoid sparkling by electrical
static discharge
Minimum prescribed tip clearance to
avoid rubbing along the impeller casing.
Directions for design of the impeller
support structure according to Howden
document 03-07.341

Howden 24-07.030r0419/25
E-series Axial Flow Cooling Fans
Service Manual
Visually inspect the blades for wear and
tear. Exposed fibreglass should be re-
coated. We recommend shipping the
worn blades to Howden for refurbish-
ment.
For wet cooling tower applications visu-
ally inspect if the leading edge protection
is still sufficient. If the leading edge pro-
tection is (partly) worn, we advise to ei-
ther install Howden stainless steel nose
caps or to apply a new PU coating. The
stainless steel caps can easily be in-
stalled over the leading edge of the
blades and attached with rivets is a
practical solution for repair inside a cool-
ing tower. Howden shall be glad to ad-
vise you the best maintenance solution
for your application.
Replace corroded bolts and nuts.
Deposits should be removed from impel-
ler and fan housing using brushes and/or
a water jet with a maximum water pres-
sure of 3 bar or 45 psi. This is even more
important after change out of any blades,
to ensure proper balance.
Check if the drainage holes at the blade
tip and blade shoulder are still open.
Repairs of the FRP blades shall be carried
out strictly in accordance with Howden pro-
cedures.
We suggest that any damage be photo-
graphed and forwarded to Howden Cooling
Fans for evaluation.
VI. CONTACT HOWDEN
Howden Cooling Fans
Lansinkesweg 4
P.O. Box 975
7550 AZ Hengelo
The Netherlands
Tel. [phone]
Fax [phone]
Email: [e-mail]
Web: www.howdencoolingfans.com

Howden 24-07.030r0420/25
E-series Axial Flow Cooling Fans
Service Manual
VII. TROUBLE SHOOTING
In case of any failure, please contact Howden stating the impeller order number as mentioned on
the nameplate located at the hub of the impeller.
Problem
Possible cause
Possible solution
Air volume low.
Fouling of system.
Clean system air-cooler
bundles or cooling tower
fill.
Obstacles in housing/air
stream.
Check actual total area of
obstacles and impeller
housing inlet shape
against original selection.
In dry-coolers the mini-
mum required free height
of the air inlet area is 1.0
times the fan diameter.
This shall be higher in
case of multiple row units.
Static pressure higher than
specified.
Increase blade angle.
(Up to 3 degrees, thereaf-
ter do selection check).
Blade angle decreased
due to rotation of the
blades. (I.e. forgot to re-
torque the U-bolt nuts).
Re-set blade angle and
refer to the blade installa-
tion instructions for the
correct torque.
Air temperature higher
than design air tempera-
ture.
Increase blade angle.
(Up to 3 degrees, thereaf-
ter do selection check).
Power absorption (too)
high. (1)
Fouling of system.
Clean system air-cooler
bundles or cooling tower
fill.
Obstacles in housing/air
stream.
Check actual total area of
obstacles and impeller
housing inlet shape
against original selection.
In dry-coolers the mini-
mum required free height
of the air inlet area is 1.0
times the fan diameter.
This shall be higher in
case of multiple row units.