04_Howden_Installation-Maintenance D-Series Fans.pdf

Service Manual

Howden 24-07.022r01E 1/20

Installation and Maintenance

D-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.

Note

The blades installation sequence has been

changed when compared with our

Z-series Manual!

Howden 24-07.022r01 2/20

D-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 ..................................................................................................... 4 Fan identification ............................................................................................................................... 4 Receiving and unloading ................................................................................................................... 5 Handling ............................................................................................................................................. 5 Storage .............................................................................................................................................. 5 Exploded view and part list ................................................................................................................ 6

III. Installation ..................................................................................................................................... 7 Required Tools .................................................................................................................................. 7 Rotation and flow direction ................................................................................................................ 7 Preparation ........................................................................................................................................ 7 Coupling flange with parallel bore ..................................................................................................... 8 Coupling flange with tapered bushing ............................................................................................... 8 Hub-plate installation ......................................................................................................................... 9 Blades installation ............................................................................................................................ 10 Minimum tip-clearance .................................................................................................................... 12 Impeller diameter reduction ............................................................................................................. 13 Retaining plate ................................................................................................................................. 13

IV. Commissioning ........................................................................................................................... 13 V. Preventive Maintenance .............................................................................................................. 15 VI. Contact Howden ......................................................................................................................... 15 VII. Trouble Shooting ........................................................................................................................ 16 VIII. Overview Tightening Torques .................................................................................................. 18 IX. Maximum Vibration Levels for Balance Vibration category BV-3 (ISO 14694) ...................... 19 X. Document Version Control .......................................................................................................... 20

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I. GENERAL INFORMATION

Introduction

This manual provides information necessary to

install, operate and maintain D-series axial

flow cooling fans. Maintenance guidelines and

procedures are set so that your equipment will

operate efficiently, with a minimum of repair or

replacement requirements.

Description

Howden D-series fans are the latest in axial

fan development with excellent operating effi-

ciencies and a significant pressure pulse re-

duction to the fan ring. The fibreglass rein-

forced polyester blades have an integral shaft,

which eliminates concentration of stress at

mechanical joints. The FRP blade material

offers superior damping of mechanical vibra-

tions and of structure borne noise compared

with metal blades, prolonging the fan‟s lifetime.

The fan blades are connected to a polyure-

thane coated mild steel hub with aluminium

clamping pieces and AISI 304 stainless steel

U-bolts, nuts and washers for an easy installa-

tion and manual blade pitch variation. The im-

pellers are connected to the drive shaft by

means of a polyurethane coated cast iron cou-

pling flange, a tapered bushing and galvanized

hardware.

Howden D-series impellers are in compliance

with EC directive 94/9EC (ATEX 100) for the

equipment of level group II, Category 2,

potentially explosive environment class 01.

Also respect the instructions in paragraph IV

commissioning.

Note: The nomenclature is ‘cooling fans’, how-

ever Howden supplies impellers only. Impel-

lers are components in the sense of European

Machinery Directive 98/37/EC.

Allowable operating temperature

Min. Max.

All diameters - 20°C + 65°C

- 4°F + 149°F

Allowable incidental upset temperature (<12 h)

Max. Max.

All diameters + 100°C + 212°F

Maximum tip speed (As well depends on duty point)

m/s ft/min

DNF 65 12795

DLF 60 11811

DVF 60 11811 Table 1

Options / Accessories (at extra cost)

Epoxy coating.

AISI 316 stainless steel hardware.

Baked epoxy on aluminium clamping pieces.

Polyurethane leading edge protection for wet applications or stainless steel leading edge protection for severe erosion.

Cylindrical bore hub-shaft connection, instead of the standard tapered bushing connection.

Retaining plates to secure the impeller to the drive shaft.

Tools (torque wrench or an inclino-meter 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.

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II. RECEIVING / HANDLING / STORAGE

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 30DNF6 EP Another example: FAN 8910DLF8 Identifies a DLF 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: 5,6,7,8

Impeller type: DNF, DLF, DVF

Fan diameter: metric or imperial (>100 = mm, <100 = feet)

HOWDEN COOLING FANS Hengelo, The Netherlands Phone +31-74 2556000 Fax +31-74 2556060 Order No. 103459 Fan type 30DNF6 EP

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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 PU filler

(i.e. 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

Howden Contract Engineer within 2 weeks

from receipt of shipment at destination.

Handling

The D-series fan blades are packed in so-

called “bunk beds”.

Figure 1

The width of the crates suits standard con-

tainer dimensions. Fan blades that will be

transported by container sea-freight, are

equipped with skids 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

damaging 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.

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 coating 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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Exploded view and part list

Figure 3 Figure 4

Item Description Material (standard construction) Quantity

1 U-bolt M24 Stainless steel AISI 304 2 / blade

2 Upper clamping piece D=145 Aluminium 2 / blade

3 Lower clamping piece D=145 Aluminium 1 / blade

4 Washer d 24 Stainless steel AISI 304 4 / blade

5 Nut M24 Stainless steel AISI 304 4 / blade

6 Blade Fibreglass reinforced polyester -

7 Hub plate Polyurethane coated mild Steel 1

8 Coupling flange bolt M30 Steel class 8.8 electro-galvanised 8

9 Washer d 30 Electro-galvanised 16

10 Nut M30 Electro-galvanised 8

11 Coupling flange 250D Nodular cast iron polyurethane coated 1

12 Split tapered bushing Manufacturers standard 1 (optional)

13 Bolt Manufacturers standard 3

14 Retaining plate Polyurethane coated mild 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 Seal ring 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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III. INSTALLATION

Required Tools

Torque wrench (190 - 1300 Nm /

140 - 1000 ft.lb)

5/8” socket and wrench (bushing U1)

M24 socket and wrench

M30 socket and wrench

Inclinometer

Straight edge:

DNF approx. 550 mm length (22 inch)

DLF approx. 950 mm length (37 inch)

DVF approx. 1400 mm length (55 inch)

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 remo-

ved.

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

centred with respect to the fan casing.

Also check if the shaft is vertical within

the prescribed tolerance.

Check the concentricity of the driver

shaft end before mounting the impel-

ler. The impeller should not be moun-

ted if the concentricity error exceeds

0.02 mm (0.0008”) see figure 6.

Figure 6

Flow

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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 electro-galvanised retaining plate bolts see table 5 of this manual.

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). Be sure the shaft is completely through the bushing. Keep a bolt length as minimum distance X between bolts (13) and flange of the drive (figure 9). For the Howden D-series supply of a tapered bushing is optional.

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 bushing 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 bus-hing damage. Some gap must remain between the flange of the bushing and coupling flange in properly tightened as-sembly.

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 electro-galvanised retaining plate bolts see table 5 of this manual.

Torque value for bolts tapered bushing to coupling flange

Bolt size: 5/8” (standard bushing) 5/8” (standard bushing) Torque (Nm) 190

Torque (lb ft) 140

Table 3

14

19

11

15

16

17

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Figure 8

Figure 9

TIP: Smear rust inhibitor (Tectyl or similar) into

all joints and corners between drive shaft and

fan hub. This will help future hub removal.

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. Both the torque

values of our standard electro-galvanised

hardware as well as our optional AISI 316

stainless steel hardware are shown. Use

original Howden hardware exclusively (the

nuts are treated with special “low friction”

coating).

9

11

7

9

8

10

18 19

13

12

11

14

16

15

17

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Figure 11

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).

Figure 12

Tip: You may also choose to install the fan

blades onto the hub-plate before bolting the

complete impeller onto the coupling flange.

Blades installation

The impellers are balanced according to ISO

1940, balancing quality grade G6,3. The blades

are marked with a unique blade number, a

project number and a balancing master code

(see figure 13).

Figure 13

Procedure:

a. Place a blade in one of the lower clamping

pieces of the hub plate.

b. Examine whether all fan blades are having

the same project number. Fan blades have

to be mounted as sets, in alphabetical

sequence. Referring to the clockwise

rotating direction of the impeller (flow

outlet), the installation sequence of the

blades is anti-clockwise. Consequently the

alphabatic sequence is seen when the fan

is (slowly) running! For example for a 5-

blade fan in the sequence 3A, 3B, 3C, 3D

and 3E (see figure 14).

Std. bolts (8.8, A3B)

1260 Nm 929 lb ft

Stainless steel (AISI 316, A4)

1180 Nm 870 lb ft

Balancing code

Blade nr

Project nr.

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Figure 14

c. 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 underneath

the hub-plate we recommend inserting the

outer U-bolt first.

d. Tighten the nuts alternating such that the

blade can still be somewhat turned in the

clamping piece.

e. Make sure that the blade stem collar is flush

against the lower clamping piece, which can

be achieved by pulling the blade outwards.

f. 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

g. 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

degrees.

h. Re-check if the blade stem collar is flush

against the lower clamping piece.

i. 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 AISI 304 stainless

steel hardware (A2) as well as our optional

AISI 316 (A4) stainless steel hardware are

shown. The material code AISI 304

(A2)/AISI 316 (A4) is stated on the nut.

Make sure that the blade angle does not

change during this operation.

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.

3A

3E

3D 3C

3B

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Std. Stainless steel (AISI 304, A2)

425 Nm 313 lb ft

Stainless steel (AISI 316, A4)

380 Nm 280 lb ft

Figure 16

Note: the polyester stem will be com-

pressed during this operation and may pro-

duce a cracking sound.

j. Repeat the above operation for all blades.

k. 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.

l. 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 impeller

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 as

standard, unless otherwise specified. Tip

clearance shall be no less than 0.25%.

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 12 measuring points. Slowly

rotate the impeller by hand to the different

measuring points.

c. Centre the impeller in the casing in case the

tip clearance is found too small and repeat

the previous steps.

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.

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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, tighten the nuts

again according the blade installation procedure

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

impeller has been installed. For torque values

of electro-galvanised retaining plate bolts see

table 5 of this manual.

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 discharge.

c. Turn the impeller by hand to check that it runs freely and does not rub or strike the impeller casing.

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 protections, mechanical and electrical must be installed before starting the fan. Make sure that all applicable local safety requirements have been met to ensure safe operating conditions.

f. „Bump” the motor to check for clockwise rotation of the impeller, when viewed into the air stream (also see figure 5).

g. Immediately after first start up check for smooth operation of the fan assembly. Listen for irregular noise / vibrations. For allowable vibration levels of the complete installation refer to the system manufacturer. Please refer to international standards that may apply for the specific application, such as, ISO-14694. ISO-14694 classifies fans according to their application and drive power as follows: For industrial processes and power-generation with a drive power level up to 300 kW, the so-called Balance and Vibration category is BV-3. For higher power levels ISO 10816-3 should be respected. For BV-3 balancing grade G6.3 is recommended (ISO 1940-1) with maximum vibration levels according to table 6 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

impeller is mounted on a horizontal shaft.

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The vibration level VR.M.S. should be measured at the drive shaft bearings or gearbox sides as per figure 18, in case the fan is mounted directly on the gearbox shaft.

Figure 18 Vibration Measuring Points measured at Fan

Units of Air Cooled Condensers

h. Measure the power. In case the fan power

(after correction for temperature) is differ-ent 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 required, after temperature correction, ve-rify 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.

Possible Measuring Points

1 Gearbox - lateral flange - horizontal

2 Gearbox - front end - horizontal

3 Gearbox - bearing cover of output shaft - vertical

WARNING

Contact with rotating fan blades can cause

severe injury or death. Never insert items

into the fan to determine movement or di-

rection of rotation. Install fan guards or

screens on arrangements with exposed

fans. Always use lockout and tag out pro-

cedures before performing fan adjust-

ments, maintenance, service or inspec-

tion.

WARNING

A strong fan-speed reduction may lead to

irreparable impeller damage. Never use a

forced impeller deceleration like a brake or

an e-motor switching to a lower drive-

speed; instead let the impeller run out.

Important

Following measures must be emphatically

respected for potentially explosive envi-

ronments 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

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V. PREVENTIVE MAINTENANCE

Though the impeller requires little mainte-

nance, it is recommended to conduct inspec-

tions 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 pro-

vide you a repair kit complete with in-

structions. For all other cracks we sug-

gest to send photographs to Howden

Cooling Fans for evaluation.

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 prac-

tical solution for repair inside a cooling

tower. Howden shall be glad to advise

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 can only be car-

ried out according to Howden procedures.

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. +31 74 255 6000

Fax +31 74 255 6120

Email: [email protected]

Web: www.howdencoolingfans.com

Important

De-energise the fan and use lock out and

tag out procedures prior to performing

adjustments, service, inspections or

lubrication.

mailto:[email protected]

http://www.howdencoolingfans.com/

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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 minimum 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, thereafter do selec-

tion 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 installation instructions for the

correct torque.

Air temperature higher than

design temperature.

Increase blade angle.

(Up to 3 degrees, thereafter 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.

Power absorption (too)

high. (2)

Static pressure higher than

specified.

Decrease blade angle.

Clean system air-cooler bundles or

cooling tower fill.

Air temperature higher than de-

sign temperature.

Check performance against current

air temperature.

Airflow too high. Decrease blade angle.

Blade angle too large. Set blade angle according fan selec-

tion details.

Transmission out of order. Check transmission.

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Problem Possible cause Possible solution

Impeller is rubbing against

fan casing.

Bolting of drive-train connection

or fan housing is not tight.

Tighten all bolts.

Impeller not centred. Centre the impeller.

Tip clearance too small. Decrease impeller diameter by

placing nylon rings between lower

clamping pieces and blade stem

collars.

Fan casing too weak. Stiffen fan casing.

Vibration level high. (1) Imbalance of impeller. Check if position of fan blades is

according to instruction.

Lack of stiffness in support

structure.

Reinforce support structure.

Bolting of drive-train connection

or fan housing is not tight.

Tighten all bolts.

Drive alignment incorrect. Realign.

Driver bearing damage. Repair or replace.

Drainage holes are blocked. Open the drainage holes.

Blade is not flush against lower

clamping piece.

Release U-bolts, pull the blade

outwards and re-tighten the U-bolts to

the correct torque.

Blade angle(s) not within ±0.5°

tolerance.

Re-set the blade angles.

Vibration level high. (2) Blades are out of tracking. The

blade tips should be reasonably

located in the same plane. A

maximum tolerable deviation of

0.5% of the fan diameter is

advised.

Contact Howden for advise.

Fan is in stall. Decrease blade angle or replace

impeller.

Resonance of the cooler

structure.

Change natural frequency of the

cooler or run the fan at a different

speed or install a fan with more or

fewer blades.

Scratches or small

damages.

Transport and handling. We advise to fill these cracks with a

touch-up material e.g. Sikaflex 252 to

prevent moisture penetration affecting

the blades (Contact Howden for a

repair kit).

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Hairline cracks on blade

surface.

Could appear in resin rich areas

around the edges of the fan

blades and will normally stop

progressing.

Hairline cracks are harm less in itself,

however we advise to fill these cracks

with a touch-up material e.g. Sikaflex

252 to pre vent moisture penetration

affecting the blades (Contact Howden

for a repair kit).

Noise higher than

predicted.

Airflow higher than specified. Reduce blade angle.

Static pressure too high.

Fan too close to obstacles. Contact Howden for advise.

Influence of mechanical noise

caused by drivetrain.

Contact drive-train supplier.

Resonance of fan-drive and/or

support structure.

Contact Howden for advise.

Table 4

VIII. OVERVIEW TIGHTENING TORQUES

Class 8.8 (A3B) AISI 304 (A2) AISI 316 (A4) Bolts size Nm lb

ft Nm lb ft Nm lb

ft Application

5/8” 190 140 Tapered bushing M24 425 313 380 280 U-bolts M30 1260 929 1180 870 Coupling flange bolts

Table for retaining plate bolts Class 8.8 / AISI 316 (A4) Bolts size Nm lb ft M16x2 200 148 M20x2.5 245 181 M24x3 300 221

Table 5

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IX. MAXIMUM VIBRATION LEVELS FOR BALANCE VIBRATION CATEGORY BV-3 (ISO 14694)

Condition Fan-application category

* Rigidly mounted mm/s

** Flexibly mounted mm/s

Peak r.m.s. Peak r.m.s.

Start-up BV-1 14,0 10,0 15,2 11,2

BV-2 7,6 5,6 12,7 9,0

BV-3 6,4 4,5 8,8 6,3

BV-4 4,1 2,8 6,4 4,5

BV-5 2,5 1,8 4,1 2,8

Alarm BV-1 15,2 10,6 19,1 14,0

BV-2 12,7 9,0 19,1 14,0

BV-3 10,2 7,1 16,5 11,8

BV-4 6,4 4,5 10,2 7,1

BV-5 5,7 4,0 7,6 5,6

Shutdown BV-1 Note 1 Note 1 Note 1 Note 1

BV-2 Note 1 Note 1 Note 1 Note 1

BV-3 12,7 9,0 17,8 12,5

BV-4 10,2 7,1 15,2 11,2

BV-5 7,6 5,5 10,2 7,1

Note 1 Shutdown levels for fans in fan-application grades BV-1 and BV-2 should be established on historical data.

Note 2 The r.m.s. values given in this Table are preferred. They are rounded to a R20 series as specified in

ISO 10816-1. Peak values are widely used in North-America. Being made up of a number of sinusoidal wave forms, these do not necessarily have an exact mathematical relationship with the r.m.s. values. They may also depend to some extent on the instrument used. * Rigidily mounted: Structure by concrete ** Flexibly mounted: Structure of steel, wood or composite Table 6

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X. DOCUMENT VERSION CONTROL

Version 01 April 22, 2009 Changed allowable operating temperature in table 1

Max.

+ 65°C

+ 149°F

Vibration measurement procedure changed in g. of chapter

IV. Commissioning

Inserted Possible to Heading Measuring Points

Added a new chapter:

IX. Maximum Vibration Levels For Balance Vibration

category BV-3 (ISO 14694)

Table 6

04_Howden_Installation-Maintenance D-Series Fans.pdf

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