The International Authority on Air System Components

AIR MOVEMENT AND CONTROLASSOCIATION INTERNATIONAL, INC.

ANSI/AMCAStandard 204-05

Balance Quality andVibration Levels for Fans

An American National StandardApproved by ANSI on September 23, 2005

ANSI/AMCA STANDARD 204-05

Balance Quality and

Vibration Levels for Fans

Air Movement and Control Association International, Inc.

30 West University Drive

Arlington Heights, IL 60004-1893

© 2006 by Air Movement and Control Association International, Inc.

All rights reserved. Reproduction or translation of any part of this work beyond that permitted by Sections 107 and

108 of the United States Copyright Act without the permission of the copyright owner is unlawful. Requests for

permission or further information should be addressed to the Chief Staff Executive, Air Movement and Control

Association International, Inc. at 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.

Authority

This edition of ANSI/AMCA Standard 204 was adopted by the membership of the Air Movement and Control

Association International, Inc., on 03 August 2003. This standard addresses the need of both the users and

manufacturers of fans for technically accurate but uncomplicated information of the subjects of fan balance

precision and vibration levels. The data presented herein is referenced to applicable national and international

standards and is in harmony with these standards, including ISO 14694:2003, Industrial fans - Specification forbalance quality and vibration levels. Information from the reference standards is supplemented by years of

experience on the part of committee members and from other contributors in the industry.

AMCA 204 Review Committee

Dr. John Cermak, Chair Acme Engineering & Manufacturing Corporation

Dick Williamson, Vice Chair Twin City Fan Companies, Ltd.

Dr. Vasanthi Iyer Air Movement Soluctions, LLC

Ralph Jackson Cincinnati Fan & Ventilator Company

Enrique Hernandez Flakt Woods Mexico Fans, S.A. de C.V.

Tim Kuski Greenheck Fan Corporation

David Marshall Howden Buffalo, Inc.

Tan Tin Tin Kruger Ventilation Industries Pte. Ltd.

Bradley F. Skidmore. P.E. Loren Cook Company

Scott Phillips The New York Blower Company

Robert W. Lipke RWL Technical Services, Inc.

Paul R. Saxon (ret.) AMCA International Staff

Joe Brooks AMCA International Staff

Disclaimer

AMCA uses its best efforts to produce standards for the benefit of the industry and the public in light of available

information and accepted industry practices. However, AMCA does not guarantee, certify or assure the safety or

performance of any products, components or systems tested, designed, installed or operated in accordance with

AMCA standards or that any tests conducted under its standards will be non-hazardous or free from risk.

Objections to AMCA Standards and Certifications Programs

Air Movement and Control Association International, Inc. will consider and decide all written complaints regarding

its standards, certification programs, or interpretations thereof. For information on procedures for submitting and

handling complaints, write to:

Air Movement and Control Association International, Inc.

30 West University Drive

Arlington Heights, IL 60004-1893 U.S.A.

or

AMCA International, Incorporated

c/o Federation of Environmental Trade Associations

2 Waltham Court, Milley Lane, Hare Hatch

Reading, Berkshire

RG10 9TH United Kingdom

TABLE OF CONTENTS

1. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

1.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

2. Normative References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

3. Definitions / Units of Measure / Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

3.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

3.2 Units of measure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

3.3 Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

4. Application Categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

5. Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

5.1 Balance quality grade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

5.2 Permissible residual unbalance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

6. Vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

6.1 Measurement requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

6.2 Fan support system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

6.3 Factory tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

6.4 Vibration limits for operation in-situ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

7. Other Rotating Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

8. Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

8.1 Balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

8.2 Vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

Annex A. SI / I-P Conversion Table (informative) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Annex B. Relationships (Informative) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Annex C. Maximum Permissible Residual Unbalance (Informative) . . . . . . . . . . . . . . . . . . . . . .15

Annex D. Instruments and Calibration (Informative) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

D.1 Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

D.2 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Annex E. References (Informative) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

AMCA INTERNATIONAL, INC. ANSI/AMCA 204-05

Balance Quality and Vibration

Levels for Fans

1. Purpose and Scope

This standard addresses the subjects of fan balance

and vibration. It is part of a series of standards and

publications listed in Annex E that cover important

aspects related to the design, manufacture and use

of fans.

Other standards exist that deal with the vibration of

machines in general. This standard considers only

fans. Vibration is recognized to be an important

parameter regarding the mechanical operation of

fans. Balance quality is a precondition to satisfactory

mechanical operation.

1.1 Purpose

The purpose of this standard is to define appropriate

fan balance quality and operating vibration levels to

individuals who specify, manufacture, use, and

maintain fans.

1.2 Scope

This standard covers fans with rigid rotors, generally

found in commercial heating, ventilating and air

conditioning; industrial process applications;

mine/tunnel ventilation applications, and power

generation applications. Other applications are not

specifically excluded, except as follows:

Excluded are installations that involve severe forces,

impacts, or extreme temperature acting on the fan.

Fan foundations and installation practices are

beyond the scope of this standard. Foundation

design and fan installation are not normally the

responsibilities of the fan manufacturer. It is fully

expected that the foundation upon which the fan is

mounted will provide the support and stability

necessary to meet the vibration criteria of the fan as

it is delivered from the factory.

Other factors such as impeller cleanliness,

aerodynamic conditions, background vibration,

operation at rotational speeds other than those

agreed upon, and maintenance of the fan affect fan

vibration level but are beyond the scope of this

standard.

This standard is intended to cover only the balance or

vibration of the fan and does not take into account the

effect of fan vibration on personnel, equipment, or

processes.

Any or all portions of this standard, or modifications

thereof, are subject to agreement between the

concerned parties.

2. Normative References

The following standards contain provisions that,

through specific reference in this text, constitute

provisions of this American National Standard. At the

time of publication of this standard the editions

indicated were valid.

All standards are subject to revision, and parties to

agreements based on this American National

Standard are encouraged to investigate the

possibility of applying the most recent editions of the

standards listed below.

[1] ANSI S2.7-1982 (R1997) Balancing Terminology,

American National Standards Institute, 11 West

42nd Street, New York, NY 10035 U.S.A

[2] ISO 1925:2001 Mechanical vibration – Balancingvocabulary, International Organization for

Standardization, 1 Rue de Varembe, Case

Oistake 56, Ch-1211, Geneve 20, SWITZERLAND

[3] ANSI S2.19-1989 (R1997) Balance Quality ofRigid Rotating Bodies (ISO 1940), American

National Standards Institute, 11 West 42nd Street,

New York, NY 10035 U.S.A.

3. Definitions / Units of Measure / Symbols

3.1 Definitions

3.1.1 Balancing: The process of adding or removing

mass in a plane or planes on a rotor in order to move

the center of gravity towards the axis of rotation.

3.1.2 Balance quality grade: The recommended

limits for residual unbalance of a rotor based upon

the intended application. (Note: Commonly used

balance quality grades in ANSI S2.19 refer to the

vibration that would result if the rotor operated in free

space, i.e., Balance Quality Grade G6.3 corresponds

to a shaft vibration of 6.3 mm/s velocity, at the

operating rotational speed of the rotor). The value

1

ANSI/AMCA 204-05

represents the product of the unbalance multiplied by

the angular velocity and divided by the weight of the

rotor.

3.1.3 Displacement: The distance that a body

moves from a stationary or neutral position.

3.1.4 Electrical run-out: The total measured

variation in the apparent location of a ferrous shaft

surface during a complete slow rotation of that shaft

as determined by an eddy current probe system.

This measurement may be affected by variations in

the electrical/magnetic properties of the shaft

material as well as variations in the shaft surface.

3.1.5 Fan application category: A grouping used to

describe fan applications, their appropriate Balance

Quality Grades, and Recommended Vibration Levels.

3.1.6 Fan assembly: The fan assembly consists of

those items typically packaged together as “a

complete fan”, including, as applicable: rotor,

bearings, belts, housing, motor, sheaves, and

mounting base/structure. In the case of a cooling

tower application, the fan assembly is considered to

consist of the rotor alone.

3.1.7 Fan rotor: An assembly consisting of a fan

impeller mounted on its shaft. (AMCA 99-0066)

3.1.8 Fan vibration level: The vibration amplitude

measured at a fan bearing and expressed in units of

displacement or velocity.

3.1.9 Filter: A device used to separate vibration on

the basis of its frequency. Vibration meters normally

have adjustable filters to allow measurements at a

frequency range of interest.

3.1.10 Filter-in; sharp: Vibration measured only at

a frequency of interest.

3.1.11 Filter-out; broad pass: Vibration measured

over a wide frequency range; sometimes called

“overall” vibration.

3.1.12 Flexible support: A fan support system

designed so that the first natural frequency of the

support is well below the frequency corresponding to

the operating rotational speed of the fan. Often this

involves compliant elastic elements between the fan

and the support structure. “This condition is

achieved by suspending the machine on a spring or

by mounting on an elastic support (springs, rubber,

etc.). The natural oscillation frequencies of the

suspension and machine is typically less than 25% of

the frequency corresponding to the lowest speed of

the machine under test”—-NEMA MG 1-1993, Rev. 1,

Part 7, Section 7.06.1.

3.1.13 Foundation: Refers to the component to

which the fan is mounted that provides the necessary

support. A fan foundation must have sufficient mass

and rigidity to avoid vibration amplification.

3.1.14 Frequency: In cyclical motion, the number of

cycles that occur per second (Hz) or cycles occurring

per minute (CPM).

3.1.15 Mechanical run-out: The total actual

variation in the location of a shaft surface during a

complete slow rotation of the shaft as determined by

a stationary measurement device such as a dial

indicator.

3.1.16 Journal: The part of a rotor which is in

contact with or supported by a bearing in which it

revolves. [ISO 1925]

3.1.17 Mils: A unit of measure that describes

displacement. One mil equals one-thousandth of an

inch (1 mil = 0.001 inch)

3.1.18 Overall fan vibration: See Filter-out; broad

pass.

3.1.19 Peak (pk): A displacement, velocity, or

acceleration value occurring at the maximum

deviation from a zero or stationary value. See Figure

3.1 and see also: RMS.

3.1.20 Peak-to-peak (pk-pk): The total range

traversed in one cycle. Peak-to-peak readings apply

to displacement only.

3.1.21 Residual unbalance: Unbalance of any kind

that remains after balancing. [ANSI S2.7-1982

(R1986)]

3.1.22 Rigid support: A fan support system

designed so that the first natural frequency of the

system is well above the frequency corresponding to

the operating rotational speed of the fan. “Note: The

rigidity of a foundation is a relative quantity. It must

be considered in conjunction with the rigidity of the

machine bearing system. The ratio of bearing

housing vibration to foundation vibration is a

characteristic quantity for the evaluation of

foundation flexibility influences. A foundation may be

considered massive if the vibration amplitude of the

foundation (in any direction) near the machine’s feet

or base frame are less than 25% of the maximum

amplitude that is measured at the adjacent bearing

housing in any direction.” —-NEMA MG1-1993, Rev.

1, Part 7, Section 7.06.2.

2

Figure 3.1 - Vibration Cycle

ANSI/AMCA 204-05

3.1.23 Rigid rotor: A rotor is considered to be rigid

when its unbalance can be corrected in any two

arbitrarily selected planes (of rotation). After the

correction, its residual unbalance does not change

significantly relative to the shaft axis at any

(rotational) speed up to the maximum service

(rotational) speed. [Adapted from ANSI S2.7-

1982(R1986)]

3.1.24 RMS: The root-mean-square value. For true

sinusoidal motion the RMS value is equal to

times the peak value.

3.1.25 Rotor: A body, capable of rotation, generally

with journals which are supported by bearings. [ANSI

S2.7] See also: Fan Rotor.

3.1.26 Speed, balancing: That rotational speed,

expressed in revolutions per minute (rpm), at which a

(fan) rotor is balanced. [ANSI S2.7]

3.1.27 Speed, design: The maximum rotational

speed, measured in revolutions per minute (rpm), for

which the fan is designed to operate.

3.1.28 Speed, service: Rotational speed,

measured in revolutions per minute (rpm), at which a

rotor operates in its final installation or environment.

3.1.29 Tri-axial set: A set of three measurements

taken in three mutually perpendicular directions,

normally: horizontal, vertical, and axial.

3.1.30 Trim balance: The balance process that

makes minor unbalance corrections which may

become necessary as a result of the fan assembly or

installation process.

3.1.31 Unbalance: A condition of a rotor in which

its rotation results in centrifugal forces being applied

to the rotor’s supporting bearings. Unbalance is

usually measured by the product of the mass of the

rotor times the distance between its center of gravity

and its center of rotation in a plane.

3.1.32 Velocity: In cyclic motion, the time rate of

change in displacement.

3.1.33 Vibration: The alternating mechanical

motion of an elastic system, the components of which

are amplitude, frequency and phase. In general

practice, vibration values are reported as:

• displacement, peak-to-peak, in mm (mils)

• velocity, peak, in mm/s (in./s)

• acceleration, peak, in g’s, or m/s2 (in./s2)

Standard gravitational acceleration (1g) = 9.80665

m/s2 (386.09 in./s2)

3.1.34 Vibration spectrum: A graphical

representation of vibration amplitude versus

frequency.

3.1.35 Vibration transducer: A device designed to

be attached to a mechanical system for

measurement of vibration. It produces an electronic

signal that can be displayed or otherwise processed,

that is proportional to the vibration of the system.

3.2 Units of measure

Units of measure shall be as given in the definitions

found in Section 3.1. In the text and examples, SI

(metric) units of measure are given as primary units

followed by IP (inch-pound) units of measure.

3.3 Symbols

Symbols used in this standard are identified/defined

where they are presented in pertinent equations.

3

APPLICATION EXAMPLESDRIVER POWER kW

(HP) LIMITS

FAN APPLICATION

CATEGORY, BV

RESIDENTIAL Ceiling fans, attic fans,

window AC

≤ .15(0.2)

> .15(0.2)

BV-1

BV-2

HVAC & AGRICULTURAL Building ventilation and

air conditioning;

commercial systems

≤ 3.7(5.0)

> 3.7(5.0)

BV-2

BV-3

INDUSTRIAL PROCESS

& POWER GENERATION,

ETC.

Baghouse, scrubber,

mine, conveying, boilers,

combustion air, pollution

control, wind tunnels

≤ 298(400)

> 298(400)

BV-3

BV-4

TRANSPORTATION &

MARINE

Locomotives, trucks,

automobiles

≤ 15(20)

> 15(20)

BV-3

BV-4

TRANSIT/TUNNEL Subway emergency

ventilation, tunnel fans,

garage ventilation

≤ 75(100)

> 75(100)

BV-3

BV-4

Tunnel Jet Fans ALL BV-4

PETROCHEMICAL

PROCESS

Hazardous gases,

process fans

≤ 37(50)

> 37(50)

BV-3

BV-4

COMPUTER CHIP

MANUFACTURE

Clean room ALL BV-5

Table 4.1 - Fan Application Categories for Balance and Vibration

ANSI/AMCA 204-05

4. Application Categories

The design/structure of a fan and its intended

application are important criteria for categorizing the

many types of fans in terms of applicable and

meaningful balance quality grades and vibration

levels.

Table 4.1 categorizes fans by their application and

driver power to arrive at appropriate Balance and

Vibration (BV) application categories.

A fan manufacturer will typically identify the

appropriate application category based on the type of

fan and power. A purchaser of a complete fan

assembly may be interested in one or more of the

following: the Balance Grade (Table 5.1), vibration

as tested in the factory (Table 6.2), or vibration in-situ(Table 6.3). Typically, one Balance and Vibration

category will cover both the application and the driver

power considerations. However, a purchaser may

request a Balance and Vibration category different

from the one listed for the application and driver

power considerations. Some may desire a more

precise balance quality grade or lower vibration level

than is typical for the application.

In most cases, the Balance and Vibration category,

the balance quality grade and vibration limits must be

agreed upon as part of the contract for the fan. In the

event that no such agreement exists, fans purchased

as being required to comply with this standard shall

meet the Table 6.2 vibration limits (assembled fan) or

the Table 5.1 residual unbalance requirements

(unassembled fan or rotor assembly only).

The purchaser may contract for a particular mounting

arrangement to be used for factory testing of an

assembled fan in order to match (as nearly as

possible) the planned in-situ mounting at the job site.

If no specific contract on balance/vibration exists, the

fan may be mounted either rigidly or flexibly for the

test, regardless of the in-situ mounting.

4

ANSI/AMCA 204-05

5

5. Balancing

The fan manufacturer is responsible for balancing the

fan impeller to acceptable commercial standards.

This standard is based on ANSI S2.19 (ISO 1940).

Balancing done in conformance with this standard

shall be performed on a highly sensitive, purpose-

built balance machine that permits accurate

assessment of residual unbalance.

5.1 Balance quality grade

The following Balance Quality Grades apply to fan

impellers. A fan manufacturer may include other

rotating components (shaft, coupling, sheave/pulley,

etc.) in the rotating assembly being balanced. In

addition, balance of individual components may be

required. See Annex E for balance requirements for

couplings and pulleys.

Table 5.1 - BV Categories and Balance

Quality Grades

* Note: In FAN APPLICATION CATEGORY BV-1

there may be some extremely small fan rotors

weighing less than 227 grams (8 ounces). In such

cases, residual unbalance may be difficult to

determine accurately. The fabrication process must

ensure reasonably equal weight distribution about

the axis of rotation.

5.2 Permissible residual unbalance

G grades as given in Table 5.1 and Balance Quality

Grades are constants derived from the product of the

relationship eperω, expressed in mm/s, where eper is

the permissible residual specific unbalance, and ω is

the angular velocity of the impeller.

Thus:

SI UNITS:

eper = 1 000(G / ω)

Uper = M eper = [30 000/π]G M /N

ω = 2πN/60

where:

eper = Specific unbalance, μm or (g mm)/kg

Uper = Permissible residual unbalance, (g mm)

ω = Angular velocity, rad/s

N = Rotor rotational speed, rpm

M = Rotor mass, kg

I-P UNITS:

eper = (G / 25.4ω)

Uper = W eper = (30/[π 25.4])G W /N for Uper in (lb in.)

ω = 2πN/60

where:

eper = Specific unbalance, in. or (lb in.)/lb

Uper = Permissible residual unbalance (moment), (lb in.)

ω = Angular velocity, rad/s

N = Rotor rotational speed, rpm

W = Rotor weight, lbm

In most applications, the permissible residual

unbalance Uper in each of two correction planes can

be set at Uper/2. Whenever possible during balancing,

a fan impeller should be mounted on the shaft that

will be used for the final assembly. If a mandrel is

used during balancing, care should be taken to avoid

eccentricity due to a loose hub-to-mandrel fit.

Refer to Annex C for graph of eper vs. service speed.

Measurement of the residual unbalance shall be

made in accordance with ANSI S2.19, Section 8.

FAN

APPLICATION

CATEGORY

BALANCE QUALITY GRADE

FOR RIGID

ROTORS/IMPELLER

BV-1* G 16

BV-2 G 16

BV-3 G 6.3

BV-4 G 2.5

BV-5 G1.0

ANSI/AMCA 204-05

6. Vibration

6.1 Measurement requirements

Figures 6.1, 6.2, 6.3 and 6.4 illustrate some of the

possible locations and directions for taking vibration

measurements at each fan bearing. The number and

location of measurements to be made during factory

or in-situ operation is at the discretion of the fan

manufacturer or by agreement with the purchaser. It

is recommended that measurements be made at the

impeller shaft bearings. Where this is not possible,

the pick-up shall be mounted in the shortest direct

mechanical path between the transducer and the

bearing. A transducer shall not be mounted on an

unsupported panel, guard, or elsewhere on the fan

where a solid signal path cannot be obtained. A

transducer may be mounted on a fan housing and or

flange where a solid signal path is obtained between

a bearing and the measurement point.

A horizontal measurement shall always be made in a

radial direction and perpendicular to the axis of

rotation. A vertical measurement reading shall

always be made perpendicular to the axis of rotation

and perpendicular to a horizontal reading. An axial

measurement shall always be made parallel to the

shaft (rotor) axis of rotation.

6.1.1 Seismic measurements. All vibration values

in this standard are seismic measurements that

represent motion of the fan bearing housing.

Observations shall include measurements made with

accelerometer or velocity-type instruments.

Particular attention should be given to ensure that the

vibration-sensing transducer is correctly mounted

without looseness, rocking, or resonance.

The size and weight of the transducer and its

mounting system should not be so large that its

presence significantly affects the vibration response

characteristics of the fan. Variables associated

with transducer mounting and variations in

instrument calibration can lead to variations in

measurements of ±10%.

6.1.2 Displacement measurements. The following

discussion applies to measurement of shaft

displacement within a sleeve bearing oil film by

means of proximity probe systems.

Such systems measure the relative motion between

the surface of the rotating shaft and the bearing

housing. Clearly, the allowable displacement

amplitude must be limited to a value less than the

diametric clearance of the bearing. This internal

clearance varies as a function of the bearing size, the

radial/axial loading, the bearing type, and the axis of

interest (i.e., some designs have an elliptical bore

with larger clearance in the horizontal axis than in the

vertical axis). Therefore, it is not the intent of this

standard to establish discrete shaft displacement

limits for all bearings and fan applications. However,

the following guideline is recommended for shaft

displacement limits. The values shown in Table 6.1

are percentages of the total available clearance

within the bearing in each axis.

Table 6.1 - Maximum Recommended

Displacements

Caution should be used when relying solely on

proximity probes for vibration alarming. It is possible

for the proximity probe support and the fan shaft to

move in phase such that no relative motion is

measured even though high vibration levels relative

to a fixed frame of reference exist. Because of this,

when proximity probes are used, seismic vibration

pickups are also recommended.

This measurement involves the apparent motion of

the shaft surface. Measurements are affected not

only by vibration of the shaft but also by any

mechanical run-out of the shaft if the shaft is bent or

out-of-round. The magnetic/electrical properties of

the shaft material at the point of measurement also

affect the electrical run-out of the shaft as measured

by a proximity probe. The combined mechanical and

electrical probe-track run-out of the shaft material at

the point of measurement should not exceed

0.0127mm (0.0005 in.) peak-to-peak, or 25% of the

start-up/satisfactory vibration displacement value,

whichever is greater. This run-out should be

determined during a slow-roll speed test (100 to 400

rpm), where the unbalance forces on the rotor are

negligible. Special shaft preparation may be required

to achieve satisfactory run-out measurement.

Proximity probes should be mounted directly in the

bearing housing whenever possible.

Condition Maximum recommended

Displacement as a

percent of available

diametral clearance (any

axis)

Start-up/Satisfactory <+25% Note: Contact bearing

supplier to obtain the available

diametral and axial clearances

within the particular sleeve

bearing being used.

Alarm Level 50%

Shut-Down Level 70%

6

Figure 6.1 - Transducer Mounting Locations - Axial Fan, Horizontal Airflow

ANSI/AMCA 204-05

EXAMPLE: Recommended guidelines for normal

152 mm (6 in.) diameter sleeve bearing having a

horizontal internal clearance of 0.33 mm (0.013

in.):

LIMITS OF RELATIVE SHAFT VIBRATION

• Start-up / = (0.25 × 0.33 mm) = 0.0825 mm,

satisfactory pk-pk (SI)

= (0.25 × 0.013 in.) = 0.0033 in.

or 3.3 mils, pk-pk (I-P)

• Alarm = (0.50 × 0.33 mm) = 0.165 mm,

pk-pk (SI)

= (0.50 × 0.013 in.) = 0.0065 in.

or 6.5 mils, pk-pk (I-P)

• Shut-down = (0.70 × 0.33 mm) = 0.231 mm,

pk-pk (SI)

= (0.70 × 0.013 in.) = 0.0091 in.

or 9 mils, pk-pk (I-P)

Combined mechanical and electrical run-out of the

shaft at the point of vibration measurement:

a. 0.0127 mm (0.0005 in.)

b. 0.25 × 0.0825 mm = 0.0206 mm (SI)

0.25 × 0.0033 in. = 0.0008 in., or 0.8 mils (I-P)

Choose the greater of the two values (a or b),

0.0206 mm (0.8 mils)

6.2 Fan support system

Fan installations are classified for vibration severity

according to their support flexibility. To be classified

as rigidly supported, the fan and support system

should have a fundamental (lowest) natural

frequency above the running speed. To be classified

as flexibly supported, the fan and support system

should have a fundamental frequency below the

running speed. Generally, a large, well-designed

concrete foundation will result in a rigid support,

whereas a fan mounted on vibration isolators will be

classified as flexibly supported.

Fans mounted on steelwork can be in either category,

depending on the structural design. In case of doubt,

analysis or tests should be performed to determine

the fundamental natural frequency. Note that in

some cases a fan could be classified as rigidly

supported in one measurement direction and flexibly

supported in another.” (From AMCA 801-01, Section

5.3.3, p.19)

6.3 Factory tests

The following vibration limit values apply to an

assembled fan tested in the manufacturer’s factory.

Table 6.2 - Seismic Vibration Limits for Tests

Conducted at the Factory

Values shown are peak velocity values, filter-in, at the

fan rotational speed during the factory test.

Fan Application

Category

Rigidly

Mounted mm/s

(in./s)

Flexibly

Mounted mm/s

(in./s)

BV-1

BV-2

BV-3

BV-4

BV-5

12.7 (0.50)

5.1 (0.20)

3.8 (0.15)

2.5 (0.10)

2.0 (0.08)

15.2 (0.60)

7.6 (0.30)

5.1 (0.20)

3.8 (0.15)

2.5 (0.10)

7

Figure 6.2 - Transducer Mounting Locations - Single Width Centrifugal Fan

Figure 6.3 - Transducer Mounting Locations - Double Width Centrifugal Fan

8

ANSI/AMCA 204-05

9

6.4 Vibration limits for operation in-situ

The in-situ vibration level of a fan is not solely

dependent upon the Balance Quality Grade.

Installation factors and the mass and stiffness of the

supporting system will influence the in-situ vibration

level (Refer to AMCA Publication 202

Troubleshooting). Therefore, in-situ fan vibration

level is not the responsibility of the fan manufacturer

unless specified in the purchase contract.

The vibration velocity levels in Table 6.3 provide

guidelines for acceptable operation of fans in various

application categories. The velocity values shown

are for filter-out measurements taken at the bearing

housings as shown in Figures 6.1 through 6.4.

The vibration velocity of a newly commissioned fan

should be at or below the START-UP level. As

operation of the fan increases with time, it is

expected that fan vibration level will increase due to

wear and other accumulated effects. In general, an

increase in vibration is reasonable as long as the

level does not reach the ALARM value for the

category.

If the severity of vibration velocity increases to the

ALARM level, action should be initiated immediately

to determine the cause of the increase, and action

taken to correct the condition. Operation at this

condition should be carefully monitored and limited to

the minimum time required to develop a program of

corrective action.

ANSI/AMCA 204-05

Figure 6.4 - Transducer Mounting Locations - Axial Fan, Vertical Airflow

ConditionFan Application

Category

Rigidly Mounted

mm/s (in./s)

Flexibly Mounted

mm/s (in./s)

Start-up BV-1

BV-2

BV-3

BV-4

BV-5

14.0 (0.55)

7.6 (0.30)

6.4 (0.25)

4.1 (0.16)

2.5 (0.10)

15.2 (0.60)

12.7 (0.50)

8.8 (0.35)

6.4 (0.25)

4.1 (0.16)

Alarm BV-1

BV-2

BV-3

BV-4

BV-5

15.2 (0.60)

12.7 (0.50)

10.2 (0.40)

6.4 (0.25)

5.7 (0.20)

19.1 (0.75)

19.1 (0.75)

16.5 (0.65)

10.2 (0.40)

7.6 (0.30)

Shut-down BV-1

BV-2

BV-3

BV-4

BV-5

NOTE 1

NOTE 1

12.7 (0.50)

10.2 (0.40)

7.6 (0.30)

NOTE 1

NOTE 1

17.8 (0.70)

15.2 (0.60)

10.2 (0.40)

Table 6.3 - Seismic Vibration Velocity Limits for Operation In-Situ

Value shown are peak velocity, mm/s (inches/s), Filter out.

Note 1: Shutdown levels for fans in Fan Application Grades BV-1 and BV-2 must be established based on historical

data

ANSI/AMCA 204-05

If the vibration velocity increases to the SHUTDOWN

level, corrective action should be taken immediately

or the fan should be shut down.

Failure to reduce the SHUT-DOWN level vibration

velocity to the acceptable recommended level could

lead to bearing failure, cracking of rotor parts and fan

housing structural welds, and ultimately, a

catastrophic failure.

Historical data is an important factor when

considering the vibration severity of any fan

installation. A sudden increase in vibration velocity

level may indicate the need for prompt inspection or

maintenance. Transitory changes in vibration level

that result from re-lubrication, maintenance, or

process upsets should not be used for evaluating the

condition of the equipment.

10

ANSI/AMCA 204-05

7. Other Rotating Components

Accessory rotating components that may affect fan

vibration levels include drive sheaves, belts,

coupling, and motor/driver device. When a fan is

ordered from the fan manufacturer “bare”, (i.e., no

drive or motor supplied or installed by fan

manufacturer), it is not always practical or possible

for the fan manufacturer to perform a final assembly

test run, or factory test, to check vibration level.

Therefore, though the impeller may have been

balanced by the fan manufacturer, the customer is

not assured of a smooth running assembled fan until

the drive and/or driver are connected to the fan shaft

and the unit is run and tested to determine the start-

up vibration levels. It is common for assembled fans

to require trim balancing to reduce vibration to

acceptable START-UP vibration levels. The final

assembly test run is recommended for all new BV-3,

BV-4 and BV-5 fan installations BEFORE

commissioning for service. This will establish a

baseline for future predictive maintenance efforts.

The fan manufacturer cannot be responsible for the

effects of vibration of drive components added after

the factory test run.

Additional information on the balance quality or

vibration of components may be found in the

references given in Annex E.

8. Documentation

8.1 Balance

Written certification of the balance achieved for an

individual rotor shall be provided upon request when

negotiated. In such cases, it is recommended that

the following information be included in the balance

certification report:

• Balance machine manufacturer and model

number

• Specify whether rotor was overhung or

between centers

• Specify whether balance method was single or

two-plane

• Specify mass of rotating assembly

• Note the residual unbalance in EACH

correction plane

• Note the allowable residual unbalance in each

correction plane for the Balance Quality Grade

• Note the applicable Balance Quality Grade

• Acceptance criteria: Note whether rotor

balance passed or failed

• Supply a Certificate of Balance if required.

In some cases, keeping a written record of an

individual rotor is impractical. In such cases, the fan

manufacturer’s records or standard operating

procedures shall be sufficient evidence of

achievement of balance.

8.2 Vibration

Written certification of the vibration velocity level

achieved for a fan shall be provided upon request

when negotiated. In such cases, it is recommended

that the following information be included in the

vibration certification report:

• Vibration instrumentation used: manufacturer

and model number

• Fan operating point

• Fan rotational speed

• Note: whether fan was flexibly or rigidly mounted

• Description of measurements:

a. method of transducer attachment to

measurement location; position and axis

b. units of measure used and reference

levels

c. frequency, bandwidth, and whether

vibration analyzer was tuned Filter-In or

Filter-Out

• Allowable vibration velocity levels

• Measured vibration velocity levels

• Acceptance criteria: Note whether rotor

balance passed or failed

• Supply a Certificate of Vibration Velocity if

required.

In some cases, keeping a written record of an

individual rotor is impractical. In such cases, the fan

manufacturer’s records or standard operating

procedures shall be sufficient evidence of

achievement of balance.

11

Annex A. SI / I-P Conversion Table (informative)

Conversion factors between SI and I-P systems:

Quantity I-P to SI SI to I-P

Length (ft) 0.3048 = m (m) 3.2808 = ft

Mass (weight) (lbs) 0.4536 = kg (kg) 2.2046 = lbs.

Time The unit of time is the second in both systems

Velocity(ft-s) 0.3048 = ms

(ft/min) 0.00508 = ms

(ms) 3.2808 = fts

(ms) 196.85 = ft/min

Acceleration (in./s2) 0.0254 = m/s2 (m/s2) 39.370 = in.s/2

Area (ft2) 0.09290 = m2 (m2) 10.764 = ft2

Volume Flow Rate (cfm) 0.000471948 = m3/s (m3/s) 2118.88 = cfm

Density (lb/ft3) 16.01846 = kg/m3 (kg/m3) 0.06243 = lb/ft3

Pressure

(in. wg) 248.36 = Pa

(in. wg) 0.24836 = kPa

(in. wg) 3.3864 = kPa

(Pa) 0.004026 = in. wg

(kPa) 4.0264 = in. wg

(kPa) 0.2953 = in. Hg

Viscosity:

Absolute

Kinematic

(lbm/ft-s) 1.4882 = Pa s

(ft2/s) 0.0929 = m2/s

(Pa s) 0.6719 = (lbm/ft-s)

(m2/s) 10.7639 = ft2/s

Gas Constant (ft lb/lbm-°R) 5.3803 = J-kg/K (j-kg/K) 0.1858 = (ft lb/lbm-°R)

Temperature (°F - 32°)/1.8 = °C (1.8 × °C) + 32° = °F

Power (BHP) 746 = W

(BHP) 0.746 = kW

(W)/746 = BHP

(kW)/0.746 = BHP

ANSI/AMCA 204-05

12

Annex B. Relationships (Informative)

Figure B.1 Relationships of Vibration Displacement,

Velocity and Acceleration for Sinusoidal Motion

Generally, there is no simple relationship between broad-band acceleration, velocity and displacement; nor is

there one between peak (pk), peak-to-peak (pk-pk), root-mean-square (rms) and average values of vibration.

However, where the vibration is totally or predominantly at a single frequency (e.g., due to residual unbalance) or

it is measured “Filter-In” then the following relationships exist, independent of the system of the units involved:

Vrms = Vpk /

Arms = Apk /

The following relationships exist and are dependent upon the units of measure used:

For SI Units of Measure:

DISPLACEMENT Dpkpk mm

VELOCITY Vpk mm/s

ACCELERATION Apk g’s

FREQUENCY F Hz

Note: 1 g = 9.80665 m/s2

RELATIONSHIP EQUATIONS: EXAMPLE: Dpkpk = 0.10 mm at N = 1800 rpm

F = N / 60 F = 1800/60 = 30 Hz

Vpk = �FDpkpk Vpk = �(30)(0.10) = 9.42 mm/s

AF D F D

pkpkpk pkpk= =

2

9 80665 1000 496 8

2 2( )

( . )( ) .

πApk = =( ) ( . )

..

30 0 10

496 80 181

2

g's

ANSI/AMCA 204-05

13

For “filter-in” readings, the following relationships exist which are dependent upon the units of measure used:

For I-P Units of Measure:

DISPLACEMENT Dpkpk mils

VELOCITY Vpk in./s

ACCELERATION Apk g’s

FREQUENCY N rev/min (rpm)

Note: 1 mil = 0.001 in.

1 g = 386.09 in./s2

RELATIONSHIP EQUATIONS EXAMPLE: Dpkpk = 2.4 mils at N = 1780 rpm

VND ND

pkpkpk pkpk= =

π( )( ) ( , )60 1000 19 100

AFV NV

pkpk pk= =

2

60 386 09 3687

π( )( . ) ( )

Apk = =( )( . ).

1780 0 224

36870 108 g's

Vpk = =( )( . )

( ).

3687 0 108

17800 224 in./sV

AN

ANpk

pk pk= =( )( . ) ( )60 386 09

2

3687

π

Apk = =−

0 108

1 4210 17802 4

8 2

.

( . )( ). milsD

AN

ANpkpk

pk pk= = −

( )( )( . )

( ) ( . )

60 1000 386 09

2 1 42102 8 2π

Dpkpk = =( , )( . )

( ).

19 100 0 224

17802 4 milsD

VN

VNpkpk

pk pk= =( )( ) ( , )60 1000 19 100

π

Apk = × =−( . )( ) ( . ) .1 42 10 1780 2 4 0 1088 2 g'sA

N DN Dpk

pkpkpkpk= = × −2

60 1000 386 091 42 10

2

2

8 2( )

( ) ( )( . )( . )

π

Vpk = =( )( . )

( , ).

1780 2 4

19 1000 224 in./s

Apk = =( )( . ).

30 9 42

15610 181 g'sA

FV FVpk

pk pk= =2

1000 9 80665 1561

π( )( . )

Vpk = =( )( . ).

1561 0 181

309 42 mm/sV

AF

AFpk

pk pk= =( )( . )1000 9 80665

2

1561

π

Dpkpk = =( . )( . ).

496 8 0 181

300 10

2mmD

AF

AFpkpk

pk pk= =( )( . )

( )

.1000 9 80665

2

496 82 2π

Dpkpk = =9 42

300 10

.

( ).

πmmD

VFpkpkpk=π

ANSI/AMCA 204-05

14

10,000

1,000

1,000 10,000

Note: See Section 5.2 for application of these values

Figure C.1 - Maximum Permissible Residual Unbalance (SI)

Annex C. Maximum Permissible Residual Unbalance (Informative)

ANSI/AMCA 204-05

15

Figure C.2 - Maximum Permissible Residual Unbalance (I-P)

Note: See Section 5.2 for application of these values

ANSI/AMCA 204-05

16

Annex D. Instruments and Calibration (Informative)

D.1 Instruments

Instruments and balancing machines used shall meet the requirements of the task and be within current calibration.

See ANSI S2.19-1989, Section 8. The calibration period for an instrument shall be that recommended by the

instrument manufacturer. Instruments shall be in good condition and suitable for the intended function for the

complete duration of the test. A portable instrument shall not require a battery change during a test.

Personnel operating instruments shall be familiar with the instruments and shall possess enough experience to

detect a possible malfunction or degradation of instrument performance. When an instrument requires corrective

measures or calibration, it shall be removed from service until corrective action is taken.

D.2 Calibration

All instruments shall have a calibration against a known standard. The complexity of the calibration may vary from

a physical inspection to a complete calibration traceable to the National Institute of Standards and Technology. Use

of a calibrated weight to determine residual unbalance such as described in ANSI S2.19-1989, Section 8.3 is one

accepted method of calibrating instrumentation.

ANSI/AMCA 204-05

17

Annex E. References (Informative)

(1) ISO 254:1998 Belt Drives – pulleys – Quality, finish and balance, International Organzation for

Standardization, 1 Rue de Varembe, Case Oistake 56, Ch-1211, Geneve 20, SWITZERLAND.

(2) NEMA MG 1-1993 Part 7 Mechanical Vibration – Measurement, Evaluation and Limits, National Electrical

Manufacturers Association, 1300 North 17th Street, Rosslyn, VA 22209 U.S.A.

(3) IEC 34-14:1998 Rotating Electrical Machines (for general information on motors), International

Electrotechnical Commission, 1 Rue de Varembe, Case Oistake 56, Ch-1211, Geneve 20, SWITZERLAND

(4) MPTA SPB 86, Sheaves and Belts, Mechanical Power Transmission Association, 932 Hungerford Drive #36,

Rockville, MD 20850 U.S.A.

(5) ANSI S2.41-1985 (R1997) Mechanical Vibration of Large Rotating machines with Speed Range from 10 to 200 rev/s – Measurement and Evaluation of Vibration Severity in situ (ISO 3945), American National

Standards Institute, 11 West 42nd Street, New York, NY 10035 U.S.A.

(6) ANSI/AGMA 9000 – C90 (R1996) Flexible Couplings – Potential Unbalance Classifications, American Gear

Manufacturers Association, 1500 King Street, Alexandria, VA 22314 U.S.A.

(7) AMCA International’s Publication 99, Standards Handbook, Air Movement and Control Association

International, Inc., 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.

(8) AMCA International’s Publication 200 Air Systems, Air Movement and Control Association International, Inc.,

30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.

(9) AMCA International’s Publication 201 Fans and Systems, Air Movement and Control Association

International, Inc., 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.

(10) AMCA International’s Publication 202 Troubleshooting, Air Movement and Control Association International,

Inc., 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.

(11) AMCA International’s Publication 203 Field Performance Measurement of Fan Systems, Air Movement and

Control Association International, Inc., 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.

(12) ANSI / AMCA 210 Laboratory Methods of Testing Fans for Aerodynamic Performance Rating, Air Movement

and Control Association International, Inc., 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.

(13) AMCA International’s Publication 211 Certified Ratings Program – Air Performance, Air Movement and

Control Association International, Inc., 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.

(14) AMCA International’s Standard 300 Reverberant Room Method of Sound Testing of Fans, Air Movement

and Control Association International, Inc., 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.

(15) AMCA International’s Publication 311 Certified Ratings Program for Air Moving Devices, Air Movement and

Control Association International, Inc., 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.

(16) AMCA International’s Publication 801 Industrial Process / Power Generation Fans: Specification Guidelines,

Air Movement and Control Association International, Inc., 30 West University Drive, Arlington Heights, IL

60004-1893 U.S.A.

(17) AMCA International’s Publication 802 Industrial Process / Power Generation Fans: Establishing Performance Using Laboratory Models, Air Movement and Control Association International, Inc., 30 West

University Drive, Arlington Heights, IL 60004-1893 U.S.A.

(18) AMCA International’s Standard 803 Industrial Process / Power Generation Fans: Site Performance Test Standard, Air Movement and Control Association International, Inc., 30 West University Drive, Arlington

Heights, IL 60004-1893 U.S.A.

ANSI/AMCA 204-05

18

AIR MOVEMENT AND CONTROLASSOCIATION INTERNATIONAL, INC.

30 West University DriveArlington Heights, IL 60004-1893 U.S.A.

E-Mail : info@amca.org Web: www.amca.orgTel: (847) 394-0150 Fax: (847) 253-0088

The Air Movement and control Association International, Inc. is a not-for-profit international association of the world’s manufacturers of related air system equipment primarily, but limited to: fans, louvers, dampers, air curtains, airflow measurement stations, acoustic attenuators, and other air system components for the industrial, commercial and residential markets.