SIST EN ISO 13691:2004

Petroleum and natural gas industries - High-speed special-purpose gear units (ISO 13691:2001)

This International Standard specifies the minimum requirements for enclosed, precision, single and double helical,
one- and two-stage speed increasers and reducers of parallel shaft design with pinion speeds of 3000 min−1 or
greater, or pitch line velocities of 25 m/s or greater, for special purpose applications. Such applications will typically
be required to operate continuously for extended periods, without installed spare equipment and are critical to the
continued operation of the installation. By agreement this International Standard may be used for other services.
This International Standard also specifies a method of rating gears which meet the following criteria:
a) gear accuracy
 teeth accuracy: accuracy grade 4 or better as given in ISO 1328-1:1995, for both single pitch deviation, fpt,
and total cumulative pitch deviation, Fp,
 total helix deviation Fβ between the helices of the pinion and wheel: accuracy grade 4 or better as given in
ISO 1328-1:1995;
b) range of the transverse contact ratios: 1,2 < εα < 2,0;
c) overlap ratio εβ W 1,0;
d) helix angle: 5 u β u 35°;
e) working flanks of the pinion or gear: provided with profile modifications to obtain a good conjugate tooth load
distribution along the path of contact;
f) working flanks of pinion or gear: modified as necessary to compensate for both torsional and bending
deflections and, when necessary for gears with pitch line velocities in excess of 100 m/s, also for thermal
distortions;
g) gear lubrication: straight mineral oil, viscosity grade VG-32 or VG-46 (see ISO 3448);
h) material of the gear teeth: quality MQ or better, in accordance with ISO 6336-5:1996.

Erdöl- und Erdgasindustrie - Schnelllaufgetriebe für spezielle Anwendungen (ISO 13691:2001)

Die vorliegende Internationale Norm legt die Mindestanforderungen an ein- und zweistufige Präzisions-sondergetriebe
mit Einfach- und Doppelschrägverzahnung und Übersetzung ins Schnelle oder Langsame mit
parallelen Wellen mit Ritzeldrehzahlen von 3000 min -1 oder mehr oder Teilkreisgeschwindigkeiten von 25 m/s
oder mehr fest. Diese Anwendungen müssen normalerweise länger kontinuierlich betrieben werden, ohne
dass Ersatzmaschinen zur Verfügung stehen. Wichtig ist ein kontinuierlicher Betrieb der Anlage. Nach Ver-einbarung
kann die vorliegende Internationale Norm auf andere Bereiche angewendet werden.
Die vorliegende Internationale Norm legt auch ein Verfahren fest, um Getriebe auszulegen, die folgende Krite-rien
erfüllen:
a) Getriebegenauigkeit
- Verzahnungsqualität: Qualitätsgrad 4 oder besser gemäß ISO 1328-1:1995 Teilungs-Einzelab-weichung
f pt und Teilungs-Gesamtabweichung F p ,
- Flankenlinien-Gesamtabweichung F - zwischen Flanken von Ritzel und Rad: Qualitätsgrad 4 oder
besser gemäß ISO 1328-1:1995;
b) Bereich der Profilüberdeckung: 1,2 <  < 2,0;
c) Sprungüberdeckung 1,0;
d) Schrägungswinkel: 5 - 35°;
e) Arbeitsflanken von Ritzel oder Zahnrad: mit Profiländerungen zum Erreichen einer optimalen Gesamt-zahnlastverteilung
entlang der Kontaktlinie;
f) Arbeitsflanken von Ritzel oder Zahnrad: geändert, um Dreh- und Biegeverformungen zu kompensieren
und, falls erforderlich, bei Getrieben mit Teilkreisgeschwindigkeiten über 100 m/s auch Wärmeverfor-mungen
zu kompensieren;
g) Getriebeschmierung: reines Mineralöl, Viskosität VG-32 oder VG-46 (siehe ISO 3448);
h) Material der Radzähne: Qualität MQ oder besser gemäß ISO 6336-5:1996.

Industries du pétrole et du gaz naturel - Engrenages a grande vitesse pour applications particulieres (ISO 13691:2001)

La présente Norme internationale spécifie les exigences minimales relatives aux multiplicateurs et aux réducteurs
de vitesse sous carter, de précision, simple ou en chevron, à un ou deux étages, de conception d'arbre parallèle,
avec des vitesses de pignon supérieures ou égales à 3 000 min−1 ou des vitesses de ligne primitive supérieures ou
égales à 25 m/s, destinés à des applications particulières. Certaines applications requièrent généralement un
fonctionnement continu pendant de longues périodes, sans installation de matériels de rechange et sont
importantes pour le fonctionnement continu de l'installation. La présente Norme internationale peut, selon accord,
être utilisée pour d'autres services.
La présente Norme internationale spécifie également une méthode d'évaluation des engrenages satisfaisant aux
critères suivants:
a) précision des engrenages:
 précision de la denture: classe de précision 4 ou meilleure de l'ISO 1328-1:1995, pour l'écart du pas
simple, fpt, et l'écart total du pas cumulé, Fp,
 écart total d'hélice, Fβ, entre les hélices des pignons-roues: classe de précision 4 ou meilleure de
l'ISO 1328-1:1995;
b) plage des rapports de conduite apparents: 1,2 < ε α < 2,0;
c) rapport de recouvrement ε β W 1,0;
d) angle d'hélice: 5° u β u 35°;
e) flancs de travail du pignon ou de la roue: fournis avec des modifications de profil afin d'obtenir une distribution
conjuguée correcte de la charge de la denture le long de la ligne de conduite;
f) flancs actifs du pignon ou de la roue: modifiés, si nécessaire, pour compenser les déformations par torsion et
par flexion et, le cas échéant, pour les engrenages dont les vitesses de ligne primitive dépassent 100 m/s,
ainsi que pour les déformations thermiques;
g) lubrification des engrenages: huile minérale pure, d'une classe de viscosité VG 32 ou VG 46 (voir ISO 3448);
h) matériau des dentures d'engrenage: conforme à la qualité MQ de l'ISO 6336-5:1996 ou supérieure.

Industrija za predelavo nafte in zemeljskega plina - Hitrotekoča gonila za posebne namene (ISO 13691:2001)

General Information

• Status: Published
• Publication Date: 30-Apr-2004
• ICS: 21.200 - Gears
• ICS: 75.180.20 - Processing equipment
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-May-2004
• Due Date: 01-May-2004
• Completion Date: 01-May-2004
• Ref Project: EN ISO 13691:2002 - Petroleum and natural gas industries - High-speed special-purpose gear units (ISO 13691:2001)

Relations

• Replaces: SIST ISO 13691:2002 - Petroleum and natural gas industries -- High-speed special-purpose gear units
• Effective Date: 01-May-2004

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 13691:2004
01-maj-2004
1DGRPHãþD
SIST ISO 13691:2002

,QGXVWULMD]DSUHGHODYRQDIWHLQ]HPHOMVNHJDSOLQD+LWURWHNRþDJRQLOD]DSRVHEQH

QDPHQH,62

Petroleum and natural gas industries - High-speed special-purpose gear units (ISO

13691:2001)
Erdöl- und Erdgasindustrie - Schnelllaufgetriebe für spezielle Anwendungen (ISO
13691:2001)

Industries du pétrole et du gaz naturel - Engrenages a grande vitesse pour applications

particulieres (ISO 13691:2001)
Ta slovenski standard je istoveten z: EN ISO 13691:2002
ICS:
21.200 Gonila Gears
75.180.20 Predelovalna oprema Processing equipment
SIST EN ISO 13691:2004 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN ISO 13691:2004
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SIST EN ISO 13691:2004
EUROPEAN STANDARD
EN ISO 13691
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2002
ICS 21.200; 75.180.20
English version
Petroleum and natural gas industries - High-speed special-
purpose gear units (ISO 13691:2001)
Industries du pétrole et du gaz naturel - Engrenages à
grande vitesse pour applications particulières (ISO
13691:2001)
This European Standard was approved by CEN on 1 August 2002.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European

Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national

standards may be obtained on application to the Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official

versions.

CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,

Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels

© 2002 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 13691:2002 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 13691:2004
EN ISO 13691:2002 (E)
Foreword

The text of ISO 13691:2001 has been prepared by Technical Committee ISO/TC 60 "Gears" of the

International Organization for Standardization (ISO) and has been taken over as EN ISO 13691:2002 by

Technical Committee CEN/TC 12 "Materials, equipment and offshore structures for petroleum and natural

gas industries", the secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by May 2003, and conflicting national standards shall be

withdrawn at the latest by May 2003.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following

countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark,

Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway,

Portugal, Spain, Sweden, Switzerland and the United Kingdom.
Endorsement notice

The text of ISO 13691:2001 has been approved by CEN as EN ISO 13691:2002 without any modifications.

NOTE Normative references to International Standards are listed in Annex ZA (normative).

---------------------- Page: 4 ----------------------
SIST EN ISO 13691:2004
EN ISO 13691:2002 (E)
Annex ZA
(normative)
Normative references to international publications with their relevant European
publications

This European Standard incorporates by dated or undated reference, provisions from other publications.

These normative references are cited at the appropriate places in the text and the publications are listed

hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply

to this European Standard only when incorporated in it by amendment or revision. For undated references

the latest edition of the publication referred to applies (including amendments).

NOTE Where an International Publication has been modified by common modifications, indicated by

(mod.), the relevant EN/HD applies.
Publication Year Title EN Year
ISO 8501-1 1988 Preparation of steel substrates before EN ISO 8501-1 2001
application of paints and related
products - Visual assessment of surface
cleanliness - Part 1: Rust grades and
preparation grades of uncoated steel
substrates and of steel substrates after overall
removal of previous coatings
ISO 10441 1999 Petroleum and natural gas industries - Flexible EN ISO 10441 1999
couplings for mechanical power transmission -
Special purpose applications
---------------------- Page: 5 ----------------------
SIST EN ISO 13691:2004
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SIST EN ISO 13691:2004
INTERNATIONAL ISO
STANDARD 13691
First edition
2001-12-15
Petroleum and natural gas industries —
High-speed special-purpose gear units
Industries du pétrole et du gaz naturel — Engrenages à grande vitesse
pour applications particulières
Reference number
ISO 13691:2001(E)
ISO 2001
---------------------- Page: 7 ----------------------
SIST EN ISO 13691:2004
ISO 13691:2001(E)
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© ISO 2001

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Printed in Switzerland
ii © ISO 2001 – All rights reserved
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SIST EN ISO 13691:2004
ISO 13691:2001(E)
Contents Page

Foreword.....................................................................................................................................................................iv

Introduction.................................................................................................................................................................v

1 Scope..............................................................................................................................................................1

2 Normative references....................................................................................................................................1

3 Terms and definitions ...................................................................................................................................3

4 Symbols and abbreviated terms ..................................................................................................................6

5 Basic design...................................................................................................................................................7

5.1 General............................................................................................................................................................7

5.2 Gear rating....................................................................................................................................................10

5.3 Gear elements..............................................................................................................................................15

5.4 Casings.........................................................................................................................................................18

5.5 Casing connections.....................................................................................................................................20

5.6 Dynamics......................................................................................................................................................21

5.7 Bearings and bearing housings.................................................................................................................24

5.8 Lubrication...................................................................................................................................................26

5.9 Materials.......................................................................................................................................................26

5.10 Nameplates and rotation arrows................................................................................................................27

6 Accessories..................................................................................................................................................28

6.1 General..........................................................................................................................................................28

6.2 Couplings and guards.................................................................................................................................28

6.3 Mounting plates...........................................................................................................................................28

6.4 Controls and instrumentation ....................................................................................................................30

6.5 Piping and appurtenances..........................................................................................................................30

6.6 Special tools.................................................................................................................................................31

7 Inspection, testing and preparation for shipment....................................................................................31

7.1 General..........................................................................................................................................................31

7.2 Inspection.....................................................................................................................................................31

7.3 Testing..........................................................................................................................................................34

7.4 Preparation for shipment............................................................................................................................37

8 Vendor's data...............................................................................................................................................38

8.1 General..........................................................................................................................................................38

8.2 Proposals.....................................................................................................................................................39

8.3 Contract data................................................................................................................................................40

Annex A (informative) Special-purpose gear unit data sheets.............................................................................42

Annex B (informative) Lateral critical speed map and mode shapes for typical rotor ......................................47

Annex C (informative) Couplings for high-speed gear units................................................................................49

Annex D (informative) Vendor requirements regarding drawings and data .......................................................54

Annex E (informative) Gear tooth inspection.........................................................................................................60

Annex F (informative) Inspector´s checklist...........................................................................................................61

Annex G (informative) Relationship of tooth rating factors between ISO 13691, ISO 9084 and API 613.........66

Bibliography..............................................................................................................................................................70

© ISO 2001 – All rights reserved iii
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SIST EN ISO 13691:2004
ISO 13691:2001(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO

member bodies). The work of preparing International Standards is normally carried out through ISO technical

committees. Each member body interested in a subject for which a technical committee has been established has

the right to be represented on that committee. International organizations, governmental and non-governmental, in

liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical

Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.

The main task of technical committees is to prepare International Standards. Draft International Standards adopted

by the technical committees are circulated to the member bodies for voting. Publication as an International

Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 13691 was prepared by Technical Committee ISO/TC 60, Gears, Subcommittee SC 2, Gear capacity

calculation.

ISO 13691 is based on API 613 and is intended to give ratings similar to those found when using API 613.

Annexes A to G of this International Standard are for information only.
iv © ISO 2001 – All rights reserved
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SIST EN ISO 13691:2004
ISO 13691:2001(E)
Introduction

This International Standard is based on the accumulated knowledge and experience of manufacturers and users of

gear units. It has been developed to satisfy the requirements of the petroleum, petrochemical and natural gas

industries, but its use is not restricted to these industries.

The purpose of this International Standard is to establish minimum requirements for design and construction so

that the equipment is suitable for the purpose for which it is required.

Energy conservation and protection of the environment are matters of concern and are important in all aspects of

equipment design, application and operation. The manufacturers and users of equipment should aggressively

pursue alternative, innovative approaches which improve energy utilization and/or minimize the environmental

impact, without sacrificing safety or reliability. Such approaches should be thoroughly investigated and purchase

options should increasingly be based on the estimation of whole-life costs and the environmental consequences

rather than acquisition costs alone.

This International Standard requires the purchaser to specify certain details and features.

Users of this International Standard should be aware that further or differing requirements may be needed for

individual applications. This international Standard is not intended to inhibit a vendor from offering, or the purchaser

from accepting, alternative equipment or engineering solutions for the individual application. This may be

particularly appropriate where there is innovative or developing technology. Where an alternative is offered, the

vendor should identify any variations from this International Standard and provide details.

A bullet (z) at the beginning of a paragraph indicates that either a decision is required or further information is to be

provided by the purchaser. This information should be indicated on the data sheets; otherwise it should be stated in

the quotation request or in the order.
© ISO 2001 – All rights reserved v
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SIST EN ISO 13691:2004
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SIST EN ISO 13691:2004
INTERNATIONAL STANDARD ISO 13691:2001(E)
Petroleum and natural gas industries — High-speed special-
purpose gear units
1 Scope

This International Standard specifies the minimum requirements for enclosed, precision, single and double helical,

one- and two-stage speed increasers and reducers of parallel shaft design with pinion speeds of 3000 min or

greater, or pitch line velocities of 25 m/s or greater, for special purpose applications. Such applications will typically

be required to operate continuously for extended periods, without installed spare equipment and are critical to the

continued operation of the installation. By agreement this International Standard may be used for other services.

This International Standard also specifies a method of rating gears which meet the following criteria:

a) gear accuracy

 teeth accuracy: accuracy grade 4 or better as given in ISO 1328-1:1995, for both single pitch deviation, f ,

and total cumulative pitch deviation, F ,

 total helix deviation F between the helices of the pinion and wheel: accuracy grade 4 or better as given in

ISO 1328-1:1995;
b) range of the transverse contact ratios: 1,2 < ε < 2,0;
c) overlap ratio ε W 1,0;
d) helix angle: 5 u β u 35°;

e) working flanks of the pinion or gear: provided with profile modifications to obtain a good conjugate tooth load

distribution along the path of contact;

f) working flanks of pinion or gear: modified as necessary to compensate for both torsional and bending

deflections and, when necessary for gears with pitch line velocities in excess of 100 m/s, also for thermal

distortions;

g) gear lubrication: straight mineral oil, viscosity grade VG-32 or VG-46 (see ISO 3448);

h) material of the gear teeth: quality MQ or better, in accordance with ISO 6336-5:1996.

2 Normative references

The following normative documents contain provisions which, through reference in this text, constitute provisions of

this International Standard. For dated references, subsequent amendments to, or revisions of, any of these

publications do not apply. However, parties to agreements based on this International Standard are encouraged to

investigate the possibility of applying the most recent editions of the normative documents indicated below. For

undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC

maintain registers of currently valid International Standards.

ISO 7-1, Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions, tolerances and

designation
ISO 261, ISO general-purpose metric screw threads — General plan
© ISO 2001 – All rights reserved 1
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SIST EN ISO 13691:2004
ISO 13691:2001(E)

ISO 262, ISO general-purpose metric screw threads — Selected sizes for screws, bolts and nuts

ISO 724, ISO general-purpose metric screw threads — Basic dimensions

ISO 965-1, ISO general-purpose metric screw threads — Tolerances — Part 1: Principles and basic data

ISO 965-2, ISO general- purpose metric screw threads — Tolerances — Part 2: Limits of sizes for general purpose

external and internal screw threads — Medium quality

ISO 965-3, ISO general-purpose metric screw threads — Tolerances — Part 3: Deviations for constructional screw

threads
ISO 1122-1, Vocabulary of gear terms — Part 1: Definitions related to geometry

ISO 1328-1:1995, Cylindrical gears — ISO system of accuracy — Part 1: Definitions and allowable values of

deviations relevant to corresponding flanks of gear teeth

ISO 1940-1:1986, Mechanical vibration — Balance quality requirements of rigid rotors — Part 1: Determination of

permissible residual unbalance
ISO 2953, Mechanical vibration — Balancing machines — Description and evaluation
ISO 3448:1992, Industrial liquid lubricants — ISO viscosity classification

ISO 6336-3, Calculation of load capacity of spur and helical gears — Part 3: Calculation of tooth bending strength

ISO 6336-5, Calculation of load capacity of spur and helical gears — Part 5: Strength and quality of materials

ISO 6743-6, Lubricants, industrial oils and related products (class L) — Classification — Part 6: Family C (Gears)

ISO 7005-1, Metallic flanges — Part 1: Steel flanges
ISO 7005-2, Metallic flanges — Part 2: Cast iron flanges

ISO 8501-1:1988, Preparation of steel substrates before application of paints and related products — Visual

assessment of surface cleanliness — Part 1: Rust grades and preparation grades of uncoated steel substrates and

of steel substrates after overall removal of previous coatings

ISO 8579-1, Acceptance code for gear units — Part 1: Test code for airborne sound

ISO 8821, Mechanical vibration — Balancing — Shaft and fitment key convention

ISO 9084:2000, Calculation of load capacity of spur and helical gears — Application to high speed gears and gears

of similar requirement

ISO/TR 10064-4, Cylindrical gears — Code of inspection practice — Part 4: Recommendations relative to surface

texture and tooth contact pattern checking

ISO 10438-1, Petroleum and natural gas industries — Lubrication, shaft-sealing and control-oil systems and

auxiliaries — Part 1: General requirements

ISO 10438-2, Petroleum and natural gas industries — Lubrication, shaft-sealing and control-oil systems and

auxiliaries — Part 2: Special-purpose oil systems

ISO 10438-3, Petroleum and natural gas industries — Lubrication, shaft-sealing and control-oil systems and

auxiliaries — Part 3: General-purpose oil systems

ISO 10441, Petroleum and natural gas industries — Flexible couplings for mechanical power transmission —

Special purpose applications
2 © ISO 2001 – All rights reserved
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SIST EN ISO 13691:2004
ISO 13691:2001(E)
ISO/TR 13593, Enclosed gear drives for industrial applications

ISO/TR 13989-1, Calculation of scuffing load capacity of cylindrical, bevel and hypoid gears — Part 1: Flash

temperature method

ISO/TR 13989-2, Calculation of scuffing load capacity of cylindrical, bevel and hypoid gears — Part 2: Integral

temperature method

IEC 60079-0, Electrical apparatus for explosive gas atmospheres — Part 0: General requirements

API 670, Vibration, axial position and bearing-temperature monitoring systems
ASME B16.11, Forged fittings, Socket-Welding and Threaded
ASME, Boiler and pressure vessel code — Section V
ASME, Boiler and pressure vessel code — Section VIII, Division 1
ASME Y 14.2 M, Line conventions and lettering
ASTM A956, Standard test method for Leeb hardness testing of steel products
ASTM E94, Standard guide for radiographic examination

ASTM E125, Standard reference photographs for magnetic particle indications on ferrous castings

ASTM E709, Standard guide for magnetic particle examination
3 Terms and definitions

For the purposes of this International Standard, the terms and definitions given in ISO 1122-1 and the following

apply.

NOTE The use of the word design in any term (such as design power, design pressure, design temperature, or design

speed) should be avoided in the purchaser’s specifications. This terminology should be used only by the equipment designer

and the manufacturer.
3.1
axially [horizontally] split casing joint
casing joint parallel to the shaft centreline
3.2
critical speed

shaft rotational speed at which the rotor-bearing-support system is in a state of resonance with any exciting

frequency associated with that speed
3.3
wheel
lower speed gear element in mesh
3.4
pinion
higher speed gear element in mesh
3.5
gear rated power

maximum power specified by the purchaser on the data sheet and stamped on the nameplate

cf. 5.2.1.
© ISO 2001 – All rights reserved 3
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SIST EN ISO 13691:2004
ISO 13691:2001(E)
3.6
normal transmitted power
power at which usual operation is expected and optimum efficiency is desired

NOTE The normal transmitted power may be equal to or less than the gear rated power.

3.7
mechanical rating
gear rated power (3.5) multiplied by the specified gear selection factor (3.17).
3.8
hunting tooth combination

·mating gearsÒ combination existing when a tooth on the pinion does not repeat contact with a tooth on the gear

until it has contacted all the other gear teeth
3.9
maximum allowable speed

highest rotational speed at which the manufacturer’s design will permit continuous operation

3.10
maximum continuous speed

·variable-speed unitÒ rotational speed at least equal to 105 % of the rated speed

3.11
maximum continuous speed
·constant-speed unitÒ rotational speed equal to the rated speed
3.12
minimum allowable speed

lowest rotational speed at which the manufacturer’s design will permit continuous operation

3.13
rated input speed
specified (or nominal) rated speed of the driver, as designated by the purchaser
3.14
rated output speed

specified (or nominal) rated speed of the driven equipment, as designated by the purchaser.

NOTE In selecting the number of teeth for the pinion and gear, it is often impracticable for the vendor to match exactly both

the rated input and the rated output speeds designated on the data sheets. The purchaser therefore indicates which of the two

is specified (that is, must be exactly adhered to by the vendor) and which is nominal (that is, permits some variation). The letter

S is used to indicate the specified speed, and the letter N to indicate the nominal speed. The purchaser also indicates on the

data sheets the allowable percentage of variation in the designed gear ratio.
3.15
contact stress number
contact stress calculated based on the Hertzian contact pressure
3.16
bending stress number

bending stress calculated from the resistance to fatigue cracking at the tooth root fillet

4 © ISO 2001 – All rights reserved
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SIST EN ISO 13691:2004
ISO 13691:2001(E)
3.17
gear selection factor

factor applied to the calculated contact stress number and the calculated bending stress number, depending on the

characteristics of the driver and the driven equipment, to account for potential overload, shock load and/or

continuous oscillatory torque characteristics
3.18
trip speed

rotational speed at which the independent emergency overspeed device operates to shut down a prime mover

NOTE 1 For fixed-frequency alternating current motor drives, the trip speed is taken to be the speed corresponding to the

synchronous speed of the motor at the highest supply frequency.

NOTE 2 For steam turbines and reciprocating engines, the trip speed is at least 110 % of the maximum continuous speed.

For gas turbines, the trip speed is at least 105 % of the maximum continuous speed.

3.19
special-purpose application

application for which the equipment is designed for uninterrupted, continuous operation in critical service and for

which there is usually no spare equipment
3.20
total indicated runout
total indicator reading
TIR
runout of a diameter or face determined by measurement with a dial indicator

NOTE The indicator reading implies an out-of-squareness equal to the reading or an eccentricity equal to half the reading.

3.21
Gauss level

magnetic field level of a component measured with a “Hall effect” probe with no interference from adjacent

magnetic parts or structures
3.22
unit responsibility

responsibility for coordinating the technical aspects of the equipment and all auxiliary systems included in the

scope of the order

NOTE Responsibility for such factors as the power requirements, speed, rotation, general arrangement, couplings,

dynamics, noise, lubrication, sealing system, material test reports, instrumentation, piping, and testing of components is

included.
3.23
purchaser
individual or organization that issues the order and specification to the vendor

NOTE The purchaser may be the owner of the plant in which the equipment is to be installed, or the owner´s agent (often

the vendor of the equipment to be dri
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