SAER-5659

Previous Issue: 30 June 2004 Next Planned Update: 1 March 2008 Revised paragraphs are indicated in the right margin Page 1 of 16 For additional information, contact Hussain, Khaleel Ma'Atug on 966-3-873031116

Copyright©Saudi Aramco 2007. All rights reserved.

Engineering Report

SAER-5659 1 July 2007 Guidelines for Setting Acceptable, Alarm and Shutdown Vibration Limits Document Responsibility: Consulting Services Department

Document Responsibility: Consulting Services Dept. SAER-5659 Issue Date: 1 July 2004 Guidelines for Setting Acceptable, Next Planned Update: 1 March 2008 Alarm and Shutdown Vibration Limits

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Table of Contents

Page

1 Definitions ...........................................................................................................3 1.1 Acceptable Level ..................................................................................................... 3 1.2 Alarm Level ............................................................................................................. 3 1.3 Shutdown Level....................................................................................................... 3 1.4 Allowable Piping and Valve Vibration Levels .......................................................... 3

2 Recommended Acceptable Vibration Levels.......................................................4 2.1 Shaft Journal Vibration Displacement ..................................................................... 4 2.2 Bearing Housing Seismic Vibration (Coupled) ........................................................ 4

A. Motors, Generators, Compressors, and Steam Turbines................................ 4 B. Vertical Motors ................................................................................................ 4 C. Pumps ............................................................................................................. 4 D. Fin Fans .......................................................................................................... 5 E. Gear Units ....................................................................................................... 5 F. Reciprocating Machines .................................................................................. 5 G. Combustion Gas Turbines............................................................................... 5

3 Recommended Workshop Acceptable Vibration Levels......................................6 3.1 Horizontal Electric Motors ....................................................................................... 6 3.2 Vertical Electric Motors............................................................................................ 6 3.3 Steam Turbines ....................................................................................................... 6 3.4 Combustion Gas Turbines....................................................................................... 6 3.5 Runout (Total).......................................................................................................... 6

4 Axial Rotor Displacement Settings ......................................................................7 5 Allowable Piping Vibration Levels .......................................................................7 6 Valve Vibration Levels.........................................................................................7 7 Shaft Relative Displacement (Non-Contacting) Sensor Orientation ....................8 8 Radial Dual Voting ..............................................................................................8 9 Alignment Tolerances .........................................................................................8 Appendix A – Vertical Motor Vibration Limits .............................................................9 Appendix B – Fin Fans Measurement Location........................................................ 10 Appendix C – Thrust Position Settings.....................................................................11 Appendix D – Allowable Piping Vibration Levels ......................................................12 Appendix E – Recommended Guideline Limits

for External Sound Pressure Levels vs. Pipe Diameter..................... 13 Appendix F – Piping Configurations with and without Reinforcement.......................14 Appendix G – Noncontact Probe Orientation ...........................................................15 Appendix H – Alignment Tolerances ........................................................................16


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The purpose of this document is to lay down guidelines for acceptable, alarm, and shutdown vibration limits for existing rotating equipment and allowable piping and valve vibration levels throughout Saudi Aramco.

This document is not applicable for establishing acceptance criteria for equipment factory tests or commissioning or for setting alarm and shutdown criteria for monitoring or protection systems of new equipment.

This engineering report will ensure that similar equipment throughout the Company will be set to the same alarm and shutdown limits. However, for special cases or unusual equipment, Consulting Services Department/Dynamic Analysis Unit will assist in selecting the acceptance, alarm, and shutdown limits which may vary significantly from the values shown in this document, depending on equipment design, operating experience and/or vendors’ recommendations.

1 Definitions

The definitions of "Acceptable", "Alarm" and "Shutdown" limits are as follows:

1.1 Acceptable Level

This is the vibration level (displacement, velocity, or acceleration) at which a machine can run indefinitely without inducing vibration related maintenance at normal operating condition.

1.2 Alarm Level

This is the vibration level at which an equipment is considered to have developed a defect that will result in related downtime. This level is usually higher than the acceptable level to allow for conservatism and machinery variance and is recommended as 1.5 times the acceptable level.

1.3 Shutdown Level

This is the vibration level at which an equipment should be shutdown as continued running could lead to accelerated degradation and possible catastrophic failure. This is recommended as 2.0 times the acceptable level.

1.4 Allowable Piping and Valve Vibration Levels

This is the vibration level (displacement or velocity) at which a piping/valve may operate below the fatigue threshold limit.


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2 Recommended Acceptable Vibration Levels

2.1 Shaft Journal Vibration Displacement

The acceptable level for shaft relative displacement (non-contacting) sensors is calculated as follows:

Acceptable Level is equal to:

pkpkmilsRPM −/12000

e.g., for a 3,600 RPM machine, the acceptable level will be:

pkpkmils −= 83.13600/12000

pkpkm −=× μ463600/120004.25

Only 0.25 mils (6.4 µm) pk-pk may be added to this level to compensate for shaft runout which should be within the limits specified in Section 4. This may also be added to alarm and shutdown levels if applicable.

2.2 Bearing Housing Seismic Vibration (Coupled)

A. Motors, Generators, Compressors, and Steam Turbines

The acceptable overall vibration level should be 0.18 in/s (4.6 mm/s) RMS.

B. Vertical Motors

The acceptable overall vibration level should be as detailed in Appendix A or:

1.0 g’s RMS on any bearing housing in any direction.

C. Pumps

The acceptable overall vibration level should be 0.22 in/s (5.6 mm/s) RMS for horizontal double casing (barrel) pumps and 0.25 in/s (6.3 mm/s) RMS for all other pumps.

pkpkmRPM −× μ/120004.25


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Vane pass related frequency vibration level should not exceed 0.15 in/s (3.8 mm/s) RMS.

D. Fin Fans

The acceptable vibration level should meet the following criteria:

• 1.0 g’s RMS and 0.18 in/s (4.6 mm/s) RMS on the bearing housing

• 10.0 mils (254 µm) pk-pk on the supporting structure measured with a seismic transducer.

All measurements should be taken at the locations indicated in Appendix-B

E. Gear Units

The acceptable casing vibration level measured on any bearing housing in any direction should meet the values listed in the following table:

Velocity Acceleration Frequency Range

10 Hz – 2.5 kHz 2.5 kHz – 10 kHz

Unfiltered RMS Level 0.20 in/s (5.0 mm/s) 7.0 g’s

In addition, gearbox protection philosophy should be based on alarm on acceleration, and alarm and trip on velocity.

F. Reciprocating Machines

For reciprocating pumps and compressors and for diesel engines, the acceptable vibration level, measured on the crankcase, adjacent to the main crankshaft bearings and on a plane perpendicular to the crank axis, should not exceed 0.5 in/s (12.7 mm/s) RMS.

G. Combustion Gas Turbines

The acceptable vibration level should be:

• 0.30 in/s (7.6 mm/s) RMS for industrial types

• 0.35 in/s (8.9 mm/s) RMS for aero-derivatives


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3 Recommended Workshop Acceptable Vibration Levels

3.1 Horizontal Electric Motors

Where shaft relative displacement (non-contacting) sensors are installed, the acceptable displacement is:

)()(/7200 pkpkmilsmRPM −μ

)(/72004.25 pkpkmRPM −× μ

The overall acceptable vibration levels measured on any bearing housing in any direction should not exceed 0.13 in/s (3.3 mm/s) RMS.

3.2 Vertical Electric Motors

The overall acceptable vibration level measured at the top bearing should be less than the 75% of the levels detailed in Appendix A.

3.3 Steam Turbines

Where shaft relative displacement (non-contacting) sensors are installed, the overall acceptable level at maximum rated speed is:

)(/7200 pkpkmilsRPM −

The acceptable overall vibration level measured on any bearing housing in any direction should be 0.13 in/s (3.3 mm/s) RMS.

3.4 Combustion Gas Turbines

The overall acceptable casing vibration should be 0.25 in/s (6.4 mm/s) RMS.

3.5 Runout (Total)

All equipment with installed shaft relative (non-contacting) vibration sensors should meet the following criteria for shaft total combined electrical and mechanical runout:

0.35 mils (9.0 µm) for rated shaft speeds up to 1,800 RPM

0.25 mils (6.4 µm) for rated shaft speeds exceeding 1,800 RPM.

)(/72004.25 pkpkmRPM −× μ


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Combined electrical and mechanical runout shall be determined by rolling the rotor on V-blocks at the journal bearing centerline.

4 Axial Rotor Displacement Settings

Equipment manufacturer limits shall be considered for axial rotor displacement settings for all bearing types.

However, if these limits are not available, then in the case of tilting-pad thrust bearings having babbitt thickness between 25 to 40 mils (635-1016 µm), the following limits may be applied:

When zero thrust position is the center of the float of the machine, then axial setting is:

½ cold float plus 10.0 mils (254 µm) for normal setting plus 5.0 mils (127 µm) on normal for alarm plus 5.0 mils (127 µm) on alarm for shutdown

These limits are graphically shown on Appendix C.

The active (normal) thrust direction is the direction of the rotor axial thrust load expected by the machinery vendor during normal operating conditions. The active (normal) thrust is the plus side of the monitor.

5 Allowable Piping Vibration Levels

The maximum overall allowable vibration levels for piping with reinforced and without reinforced branch piping are:

1.0 in/s (25.40 mm/s) RMS with reinforced branch piping see appendix F.

0.75 in/s (19.10 mm/s) RMS without reinforced branch piping see appendix F.

Provided that the overall displacement does not exceed 100.00 mils (2.54 mm) pk-pk and specific frequencies do not exceed the marginal level as indicated in Appendix D.

In addition, for broadband frequency type vibration sound pressure level should also be measured and values should not exceed recommended limit indicated in Appendix E.

6 Valve Vibration Levels

The acceptable vibration on valve body should not exceed 0.5 in/s (12.70 mm/s) RMS measured in any direction.


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7 Shaft Relative Displacement (Non-Contacting) Sensor Orientation

Shaft relative displacement sensors should be identified as X & Y, not horizontal and vertical and should be oriented as shown in Appendix G when viewed from driver end.

8 Radial Dual Voting

Based on 34-SAMSS-625 paragraph 5.4.2.4, radial vibration monitors shall be configured to shutdown if one of the two transducer signals equals or exceeds the shutdown set point i.e., not dual voting logic.

However, dual voting logic may be considered for specific cases with the following conditions:

• Strong justification shall be provided to Plant Manager for the use of dual voting logic, i.e., criticality of the machine to plant operation.

• Monitors must indicate high-high alarm for each probe as they reach danger limit.

• Single vote high-high alarms shall be thoroughly investigated as soon as the alarm level is reached.

• A written procedure shall be agreed upon between Plant Operations and Engineering to immediately investigate the high-high alarm condition.

9 Alignment Tolerances

Alignment tolerance figures are presented in Appendix H. These figures are intended as a general guide rather than a standard, since actual cases will vary significantly depending on the coupling type, application and even the time of the day. Although this graph in Appendix H presents an acceptable region, the aim should always be for zero.

Revision Summary 26 February 2003 Revised the "Next Planned Update". Reaffirmed the contents of the document, and

reissued with minor changes. 30 June 2004 Minor revision. 1 July 2007 Minor revision.


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Appendix A – Vertical Motor Vibration Limits


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Appendix B – Fin Fans Measurement Location

Vibration measurement points on fan mount and motor


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Appendix C – Thrust Position Settings

Referenced to 200 mV/mil probe sensitivity


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Appendix D – Allowable Piping Vibration Levels

1 EDI Report 85-305, Vibration in Reciprocating Machinery and Piping System, San Antonio, October 1985.

Allowable Piping Vibration Levels 1


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Pipe Diameter, in

100

105

110

115

120

125

0 5 10 15 20 25 30 35 40

Maximum allowable noise levels

Recommended limit/calculated values

Allo

wab

le E

xter

nal S

PL L

evel

in D

B a

t 1 m

eter

Appendix E – Recommended Guideline Limits for External Sound Pressure Levels vs. Pipe Diameter

Jungbauer, D and Blodgett, L. Acoustic fatigue involving large turbomachinery and pressure reduction systems.

Proceedings of the 27th Turbomachinery Symposium, 1998.


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Appendix F – Piping Configurations with and without Reinforcement

Pipe branch without reinforcement

Reinforced pipe branch


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Appendix G – Noncontact Probe Orientation

Orientation of Proximity Probes Viewed Along Train from Driver-NDE Regardless of Direction of Rotation

Note: The preferred proximity probe orientation is as shown above. However, if this cannot be achieved, the probes may be oriented at any position around the shaft, provided that the included angle between the probes is always 90 ° and that the "X" probe is always positioned in a clockwise direction, relative to the "Y" probe.


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Appendix H – Alignment Tolerances

Hot Alignment Tolerances T.I.R 2 2 Pitorowski, J. “Shaft Alignment Handbook”, Marcel Dekker Inc., New York. 2nd Ed., 1995.

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SAER-5659