SABP-G-002

Previous Issue: New Next Planned Update: 1 November, 2009 Revised paragraphs are indicated in the right margin Page 1 of 7 Primary contact: Khaleel M. Al-Hussain on 873-0311

Best Practice

SABP-G-002 31 October, 2004 General Purpose Steam Turbines Dynamic Analysis Factory Acceptance Test Document Responsibility: Consulting Services Dept.

Saudi Aramco Desk Top Standards Table of Contents 1 Introduction.................................................... 2 2 References.................................................... 2 3 General.......................................................... 3 4 Definitions...................................................... 3 5 Vibration Detectors........................................ 4 6 Shop Verification of Unbalanced Response Analysis.………………..…… 4 7 Tests Procedure............................................ 5 8 FAT Acceptance Criteria............................... 6

Document Responsibility: Consulting Services Dept. SABP-G-002 Issue Date: 31 October, 2004 General Purpose Steam Turbines Next Planned Update: 1 November, 2009 Dynamic Analysis Factory Acceptance Test

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1 Introduction

1.1 Purpose

The purpose of this Practice is to establish guidelines in reviewing the dynamic analysis of general purpose steam turbines during Factory Acceptance Test (FAT).

1.2 Scope

This Best Practice gives general guidelines for reviewing vibration instrumentation requirements, test procedure and acceptance limits during the Factory Acceptance Test and does not include performance test criteria.

1.3 Disclaimer

This Best Practice is being provided for the general guidance and benefit of Saudi Aramco engineers attending general purpose steam turbines Factory Acceptance Test (FAT). The use of this Best Practice during factory acceptance test, however, does not relieve the manufacturer from his responsibility or duty to confirm or to verify the accuracy of any information presented or from his contractual liability to perform an accurate FAT that conforms to Mandatory Saudi Aramco Engineering Requirements. The use of the information or material contained herein will not guarantee that the resulting product satisfies the applicable requirements of Saudi Aramco Standards. Saudi Aramco assumes no responsibility or liability whatsoever for any reliance on the information presented herein or for FAT performed by manufacturer in accordance with this Best Practice document. Moreover, this Best practice is intended only to provide guidelines for Saudi Aramco engineers attending the Factory Acceptance Test and shall not be considered as a replacement for the Mandatory Saudi Aramco Engineering Requirements. Saudi Aramco® is a registered trademark of the Saudi Arabian Oil Company. Copyright, Saudi Aramco, 2004.

1.4 Conflicts with Mandatory Standards

In the event of a conflict between this Best Practice and other Mandatory Saudi Aramco Engineering Requirement, the Mandatory Saudi Aramco Engineering Requirement shall govern.

2 References

This Best Practice is based on the below referenced standard:

2.1 Saudi Aramco References


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Saudi Aramco Engineering Standard

SAES-K-501 Steam Turbines (30 September, 2003)

Saudi Aramco Materials System Specifications

32-SAMSS-009 General Purpose Steam Turbines (29 October, 2003)

34-SAMSS-625 Machinery Protection Systems (30 June, 2002)

2.2 Industry Codes and Standards

American Petroleum Institute (API)

API STD 611 General Purpose Steam Turbines for Petroleum, Chemical and Gas Industry Services, 4th Edition

API STD 670 Machinery Protection Systems, 4th Edition

3 General

This best practice gives general guidelines for the vibration instrumentation requirements, test procedure and acceptable limits during general purpose steam turbines factory acceptance test. The attendee should review the rotordynamic analysis prior the test.

The vendor shall notify the purchaser not less than five working days before the date the equipment will be ready for testing. This requires written notification of a successful preliminary test. If the testing is rescheduled, the vendor shall notify the purchaser not less than five working days before the new test date. (API STD 611/ P 6.3.1.2)

4 Definitions

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

Factory Acceptance Test (FAT): is a test conducted at a factory to ensure that the turbine meets its required performance and mechanical integrity.

General purpose steam turbines: are those turbines used to drive equipment that are spared or not critical to plant operation. General purpose steam turbines shall not be used for applications requiring a rated power exceeding 2,250 kW (3,000 HP), a maximum continuous speed exceeding 5,000 RPM or for steam conditions exceeding a pressure of 4,800 kPa Gauge (700 psig) and a temperature exceeding 400°C (750°F). (32-SAMSS-009 / P 1.1.1.1).


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Hydrodynamic bearings: Bearings that use the principles of hydrodynamic lubrication. Their surfaces are oriented so that relative motion forms an oil wedge to support the load without journal-to-bearing contact. (API STD 611 / P 3.5).

Maximum continuous speed (revolutions per minute): The speed at least equal to 105% of the highest speed required by any of the specified operating conditions. (API STD 611 / P 3.10).

Minimum allowable speed (in revolutions per minute): The lowest speed at which the manufacturer’s design will permit continuous operation. (API STD 611 / P 3.14).

Trip speed (in revolutions per minute): The speed at which the independent emergency over-speed device operates to shutdown the turbine. The trip speed setting will vary with the class of governor. (API STD 611 / P 3.28).

5 Vibration Detectors

Vibration detection equipment shall be provided as per the below Table-1. (For more detail see 32-SAMSS-009 Paragraph 4.9.32):

Table-1: Required Vibration Instrumentation for General Purpose Steam Turbine

Relative Measurement Seismic Measurement Reading at the monitor HP Rating

Applicable Standard Radial Thrust KeyΦ Velocity

(RMS) Acceleration

> 300 HP with Anti-friction Brg. & with no relative displace. probes

32-SAMSS-009 (Sec. 4.9.32) One/Brg.

300 -1000 HP (Hydrodynamic Radial + Anti-Friction Thrust Brg.)

(Sec. 4.9.32) Provisions Provision

300 -1000 HP Hydrodynamic Thrust Brg. (Sec. 4.9.32) Provisions Dual Yes

> 1000 HP (Sec. 4.9.32) X & Y Dual Yes

Vibration detectors shall be provided, installed and calibrated in accordance with 34-SAMSS-625.

6 Shop Verification of Unbalance Response Analysis

6.1 Shop verification of unbalance response analysis shall be performed as part of the mechanical test and the results shall be used to verify the anlytical model. The method to cdonduct the shop verifcation test is described in (API STD 611, Appendix B.1 Shop Verification of Unbalanced Response Analysis).


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6.2 The results of the verification test shall be compared with those from the original analytical model. The vendor shall correct the model if it fails to meet any of the following criteria: (API STD 611/ Appendix B.1.2.2)

a) The actual critical speeds shall not deviate from the predicted speeds by more than ±5%.

b) The predicted amplification factors shall not deviate from the actual test-stand values by more than ±20%.

c) The actual response peak amplitudes, including those that are critically damped, shall be within ±50% of the predicted amplitudes.

6.3 When the test data does not meat the requirements of API STD 611, Appendix B.1.3, additional more stringent testing is requires as per API STD 611, Appendix B.1.4. The purpose of this additional testing is to determine on the test stand that the machine will operate successfully.

7 Tests Procedure

7.1 The Vendor shall prove compatibility between contract probes and his test stand readout equipment. Contract axial thrust position probes and oscillator-demodulator shall be used during shop test. (32-SAMSS-009 / P 6.3.3.1.6).

7.2 Bearing housing overall velocity should be measured in in/sec (mm/sec) RMS and shaft vibration in mils (µm) pk-pk.

7.3 The combined total electrical and mechanical runout is presented in Table-2 (for more detail refer to API STD 611, paragraph 4.6.2).

Table-2: Allowable Total Runout

Probes Location Applicable Standard Allowable Total Runout (TR)

Radial

API STD 611 (Sec. 4.6.2. a)

whichever is greater • TR ≤ 0.25 x maximum allowed pk-pk

vibration amplitude

• TR ≤ 0.25 mils pk-pk

Axial API STD 611

(Sec. 4.6.2. b)

whichever is greater • TR ≤ 0.25 x maximum allowed pk-pk

vibration amplitude

• TR ≤ 0.5 mils pk-pk


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Note: If the vendor can demonstrate that electrical or mechanical runout is present and the total runout is within the above acceptable limit, then the runout may be vectorially subtracted from the vibration signal measured during the factory. (API STD 611/ P4.8.4.7).

7.4 When noncontacting probes or provisions for them have been specified, electrical and mechanical runout shall be determined and recorded by rolling the rotor in V-blocks at the journal centerline while measuring runout with a non-contacting vibration probe and a dial indicator at the centerline of the probe location and one probe-tip diameter to either side. Accurate records of electrical and mechanical runout, for the full 360 degrees at each probe location, shall be included in the mechanical test report. (API STD 611 / P 4.8.4.6).

7.5 When noncontacting probes are not provided and when vibration cannot be measured on the shaft, radial vibration of the housings shall be recorded using shop instrumentation during the test. The measurements shall be taken on the top and side of each bearing housing. (API STD 611/ P 6.3.3.1.5).

7.6 Turbines shall be given a 1-hour uninterrupted no-load running test at maximum continuous speed. (API STD 611/ P6.3.3.2).

7.7 The equipment shall be operated at speed increments of approximately 10% from zero to the maximum continuous speed and run at the maximum continuous speed until bearings, lube-oil temperature and shaft vibrations have stabilized. (API STD 611/ P6.3.3.3.2).

7.8 The speed shall be increased to 110% of the maximum continuous speed, and the equipment shall be run for a minimum of 15 minutes at the increased speed. (API STD 611/ P6.3.3.3.3).

8 FAT Acceptance Criteria

Vibration readings shall be taken at maximum continuous speed, just below trip speed, and at minimum operating speed after the stabilization described in step 7.7. Maximum allowable vibration limits are described in the below Table-3 which is a combination of API STD 611 4th edition and 32-SAMSS-009 exceptions. Any critical speeds below maximum continuous shall be determined. (API STD 611/ P 6.3.3.3.4).


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Table-3: Vibration Limits for General Purpose Steam Turbines

Notes:

(*) These specifications are from 32-SAMSS-009 – paragraph 4.8.4.8 not API STD 611.

Where:

Vu = unfiltered velocity. Au = unfiltered displacement determined by FFT. N = rotational speed (RPM).

Revision Summary 31 October, 2004 New Saudi Aramco Best Practice.

Location of vibration Measurement Item

Vibration On Inboard & Outboard Bearing Housing

Turbine Shaft (adjacent to bearing)

(i) Maximum continuous speed or at any other speed within the specified operating speed range

Overall Vibration

Vu ≤ 2.5 mm/sec RMS *

(0. 10 in./sec RMS)*

whichever is less • Au ≤ (5.2X106 /N)0.5 µm pk-pk

((12000/N)0.5 mils pk-pk)

• Au ≤50 µm pk-pk (2.0 mils pk-pk)

(ii) Vibration limits at any speed greater than the maximum continuous speed, up to and including the trip speed

150 % of the recorded value at

maximum continues speed

150 % of the recorded value at

maximum continues speed

Documents

SABP-G-002