Memo Name: Hulisani Khorommbi Title / Designation: Junior Vibration Specialist Ref No: X-4587394-039 Jj Groenewald; P Stangroom; F Mariba; Z Ledwaba; R Neerputh; G Baldwin To Kriel Power Station Copy to C. Burger; A Beeslaar; R. Da Veiga and M. Ngobeni Date 06 October 2020 Subject: Kriel Unit 3 Steady State Vibrations Behavior. INTRODUCTION The purpose of this memo is to bring attention to Kriel Power Station the vibration behavior of Unit 3 Turbo-Generator after the Unit experienced vibration excursions. NOTE: Engineering Turbine Specialised Services (ETSS) analysis is based on the assumption that all vibration signals are correct and that the installation of the vibration monitoring system conforms to the ISO 10817 Standard and that all operational parameters were within acceptable limits during the monitoring period. The vibration monitoring systems used for analysis was Bently Nevada Adre 408 and PI Process Book. NB: Electrical Discharge is evident on bearing 3Y. VIBRATION BEHAVIOR On Monday the 05th October 2020 with the Unit at 20MW, the shaft relative and pedestal absolute vibration amplitudes were trending stable across the Unit. With the Unit still at 20MW, at about 16h10, both the shaft relative and pedestal absolute vibration amplitudes started to gradually increase across the Unit, however the increase was mostly significant on bearing 1 to 5 – Refer to plots 1 to 7. During this period bearing 1 metal temperature also increased from 90°C to 96°C. At 16h54 the Unit tripped due to high vibrations. The analysis of the vibration data indicated a shaft movement drop of over 700µm on bearing 4 and 100µm movement on bearing 3 with the Unit back on barring – Refer to plots 8 to 9. ETSS is of opinion that this shaft lift drop is an indication of possible severe bearing damage on bearing 4. Tel: +27(11)629 4521 Fax: +27(11)629 4557 Cell: 079 863 0770 E-mail: khoromhu@eskom.co.za 10/6/2020 Form No.: H-72 Rev 1 CONCLUSION After analyzing the steady state and transient data ETSS is of opinion that the vibration excursions were caused by a severe rub condition that led to temporary thermal bow on these rotors. This rub condition probably originated as a result of possible severe bearing damage on bearing 4. RECOMMENDATIONS The following recommendations are presented for possible implementation: Inspect bearing 3 and bearing 4 for wear / damage. Hulisani Khorommbi Adriaan Beeslaar Junior Vibration Specialist Vibration Specialist Engineering Turbine Specialised Services Engineering Turbine Specialised Services Turbo Gen Services Turbo Gen Services Christo Burger Chief Engineer Engineering Turbine Specialised Services Turbo Gen Services Tel: +27(11)629 4521 Fax: +27(11)629 4557 Cell: 079 863 0770 E-mail: khoromhu@eskom.co.za 10/6/2020 Form No.: H-72 Rev 1 PLOTS Plot 1 Bearing 1 – 2 Shaft Vibrations Before and After Vibration Excursion Tel: +27(11)629 4521 Fax: +27(11)629 4557 Cell: 079 863 0770 E-mail: khoromhu@eskom.co.za 10/6/2020 Form No.: H-72 Rev 1 Plot 2 Bearing 3 – 4 Shaft Vibrations Before and After Vibration Excursion Tel: +27(11)629 4521 Fax: +27(11)629 4557 Cell: 079 863 0770 E-mail: khoromhu@eskom.co.za 10/6/2020 Form No.: H-72 Rev 1 Plot 3 Bearing 5 – 6 Shaft Vibrations Before and After Vibration Excursion Tel: +27(11)629 4521 Fax: +27(11)629 4557 Cell: 079 863 0770 E-mail: khoromhu@eskom.co.za 10/6/2020 Form No.: H-72 Rev 1 Plot 4 Bearing 7 Shaft Vibrations Before and After Vibration Excursion Tel: +27(11)629 4521 Fax: +27(11)629 4557 Cell: 079 863 0770 E-mail: khoromhu@eskom.co.za 10/6/2020 Form No.: H-72 Rev 1 Plot 5 Pedestal 1 – 2 Absolute Vibrations Before and After Vibration Excursion Tel: +27(11)629 4521 Fax: +27(11)629 4557 Cell: 079 863 0770 E-mail: khoromhu@eskom.co.za 10/6/2020 Form No.: H-72 Rev 1 Plot 6 Pedestal 4 – 6 Absolute Vibrations Before and After Vibration Excursion Tel: +27(11)629 4521 Fax: +27(11)629 4557 Cell: 079 863 0770 E-mail: khoromhu@eskom.co.za 10/6/2020 Form No.: H-72 Rev 1 Plot 7 Pedestal 7 Absolute Vibrations Before and After Vibration Excursion Tel: +27(11)629 4521 Fax: +27(11)629 4557 Cell: 079 863 0770 E-mail: khoromhu@eskom.co.za 10/6/2020 Form No.: H-72 Rev 1 Plot 8 Bearing 3 Shaft Movement Tel: +27(11)629 4521 Fax: +27(11)629 4557 Cell: 079 863 0770 E-mail: khoromhu@eskom.co.za 10/6/2020 Form No.: H-72 Rev 1 Plot 9 Bearing 4 Shaft Movement Tel: +27(11)629 4521 Fax: +27(11)629 4557 Cell: 079 863 0770 E-mail: khoromhu@eskom.co.za 10/6/2020 Form No.: H-72 Rev 1
