classic | mobile
 

Search...

SA Instrumentation & Control Buyers' Guide

 

Africa’s largest rotor pole ­refurbishment
July 2017, Electrical Power & Protection


In the largest repair of this nature in Africa, Marthinusen & Coutts recently refurbished 11 of the full set of 14 rotor poles of Motor Generator Unit Three at Eskom’s Ingula Pumped Storage Scheme on the Drakensberg escarpment. The rotor poles were extensively damaged during a fault condition at the station, and the return to service of the unit was of national importance.

Working closely with stakeholders, an extensive local programme of testing, dismantling, inspection and repair was conducted by Marthinusen & Coutts within extremely tight time-frames to accommodate the criticality of the project. A technical audit confirmed that facilities at the company’s 8000 m² main workshop in Cleveland, Johannesburg, and its 12 000 m² Power Generation division in Benoni, were up to the daunting task. All 14 main rotor poles were then collected from Ingula Pumped Storage Scheme and dispatched to the Benoni works. Each pole weighed 12 tons, with the coil alone weighing in at over two and a half tons.

It was vital that Marthinusen & Coutts determined not just the electrical status of the windings, but the health and physical integrity of each entire rotor pole (body and coil). They were therefore subjected to insulation resistance and inter-turn insulation tests, comprising both impulse and power frequency inter-turn insulation tests. Extensive visual inspections were also conducted. The test results were analysed, resulting in the decision to refurbish 11 of the 14 poles; two coils were accepted as healthy and the station owned a spare universal coil.

To facilitate the grinding procedure necessary to remove the support side brackets from the main rotor poles, a customised heavy duty jig was manufactured. After the severity of the damage was determined, various techniques and repair concepts were tabled and discussed in detail. It was finally agreed that the coils be stripped of their existing inter-turn insulation layers and the coils be reinsulated, heat cured using 2500 A, including pressing at up to 1000 tons, and re-assembled to the main poles. To fast track the process, Marthinusen & Coutts prepared custom parallel operations at the two facilities by separating the dirty and clean processes, with full clean conditions areas for the critical pressing and heat curing processes.

Manufacturing the tools and equipment for the work demanded substantial engineering and sourcing capacity. Among the items to be custom made were various tables and jigs to help move the coils in and out of the burn-out oven. A coil removal rig to remove coils safely from the main pole body was built, as well as two heavy duty consolidation rigs with a set of 1000 ton hydraulic jacks and their dedicated power control unit.

Marthinusen & Coutts also designed and constructed a dimensionally accurate dummy pole centre to help ensure correct fitment of coils to the main poles. Other items included a 2500 A direct current controlled rectifier to assist with the curing cycle, heavy duty turning rigs, lifting assemblies and a magnetic link for inter-turn insulation testing.

The scope of work included pyrolising the coil insulation in a controlled oven environment at 300°C and removing the existing insulation. The copper stacks were cleaned and polished, new insulation was pressed and prepared, and all new insulation kits were manufactured with pre-impregnated Aramid paper. All pole coils were reinsulated and thermo-electrically cured with a 1000 ton consolidation pressure, after which they were cleaned and tested.

Work on the main pole bodies included removing the existing insulation and checking and testing the copper damper winding and series connectors. Weld scars were cleaned and polished and new insulation kits were supplied and fitted. In the final assembly and test stage, Marthinusen & Coutts repaired the existing support brackets to as-new OEM specification and tested them to meet international standards. Coils were fitted to the rotor poles and the coils sealed onto the main poles. Finally the finished rotor poles with coils were tested, crated and transported back to Ingula by Marthinusen & Coutts. Unit 3 is now operating to full capacity. The entire project was carried out under extreme pressure, in record time, and according to all the OEM specifications and requirements for new rotor poles.

For more information contact Richard Botton, Marthinusen & Coutts, +27 (0)11 607 1700, richardb@mandc.co.za, www.mandc.co.za


Share via email     Share via LinkedIn   Print this page

Further reading:

  • Increased safety in mine charging stations
    November 2017, Electrical Power & Protection
    Increasingly, mines are using battery-powered electric vehicles underground as they help eliminate the problem of air pollution from diesel exhaust emissions. However, there is also an inherent risk in ...
  • Shaw Controls provides containerised switchgear solution at DRC mine
    November 2017, Zest WEG Group Africa, Electrical Power & Protection
    Leveraging the advantages of a containerised solution, Zest WEG Group’s Shaw Controls has provided an optimal medium voltage switchgear solution for the supply of power at a copper mining project in the ...
  • Switch-mode power supply with reserve
    November 2017, ifm Electronic RSA, Electrical Power & Protection
    ifm’s powerful new switch-mode power supplies provide an excellent power reserve of 50% for up to four seconds to cope with high current loads. Instead of an inrush current limitation with a simple NTC ...
  • Africa’s call for dry-type transformers hikes
    November 2017, Electrical Power & Protection
    Already popular in North America and Europe, dry-type transformers will soon be seeing greater take-up in Africa through a more concerted entry and support strategy from global supplier Hammond Power ...
  • Self-generated power needs a focus on efficiency
    November 2017, Zest WEG Group Africa, Electrical Power & Protection
    Remote projects that happen far from national power grids tend to pay a premium for generating their own energy; so they need to plan carefully and use it as efficiently as they can. This is the advice ...
  • Dry-type transformers for modular substations
    October 2017, Electrical Power & Protection
    The introduction of Trafo dry-type transformers to the African market comes just at the time that end-users, in a number of industry sectors, embrace the growing trend towards modularised substations. “Due ...
  • Legrand’s solutions for power ­outages
    October 2017, Legrand, Electrical Power & Protection
    Legrand’s power solutions ensure continuity of service and protection of electrical equipment during planned and unexpected power outages. These modular systems include cast resin transformers, with low ...
  • Improve battery management in solar powered applications
    October 2017, Omniflex Remote Monitoring Specialists, Electrical Power & Protection
    The Powerterm industrial grade power supply/battery backup range from Omniflex has been standardised by many major utilities around the world. It is the ideal solution where battery backup is necessary ...
  • Low-voltage electric motor ­management system
    October 2017, Zest WEG Group Africa, Electrical Power & Protection
    The modular design of the WEG low-voltage electric motor management system offers the flexibility of expanded functionality. Engineered as a plug-and-play solution, the compact WEG SRW01 is ideal for ...
  • Contactless energy transfer system at Sasol Wax
    October 2017, SEW-Eurodrive , Electrical Power & Protection
    SEW-Eurodrive has supplied its Movitrans contactless energy transfer system to Sasol Wax, a major manufacturer of mineral-oil based and synthetic paraffin waxes, petroleum jellies, and liquid paraffins, ...
  • Project disruption and its cost to electrical contractors
    October 2017, Zest WEG Group Africa, Electrical Power & Protection
    EnI Electrical bases its success on customer satisfaction through transparent and ethical leadership.
  • Voltage detector enhances safety of electrical installations
    September 2017, Dehn Africa, Electrical Power & Protection
    DEHN Africa has introduced the new PHE4 series of voltage detectors to improve safety during maintenance of electrical systems and installations. The detectors provide reliable information in all weather ...

 
 
         
Contact:
Technews Publishing (Pty) Ltd
1st Floor, Stabilitas House
265 Kent Ave, Randburg, 2194
South Africa
Publications by Technews
Dataweek Electronics & Communications Technology
Electronic Buyers Guide (EBG)

Hi-Tech Security Solutions
Hi-Tech Security Business Directory

Motion Control in Southern Africa
Motion Control Buyers’ Guide (MCBG)

South African Instrumentation & Control
South African Instrumentation & Control Buyers’ Guide (IBG)
Other
Terms & conditions of use, including privacy policy
PAIA Manual





 

         
    classic | mobile

Copyright © Technews Publishing (Pty) Ltd. All rights reserved.