Managing repairs

Published:  12 November, 2014

PWE takes a look at managing motor and generator repairs at nuclear power stations.

In the nuclear energy industry more than most, safety is paramount and the design and specification used for equipment involved in nuclear generating plants are governed by a series of stringent regulations. The maintenance programmes follow strict timetables with only certified contractors permitted to provide products and services, so when it comes to high voltage motors and generators, it is important to ensure that any repairs are going to make the grade.

Graeme Robertson, head of operations UK for Sulzer, explains that nuclear power generation makes up an important part of meeting the global demand for energy, with 31 countries across the world using over 430 nuclear power plants to meet close to 14% of global electricity demand, a similar proportion to that developed by the hydro industry. With so many people relying on the nuclear industry, it is essential that it operates faultlessly, which means strict adherence to maintenance programmes.

Robertson highlights that the typical nuclear power plant is segregated between the conventional island and the nuclear island, with the former containing the steam turbine generator and water cooling systems, which require large high voltage motors to ensure the huge volumes of cooling water are successfully circulated around the plant. As with any large rotating machine, condition monitoring offers a very useful insight into the performance status as well as the expected service life of the equipment.

The turbine within a nuclear power plant requires considerable support from a number of pumps and motors that ensure the condensate water and cooling water systems are maintained properly. In addition to the regular pumps, auxiliary pumps are required to provide support in the event of a breakdown, ensuring there is always sufficient capacity to maintain safe operation of the plant.

The required capacity of these pumps leads to the majority being powered by high voltage motors and many of them are now in excess of 20 years old. After so many years of continual stress the regular testing regime can start to indicate problems within the insulation system. Initially, these can be monitored without cause for alarm, but plans for a major overhaul should start to be put in place in order to manage the project effectively and efficiently.

Most equipment of this size contains built-in vibration and temperature sensors to provide live data, while periodic maintenance, inspection and testing can provide some further insight into the integrity of the windings in these machines. Some of this preventative work can be completed by in-house engineers, but in some cases it may be necessary to call in expert engineers to carry out a complete suite of tests and to produce a definitive status report.

Since they were originally built, the technology used in the coil insulating systems has moved on considerably, which means that when a complete overhaul is planned, the refurbished motor will not only provide another long period of service, but it can also operate more efficiently, reducing running costs and increasing the return on investment (ROI).

For those involved in the operation and maintenance of large HV rotating machines, there are many choices when looking at the repair or rewind of such equipment. The key to a successful project is ensuring that those involved will be able to deliver a high quality product, precisely, quickly and with the necessary support to ensure a timely completion, regardless of how the scope of the work changes.

Sulzer is a leading supplier to the power generation market, especially the nuclear sector, providing customised maintenance, repair and overhaul (MRO) solutions for pump requirements and all LV and MV/HV motors including monitoring, test and assessment, rewind and repair services. This capability also extends to the turbine and main generators. Capable of delivering bespoke engineering projects to the highest standard, Sulzer says it has demonstrated its ability to meet the tightest deadlines, ensuring that power plants continue to operate at maximum efficiency.

For further information please visit: www.sulzer.com

Pic caption1: Nuclear power generation makes up an important part of meeting the global demand for energy, with 31 countries across the world using over 430 nuclear power plants to meet close to 14% of global electricity demand

Pic caption2: The turbine within a nuclear power plant requires considerable support from a number of pumps and motors that ensure the condensate water and cooling water systems are maintained properly

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