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Double Girder crane solution ensuring safe handling of turbine!

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Solution for safe handling of turbine during installation and maintenance at a geothermal power station in Kenya.

About the Olkaria-V project

The Olkaria Geothermal Station located in Hell’s Gate National Park is the first of its kind in Africa. It was established in 1981 and generates geothermal power underneath Hell's Gate from the area's hot springs and geysers. It is one of the seven sectors of the Greater Olkaria geothermal area in the central part of the Rift Valley in Kenya.

To tap these huge energy resources, three more geothermal stations were added over the years. Subsequently, the fifth geothermal station in the Rift Valley was planned during the year 2017 and execution began soon after. The project is owned and managed by the Kenya Electricity Generating Company (KenGen) and will add 140 MW into Kenya’s electricity grid. The project was jointly executed by leading global corporations for setting up a 2 x 70MW geothermal power plant.

About geothermal energy

Geothermal energy is the heat that comes from the subsurface of the earth. It is contained in the rocks and fluids beneath the earth’s crust and can be found far below till the earth’s hot molten rock, magma. To produce power from geothermal energy, wells are dug a mile deep into underground reservoirs to access the steam and hot water there, which can then be used to drive turbines for generating electricity.

Handling challenges

Ready availability of steam makes geothermal power plants less complex to construct and they require less equipment compared to thermal power plants. The Turbine Generator (TG) is the most critical and important component in such plants and its perfect alignment is extremely important for the desired performance. While handling such a heavy and precision-manufactured turbine during its installation, special care is needed. This calls for a specially developed handling system, which can offer excellent manoeuvrability and ensure high level of safety.

In this particular case, the turbine, along with a few other auxiliary components weighed approximately 55t. The customer was looking for a suitably designed crane for the TG Hall, which would offer the much-needed manoeuvrability and safety. The crane was required mainly to handle the turbine and other components during installation. After the commissioning of the plant, during routine maintenance operations, the turbine casing and rotor are required to be lifted, removed and refitted for which the same cranes would be used.

Another challenge in this case was the presence of hydrogen sulphide gas in the atmosphere, which is peculiar in almost every geothermal plant. All the electricals require special insulation and other equipment require special care for corrosion resistance in such plants. The Olkaria-V geothermal plant is situated at an altitude of nearly 2000m, which meant that the selection of appropriate motors while designing the lifting equipment was important.

There was also a requirement for a smaller capacity crane in an adjacent bay for handling other aggregates such as absorber pumps, compressors, etc.

Solution from ElectroMech

The company that was allocated the responsibility of plant installation was acquainted with ElectroMech as we were suppliers for their earlier projects in India. The perfect material handling solution for the new requirement at TG Hall came in the form of a double girder crane packed with several features.

The 65/20t capacity double girder crane has a main hoist of 65t and an auxiliary hoist of 20t fitted with encoders on the motor shafts for continuous feedback. The arrangement ensures that the crane has an anti-fall feature, which is automatically activated in case of a brake failure and avoids sudden free-fall of the load. The crane is also provided with a load limiter and a load summation device.

In the adjacent bay, another single girder crane of 10t has been provided for handling smaller components. Both the cranes are provided with the following features to take care of atmospheric conditions:

  • Instead of the standard PVC cables, PE (Polyethylene) cables of renowned make are used. PE cables demonstrate excellent resistance to corrosion, chemical and abrasion. They have good quality insulation and can withstand temperatures ranging from -55°C to 600°C. Also, special cable glands made up of brass are used instead of rubber glands.
  • The stainless steel electrical panel is designed as per IP 65 and the motor covers are also of stainless steel to avoid external damage.
  • The bus bars of both the cranes are made up of copper conductors with stainless steel strips and powder coated accessories are used for higher corrosion resistance.
  • For surface preparation, the crane structure is shot blasted to a grade of SA 2&1/2. The cranes are applied one coat of epoxy primer and two coats of PU paint.

Total number of cranes: 2

Type SWL Span Height Of Lift
SG EOT Crane 10t 23.6m 7.0m
DG EOT Crane 65/20t 18.5m 17.7m

How the customer benefits from the ElectroMech solution

ElectroMech has supplied several crane solutions to different types of power plants including nuclear power plants. We also have a vast experience of executing projects for challenging requirements across 60 countries. This has culminated into a precisely crafted solution for Olkaria-V project and that too in the shortest possible time.

We have a sizeable number of installations in Kenya, which assured the customer about our ability to provide local support. The customer has benefitted from our solution mainly by getting

  • a most appropriate solution for their requirements
  • cranes of excellent quality in the shortest possible time
  • cranes designed to work in a corrosive environment
  • cranes that ensure a high level of safety
  • timely service support during installation and commissioning through local teams
  • assurance of prompt after-sales support through our global network

Challenges

  • Handling critical equipment such as turbines requires a crane of reliable design
  • Presence of hydrogen sulphide in the atmosphere makes cranes prone to corrosion
  • Support for E&C as well as for after-sales service through a local team

Solution

  • Cranes of the highest quality, designed to ensure high levels of safety
  • Use of PE cables for electricals, SS control panel with IP 65 protection, SS covers for motors, powder coated accessories, and PU painting
  • Excellent support through our local office