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TAOM Geothermal Project

OGV XL provides wellhead control valves to handle geothermal steam

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The Challenge

New Zealand’s The Te Ahi O Maui geothermal power plant will generate 25MW of electricity to power 25,000 homes helping the country to transition to cleaner energy and meet current and future energy needs.

The plant’s wellhead control valves supplied previously had suffered from wear and seizures due to the abrasive nature of the media through the valves.

 

Our Solution

With our reputation for manufacturing high performance valves which improve triple offset technology, OGV XL was contacted to quote for replacement valves that would withstand the abrasion.

OGV XL delivered a cost-effective solution by offering sealing rings in solid Inconel 625 material rather than standard laminate. In addition, we offered body seats in stainless steel material with chrome carbide coating to reduce the effects of the abrasive nature of the media. We also offered the shaft bearing material in Stellite 6 with Graphite protectors plus ‘live loading’ on the compression collar as we knew that valves previously installed on this type of duty had ‘seized’ in operation.

 

For Triple Offset Butterfly Valves to work efficiently the seat angles need to be in a specific range.

We are using seat angles at the lower end of this range.  This enables us to use a smaller second offset, which has a big effect on the torque.  This also has a positive effect on the differential between the minor and major axis of the elliptical seat, reducing the difference almost to the point of it being circular.  This reduces the area under pressure in both the preferred and non-preferred direction of sealing and so again reduces the amount of torque required to operate and close the valve.

 

The Proof

The valves were successfully installed and have been operating effectively with no wear or seizures. We had an immediate and major advantage over our competitors due to our lower torque requirements, making the actuators required both smaller and less expensive.

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