What is a Wellhead?
With the demand for renewable energy continuing to increase, Geothermal power is quickly becoming a focal point in generation company portfolios. Producing about one-sixth of the carbon dioxide emitted by a clean natural gas-fueled plant, geothermal energy production ensures a sharp reduction in greenhouse gas emissions. There are three types of geothermal power plant designs – dry steam, flash and binary cycles.
Regardless of plant design, everything begins at the wellhead. Often separated from the plant by significant distances, production wells include Emergency Shutoff Valves (ESVs) and flow control valves – both of which play key roles in the process. Therefore, they need to function reliably to ensure no interruption of the flow of steam or brine to the plant.
A Geothermal power plant in New Zealand recently experienced unstable control of their production wellhead valves and sought out REXA for a solution. The previously-installed pneumatic actuators were not able to accurately control the valves during both start-up and normal operation. This caused large pressure swings in the process and immense water hammer down the line. Consequently, this resulted in bending pipework and broken pipe brackets – causing unnecessary expenses for repairs.
Leaks within the valves’ stem packing required tightening, making it even harder for the pneumatics to overcome the packing stiction to control the valves. This stiction caused the water hammer as the pneumatic actuator built up pressure in the piston and dramatically jumped up once it overcame the stiction.