Geothermal

Steam Turbines Steam Turbines are used in utility and industrial power accounts to generate electricity.   The steam turbine is directly coupled to the generator in this application. The steam turbine governor controls the flow of steam into the turbine casing to maintain the turbine rotor speed of rotation at a constant value. The governor may be controlling a number of control valves, or a number of control nozzles that are staged in operation by a camshaft or bar assembly. A hydraulic cylinder, powered by the lube oil system or by an electrohydraulic control oil (EHC) system, utilizing servo or proportional valves, is typically the motive force for operating the governor valve. Accurate and repeatable speed control is essential in this application to synchronize frequency with the electric power system.  Traditional HPU based hydraulics are compromised by degradation of oil cleanliness over time, requiring these systems to have a high maintenance level. REXA’s self-contained design eliminates the need for HPU based servo/proportional systems that are maintenance intensive. REXA Actuators require no filters, and absolutely no oil based preventative maintenance, making them highly reliable. Maintenance intervals for REXA Actuators on steam turbine governors are not typically required until after 7-10 years in service. REXA’s high performance allows for control at +/- 1 RPM, allowing for fast synchronization and premium load control.  Literature Download our Steam Turbine Control Application Spotlight to learn more! Download

Geothermal Steam Turbine Governor Geothermal Power Plants see some of the most harsh and abrasive services found in any industry segment. Regardless of plant design type, toxic chemicals are withdrawn from the earth as part of the process that compromise process equipment rapidly. Hydraulic systems associated with Steam Turbine Controls are highly susceptible to oil breakdown in this environment. REXA’s self-contained, positive pressure, sealed system provides the highest level of system integrity and reliability. REXA’s technology is designed for critical applications such as steam turbine control, offering resolution to 0.05%, high frequency response, and full speed trip capabilities under 500mS.  Literature Download the Steam Turbine Governor Control Application Spotlight! Download

Wellhead Shut Off and Control Background With the demand for renewable energy continuing to increase, Geothermal power has become a focal point in generation company portfolios. Geothermal energy is extracted without burning any fossil fuels, ensuring a reduction in greenhouse gas emissions. Geo-fields are currently producing about one-sixth of the carbon dioxide of a clean natural gas-fueled plant. Moreover, geothermal energy is always available unlike solar and wind power.  Whether it is a dry steam, flash, or binary cycle plant design, everything begins at the wellhead. Often separated from the plant by significant distances, production wells include emergency shutoff valves (ESV) and flow control valves which play a key role in the process. Therefore, they must function dependably to ensure no interruption of the flow of steam or brine to the plant.  Reliable shutoff and flow control valve operation at production wells can cause a major headache thanks to scaling and potential harsh environmental conditions. As geothermal fluids travel through the earth’s crust towards the wellhead, they absorb many dissolved minerals and gases. Reservoir temperature and saturation levels dictate the amount of scaling at the well caused by these minerals. Consequently, build-up on valve internals begins immediately and can reach catastrophic levels soon after.  Literature Click to download our full Application Spotlight to learn how REXA Actuators provide the best solution for Production Wellhead Shut Off and Control!  Download

Geothermal Separator Level Control Background In areas of the world where steam or two-phase flow are the dominant sources of geothermal energy, it is vital to remove the fluid portion of the mixture from the well. Otherwise, salts and dissolved solids will cause scaling and corrosion of the turbine and related equipment. To combat damage to the turbine, plants install separators –  the most important components at a geothermal plant. Separators ensure only clean, dry steam enters the turbine.  There are two common separator designs – the vertical cyclone and the horizontal separator. Both designs essentially work the same in that a high-velocity two-phase flow enters the separator in a spiral pattern. Next, the centrifugal force moves the fluid to the outer surface, therefore allowing steam to direct toward the outlet tube. The separator fluid then collects in the base of the separator or freestanding tank, with the level controlled by an external control valve. Finally, the salts and solids are discarded and sent to a reinjection well, or vent silencer. Both vertical cyclone and horizontal separator have a 99% or better separation efficiency rate.  Problem Maintaining specific fluid velocities and internal pressure drops are imperative for separators to function as designed. The fluid level has a large impact on separation efficiency and the potential for moisture to carry over into the steam. During production well operation, separator tanks quickly fill with brine and contaminants that must be continuously removed to maintain a proper level. Consequently, this leads to excessive cycling of the separator level control valves –  normally operated by electro-mechanical actuation. Frequent cycling in high ambient temperatures can push these electric actuators to their limit.  Solution So how can REXA solve this problem? Our Electraulic Actuation™ offers a responsive and dependable solution for geothermal separator level control valve applications. We specifically engineer our actuators for critical applications within the harshest environments requiring continuous modulating duty cycle, as well as accurate and repeatable positioning. We specifically engineer our actuators for critical applications within the harshest environments requiring continuous modulating duty cycle, as well as accurate and repeatable positioning.  Literature Read more about our solution in the full Geothermal Separator Level Control Application Spotlight! Download

Injection Well Control What are Injection Wells? Within the last few decades, injection wells have become a necessity for maximum geothermal power generation and reservoir management. Fluid injection is one of the most important parts of this process, eliminating any environmental impact of surface disposal and providing pressure support to the well. To ensure reservoir replenishment and the highest production well output, injection sites need to meet specific requirements to be selected. These include exploration, testing, conceptual modeling and proper well design.  Why is Accurate Control so Essential? Reliable flow control keeps fluid velocities high enough to prevent the settling of suspended solids. It also allows multiple units to feed a reduced number of injection wells. Controlling fluid flow to an injection well while maintaining system backpressure, however, is a difficult task in itself. Potential major issues, such as gradual plugging of the well or pipeline due to silica scaling, increase injection pressure. Cooling of the fluid at production wells or declining enthalpy happens if there is “short-circuiting” of the injected fluid through a fault or fracture zone during high pressure conditions.  The wrong type of actuation technology could spell disaster for a geothermal plant.  The REXA Solution With more than 20 years of experience in the Geothermal power market, REXA Electraulic™ Actuators ensure efficient injection well control. The self-contained, closed-loop hydraulic circuit provides stiff and stable control independent of load variation. Unscheduled downtime due to overheated actuators tripped offline from high ambient temperatures and scaled-up valves becomes a thing of the past!  Literature Check out our full Application Spotlight to read more about our solution for Injection Well Control!  Download