High thrust linear actuators on steam control valves improve turbine performance
The Amoco Oil Company refinery at Texas City, TX was concerned about erratic speed control of some of the approximately 165 steam turbines which are used to drive pumps, fans, compressors and other rotary equipment. The exact speed of each turbine to meet service demands is controlled by an electronic governor that sends a signal to a fail-safe, air-to-open and spring-to-close diaphragm-type actuator. Instantaneous positioning of a valve by the actuator without overshooting is essential for accurate speed control. Even small changes in steam flow to the blades result in extremely large changes in turbine speed. Some of the diaphragm-type actuators were replaced in 1981 with linear motion cylinder actuators and positioners that are designed to operate with air pressures to 150 psi. The 25 sq in cylinder actuator selected for this application has a maximum thrust of 3500 in-lb, compared to 1200 in-lb for the units being replaced. The additional thrust overcomes stem friction, misalignment, valve unbalance and other conditions that caused erratic stem movement. High air handling capacity and relatively low cylinder volume also provide fast stroking speed with virtually no overshoot. The pneumatic positioner assures high dynamic response, speed and position accuracy by supplying air to either side of the piston while exhausting the other side to the atmosphere. Turbine operation has been significantly improved by the pneumatic linear spring cylinder actuators and positioners which have virtually eliminated excessive turbine speed variations due to erratic valve positioning.
- Research Organization:
- Amoco Oil Co., Texas City, TX
- OSTI ID:
- 5339979
- Journal Information:
- Chem. Process. (Chicago); (United States), Journal Name: Chem. Process. (Chicago); (United States) Vol. 48:8; ISSN CHPCA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
320303* -- Energy Conservation
Consumption
& Utilization-- Industrial & Agricultural Processes-- Equipment & Processes
ACTUATORS
CONTROL EQUIPMENT
EFFICIENCY
ENERGY EFFICIENCY
EQUIPMENT
FLOW REGULATORS
FLUID MECHANICS
MACHINERY
MECHANICS
PERFORMANCE
PNEUMATIC CONTROLLERS
PNEUMATICS
SPEED REGULATORS
STEAM TURBINES
TURBINES
TURBOMACHINERY
USES
VALVES