The Motion Industry Meets the Process Industry To Deliver Perfect Valve Control

Control Valve Performance Does the Valve Move?  Is the assembly capable of small control steps over the range of use How Fast Does the Valve Move?  Does the valve get to setpoint quickly when changes are made  Does the valve overshoot? How Stable is the Valve at Steady State?  Negative gradients  Cavitation

Process Benchmarking - Variability 80% of control loops demonstrate excessive process variability 30% due to control valve performance The undesirable behavior of control valves in the biggest contributor to poor loop performance Source: Entech---Results from audits of over 5000 loops in Pulp & Paper Mills Loops The Reason Source of Variability

Process Benchmarking

Servo Electric Valve Actuation Technologies Hydraulic Pneumatic Electric

Pneumatic Actuators 70% of the market Good reliable actuation Low stiffness Limited forces Will overshoot/hunt Air supply needed

Pneumatic Actuators Pneumatic Positioners  Guarantee that the valve does in fact move to the right position  Used for better accuracy  Diagnostics Most are related to air

Hydraulic actuator Very Stiff Fast High forces Very energy inefficient Hazardous fluids Tend to leak  Environmental problem Difficult to maintain

Electric Actuator Typically intermittent motors  Cycled on and off  For modulation, 3600 ‘start’/hour needed Uses physical limit switches to indicate valve closure/position Position sensor  potentiometer

Electric Actuator Rotary to linear conversion  Worm Gears  Ball screws  Acme screws Not robust for high duty cycles  Gear or ballscrew wear  Motor burn-out

What If…..? Electric actuator designed for modulating control  Unaffected by valve stiction  Perfect tracking of closed-loop controller demand  No dead time, lag, or overshoot  No duty cycle (100% continuous torque)  Fast response  Long life  No maintenance

Motion Control Industry Very precise positioning Rapid repetitive motion (high duty cycles) High speeds Large range of forces High Repeatability High Efficiency Low Maintenance

Design Criteria Robustness to shock High speed High positioning accuracy High response High mechanical stiffness Moderate cost High efficiency Very small size Low maintenance Completely sealed Rotary and Linear designs Position Feedback capable Industrial Grade Electric Valve Actuator

Rotary to Linear Converter Ball Screw Technology Short service life Low shock resistance Nearly impossible to clean and regrease Rotational speeds limited to ~ 1,000 rpm Noisy Tricky disassembly

Rotary to Linear Converter Roller screw Technology Up to 15x the travel life of a (equivalent size) ball screw High Shock Resistance Easy disassembly Easy cleaning and re-greasing Rotational speeds up to 6,000 rpm Design can be inverted Quiet operation

Ball Screw Roller Screw Roller Screws have 15 times more contact area Roller Screws have 15 times more contact area Load Points ( ) same space in the same space Why Longer Travel Life?

Adjacent balls within a ball screw have conflicting friction leading to heating and wear. Ball Screw Roller Screw Roller screw rollers are separated by journals. Why More Efficient?

Why Higher Rotation Speeds? Roller Screws Ball Screws Sharp turns of ball returns cause vibration and noise. There is no loading and unloading of balls and no sharp turns of ball return tubes. Therefore, planetary roller screws operate efficiently up to 6,000 rpm.

Servo Motor vs Induction Motor Small size  High output relative to size and weight AC induction motor 7.6in Brushless servo motor 3.5in Closed loop feedback  Resolver, Encoder, Hall effect High efficiency (90%) All Voltages  24VDC to 460VAC

Servo Motor vs Induction Motor High torque to inertia ratios  Rapid acceleration Reserve power  (2x over continuous) Cool running  current draw proportional to load Quiet Vibration free

Rotary Servo Motors Very high torque density High side load bearing design Planetary Gear Reduction  Single and Double Reduction  4:1 to 100:1

Digital Controller Closed loop control of motor Digital/Analog feedback Position Control Force (current) control Diagnostics

Combining Technologies ServoMotor Inverted Roller Screw Position Controller Feedback Linear

Combining Technologies Rotary Gear Reduction Feedback Position Controller ServoMotor

Applying Technology to a Valve Built in digital feedback High Stiffness Built in positioner 100% Torque at all times Custom Valve Seat High Repeatability Extreme Accuracy Fast Response Fast Stroke

Sample Valve Applications Forces up to 12,000 lbf Torque up to 4600 lbf-in

Steam Turbine Application Steam Turbine Retrofit GE turbine steam control Direct replacement of 10 inch diameter single acting, hydraulic cylinder Elimination of mechanical governor operated pilot valve. Servo actuator with a 10 inch stroke Handwheel for manual operation

Turbine Fuel Valve Control Application Steam Turbine Retrofit Nuclear Power Plant Feedwater Turbine Rack seating 6 valves 1100 lbf peak 3” cylinder with 6” stroke 85% efficient Much Lower Routine Maintenance Better performance

Pilot Valve Control Application Steam Turbine Retrofit Turbine pilot valve Linear Servo Actuator High static and dynamic control accuracy Stiction and friction problems eliminated Control valve's oscillation was eliminated thereby extending steam distribution system's life, and reducing spare parts costs.

Gas Turbine Control Inlet Guide Vanes  Precise positioning and feedback  Ability to fine tune injector airflow to maintain CO and NOx emissions. Bleed Valve  Variable air bleed valves and inlet bleed heat valves Fuel Metering Valve  Ball valves

Cooling Water Centrifugal Pipe Casting  Molten iron is poured into a water-cooled rotating pipe mold  Cooling water is precisely controlled by linear actuators on globe valves  Speed of response was critical

Aluminum Plate Production of Aluminum for the aircraft and space markets Application: Quenching of aluminum plates Flow control of water,  35 to 85 psi, 280 to 875 gpm. 21 Ball Rotary Control Valves 21 Servo electric actuators Original actuators had problems with deadband and hunting- seeking behavior

Fuel Valves Replacement of hydraulic actuators on gas valves for a gas turbine 18 servo actuators

Damper Applications Low-NOx (nitrous oxide) burners need accurate air flow Windbox Dampers 44 electric linear servo actuators  4 or 8 ‘corners’ retrofitted  Replaced failing electric ballscrew actuators

Cement Hopper Valve Control Original actuator caused overfilling of trucks due to response time Improved Control Elimination of waste