ROTORK /YCT  YT-1200  Series - YT-1200RD112L2

The YT-1200 pneumatic positioner controls a valve by receiving a pneumatic input signal to move an actuator to the correct position. It works on a feedback principle: when the input signal changes, the device moves the valve, and a feedback mechanism (e.g., a lever) senses the new position. The device compares the required position with the actual position and exhausts or pressurizes the actuator's chamber with air until the valve reaches the target position and the feedback matches the input signal.

Step-by-step working principle

1. Input signal reception: A pneumatic control signal (e.g., 3-15 psi) from a controller is received by the positioner.
2. Initial movement: An increase in the input signal causes a bellows to stretch, which moves a flapper away from a nozzle, widening the gap.
3. Exhausting air: This gap allows air to exhaust from the pilot chamber through the nozzle, which causes the spool to move to the right.
4. Actuator response: As the spool moves, it unblocks a seat, allowing compressed air to flow to the actuator's chamber (OUT1).
5. Valve movement: The increased pressure in the chamber moves the actuator's stem, which rotates the valve to the new position.
6. Feedback loop: The valve's rotation is transferred to a cam and a feedback lever, which pulls on a span spring.
7. Position alignment: The system continues to adjust the air supply until the force from the bellows and the force from the feedback spring are balanced.
8. Stable state: At this point, the flapper is moved back to its original position, the gap to the nozzle is reduced, and the air exhaustion stops. The actuator and valve are now holding the new position that corresponds to the input signal.

The working principle step-by-step

1. Input signal: The positioner receives a low-pressure input signal (typically 3–15 psi) from a controller. This pressure acts on a bellows inside the positioner.
2. Flapper and nozzle mechanism: The bellows' expansion or contraction, caused by the input pressure, moves a flapper. The flapper controls the gap at a nozzle, regulating the flow of a higher-pressure supply air.
3. Spool valve activation: The pressure change from the nozzle affects a spool valve, causing it to shift position. If the input signal increases, the gap at the nozzle widens, causing the spool to move and direct supply air to the actuator.
4. Actuator movement: The high-pressure air from the spool valve is sent to the pneumatic actuator, causing it to move and adjust the valve's position.
5. Position feedback: The movement of the valve stem is mechanically fed back to the positioner via a feedback shaft and a cam. This motion repositions the flapper.
6. Equilibrium: As the valve moves closer to the desired position, the feedback mechanism adjusts the flapper, which alters the pressure at the nozzle. The system reaches equilibrium when the force from the input signal bellows is balanced by the feedback mechanism, at which point the spool valve closes and the actuator stops moving.
7. Signal amplification: The positioner also acts as a signal amplifier or booster. It uses its own higher-pressure air supply to provide the necessary force to the actuator, allowing a low-pressure control signal to command a powerful output.

Key components

• Bellows: A pressure-sensitive element that expands and contracts in response to the input signal pressure.
  Flapper and nozzle: A mechanical assembly that converts the bellows' movement into a pneumatic pressure signal.
• Spool valve: A key component that, based on the nozzle pressure, directs supply air to the actuator or exhausts it.
• Actuator: The pneumatic device that physically moves the valve based on the positioner's air supply.
• Feedback mechanism: A cam and lever assembly that transfers the valve's position back to the flapper, completing the control loop.

 Full Datasheet

Positioner Transmitter Feature   YT-1200RD112L2

Basic Ordering Information 

ROTORK /YCT  YT-1000  Series - YT-1000RDF535S00

The YT-1000 electro-pneumatic positioner works by converting an electrical input signal into a pneumatic output to precisely control a valve actuator. When the electrical signal increases, a torque motor moves a flapper, which changes the nozzle-flapper gap to drop the back pressure in a pilot valve chamber. This causes an exhaust valve to open, supplying air pressure (OUT1) to the actuator, causing it to rotate. The actuator's rotation is fed back mechanically to a cam, which tensions a feedback spring. The actuator stops when the force from the feedback spring balances the force from the input signal. When the input signal decreases, the process is reversed to move the valve back to the new position.

Detailed explanation

• Input Signal: The positioner receives a 4-20mA DC electrical signal from a control system.
• Torque Motor and Flapper: A torque motor responds to the input signal. As the signal increases, it turns the torque motor, causing the flapper to move. This widens the gap between the flapper and a nozzle.
• Nozzle and Pilot Valve: The widening gap allows air to escape from the nozzle, which lowers the back pressure in a pilot valve chamber. This pressure drop causes the pilot spool to move to the right.
• Pneumatic Output: The movement of the pilot spool opens an inlet valve, allowing supply air to flow to the actuator through the OUT1 port. At the same time, an exhaust valve opens, venting pressure from the opposite port (OUT2) if it's a double-acting actuator.
• Actuator Movement and Feedback: The air pressure in the actuator chamber causes the actuator stem to rotate. This rotation is mechanically linked to a feedback mechanism, which includes a cam and spring. The cam increases the tension on the feedback spring as the actuator moves.
• Balancing Point: The actuator stops rotating when the force from the feedback spring balances the force from the torque motor. At this point, the flapper and nozzle are in a new position, and the pilot valve is in a balanced state, maintaining the current pneumatic output.
• Reversal: When the input signal decreases, the torque motor reverses, closing the nozzle-flapper gap, raising the back pressure, and causing the pilot valve to move the opposite way. This vents air from the OUT1 port and supplies air to OUT2 (if applicable), causing the actuator to rotate in the opposite direction until the feedback spring and input signal forces are balanced again.

YT-1000 components and their function

The key components of the YT-1000 work together to translate the electrical signal into mechanical motion:

• Torque motor: An input signal (typically 4–20 mA) from a control system energizes the torque motor.
• Flapper and nozzle: The torque motor's force is transmitted to a flapper, which controls the gap to a nozzle. An increase in the input signal causes the flapper to move, changing the gap.
• Pilot valve (spool): The change in the nozzle's back pressure causes a spool in the pilot valve to move. This movement directs the flow of compressed air to and from the actuator.
• Actuator: The pneumatic output pressure from the pilot valve causes the actuator to move. Depending on the model (YT-1000L or YT-1000R), this results in linear or rotary motion.
• Feedback mechanism: A feedback lever and spring are mechanically connected to the actuator's shaft. As the actuator moves, the lever and spring also move, creating a balancing force.
• Balance of forces: The system continues to operate until the feedback spring's force balances the force from the torque motor, bringing the flapper back to its neutral position and stopping the actuator's movement.

Step-by-step working principle

1. Receive input signal: The YT-1000 receives a 4–20 mA current signal from a control system.
2. Convert to pneumatic signal:

• The current signal energizes a torque motor.
• The torque motor's magnetic force moves a flapper away from a nozzle.
• This widens the gap, causing the air pressure at the nozzle to decrease.
• The change in pressure shifts the pilot valve's spool, which directs a burst of compressed air to the actuator.

3. Move the actuator: The pressurized air enters the actuator's chamber, causing the valve stem to move to its new position.
4. Send feedback: As the actuator's stem moves, a feedback lever attached to the stem rotates a feedback cam. This action increases or decreases the tension on a feedback spring.
5. Achieve balance: The system reaches its desired position when the opposing forces of the torque motor and the feedback spring are balanced. This causes the pilot valve to stop the air flow, and the actuator holds its new position.
6. Maintain position: If the input signal remains constant, the positioner will maintain the actuator's position by balancing the forces. If the input signal changes, the cycle repeats to find the new balanced position.

 Full Datasheet

Positioner Transmitter Feature   YT-1000RDF535S00

Basic Ordering Information 

ROTORK /YCT  YT-1000  Series - YT-1000LDN132S00

The YT-1000 electro-pneumatic positioner works by converting an electrical input signal into a pneumatic output to precisely control a valve actuator. When the electrical signal increases, a torque motor moves a flapper, which changes the nozzle-flapper gap to drop the back pressure in a pilot valve chamber. This causes an exhaust valve to open, supplying air pressure (OUT1) to the actuator, causing it to rotate. The actuator's rotation is fed back mechanically to a cam, which tensions a feedback spring. The actuator stops when the force from the feedback spring balances the force from the input signal. When the input signal decreases, the process is reversed to move the valve back to the new position.

Detailed explanation

• Input Signal: The positioner receives a 4-20mA DC electrical signal from a control system.
• Torque Motor and Flapper: A torque motor responds to the input signal. As the signal increases, it turns the torque motor, causing the flapper to move. This widens the gap between the flapper and a nozzle.
• Nozzle and Pilot Valve: The widening gap allows air to escape from the nozzle, which lowers the back pressure in a pilot valve chamber. This pressure drop causes the pilot spool to move to the right.
• Pneumatic Output: The movement of the pilot spool opens an inlet valve, allowing supply air to flow to the actuator through the OUT1 port. At the same time, an exhaust valve opens, venting pressure from the opposite port (OUT2) if it's a double-acting actuator.
• Actuator Movement and Feedback: The air pressure in the actuator chamber causes the actuator stem to rotate. This rotation is mechanically linked to a feedback mechanism, which includes a cam and spring. The cam increases the tension on the feedback spring as the actuator moves.
• Balancing Point: The actuator stops rotating when the force from the feedback spring balances the force from the torque motor. At this point, the flapper and nozzle are in a new position, and the pilot valve is in a balanced state, maintaining the current pneumatic output.
• Reversal: When the input signal decreases, the torque motor reverses, closing the nozzle-flapper gap, raising the back pressure, and causing the pilot valve to move the opposite way. This vents air from the OUT1 port and supplies air to OUT2 (if applicable), causing the actuator to rotate in the opposite direction until the feedback spring and input signal forces are balanced again.

YT-1000 components and their function

The key components of the YT-1000 work together to translate the electrical signal into mechanical motion:

• Torque motor: An input signal (typically 4–20 mA) from a control system energizes the torque motor.
• Flapper and nozzle: The torque motor's force is transmitted to a flapper, which controls the gap to a nozzle. An increase in the input signal causes the flapper to move, changing the gap.
• Pilot valve (spool): The change in the nozzle's back pressure causes a spool in the pilot valve to move. This movement directs the flow of compressed air to and from the actuator.
• Actuator: The pneumatic output pressure from the pilot valve causes the actuator to move. Depending on the model (YT-1000L or YT-1000R), this results in linear or rotary motion.
• Feedback mechanism: A feedback lever and spring are mechanically connected to the actuator's shaft. As the actuator moves, the lever and spring also move, creating a balancing force.
• Balance of forces: The system continues to operate until the feedback spring's force balances the force from the torque motor, bringing the flapper back to its neutral position and stopping the actuator's movement.

Step-by-step working principle

1. Receive input signal: The YT-1000 receives a 4–20 mA current signal from a control system.
2. Convert to pneumatic signal:

• The current signal energizes a torque motor.
• The torque motor's magnetic force moves a flapper away from a nozzle.
• This widens the gap, causing the air pressure at the nozzle to decrease.
• The change in pressure shifts the pilot valve's spool, which directs a burst of compressed air to the actuator.

3. Move the actuator: The pressurized air enters the actuator's chamber, causing the valve stem to move to its new position.
4. Send feedback: As the actuator's stem moves, a feedback lever attached to the stem rotates a feedback cam. This action increases or decreases the tension on a feedback spring.
5. Achieve balance: The system reaches its desired position when the opposing forces of the torque motor and the feedback spring are balanced. This causes the pilot valve to stop the air flow, and the actuator holds its new position.
6. Maintain position: If the input signal remains constant, the positioner will maintain the actuator's position by balancing the forces. If the input signal changes, the cycle repeats to find the new balanced position.

 Full Datasheet

Positioner Transmitter Feature   YT-1000LDN132S00

Basic Ordering Information 

ROTORK /YCT  YT-3700  Series - YT-3700LSZ0420L

The YT-3700 is a smart valve positioner that accurately controls a valve's position based on a 4-20mA input signal from a controller. Its working principle involves using a built-in microprocessor to interpret the control signal and a non-contact sensor to monitor the valve's actual position, using this data to adjust the valve stroke. Key functions include automatic calibration, PID control, and HART protocol communication for diagnostics and remote monitoring.

Core components and process

• Input signal: Receives a 4-20mA current signal from a controller, which represents the desired valve position.
• Microprocessor: Interprets the input signal and processes it with algorithms for precise control.
• Non-contact sensor: Continuously monitors the actual position of the valve stem without physical contact, ensuring accuracy and durability.
• Output and feedback loop: The microprocessor sends a signal to pneumatic actuators or other control mechanisms to move the valve. The positioner then uses the sensor to get feedback on the new position and corrects it as needed, creating a closed-loop system.

Key features and functions

• Auto-Calibration: An automated process to set the valve's zero and travel range, simplifying setup.
• PID Control: Allows for more sophisticated control by adjusting the position based on a proportional, integral, and derivative algorithm.
• HART Communication: Enables two-way digital communication for remote monitoring, configuration, and diagnostics via devices like a handheld communicator or a computer with the correct software.
• Diagnostic tools: Includes features like a deviation timeout alarm, which triggers if the valve doesn't reach the target position within a preset time, and stores alarm and test logs for system verification.
• Robust operation: Designed to maintain performance despite fluctuations in supply pressure or high-vibration environments.
• User interface: Features an LCD display and four physical buttons for on-site monitoring and configuration

The operational cycle

1. Receives an input signal: The YT-3700 receives a standard analog control signal, typically 4–20 mA, from a controller (like a Distributed Control System or PLC). This signal represents the desired position of the valve.
2. Monitors valve position: A built-in, non-contact sensor continuously monitors the actual physical position of the valve stem or shaft. This sensor provides real-time feedback on the valve's travel.
3. Microprocessor compares data: The internal microprocessor acts as the control center. It compares the control signal (the target position) to the feedback from the non-contact sensor (the actual position).
4. Generates an output signal: If there is a difference between the target and actual position, the microprocessor uses its internal PID (Proportional-Integral-Derivative) control algorithm to calculate the necessary pneumatic output pressure.
5. Actuates the valve: The positioner adjusts the air pressure supplied to the pneumatic actuator. This moves the valve until the actual position matches the desired position.
6. Continuous adjustment: The cycle repeats constantly, allowing the positioner to make continuous, fine adjustments to keep the valve precisely at the setpoint, even under varying process conditions like pressure or flow changes

Key smart features

• Auto-calibration: The YT-3700 can automatically calibrate itself, a key function that simplifies setup by self-adjusting to the attached valve and actuator.
• HART communication: Support for the HART protocol allows for digital communication over the same wiring as the analog signal. This enables remote setup, monitoring, and advanced diagnostics.
• Enhanced diagnostics: The positioner can run advanced tests, such as Partial Stroke Testing (PST), and monitor critical data like valve signature, temperature, and alarm logs. This information is crucial for predictive maintenance.
• Low air consumption: The smart design allows the positioner to maintain its position with very low air consumption, which reduces operating costs.

 Full Datasheet

Positioner Transmitter Feature   YT-3700LSZ0420L

Basic Ordering Information 

ROTORK /YCT  YT-3700  Series - YT-3700LSI2421S

The YT-3700 is a smart valve positioner that accurately controls a valve's position based on a 4-20mA input signal from a controller. Its working principle involves using a built-in microprocessor to interpret the control signal and a non-contact sensor to monitor the valve's actual position, using this data to adjust the valve stroke. Key functions include automatic calibration, PID control, and HART protocol communication for diagnostics and remote monitoring.

Core components and process

• Input signal: Receives a 4-20mA current signal from a controller, which represents the desired valve position.
• Microprocessor: Interprets the input signal and processes it with algorithms for precise control.
• Non-contact sensor: Continuously monitors the actual position of the valve stem without physical contact, ensuring accuracy and durability.
• Output and feedback loop: The microprocessor sends a signal to pneumatic actuators or other control mechanisms to move the valve. The positioner then uses the sensor to get feedback on the new position and corrects it as needed, creating a closed-loop system.

Key features and functions

• Auto-Calibration: An automated process to set the valve's zero and travel range, simplifying setup.
• PID Control: Allows for more sophisticated control by adjusting the position based on a proportional, integral, and derivative algorithm.
• HART Communication: Enables two-way digital communication for remote monitoring, configuration, and diagnostics via devices like a handheld communicator or a computer with the correct software.
• Diagnostic tools: Includes features like a deviation timeout alarm, which triggers if the valve doesn't reach the target position within a preset time, and stores alarm and test logs for system verification.
• Robust operation: Designed to maintain performance despite fluctuations in supply pressure or high-vibration environments.
• User interface: Features an LCD display and four physical buttons for on-site monitoring and configuration

The operational cycle

1. Receives an input signal: The YT-3700 receives a standard analog control signal, typically 4–20 mA, from a controller (like a Distributed Control System or PLC). This signal represents the desired position of the valve.
2. Monitors valve position: A built-in, non-contact sensor continuously monitors the actual physical position of the valve stem or shaft. This sensor provides real-time feedback on the valve's travel.
3. Microprocessor compares data: The internal microprocessor acts as the control center. It compares the control signal (the target position) to the feedback from the non-contact sensor (the actual position).
4. Generates an output signal: If there is a difference between the target and actual position, the microprocessor uses its internal PID (Proportional-Integral-Derivative) control algorithm to calculate the necessary pneumatic output pressure.
5. Actuates the valve: The positioner adjusts the air pressure supplied to the pneumatic actuator. This moves the valve until the actual position matches the desired position.
6. Continuous adjustment: The cycle repeats constantly, allowing the positioner to make continuous, fine adjustments to keep the valve precisely at the setpoint, even under varying process conditions like pressure or flow changes

Key smart features

• Auto-calibration: The YT-3700 can automatically calibrate itself, a key function that simplifies setup by self-adjusting to the attached valve and actuator.
• HART communication: Support for the HART protocol allows for digital communication over the same wiring as the analog signal. This enables remote setup, monitoring, and advanced diagnostics.
• Enhanced diagnostics: The positioner can run advanced tests, such as Partial Stroke Testing (PST), and monitor critical data like valve signature, temperature, and alarm logs. This information is crucial for predictive maintenance.
• Low air consumption: The smart design allows the positioner to maintain its position with very low air consumption, which reduces operating costs.

 Full Datasheet

Positioner Transmitter Feature   YT-3700LSI2421S

Basic Ordering Information