Jun 01, 2021
Digital Valve Controller
Digital Valve Controller (DVC) is a device that is smart and is attached to the valve actuator, which controls and monitor the valve operation. The DVC is capable of operating in 4-20mA, HART, Fieldbus or Profibus protocol.
Functions of DVC:
- Reducing the dead-band on the control valve
- Controlling single-acting actuators and double-acting actuators
- Can be used in split range applications
- Increase torque for seat load
- Make the control valve work in accordance with the command signal from the control room
- Modify characteristic flow
- Reduces slow response to control valve
- Reverse the action of the control valve
DVC gets a signal from the control room, the signal goes into the Printed Wire Board (PWB) for processing then the electrical signal from the PWB enters the I/P transducer for conversion to pneumatic signals. The pneumatic signal from the transducer goes into the relay to strengthen the pressure which then enters the actuator. After there is movement in the control valve, the feedback magnet reads the position of the control valve and sends the results of the reading to the PWB to be corrected if something goes wrong. And the correction signal is sent to the actuator via the I/p transducer and then to the relay and into the actuator so that the position of the control valve opening is more precise.
There are three types of DVC. The first type of DVC is DVC type 2000, which is equipped with a display and push-button so that the user can calibrate the control valve directly without any additional devices such as the Hart communicator. DVC type 6000 is the second type of digital valve controllers, this type uses feedback still uses the linkage type. So, the possibility of contact is still large. Lastly, DVC type 6200 is the same type as DVC 6200. The only difference is the feedback system that has a magnetic system, so there is no contact between the control valve and DVC.
Digital Valve Controller is available through Quick Time Engineering Inc.
Valve Positioner
A valve positioner is a common control valve accessory, the valve positioner delivers pressurized air to the valve actuator so that the position of the valve stem or shaft corresponds to the setpoint from the control system. Valve positioners are typically pneumatic or analog I/P and are used when a valve requires throttling action. They require position feedback from the valve stem or shaft and deliver pneumatic pressure to the actuator to open and close the valve.
Positioner Advantages:
- Precise positioning
- Can cope with large variations in forces acting on the plug.
- Rapid positioning
- Removes stiction and friction effects of the gland.
- Removes effects of large distances between valve and positioner
- Eliminates hysteresis
When should a positioner be fitted:
A positioner should be considered in the following circumstances:
- When accurate valve positioning is required;
- To speed up the valve response. The positioner uses higher pressure and greater airflow to adjust the valve position;
- To increase the pressure that a particular actuator and valve can close against. (To act as an amplifier);
- When the valve pressure drop at the maximum operating flowrate, exceeds 5 bar for single-seated valves or 10 bar for double-seated valves;
- To linearize a non-linear actuator;
- Where varying differential pressures within the fluid would cause the plug position to vary;
- When controlled with a wide throttling range; and
- When valves are handling sludge or solids in suspension.
Valve Positioner is available through Quick Time Engineering Inc.
Intelligent Positioner
An intelligent positioner is designed to operate pneumatic c valve actuators and can be operated from control systems, controllers or PC-based configuration- and operational tools. The positioner is available with different communication protocols.
The multi-lingual full-text graphical-LCD in connection with the 3 push buttons allows a comfortable and easy local configuration and operation as well as the display of valve specific data, and status- and diagnostic messages.
Intelligent Positioner is available through Quick Time Engineering Inc.
Quick Time Engineering Inc is an international company with offices and distribution networks in the USA, Hong Kong, Europe and Malaysia.
In its 20 years of operation since 1998, Quick Time Engineering Inc had emerged from a local engineering company with a single staff that provided solutions in factory automation to become nowadays a company that serves the Oil & Gas industries, EPC contractors, System Integrators and other industrial automation and process control companies worldwide. Customers from over 50 countries worldwide trust us with their need for process control instruments and industrial automation products.
For more information about Quick Time Engineering Inc, visit www.quicktimeonline.com or email enquiry@quicktimeonline.com
