Valves, Actuators & Pump Control

A new generation control valve

May 2002 Valves, Actuators & Pump Control

Today’s valves must be fast, accurate and reliable. The new nelesCV Segment from Metso Automation yields a fast and accurate response to the control signal, providing a solution that can be easily tuned to the optimal objectives of the process.

With mechanical solutions, as implemented in the pulp and paper industry slow response and the lack of accuracy can destroy the most ingenious control solution. Metso Automation has developed a new control valve, whose features exceed, by far, the achievements of its previous generation. NelesCV Segment is a complete control valve unit containing decades of flow control experience in developing solutions for various processes.

The digital valve controller, actuator and valve are an integrated unit, with the three components correctly matched. All three work in unison, providing fast and accurate response to the control signal. The role of the control valve is central as the provider of the control result.

The intelligence of the valve control is integrated in the unit

* The heart of the intelligent operation of the new control valve is in the digital ND800 valve controller. With its help, the entire operational capability of the actuator and valve assembly is used to the maximum benefit. The digital valve controller is connected to the double diaphragm actuator without brackets. Centred shaft and internal impulse piping ensure that installation and service is simple and faultless.

Double diaphragm actuator-simple, effective and durable

* Converting the control signal effectively to a rotary torque is a complex task. Metso's solution to the problem is the double diaphragm actuator, which although simple, is very effective. Any friction affecting the actuator has been reduced to a minimum.

* Symmetric construction of the double diaphragm solution allows the torque to transfer evenly and smoothly throughout the entire cycle. Complicated connection pieces that can cause backlash or lost motion have been eliminated and forces that resist the movement have been minimised.

* Operational and service targets for the equipment have been considered in the selection of materials for the actuator. The torque transmission components are made of case hardened steel.

* The new double diaphragm actuator can perform millions of cycles, many times more than traditional actuators.

* The backlash free integration of parts makes control changes instant.

Small volume brings a fast response

* A considerable source of deadtime in the actuator is air volume. In the new double diaphragm actuator the air volumes have been minimised and thus the pneumatic stiffness has been improved one class better. The result is a fast response to the control signal, with minimal air consumption.

Piping vibration effects minimised

* The valve package is compact, and significantly smaller than traditional solutions, making the installation requirements less complex. The smaller dimensions considerably improve the vibration tolerance and potentially harmful pipe vibrations effect the operation far less.

Backlash free integration

* The actuator is connected to the valve without brackets and the valve shaft connects to the valve actuator with a conical bushing. This joint is free of play or backlash, ensuring fast and accurate valve response.

Spring return option

* The spring return option uses the double diaphragm so that the output torque is the same as it would be without the spring.

* The actuator can be assembled either spring to close or spring to open.

The benefits of the actuator can also be retrofitted to an existing installation

* In the nelesCV Segment, the double diaphragm actuator is installed in new Neles segment valves without brackets. In other valve models the joint can be made with ISO 5211 mounting parts. The ND800 valve controller is flush mounted directly to the double diaphragm actuator or the traditional positioners with VDE/VDI mounting parts.

Metso Automation RSA

011 314 1234

031 502 9350

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