Steam turbines

Servo-controls on steam turbines

The functioning of the steam turbine is based on the thermodynamics principles: with the expansion the steam undergoes a temperature decrease, because part of its thermal energy turns into mechanical energy with the movement of its forming particles. Such transformation allows the availability of a huge amount of mechanical energy.

The generation of the alternated current requires a precise control of the turbine speed and it is subject to the energy request in the network. Duplomatic developed a series of intelligent servo-cylinders, which can manage the turbine speed with an integrated closed-loop system and control the position of the actuator which determines the opening of the steam valves.

The Duplomatic product consists of:

Servo-cylinder (custom drawing)

Proportional valve with two solenoids, integrated electronics (DSE3G Z*/11N-E1K11/D) and 4÷20mA current control

ERM modular card or EDB box card for the remote control of the actuator position and for the availability of a digital contact when the servoactuator is in target.
Servo-cylinders
Duplomatic boasts a valuable experience in the design of simple or servo-controlled actuators for the energy sector, which is featured by precise needs: reliability, particular designs to be adapted to the most different requirements of steam or gas valves producers, integrated fail-safe condition.

Software
Not long ago the servo-cylinders in the power plants were controlled through traditional Eurocard cards positioned into electric cupboards far away from the controlled actuator. Such an analog control implied a good knowledge of the product and the use of a series of measurement tools for the start-up.

The technologic evolution has introduced the use of digital controls which make the start-up easier and are of great help in the possible replacement of the product. But Duplomatic has done even more: it has worked to make the start-up easier, thus applying the “plug&play” philosophy, which implies the realization of a product that is supplied assembled to the servo-cylinder and requires the final user to simply set the “electrical zero” to be combined to the mechanical zero (steam valve). The whole procedure is possible via the CANPC-SOF/ R001 digital tool.

In order to complete the control of the steam turbine Duplomatic has also developed a card for the remote control of the signals necessary to verify the actuator condition – in the control room of the power plants - and the speed of the turbine itself. The card is available both in the modular and in the box format. The latter can be supplied pre-wired and mounted on the actuator.

One of the most remarkable advantages, among the several offered by the Duplomatic solution, is the shorter time needed for the start up; as a matter of fact the “plug&play” solution reduces to the minimum the possibility of errors and thanks to an user-friendly software the final user only has to perform a simple “zero calibration” procedure of the sensor placed on the actuator. The advantages of the digital solution become evident in case of replacement of the proportional valve or of the electronics because it foresees the factory storage of all the data (PID, ZERO, MAX STROKE, DEAD BAND etc.) which can be downloaded in the new product without requiring a new system setting. The CANPC-SOF/R001 software allows to control the servo-cylinder and to perform the diagnostics via the CAN Bus.