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The steam and condensate system is a part of the paper and board machine. Its purpose in the paper machine is to provide steam for drying. The final drying is carried out in the drying section. This is achieved by means of several steam-heated dryers or cylinders. These are driven in groups of a few dryers together. The paper sheet runs over a large number of dryers. Moisture is evaporated as the sheet is pressed between the fabric and the hot drying cylinder. The surface temperature of each dryer must be precisely controlled. The temperature is lower in the first groups of dryers and then is slowly raised in the later groups at the end of the drying process.
Fast and accurate control
The biggest single expenditure in a paper and board mill is energy consumption. That is why faultless valve operation has an important role in the steam and condensate system. Valmet offers a wide choice of on-off and control valves for this system. Good tightness is a preferred feature for all steam valves. If accurate control is your concern, the R-series segment valve is the obvious choice. It will help you fast and accurately adjust temperatures in the steam and condensate system, for example, during a grade change. Furthermore, our cost-effective triple eccentric butterfly valves offer excellent tightness and good control properties for steam and condensate systems.
Steam and condensate handling
Due to elevated temperatures, metal-seated valves are used in this process. These valves should provide a certain minimum level of tightness. The steam valves have to close if the paper sheet breaks or for other short shutdown reasons. Elevated temperature in the dryers may damage the fabrics. The collection of condensate may be harmful to the restart and cause problems for the machine drives.
If the paper machine is to produce only one bulk paper grade, no big adjustments to the steam flow are necessary. Here, a butterfly-type valve can be successfully used as the control element if the system design data is calculated accurately. The basis weight and steam consumption of board machines often must be changed in large increments during operation. The valves used for control purposes must provide good controllability and rangeability.
Learn more about basis weight control
Basis weight control is one of the most critical applications for a valve in a paper machine. Our nelesACE™ is the ultimate solution for this application. The unit consists of a reliable V-port segment valve, complete with a high-resolution step-motor-driven rotary actuator, limit switches, and a potentiometer. The nelesACE control unit's unique feature of running a valve in various step sizes depending on the error between the actual and desired flow rate makes it a superior element for basis weight control.