Paper Machine Cascade Steam Systems

Paper and board machines use steam-heated dryer cylinders to dry the sheet to its final moisture target. In a cascade steam system, fresh steam is typically introduced to the main steam group and then it is cascaded upstream to the intermediate and wet end steam groups. This arrangement automatically stair steps steam pressures (and steam temperatures) upwards as the sheet travels through the dryer section and moisture becomes harder to remove. This module describes the steam and condensate flows and controls for cascade steam systems. It also discusses their advantages, limitations, and safety hazards and guidelines.

•List the main objectives of a paper or board machine dryer section •Identify and describe the purpose of dryer cans, dryer felts, dryer hoods, drive sections, and steam groups in a dryer section •Explain how thermocompressor systems and cascade steam systems allow steam to be reused in dryer sections •Describe the differential pressure controls that are used within and between steam groups in a cascade steam system •Identify and describe blow-through steam flows in a typical cascade steam system •Identify and describe safety hazards and safety guidelines related to paper machine cascade steam systems