Jet/Wire Ratio Control for air pad and hydraulic headboxes.

A Metso Automation IQControl for improved paper quality and headbox stability.

Description

Jet/Wire Ratio Control is used to maintain consistent formation and tensile ratio for air pad and hydraulic headboxes.

Jet/Wire Ratio Control calculates the pressure setpoint for the headbox pressure controller. The setpoint for the headbox pressure controller is automatically adjusted when machine speed or the jet/wire ratio setpoint is changed.



The operator may enter a rush-drag target instead of jet/wire ratio depending on mill practice.

Benefits to the Papermaker

• Jet/Wire Ratio Control provides improved paper quality and headbox stability.
• Fewer upsets and breaks.
• Reduced off-spec paper during grade chance and production speed change.
• Comprehensive tools simplify maintenance and troubleshooting thus resulting in ongoing good performance.

Technical features

• Jet/Wire Ratio Control can be applied to either hydraulic or air padded headbox designs.
• Jet velocity is calculated from headbox pressure, slice opening and headbox geometry parameters.
• Jet/wire and rush-drag ratios are then calculated from jet velocity and wire speed.
• The Jet/wire loop then calculates the required total head setpoint.
• The following calculated variables are provided:
  • jet speed
  • rush-drag
  • headbox flow
  • square head pressure
• Standard headbox pressure controller is included as the necessary low-level controller.

Engineering support features

• Jet/Wire ratio control is equipped with a comprehensive set of tools for tuning, maintenance and troubleshooting.
• All operations are performed via dedicated tuning displays which are carefully designed for each task and step. Examples are shown on this page.
• Control package is configured by standard system CAD tools.

Configuration options

• The operator interface can be either rush-drag or jet/wire.
• The standard package can be modified to use an alternate customer-specific jet speed calculation.
• For Metso headboxes a more sophisticated jet velocity calculation package (IQJet) is available. It utilizes real headbox geometry and sophisticated flow equations to obtain more accurate jet velocity and information on impingement conditions.
• A low-level controller can output to either fan pump speed or a stream flow valve.