The Z-Plate Design - US patent 7,634,860 

The Z Plate design provides a mechanical barrier to deflect boundary air while protecting the steam diffuser jets from the disruption that boundary air would cause.

This innovation allows the use of lower velocity steam to be applied to the moving web at a reduced distance from the web.

The Z Plate then slops toward the web, making a converging path for the steam flow to be held against the web. This convergence of the steam flow combined with the low, matched velocity of the steam results in a very intense, narrow band of steam being acted upon by vacuum before the steam has a chance to spread in the CD or MD.

Depending on space availability, multiple Z-Plates are used in the MD.

Steam contacts the sheet immediately under the Diffuser steam jets. Condensation begins.

At T1 , the sheet has moved and the steam column above it has shrunk as the steam is condensed. The Z-Plate slopes toward the sheet, reducing the volume, keeping the steam in contact with the sheet.

At T2 , the sheet has moved further and the steam column above it has shrunk further due to condensing. The Z-Plate reduces the volume above the sheet. This results in a reduction of turbulence and drift of the steam. A sharper bump response is created.

At T3 , the sheet has moved further and the column of steam above it has shrunk more due to condensing into the sheet.

At T4 , the sheet has moved under the next set of jets and the process begins again.

Transphase is a company specializing in the design, manufacture and application of advanced steam box designs to improve heat transfer from a steam box to the paper web or press felt.