Accuracy of Suction Top Resurfacing

Why Resurfacing or Grinding?

The wire part of the paper machine serves for stock dewatering and consequently it transforms the stock into the “paper sheet“. The stock goes out of the headbox on a longitudinal endless wire where the paper stock is dewatered so that the fibres settles down on the wire surface.

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The endless wire is embraced at the headbox side by a breast roll and on the other side by a suction roll (couch roll) and driving roll. The suction and driving roll combination is recommended for each wire part version both from the drive perspective (better driving force distribution and more cautious influence on the wire itself) and from the perspective of the subsequent paper web removal and its transfer into the press part. In the upper part between the rolls, dewatering elements are located, which have plastic or ceramic foils attached to them. The longitudinal endless wire with the stock is moving on their surface and in case of the contact the stock is dewatered.

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Dewatering elements are located on the wire table in a following order:

• Forming board

• Dewatering foils

• Hydrofoils boxes

• Vacuum water box

• Suction boxes

The correct placement of the dewatering elements is essential for a quality dewatering to reach the required percentage of the dryness behind the wire part. A steam box is used to increase a temperature of the paper before it enter the press part to get more of the dryness during pressing.

The wire part length depends on the PM performance and on types of paper produced there. The wire length is also determined by the number of dewatering elements. The PM endless wire is carried, guided and stretched by a row of rolls in the lower part of the wire table. The wire guide is located there and it guides the wire so that the wire would not leave the machine axis.

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Forming board

• Is a weldment made of stainless steel. It is fixed to carriers on stands which enable its height adjustment against the breast roll in a range of 0 - 80 mm. It is fitted with a wide foil with foils of 65 mm width. These foils can be made of polyethylene or ceramics. With respect to a possible wearing the forming board is height-adjustable. All the foils are fixed on the table by T-shaped grooving.

Dewatering foil

• is as a weldment made of stainless steel. It is fixed to the beams with stands which enable its height adjustment. The foil design can be stationary or turnable for possible changes of its scraping angle (0° - 2,5°). In case of the turnable design when changing the angle, is always necessary to adapt also the height adjustment accordingly. The dewatering foil body is provided with a foil wide of 65 mm. This foil can be made of polyethylene or ceramics and fixed by a T-shaped groovings.

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Hydrofoils box

• is a weldment made of stainless steel. It is fixed to the beams with using stands which enable its height adjustment with respect to a possible the foils wearing off. It is fitted with 5 - 7 foils with width of 65 mm. The foils can be made of polyethylene or ceramics. All the foils are fixed to the box by T-shaped groovings.

Depression water box or Low Vac Box

• is a weldment made of stainless steel. It is fixed to the beams with stands which enable its height adjustment with respect to possible wearing of the foils. It is fitted with 5 - 7 foils with a width of 65 mm (generally). These foils can be made of polyethylene or ceramics. All the foils are fixed to the box by T-shaped groovings. The depression in the box is created by a fan. The depression value can be regulated by a suction valve. The suction zone width profile can be regulated by sliding gates.

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Suction box

• is a weldment made of stainless steel. It is fixed to the beams with stands which enable a height adjustment of the box with respect to a possible wearing of the lining. The cover can be made of polyethylene or ceramics and its height ranges from 30 to 40 mm. The suction zone comprises slots or round holes. The free cover area ranges from 40 to 50 % of the total lining surface. The suction zone width in the cover is adjustable by sliding gates. The box vacuum is created by a vacuum pump. Connection to PM vacuum system is through a water separator. The vacuum regulation runs automatically using a control valve or can be done manually. 

Multi-chamber suction box

• is a weldment made of stainless steel. It is fixed the beams on stands which enable a height adjustment of the box with respect to a possible wearing of the foils. The foils are fixed to the box by T-shaped groovings. Each chamber is provided with a different number of foils installed with a different spacing. The vacuum value in each chamber differs from each other in order to reach optimal stock dewatering rates in the PM wire part. Each chamber is separately connected with the PM vacuum system through a water separator. The box underpressure is created by a vacuum pump. The vacuum regulation runs automatically by means of a control valve or manually. The suction zone width is adjustable by means of sliding gates. Each chamber is separately connected with the PM vacuum system through a water separator. The box vacuum is created by a vacuum pump. The vacuum regulation runs automatically by means of a control valve or manually. The suction zone width is adjustable by means of sliding gates.

With continuous use and abrasion on the dewatering element surface because of forming fabric and other abrasives in pulp, the surface deforms and slowly some passages are developed which allow water capillaries to be sucked by vacuum or air leakages in the vacuum zone. It is highly necessary to plug these irregularities for efficient working of the paper machine.

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At Nordstern we achieve the precision required by your machine by resurfacing the suction tops. The benefits so achieved are:

1. Better Formation.

2. Energy Conservation.

3. Higher Fabric Life.

4. Increased Retention of fibre.

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