NLS Series Multifunction Influx Type Pressure Screen for paper machinery - NLS

NLS Series Multifunction Influx Type Pressure Screen for paper machinery

I. Overview

NLS inflow pressurized screen is a new type single-drum inflow pressurized screen based on the imported prototype. As the outflow pressurized screen throws the fiber and heavy impurity to the screen drum at the same time through the centrifugal force, it will result in the clogging and abrasion of drum and reduce the equipment working capacity and service life. While the inflow pressurized screen is provided with special rotor to make the pulp enter the pressurized screening zone under the centrifugal force and the heavy impurity will be thrown out of the drum. Therefore, if the screening object of the pulp is the high specific weight impurity, NLS inflow pressurized screen has higher screening efficiency than the outflow pressurized screen. Furthermore, the drum service life is long, the drum is not easy to get clogged by the impurity, the yield is high and the power consumption is low. As the new type substitute of various domestic pressurized screens, it can be widely used for the rough sizing and fine sizing of various pulps and the pulp screening before paper machine.

II. Working Principle

The pulp flows into the screen from the top in the tangential direction and rotates out of the drum. A special rotor is provided at the pulp inlet side drum, through the rotation of which the pulp return current is accelerated. While the pulp enters the drum through the sieve plate under the pulse positive pressure of rotary wing, some of the heavy impurity will move reversely due to the centrifugal force to separate from the fiber and then move downward along the drum wall to discharge from the thick scum port.

The experiments have proven that in the case of screening high specific weight or heavy impurity from the pulp, compared with the conventional outflow pressurized screen, NLS inflow pressurized screen has higher screening efficiency, lower power consumption and longer drum service life.

III. Structure and Features

1. Screen drum: depending on the screening object, bar screen drum or wave slotted screen drum of 0.08mm as a minimum can be used; the hole sizer screen drums of various types can be used as well.

2. Rotary wing rotor: the fine sizing rotor is provided with 3 - 8 rotary wings and the rotor is mounted on the main shaft. The rotor of special structure allows high screening efficiency and no clogging will occur even if the screen slot width is 0.08mm.

3. Mechanical seal: special type graphite material seal, falling into dynamic seal and static ring. The static ring is pressed to the dynamic seal through spring and water flushing of seal is available to prevent impurity access and allow compact structure, safe operation and long service life.

4. Driving device: it includes motor, pulley, V-belt, belt tensioner, main shaft and bearing etc.

IV. Advantages

1. As the heavy impurity will separate from the pulp once the pulp enters the screen, the impurity will cause less abrasion to the drum, which greatly prolongs the service life of drum compared with other screens. As shown in this figure:

Difference of impurity flow direction of outflow and inflow pressurized screen

1—Pulp inlet 2—Centrifugal force 3—Wall 4—Drum

2. As special rotor is used, the fiber classification is very weak. The impurity is far from the screen drum due to the centrifugal force, which makes the screen mesh (or slot) difficult to be clogged by the impurity. Therefore, the screening efficiency and yield are high while the power consumption is low.

3. Where used for the fine sizing of pulp before paper machine, as the pulse strength of pulp out of the pressurized screen is low, it will not generate disturbance to the pulp feeding.

4. NLS can use the fine slot screen drum to produce high quality sheets such as coated paper, cigarette paper, supercalendered paper and tissue. It will reduce the sheet end break on the machine and no pulp will attach to the slot.