Prevent damage to the forming fabrics

1.Ensure that the surface of the roller is always smooth enough;

  1. Release air at both ends of the roller (about 2.5cm from the vacuum area) so that there is no slurry deposit on the roller;

-. Usually, deposits on the rollers are not visible, but can be felt by hand;

  1. Check the spray water filter:

– prevent any corroded metal from passing through;

– maintain proper water quality to avoid blockage of nozzle;

  1. Check the scraping condition of steering roller and breast roller;

– Deposits on these rollers can cause wrinkling of the forming wire;

  1. Before installing the new net, check all rollers for damage.
  2. Ensure that all nozzles are tightly fastened;
  3. Check the net correction, pendulum and extension devices to ensure that they are in good working condition;
  4. Ensure that the high-pressure needle spray is swinging and the water pressure does not exceed 35 kg/cm2 (500 psig/in2);
  5. Use a good cleaning procedure:

– Do not wash any debris into the running mesh;

– Do not flush the edge of the net directly with high pressure water;

– Ensure that the flushing hose water source does not contain debris;

Forming fabrics correction failed

  1. Check the forming fabrics by hand until a repair is made;
  2. If the forming fabrics with manual correction is not stable enough, it needs to stop repairing and correcting;
  3. Reduce the degree of vacuum to prevent the forming fabrics from catching or blocking on the vacuum suction box;

Reduced net life

  1. The components of the Fourdrinier paper machine network must be accurately lined up and in good mechanical condition;

– All filter elements must be fastened and at the same height;

– Check that the tension roller and automatic tensioning device cannot bounce;

  1. Poor cleaning of the case and poor routine maintenance are one of the main reasons for the shortened network life.

(a) Ensure that no fibrous aggregate forming slugs fall inside the forming fabrics;

(b) Keep the scraper in good condition;

– Prevent the slurry from accumulating on the guide roller and the breast roller;

– The first outer roller is essential to prevent the net from being damaged by the slug;

– Squeegee angle (about 25~30 degrees) is very important for ensuring proper wipe without scratching sound;

– The scraper load must be tested repeatedly, but overload must be avoided;

– Swing is a good warning for any and all squeegees;

– The breast roller scraper should always be inspected so as not to cause net marks or too much water on the breast roller;

(c) Check the water tray holes, rusted bolts or spray valves;

– Non-uniform flow of water around the spray valve may cause the metal to break off and flow through the spray pipe;

  1. Eliminate abrasive fillers, such as: calcium sulfate;
  2. Check the trajectory, calibration, tension, load and slip of the net;

– Ensure that the horizontal tension of the paper machine is even;

– Do not run the forming fabrics under too loose conditions;

  1. Maintain spray water temperature and pH consistent with the slurry;

– Ensure that the spray water pipes on both sides are not blocked;

  1. Adopt the low friction coefficient on the upper surface of the vacuum suction box;

– Check whether the upper surface of the vacuum suction box is flat;

  1. Reduce the number of vacuum suction boxes, increase the opening;

– reduce the degree of vacuum to prevent the forming fabrics from catching or blocking on the vacuum suction box;

  1. Remove grout in the pulp (centrifugal cleaner);

– Check for scratches and burrs on the forming plate, vacuum suction box surface and the cutting board;

  1. Use the net life extension agent (net cleaning agent);
  2. Adequate traction should be provided to ensure that the net does not slip at the breast roller;
  3. Operate at the lowest vacuum level of water absorber in operating procedures;

– ensure free flow of water from the suction box into the water seal tank;

  1. Check the installation of the forming plate to ensure that there is sufficient space for even and minimal drainage of the breast rollers;
  2. Check the cleaning of the roller steering system;

– check the load of scraper, scraper, spray water, bearing and excessive spray water pressure;

  1. Check the wear strip on the side setting device or the cheek plate of the slurry tank to determine whether it is installed too low;

The net is raised/wrinkled

Note: the net bulge often develops into wrinkles, which may gradually form a cord or overlap.

  1. In general, oblique uplift due to unalignment;
  2. Straight line heave is usually caused by the following reasons:

– slurry deposition between breast roll and lip plate;

– slag forming on dewatering element;

– resin concentration;

– too much water when rotating;

  1. Drumming may come from:

– the vibration distance of the network case is too long;

– roll deflection;

– There is a twist zone in the multiple vacuum box unit

– after the paper is on the web, the vacuum pump has shear force;

– the steam box is still running when the net crawls slow or stops running;

4.- the whole net wear may be due to:

– rough surface hairiness of vacuum water absorber;

– roller corrosion;

– surface abrasion or breakage of glass fiber rollers;

Network vibration

Note: In general, when the slurry is connected to the grid, the vibration will have a negative effect on correcting the deficiencies of the slurry, but it can suppress the flocculation during filtration;

  1. Observe the opening and stopping of the forming network;

– Adjust the network corrections;

  1. Once vibration stops, the web will dry on the forming fabrics;

– To maintain the quality of the sheet, it is necessary to add water;

  1. When the speed is lower than 300~400 meters/minute, the vibration is effective;
  2. At lower speeds, the web will resist flocculation more effectively if the vibration frequency increases;
  3. Increase the frequency of vibration and remove more water from the net;
  4. As the frequency of vibration decreases, the filtered water speeds up, and the web of clouds becomes heavier;
  5. Vibration efficiency and vibration amplitude are proportional to the square of the frequency, and indirect proportion to the speed;

Network slip or flutter

  1. Maintain proper distribution of traction loads;
  2. Use snake woven nets;
  3. Tighten the forming fabrics;
  4. Reduce vacuum:

– If possible, remove the water to reduce the vacuum;

  1. If possible, increase the vacuum level of the couch roller;
  2. Check the flow of paper on the forming board;
  3. Check for turbulence that is 3 to 5 meters beyond the original forming area;
  4. Excessive delay in the initial filtration stage can cause turbulence;

Acidity

  1. High acidity (free or total) is almost always detrimental to machine performance and product quality;

– check pH controllers, charts, and acid or base addition points;

  1. High acidity (low pH) is corrosive to mechanical equipment;

– Fouling and rust can come off the pump and pipes and create dirt, spots or holes in the web;

  1. Check the paper pH value;

– The faded paper may produce residual acid;

  1. Control the pH of the factory’s incoming water;
  2. High acidity has a bad influence on quality:

– Causes hair loss and powder loss;

– Degrades fiber, thus reducing strength and long-lasting properties;

– Most dyes react differently when the pH is changed, thus affecting the color;

– Seminal plasma requires more energy to change fiber shape;

  1. The negative impact of paper machine operations:

– In the case of blankets, the jamming trend has increased;

– It takes longer to dry the web;

– Due to the poor absorption of the paper by the paint, it weakens the absorption of the paint and fiber surface;

See the “Changes in pH” section.

Aluminum sulfate added

  1. Aluminum sulfate can be used to control pH value, fixed rosin gum, auxiliary retention and flocculation, and resin sediment control;
  2. The change of pH value caused by changing the amount of aluminum sulfate can change the color and influence the adsorption force between wet paper width and press roller;
  3. The peeling or “anti-stripping performance” of wet paper amplitude changes with the content of alumina;

– if the pH value is too high, crushing paper may be produced; When the pH value decreases, the paper will disappear.

  1. Too much aluminum sulfate in the system will have a negative impact on the strength of paper pages, the filtration water at the screen and the combination of fibers, and may even reduce the efficiency of rosin sizing.
  2. Many problems are related to low levels of alum or bauxite ions in the system. Low sizing, foam problem, formation of free rosin deposits, decrease of fiber binding force, deterioration of water filtration and significant trend of resin deposition all testify to this.

See the section “sodium aluminate”.

Wet-end chemistry

  1. Many chemicals used in the wet part can improve the water filtration to varying degrees, and improve the internal binding force of fine fiber, the retention rate of fillers and the dry and wet strength.
  2. Too little essential chemicals will not achieve the desired effect:

– may lead to poor water filtration, loss of fine materials and fillers, as well as reduction of binding force and strength between fibers;

  1. However, excessive use of chemicals may have the opposite effect. For example, overflocculation leads to poor evenness, which in turn has a negative effect on almost all strength properties;
  2. It is very important to strictly control the solid content and viscosity when preparing the auxiliary materials;

– temperature is also important for viscosity control;

  1. Increasing the amount of water entering the sizing press paper can increase the amount of glue hanging and the retention of surface glue;
  2. Reduce the pressure of the sizing press line, increase the amount of glue hanging, and ensure more treatment of the page surface;
  3. Reduce the amount of glue applied in the slurry to improve the amount of glue applied on the surface;

 

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