A simple solution to the problems encountered in t

A simple solution to the problems encountered in the use of pressure screens

medium consistency pressure screens are relatively advanced pulp screening equipment in the world at present. Compared with traditional low consistency pressure screens, they have the advantages of energy saving, water saving and high screening efficiency, and have been widely used in China. For the problems encountered in production and operation and their solutions, as well as the problems needing attention in installation and commissioning, here we take the reed pulp production line as an example to introduce some practical experience

outflow medium concentration pressure screen structure

1 operation problems and solutions

reed pulp has shorter fibers and is easier to screen. During the actual operation of the reed pulp production line in a domestic paper mill, there were many problems due to improper operation of workers and insufficient raw materials

1.1 bearing damage

the bearing of the pressure screen is damaged after running for about a month (see Figure 2). From the removed bearing, the main reason is the lack of lubricating oil on the upper part of the bearing, and the friction between the ball at the upper end of the bearing and the bearing sleeve leads to bearing damage

this is determined by the structure of the vertical transmission device of the pressure screen (see Figure 3). During assembly, about two-thirds of the volume of lubricating oil is added to the inner cavity of the upper and lower bearings. However, due to the high temperature of the slurry screened by the pressure screen, which is about 60-80 ℃, the temperature of the bearing and the main shaft will also be between 60-80 ℃, or even higher. After the equipment operates for a period of time, the lubricating oil will be heated and become viscous liquid flowing downward, There may be no lubricating oil in the upper half of the bearing, causing the bearing to be damaged soon. Therefore, the pressure screen must be supplemented with lubricating oil after running for a period of time

1.2 belt burnout

the transmission belt of the pressure screen selects 6-10 combined belts, and the transmission efficiency of 6-10 single belts is 90% - 95%, while the efficiency of the combined belt should be greater than 9 and improve the comfort by 5%. However, the operation requirements of the combined belt are high, so the assembly center of the motor pulley and the transmission shaft pulley must be in a straight line

during the actual operation of the equipment, the belt was quickly burned (see Figure 5), and the belt was sticky and had a great paste smell. The biggest reason was that the manufacturer did not notice that the two centers of the belt were different after self-adjustment, and the belt rubbed at high speed. Therefore, after removing the pulley every time, the two pulleys must be readjusted to be in the same straight line. If the workshop does not have a ruler, it can also be straightened with a thin line and then corrected

make sure that the rotation direction of the main engine is correct. When looking from top to bottom, the rotating cylinder should rotate clockwise. Start the motor and adjust the tightness of the V-belt to make it suitable. The correct tension should be at the peak value. We will try our best not to slip under the load. When operating with load, the loose side should be slightly arched. When the belt will loosen after running for a period of time, adjusting the jacking bolts and nuts of the jacking device (see Figure 6) and driving the motor carriage can make the belt reach the best working state

1.3 screen drum blockage

due to the insufficient supply of reed pulp raw materials, the production line starts and stops, and the pressure screen drum is often blocked (see Figure 7). It is very troublesome to take out the screen drum and wash it with acid every time it is blocked. The reason is that the operating workers do not flush out the remaining slurry in the pressure screen in time every time they stop due to insufficient raw materials, resulting in the deposition of slurry on the screen drum, which makes the screen drum blocked

2 precautions for installation and commissioning

(1) before starting up, be sure to check whether the mechanical sealing water and flushing water are normal (ensure the pressure and flow of sealing water)

(2) when starting up, first open the exhaust valve, open the dilution water valve, fill the pressure screen with water, and then close the exhaust valve, then start the main motor of the pressure screen, run the water for 3-5min, repeatedly flush the screen drum for several times, and then start the slurry pump

(3) when feeding slurry, the flow and concentration should be slowly increased (to prevent excessive flow and concentration from blocking the screen drum), and gradually adjusted to the required flow and concentration

this kind of bottom gas comes from Jin min's strong technical strength on the one hand

(4) the blockage of the screen drum during startup is manifested in the increase of the current of the motor, the increase of the pressure difference and the decrease of the pressure at the outlet of the good slurry. At this time, the outlet valve of the good slurry should be closed quickly, and the dilution water valve and the tail slurry valve should be opened to flush the screen drum; When the outlet pressure of good slurry rises to close to the inlet pressure, it indicates that the blockage has been cleared. At this time, slowly open the good slurry pipe valve, and adjust the tail slurry outlet pipeline valve and dilution water valve to the required opening

(5) if it is found that the pressure screen motor suddenly trips and does not operate during startup, the slurry feeding pump should be stopped quickly first, and then the cause of tripping should be analyzed

(6) when shutting down, stop the slurry pump first, and then flush the pressure screen with water to prepare for the next startup

(7) do not make the pressure screen work at a particularly low flow rate. When the slurry flow rate is low, the screen drum will produce a concentration effect, which will lead to the blockage of the screen drum or the blockage of the slurry port pipeline for the raw materials required by the tail production