Unloading system of the hottest wood chip bin

2022-08-05
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Unloading system of wood chip bin (Part 2)

2.1.2 control logic design - material level control between high and low limits

it takes about 13min to reduce the material level of small wood chip bin from 90% to 60%. In order to keep the material level as high as possible for full steaming, the start and stop control of unloading screw is improved as follows: when the material level of small wood chip bin is between 60% and 90%, the start and stop of unloading screw is controlled by a certain clock, which is designed as a square wave with a pulse width of 5min, Make it open for 5min and stop for 5min. The unloading control logic diagram is shown in Figure 2

two delay opening relays and a non gate generate a square wave with a period of 5min. This leads to: when the material level of the small chip bin is less than 90%, Dr. Wolfgang Feist, the scientific and technological director of the German Passive House Research Institute, said: "compared with traditional buildings (% auto-stop=0), if the small chip bin has started to supply wood chips to the subsequent process (1002m-run=1), a large chip bin unloading spiral control signal (auto-p) with a cycle of 5min will be generated 。

2.2 the unloading trolley passes the middle line for unloading

after modification, the surface is modified as shown in Figure 1. There is a limit switch (SW) at both ends of trolley A and trolley B, with numbers of swal, Swar, swbl, wsbr and wsff respectively. SW is the English abbreviation of switch, a and B respectively represent trolley A and trolley B, l means "left", R means "right", and FF means "relative"

the way to solve the problem that the two trolleys cross the center line is to move the right limit switch Swar of trolley a by 3M to the right, and the automatic stop signal generated when the unloading screw control logic diagram

auto-stop-small chip bin material level is greater than 90% is 1002m-run-small chip bin unloading screw start signal auto-p-cycle automatic start and stop signal, Control the unloading screw of the large chip bin

Figure 3 〓 control logic diagram of the running direction of trolley a

Figure 4 〓 screw anti break control

the left limit switch swbl of trolley B moves to the left by 3M, which increases the "addressing capacity" of the two trolleys and increases the unloading range. The consequence of this is that the two cars will collide. The solution to the collision problem is to add a double contact relative position limit switch SWFF on trolley A and a contact arm of appropriate length on trolley B. when the two vehicles approach a certain position, the contact arm touches the relative position limit switch SWFF, the contact K1 of SWFF is in parallel with the contact of Swar, and the contact K2 of SWFF is in parallel with the contact of swbl, so that the two vehicles change the direction of movement at the same time. Adding the contact arm is to provide a buffer zone for the two trolleys to prevent collision due to inertia after the switch action. The control logic is shown in Figure 3 (taking the normally open point as an example)

2.3 anti break control of screw shaft

in order to solve the problem of screw shaft fracture, the mechanical discipline has carried out many repairs, including the thickening and reinforcement of screw shaft, but the repair is broken once, and the frequency is getting higher and higher. To solve the problem thoroughly, there are several solutions considering the equipment itself: ① redesign and process the screw to enhance the strength of the shaft; ② Redesign and process the gearbox, reduce the moving speed of the trolley, etc. However, I made a little change in the DCS configuration. Since then, the failure rate has been greatly reduced. Since the operation for more than half a year, the screw has not been broken again. The control logic diagram is shown in Figure 4

after 5S of screw operation (to ensure that the wood chips near the screw are dug loose), the trolley starts and runs a 5S pulse. Then, the trolley stops running and the screw continues to unload. The reason is very simple. Try to shorten the running time of the trolley, so as to reduce the self radial force on the screw shaft and prolong the service life of the screw

3 summary after the completion of the three improvements,

the effect is very obvious. For example, the first one enables the high material level control of the small chip bin, significantly improves the mechanical structure of the electrohydraulic servo universal testing machine for the steaming effect of wood chips, and improves the washing effect of wood chips. Although the constant material level control can not be achieved, it has fully met the process requirements. From the perspective of direct economic benefits, it is equivalent to saving two frequency converters. It determines the size of the fixture structure and the labor intensity of fixture operation. Through the improvement of control, the equipment performance is optimized and good benefits are created

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