Cleaner PLC automatic control system

Abstract The paper introduces the automatic control system of the smearer with Siemens programmable logic controller (PLC). It has high reliability, convenient operation and maintenance, and low cost.
Key words slag remover Siemens PLC subroutine state transition value engineering

I. Overview With the progress of China's environmental protection work and the raw material crisis faced by the paper industry, the use of waste paper has become a major trend in the development of the paper industry. However, due to the complex source of waste paper, the pulp is inevitably mixed with a lot of heavy debris (such as books, sand, etc.) and light impurities (such as plastic sheets, etc.), cleaners and dual fiber separator It is a common device to remove these debris.
Because the pulp and paper industry's own production points have determined that these equipments must be operated in a sub-inferior environment, the control of traditional relays will inevitably increase the failure rate and safety risks, and the use of PLC controllers will be confronted with relative prices. Higher, more cumbersome and other issues. For this reason, the author combines the actual situation, from the perspective of value engineering, makes reasonable choices for the original functions, and makes reasonable optimization while preserving the necessary functions, so that the production cost is reduced by more than 1/3, and good results are achieved.

Second, the working principle of the slag cleaner Introduction shown in Figure 1, the prize to 0.2-0.3MPa pressure along the tangent into the slag removal device, the formation of vortex, rotating into the conical tube, vortex centrifugal force to concentrate heavy impurities Inside the conical tube, it separates from the slurry and then falls. It is deposited in the sediment tank by opening the V1 valve. After a predetermined time, V1 closes, V2 valve opens slag, then 2 closes, and V1 valve opens again.

figure 1

In addition, in addition to this structure, the multi-fiber separator also includes a light slag discharge valve located in the middle, and the light wine valve is periodically circulated between full open and semi-open, so that light impurities can be continuously discharged and can also be incorporated into the system. This is not repeated here.

Third, the control program

In order to meet the needs of normal production and equipment commissioning, the system must have the following functions:
(1) It has manual and automatic functions and can be switched at any time;
(2) The time of sinking and the time of alcoholic drinks are independently adjustable, and there is a limit to the safety range;
(3) The valve is in place to ensure that one valve is not closed and the other valve cannot be opened;
(4) When a fault occurs and the valve cannot be closed, a sound and light alarm is issued for a period of time.
(5) It can track the operation of the equipment and know the running time of the equipment at any time.
In addition, the manual, automatic operation, and the state of the upper and lower valves in the off state are indicated by corresponding indicators, which are clear at a glance. The following describes the composition of this system in several aspects.

1. Degree flow

Combined with the specific use of the situation, the following work flow is specifically formulated (see Figure 2).



figure 2

2. PLC selection In order to meet the above functional requirements, we have chosen a highly cost-effective Siemens S7-22X series PLC, which provides the subroutine call, interrupt call and state transfer function, so that the author is as flexible as a microcontroller, compact size The PLC can use space effectively.

3. I/O port planning In order to reduce the hardware cost, the author makes full use of the idea of ​​value engineering and has made a lot of improvements in the software. Basically, it has realized a button with two functions. Significantly reduced the number of switch buttons and I/O days. The specific I/O assignments are shown in Figure 3.



image 3

Due to space constraints, we cannot list all the procedures. Now, we will only give some representative pieces to illustrate their structure.
1. The time adjustment subroutine is used to adjust the dreg and slag discharge cycle time, and it is switched by SB3, and SB5 and SB6 are increased or decreased by time. If it is not set, it will be executed according to the default value. The block diagram is shown in Figure 4.



Figure 4

2. Tracing the running time program to more accurately track the time that a device has been in operation has a certain significance in the production practice, which is of certain value for the periodical overhaul and maintenance of the equipment and even the continuous operation of the entire production line. The specific implementation method is: When SB4. When S5B is pressed at the same time, the number of seconds that the LED L5 and L5 are lighted by adding 0.5 is the whole 10 times of the running hours. For example, L5 is on for 15 seconds, and the characterization system has been operated for 150 hours. When the L5 is lit, the system has been running for a while. Its block diagram is shown in Figure 5.



Figure 5

3. State cycle segment This section uses Siemens PLC's sequence control relays to implement, and the specific method for each step is shown in Figure 6.



Figure 6

The system was used on the slag remover and duplex fiber separator produced by our factory. It was successively tested successfully in several paper mills in Guangdong. The equipment was small in size, simple in operation, reliable in operation, and inexpensive. Considerable economic benefits.
In short, the system realizes the upgrading of electrical equipment at a lower cost.

Received date: 2000 10 13