PLC control system design of hydraulic device of d

Paper on the design of PLC control system of hydraulic device of beer diatomite filter

[Abstract] this paper introduces the design method and implementation process of applying PLC technology to transform the hydraulic control system of diatomite filter. The example of actual transformation shows that the reliability of hydraulic control of diatomite filter is improved by using PLC control, and the economic benefit of the enterprise is improved

in the beer and beverage industry, diatomite filter has become a common machine and equipment in the production process of the industry because of its excellent performance and good filtration effect of liquid media

the control of the hydraulic device in the diatomite filter is the most important part of the whole diatomite filter. At present, the control of the hydraulic device of diatomite filter mostly adopts the control mode of relay plus discrete electronic components. This control method has complex electronic circuits and a large number of relays, resulting in poor reliability, high failure rate and large amount of daily maintenance of the electrical control part

with the development of programmable controller (PLC) technology, PLC control technology is applied to the control of hydraulic device in diatomite filter to replace the original hydraulic device control circuit. Good results have been achieved

I. main technical parameters and functions of diatomite filter

1. When the filter is working, the jacking working pressure of the device is: 11.5~24mpa

2. When the filter is sterilized, the working pressure of the device is: 3.5mpa

3. Full stroke of oil cylinder piston rod: 1400mm

4. Oil cylinder output force: 6 × 105N~11,7 × 105n

5. Lock and maintain pressure at the oil cylinder: when the system pressure is 15MPa and maintain pressure for 5 hours, the pressure drop is not greater than 3.5mpa

6. Program operation functions: (1) compression sterilization (2) filtration (3) depressurization sterilization (4) release the plate and frame (5) manual operation

7. Piston rod stroke control function: when the piston backward travel reaches 2+0.5mm due to the increase of the plate and frame filtration pressure difference, the device can automatically compensate the piston rod stroke

II. Structural principle

1. Composition system

the hydraulic device of diatomite filter is composed of hydraulic system and electric control system. The system block diagram is shown in Figure 1. The hydraulic system is composed of double oil pump, precision oil filter, unloading valve, electromagnetic directional valve (MV1, MV2), ball seat valve (MV3), oil tank, oil cylinder, etc. The electric control system consists of an electric control box and an operation panel. The electrical control box is mainly PLC, automatic protection switch and control appliance. The command switch for program operation (the first report indicates the 5th gear band switch) and the signal indicator are concentrated on the operation panel

2. Working principle of hydraulic system

see the schematic diagram of hydraulic device (Figure 2) for the working principle of hydraulic system. The output hydraulic oil of the high and low pressure pump is combined with the unloading valve (4). When the system pressure is higher than the set pressure of the unloading valve (4) (2.5MPa), the low pressure will unload automatically. When the hydraulic pump is started, the duplex pump supplies oil to the system at the same time. When the system pressure is higher than 2.5MPa, the low-pressure pump unloads and the high-pressure pump supplies oil to the system at a small flow rate. At this time, the high-pressure pump continues to output high pressure to boost the system. When there is no operation command, the hydraulic oil returns to the oil tank through the precision oil filter (high-pressure oil filter 3) to the three position four-way valve solenoid directional valve (12). When (MV1) is powered on, the high-pressure oil enters the rod free chamber of the oil cylinder through the hydraulic control check valve (9), (MV2) is powered on, the hydraulic oil enters the rod free chamber of the oil cylinder (11), and (MV3) is powered on, the rod free chamber pressure oil returns through the ball seat valve (5) to open the hydraulic control check valve (9), realizing the piston to retreat. When (MV3) is powered on alone, the rod free chamber pressure decreases. There are two (P2) pressure relays (8) that control the sterilization pressure of 3.5Mpa, (P1) control the working pressure of filtration to 12 MPa, which can realize the functions of maintaining and supplementing pressure and other program operations. The overflow valve is used to limit the maximum self-locking pressure of the oil cylinder

3. Operation procedure of diatomite filter

3. 1 turn on the power switch (1) K0, and the power indicator (2) is on

3, 2 cleaning, sterilization

program selection switch (3) is set to gear 1

cleaning: press the button (6) and the piston moves back. When it moves back to the limit position, carry out soil removal and cleaning

sterilization: press the button (4) to advance the piston, press the plate and frame, and then start boosting pressure. When the pressure of the pressure gauge rises to 3.5Mpa, the hydraulic motor stops. At this time, the disinfection indicator light (5) is on, and the pressure of the press is maintained, and then sterilization can be carried out. During pressure maintaining, when the pressure drops to 2.5MPa, the hydraulic pump motor starts automatically to realize the pressure supplement function

3, 3 filtration

after the sterilization work is completed, the selector switch (3) is set to gear 2, the hydraulic pump motor automatically pressurizes the plate and frame, and the machine stops when the pressure gauge pressure rises to 11.5MPa. At this time, the filtration indicator light (7) is on, and the diatomite precoating and beer filtering work can be carried out. In the filtration process, nearly 90% of the friction pairs in the friction testing machine are carried out in this way, and when the pressure drops to 10.5mpa, the hydraulic pump motor starts automatically, Realize the pressure supplement function

3, 4 step-down sterilization

after the wine filtering work, place the selector switch (3) in gear 3, the oil cylinder pressure will automatically drop to 3.5Mpa, and the disinfection indicator light (5) will be on, ready for loosening the plate frame

3? When loosening the plate frame

for soil removal and cleaning, place the selector switch (3) in gear 4, press the forward button (4) and the reverse button (6), and the piston can retreat. When it retreats to the limit position, soil removal or cleaning is carried out

3, 6 manual operation

when manual operation is required 14. Control function: when there is constant speed control mode operation, place the selector switch (3) in gear 5, press the forward button (4) to move the piston forward or pressurize, and press the backward button (6) to move the piston backward or depressurize

III. design principle of hydraulic device control system

the hydraulic device control system of diatomite filter adopts two control modes of "automatic operation" and "manual operation"

1, system hardware design

1, 1 system i/o point, memory capacity and selection basis

system input signals include; A 5-gear band switch, 2 button switches, a travel switch, 2 pressure detection switches, a total of 10 inputs

system output signals include; There are 2 working status indicators, 3 solenoid valves (MV1, MV2, MV3) and a hydraulic pump motor, with a total of 6 outputs

therefore, the day is adopted