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Modification and Application of Automatic Control System for Pipe Pile Pumping Fabric

2019-07-26

As the country's requirements for safety, environmental protection and energy conservation become more and more strict, precast concrete pipe pile production enterprises are also actively seeking safer, greener and more energy-efficient production methods. Cloth is the intermediate link in the production of pipe piles, which restricts the progress of cage processing and pipe pile mold centrifugation. Therefore, the strict implementation of the cloth process is particularly important. Under this circumstance, the traditional fabric method is technically modified, and the concrete pump is used for automatic fabric, which not only saves labor, improves the production environment, reduces the loss, but also can strictly carry out the fabric according to the process requirements, thereby achieving the purpose of improving the quality of the control. Provide technical support for production activities.
 
First, the situation before the transformation
 
In the traditional cloth-laying method of concrete pipe piles, it is common to use the cloth before the mold clamping. First, the concrete is poured into the bottom mold by the feeder, and then the mold is closed. This method mainly has the following problems:
 
(1) The material of the traditional feeder is affected by the equipment and materials. It is impossible to accurately pour all the concrete into the bottom mold according to the requirements. The ground in the cloth area will be scattered with many stones, which will affect the working environment.
 
(2) The concrete slump is small, and the concrete filling rate in the pipe pile mold is high. It is necessary for the mold clamping staff to shovel and grout many times in order to make the concrete piled evenly in the pipe pile mold, which causes great work intensity for the employees.
 
(3) The manual operation of the cloth method cannot guarantee the product quality, and the production process control is difficult.
 
Second, the transformation content
 
2.1 Principle of the transformation plan
 
The automatic control system for pipe pile pumping fabric consists of concrete pump, concrete conveying pipe, weighing system, metering flat car and system operation table. The control system collects the real-time data of the pumping equipment, the metering flat car and the weighing system, and automatically controls the operation of the concrete pump and the metering flat car according to the set program to realize the automation of production.
 
2.2 Technical requirements
 
(1) After the pipe pile is used, the concrete distribution in the pipe pile mold is uniform.
 
(2) The accuracy of measuring the weighing of flat cars and the stability of operation need to be guaranteed.
 
(3) Effective linkage control is required between the metering flat car, the system console and the concrete conveying equipment.
 
(4) When the support of the concrete conveying pipe is lifted, the weighing system measurement cannot be affected.
 
(5) The metering flat car needs to be able to carry a weight of 20t, the speed of 50Hz operation is not less than 35m/s, and the speed is adjustable.
 
(6) There are no less than 20 kinds of pipe pile fabrics stored in the control system.
 
(7) The system has modification authority, and only the manager can modify the process parameters.
 
(8) The system has information related to the display of the fabric process, the cloth process can be displayed online in real time, and the production record can be saved, viewed online and printed.
 
2.3 Scheme selection
 
Conventional concrete pumps have a gate valve pump and a S valve pump. In theory, the gate valve pump is more controllable, but the concrete used for the pipe pile is a C80 formula, and the pump needs to transport about 800 m3 of concrete per day. Judging from the use of the previous gate valve pump, the damage of the wear parts of the gate valve pump is serious, the washing pipe is inconvenient, and the conveying efficiency is difficult to meet the production demand; after comprehensive consideration, it is decided to adopt the S valve pump. Control plan.
 
The control principle of the S-valve pump is: the automatic control system collects the data of the weighing instrument, the encoder, the detection switch, and the pump operation, and controls the operation, the delivery volume, and the metering operation of the concrete pump according to the formula selected on the touch screen. Speed ​​and walking distance, to achieve the uniform accumulation of concrete inside the pipe pile mold, automatically complete the pipe pile fabric.
 
2.4 Equipment transformation
 
The original mold-opening cloth equipment of the pipe pile production line has not adapted to the pumping cloth system. In order to ensure that the S pipe can be taken out during maintenance and replacement, the mixer hopper opening is raised to 30cm above the pump hopper to prevent the pump from feeding. When the pile is clothed, the residual material flowing out from the end of the pipe mold is scattered on the ground, polluting the environment. A surplus material flap is added to the metering flat car to add excess hopper and conveying device on the ground.
 
Considering that the pump must work to ensure its own stability, the four legs of the pump are reinforced and the center height of the pump and the parallelism between the pump outlet and the two rails are adjusted. The rail horizontal error of the metering flat car is adjusted to within 8mm.
 
2.5 Control System Software Structure
 
The software system of pipe pile pumping cloth automatic control system is divided into three parts: HMI man-machine interface, PLC operation control program, fault diagnosis, etc. The software runs on each hardware platform of the system and cooperates with each other through system communication software and communication interface. Coordinate with each other, exchange various data, management and control information, and complete various functions of the entire system.
 
The system reads the display value of the weighing instrument through the RS command, and converts the read decimal ASCI code into a hexadecimal BIN value, stores it in the data register D2040, and participates in the program operation.
 
The control system sets the actual data of the pipe pile fabric and the collection equipment according to the touch screen, and automatically controls the operation of the concrete pump and the metering flat car after analysis.
 
Third, problems and solutions
 
The S-valve pump is easy to be affected by many factors such as concrete pumpability, equipment, operation, etc., resulting in blockage of concrete conveying pipes, which not only affects production efficiency, but also directly affects product quality.
 
3.1 Concrete pumpability problems and solutions
 
(1) To solve the pumpability of concrete, it is necessary to do the gravel grading. The overall large particle content of the crushed stone should not be too large, and it should have good continuity. The needle-like content is less than 5% and the mud content is less than 0.5%. The fineness of the sand is preferably between 2.6 and 3.0. If the average particle size is too small (ie, too much fine sand), the water consumption and cement dosage of the concrete need to be increased; if the average particle size is too large, the sanding rate needs to be increased.
 
Under the premise of improving the workability of concrete, the sand rate can be effectively reduced for production, which can not only solve the delamination of the internal structure of the pipe pile concrete, but also improve the resistance of the pipe pile and reduce the production cost. The recommended sand ratio is controlled between 38% and 42%.
 
When the water-to-gel ratio is too small, the concrete is dry, which is easy to cause pumping. When the water-to-binder ratio is too large, the concrete is thin and the coarse aggregate is easy to settle. It is recommended that the water-to-binder ratio be between 0.32 and 0.35.
 
Concrete can not be excessively pursuing large fluidity due to its favorable pumping. The slump should be guaranteed to be 120~180mm when the mixer is discharging, and the pumping mouth should be controlled between 60~120mm.
 
(2) The gap between the S valve and the glasses plate of the pump is too large, the mortar is easy to flow out from the gap, and the system pressure will be lost during operation to block the pipe. When the gap is too large, the adjusting nut on the swing arm should be adjusted to maintain a certain pre-tightening force of the rubber spring. When the wear is serious, the cutting ring and the glasses plate should be replaced.
 
The diameter of the conveying pipe must conform to the requirements of coarse aggregates, and it must pass through the hole of the tail pipe of the pipe. It is recommended to select the steel pipe with the diameter of ¢159, and ensure that the joints of the pipe clamps are reliably sealed to prevent the pipe from leaking. .
 
(3) The operator needs to control the pumping speed according to the condition of the fabric. When starting the fabric, it should be at a slow speed. When the pumping is normal, it will be transferred to the normal speed. It cannot be blinded quickly. Blindly increase the pumping pressure and cause the tube to be blocked. Always pay attention to the reading of the pumping pressure gauge. Once the pressure gauge reading suddenly increases, the pressure gauge reading suddenly increases. Large, should immediately reverse the pump 2~3 strokes, reduce the displacement and then the positive pump, and return the displacement to the set value after the concrete passes.
 
3.2 Measurement error problems and solutions
 
The pumping cloth system works as a continuous process. While reading the distance of the metering flat car and the weight of the concrete in the pipe mold, the pumping volume and the metering movement are controlled. This measurement error cannot be eliminated; plus concrete conveying The difference between the influence of the pipe pressure and the performance of the pump makes the uniformity of the weight distribution of the concrete in the mold not as stable as the traditional open fabric, especially the small diameter pipe pile is relatively small due to the weight per meter, subject to measurement error. The impact is even greater. Therefore, it is recommended to control the pump displacement to adapt to different specifications of pipe piles. For example, when producing pipe piles with a diameter of 400mm or less, the pump displacement is controlled within 60%; when producing pipe piles with a diameter of 500mm~600mm, the displacement is controlled. Within 85%.
 
3.3 Weighing system and control system problems and solutions
 
The data transmission of the weighing system and the control system has two communication modes: wireless transmission and wired transmission. For pipe pile enterprises, wired communication is required because the harmonics generated by the centrifuge inverter in the workshop interfere with the signal sent by the weighing system wireless communication. In order to ensure the stability of the weighing data, it is recommended to use RS232 wired communication between the weighing system and the control system.
 
Fourth, the transformation effect
 
4.1 Economic benefits
 
The total investment of the project (single equipment) is about 500,000 yuan. After deducting the daily labor cost investment, it is expected that the investment cost can be recovered within two years.
 
4.2 Application effect
 
(1) The number of employees in the workshop fabric work area has been reduced from 8 to 3, reducing the number of employees.
 
(2) By pumping the cloth, the concrete will not fall on the ground, the workshop is clean and sanitary, and dust should not be generated.
 
(3) The quality of the joint leakage is no longer present in the prefabricated piles.
 
(4) The quality problem of the depression of the skirt at the head end of the pipe pile is eliminated, and the skirt is clean.
 
(5) The service life of the clamping bolt is improved; at the same time, the running wheel of the upper and lower molds is closely fitted, and the jumping of the mold is small when centrifugal. Not only does the noise get a certain degree of control, but it also prolongs the service life of the running wheel and centrifuge tug of the mold.
 
Conclusion
 
With the development and progress of the society, when the front-line employees of the enterprise work, the requirements for safety, work environment and labor intensity will become higher and higher. The application of automation technology is one of the key research directions of pipe pile enterprises in the future. This paper introduces the automatic transformation of the pumping and pumping process of the pipe pile, and hopes to attract the attention of the peers and continuously improve and innovate the production process.

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