1. Industrial Control Abstract : In the process of papermaking with neutral sizing, it is necessary to add trace amounts of additives AKD and PAM in its process. Because such additives are easy to decompose, it is not appropriate to use conventional centrifugal pumps in the process of adding. delivery. The two paper machines were changed from the original acid sizing process to the neutral sizing process. The original use of domestic electric diaphragm pumps, after more than a year of use to reflect the following issues: large flow fluctuations (5% to 10%), flow adjustment difficulties, high failure rate, etc., have a greater impact on product quality costs. For this purpose, a test and control system using a pneumatic diaphragm pump was designed.
2, the working principle
The AKD solution is boosted by a pneumatic diaphragm pump to 0.1 to 0.3 MPa. After being regulated by a voltage regulator to reduce the pulsation, the AKD solution passes through an annular tube flow transmitter to convert the flow rate change value into a current signal. This current signal is input to the regulator. In the regulator, this signal is compared with a given value. After the difference is proportional and integral, the corresponding regulated current is output and input to the electrical converter. The electrical converter converts the current signal into a gas signal, pushes the pneumatic diaphragm-lined plastic regulating valve, and adjusts the opening degree of the valve so as to achieve the purpose of automatically controlling the flow. Because the instrument selects the regular DDZ type instrument to adopt the fixed value adjustment method, so does not describe the instrument type selection and the adjustment parameter hypothesis. In addition, the photo-electric relay installed in the press section of the paper machine reflects the condition of the web break, outputs a contact signal, and controls the opening and closing of the solenoid valve. When the paper breaks, the pneumatic pump temporarily stops working, and the purpose of not adding AKD when stopping the car and breaking the paper is reached.
3, pneumatic diaphragm
Pneumatic diaphragm pumps use compressed air as the power source, which can pump out light for all kinds of particles with high viscosity liquids. It does not require irrigation, suction lift up to 7m, head lift 50m, outlet pressure up to 0.6MPa, good circulation performance, allowing maximum particle size of 1mm, outlet pressure can be adjusted steplessly by adjusting the input air pressure. The diaphragm in the pump completely separates the liquid from the moving parts. Because compressed air is used as a power source, it is suitable for use in flammable, explosive, and humid places.
3.1 The working principle of pneumatic diaphragm pump
In the two symmetrical working chambers of the pump each is equipped with a flexible diaphragm, which is integrated into one body. Compressed air enters the air distribution valve from the air inlet of the pump and pushes the diaphragm in the two working chambers to drive the connecting rod. The two diaphragms move synchronously. At the same time, the gas in the other working chamber exits the pump from the back of its diaphragm. Once at the end point, the valve train automatically introduces compressed air into the other working chamber and pushes the diaphragm to move in the opposite direction, thus creating a synchronized reciprocating movement of the two diaphragms. Each working chamber is provided with two one-way ball valves. The reciprocating motion of the diaphragm changes the internal volume of the working chamber, forcing the two one-way ball valves to open and close alternately, and the liquid is sucked in and discharged to achieve the purpose of boosting pressure.
3.2 Pump Improvement Section
It is known from the working principle that there are two unidirectional ball valves in each working chamber that alternately open and close. The actual operating frequency is 30 to 90 times/min. All of them are made of stainless steel, so the seats and balls wear faster. Generally use 1 to 2 months to leak, boost pressure significantly reduced. For this purpose, improvements have been made to the seats and balls. The seat is modified with nylon material, and the ball body is made of polished glass balls. The service life of the pump is greatly increased through improvement, and the actual trial period can reach 6 to 12 months. Moreover, when the valve seat and ball are damaged, just replace the valve seat and the ball can continue to use.
4, regulator
Since the output pressure of the diaphragm pump is pulsed, the pressure of the fluid is required to be stable in the measurement flow in order to ensure its measurement accuracy. Therefore, the pulsating pressure must be regulated to reduce the pulsation within a certain range. For this purpose, a voltage regulator must be designed. In pneumatic lines, a gas chamber with a certain capacity is generally used, and a fixed volume gas chamber is called a constant volume gas chamber. The increase or decrease in volume as the pressure increases or decreases is called an elastic chamber.
The pressure in the air chamber increases with the amount of gas stored in the air chamber. For different volumes of gas chambers, the same increment of pressure is obtained and the required gas increments are not the same. The volume of gas in a large-volume chamber is larger than that in a chamber with a smaller volume, so it is usually also called a large storage capacity of the chamber and a small storage capacity.
5, ring flow meter
Why trial-production circular flow meter? Because in our plant No. 2 machine is first used is the unit instrument LZS-type electric rotor flow transmitter. Due to its structural reasons, it is often blocked by impurities in the AKD solution during actual use, affecting the normal operation of the system, and the amount of maintenance is large. Therefore, the differential pressure transmitter is used as a transducer, the annular tube is a sensor, and a ring is reformed by itself. Flow meter. The actual use of plugging was resolved.
The measuring principle of the loop tube sensor is based on the fluid flowing in the curved tube, which forces the fluid to flow along the curve. The liquid has centrifugal force and acts on the tube wall. The magnitude of the centrifugal force is related to the flow velocity and the bending radius and can be detected by the pressure increase in the tube wall.
Dongguan HengTaichang Doors Co, Ltd. , https://www.dghtcdoors.com