introductory

The coal slurry water treatment system of our mine consists of three parts: main washing slurry, dynamic screening slurry and mine water slurry. Due to the geological conditions of the underground, the content of mudstone and ultrafine particles gradually increases, which puts more pressure on the coal slurry water treatment.

1 Problems with the system

(1) filter press head plate travelling thrust device running work, head plate positioning gate and plate fixing device appeared many times damaged, positioning gate up and down movement is easy to jam, monitoring device is not perfect, found not timely will top bad head plate and hydraulic cylinder, resulting in electromechanical accidents.

(2) The operation between the filter press and the feed pump and scraper is not perfect, which brings extreme inconvenience to the electromechanical maintenance work and the operation of the production personnel.

(3) Filter press work into the blowing procedure when the feed valve is not closed tightly generated backflow caused by the feed pump reversal damage to the mechanical seal of the accident, the economic losses and maintenance efforts greatly increased.

(4) Filter press in the implementation of the press procedure when the blowing valve and the return valve switching time is not coordinated in the discharge of material so that the residual pressure generated inside the filter chamber can not be released resulting in the spraying of material between the filter plate to pollute the environment and the filter cloth is seriously damaged.

2 Four adaptations made to the control system

2.1 The transformation of the stop-promotion plate device mobile cylinder frame, stop-promotion, compression plate for the trinity, is an important part of the fast-opening filter press. In each cycle after the completion of the clamping plate to play a role in the positioning of compression. Position monitoring point is achieved by the proximity switch inductive signal, the original design of walking stop pin device is by the motor sprocket toothed plate traction stop pin up and down to move the work, the failure is easy to come out of the reason, the motor brake working frequency is high, the phenomenon of braking failure, in the process of walking is not in place in the process of the automatic fall of the accident, stop pin lugs rotating chamfer is small, in the process of vertical fall of the inclination of deflection, resulting in the top of the bad stop pin plate The rack and pinion lugs are ruptured and deformed, the monitoring device is not perfect, the proximity switch signal cannot be detected when the mobile cylinder frame is displaced, and the stop pin is not in place when the compression procedure is executed, resulting in serious deformation of the hydraulic cylinder bracket and serious accidents of distortion and deformation of the connection between the hydraulic cylinder head and the head plate. After on-site research and observation confirmed that the walking stop device to improve the perfect, the motor sprocket drive instead of two hydraulic cylinders, respectively, traction two stop pin plate, to avoid the stop pin up and down to avoid the occurrence of the accident of the phenomenon of vertical tilt deflection phenomenon, motor brake failure malfunctioning accidents, the monitoring and control points from the original two proximity switch monitoring to increase the number of proximity switches to monitor the four monitoring points, to avoid the occurrence of the accident due to the two Hydraulic cylinder movement is not synchronous, a stop pin in place and the other stop pin is not in place, in the pressure of the hydraulic cylinder and bracket caused by serious deformation damage accident, the movement of the hydraulic cylinder is by adding a hydraulic station through the bidirectional solenoid reversing valve to achieve the efficiency of more than 98%. The return signals of the four Dc24V proximity switches do not directly enter the PLc input point, the system adopts the isolation design technology, the switching quantity is isolated by relay, which completely puts the host part of the monitoring system in the floating state, and better solves the problem of false starting and stopping of the equipments that may be caused when the signal sensing voltage is high, and the system is strong in anti-jamming ability and high in reliability. The return signal of the proximity switch is connected to a Dc24V small relay, the normally open point of the intermediate relay connected to the two upper proximity switches SQl and SQ2 is connected in series with the DC+24V power supply and input into PLcl2 and 2 points, the normally open point of the intermediate relay connected to the two lower proximity switches SQ3 and SQ4 is connected in series with the Dc+24V power supply and inputted into PLcl2 and 3 points, and the PLc outputs the execution command points 002 and 007, which are connected to two small relay points respectively. PLc output execution command point 002, 007, respectively, connected to two small relay Ac220V, so that the two relays open point to open and stop the pumping station motor 2 and the implementation of the forward and reverse solenoid reversing valves, so that after the transformation, in the case of the original PLc control points unchanged to achieve the purpose of the control, so that the system operates more smoothly, with high reliability, accident rate is low for the original more than 80 per cent, and greatly reduces the intensity of the work of the mechanical and electrical repair.

2.2 Modification of the operation mode of the quick-opening filter press and the feeding pump SA changeover switch has three operation modes: "local", "centralised control" and "automatic". Sw a 16 type.

(1) When the change-over switch is playing from the centralised position: (1, 2), (5, 6) two pairs of contacts are closed, the rest of the contacts are disconnected.

(2) When the change-over switch is hit from the local position: (3, 4), (7, 8) two pairs of contacts are closed, the rest of the contacts are disconnected.

(3) When the change-over switch is playing from the automatic position: (9, 10), a pair of contacts closed, the rest of the contacts are disconnected. Because of the original way to limit the efficiency of the work, after the transformation, can achieve logic control, chain control, off-site control. Because the feed pump, scraper conveyor and fast open filter press three equipment in the plant on the downstairs layout, the operation of the three equipment to the post production staff to bring great inconvenience, in different cases, start and stop the way is not the same, before the transformation, feed pump, scraper conveyor in the operation of the ground floor, when the filter press to be completely pressed to open the feed pump, resulting in the work is not coordinated to increase the labour intensity of workers, the safety coefficient is low. After the completion of the transformation, in the centralised control cabinet to add a changeover switch "three" operation, when the changeover switch to play from the local position, can be operated locally into the feed pump, scraper single machine operation. When the changeover switch is played from the centralised control position, the feeding pump and scraper can be operated beside the filter press to start and stop. When the change-over switch is played from the automatic position, there is no need for manual intervention, and the quick-opening filter press automatically starts and stops the feeding pump and scraper for each cycle, which can be switched smoothly without affecting each other. It is easy to operate and fully automated.

2.3 Feed valve control transformation fast-opening filter press feed into the head plate and tail plate both sides of the common feed two ways, feed valve has two valves 1#, 2#, such as the two valves are not closed tightly or the operation is not sensitive, it will feed slurry pumps pose a serious threat to the feed is completed, the feed valve is closed into the press, blowing, this time, the system high-pressure wind pressure reaches 0.6MPa, if the Valve closure is not tight, the system pressure will be through the valve gap, into the pump body, so that the feed pump reverse rotation, resulting in pump impeller loose and mechanical seal leakage damage. Therefore, considering the seriousness of the accident, it was taken to replace the pneumatic ball valve with a hydraulic gate valve. After the transformation is completed, the filter press in the work will not be due to the valve is not closed tightly caused by the system pressure backflow caused by the feed pump reversal phenomenon occurs, to solve the feed pump due to the generation of reflux caused by the pump body and mechanical seal damage accidents occur. The system runs smoothly, the accident rate is greatly reduced to more than 95%, the operation is convenient and flexible, and it meets the requirements of production monitoring and management well. Electrical control principle: the original design of the feed valve for pneumatic ball valves and PLc programme is designed for a single open valve output point, the ball valve closes by high-pressure wind into the solenoid valve power failure reset state closes itself. The hydraulic gate valve is different, each valve with a hydraulic station, by controlling the motor forward and reverse to achieve the switching valve, with manual and automatic operation.

2.4 Return Valve Control Modification The return valve is used when the fast-opening filter press enters the blowing procedure after the feeding is completed, the function is that when the blowing is completed, the blowing valve and the return valve are opened at the same time, and the feeding valve is closed, and the high-pressure wind enters into the inside of the filter press, and the residual slurry water in the feeding channel between the filter plates enters into the feeding drum through the pipe of the return valve to provide the use of slurry water for the second feeding and ensure that there is no leakage, and the high pressure wind is synchronised with the closure of the return valve when the blowing is completed. When the blowing is finished, the closing of the blowing valve and the return valve is synchronous. The disadvantage is that due to the difference in time, the residual pressure generated by the high-pressure air system into the filter press is not completely released, so that the filter press has a certain internal pressure. When the programme enters the released state, the oil cylinder releases pressure, while the internal residual pressure and coal sludge water mixed gas is ejected through the gap between the filter plate, causing serious damage to the filter cloth, and the coal sludge water mixed gas causes pollution of the environment, resulting in the safe operation of the equipment. Therefore, through the EM223, PLc021 output point connected to an intermediate relay, so that the intermediate relay of the normally closed point connected to a digital time relay, with the time relay of the delayed disconnection of the normally closed point to control the reflux valve shutdown delay control, and the reflux valve is a pneumatic ball valve, closed by the high-pressure wind power failure to close themselves, by adjusting the time relay to control the reflux valve lagging blowing the valve closing time, so that reflux valve closure By adjusting the time of the time relay to control the return valve lag blowing valve closure time, so that the return valve closure lag blowing valve 10 seconds. Waiting for the system pressure to be completely released before closing the valve, thus avoiding the phenomenon of damage to the filter cloth and pollution of the environment due to the difference in the switching time of the reflux valve. After the modification, the system runs safely, stably and reliably, avoiding the economic loss caused by damage to the filter cloth and improving the production efficiency.

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