Discover the essential guide to using slurry pumps in coal preparation plants. Learn best practices, maintenance tips, and optimal operating procedures to enhance efficiency and performance. Optimize your coal processing with our comprehensive insights on slurry pump applications and benefits.

 

In the field of coal washing and processing, with the vigorous development of heavy - medium and flotation coal washing technologies and the in - depth popularization of the concept of closed - loop washing water circulation, coal washing processes are advancing rapidly towards high efficiency and environmental protection. In this process, slurry pumps, with their excellent hydraulic performance and stable and reliable operation, have become indispensable core equipment in all process links of coal preparation plants. The performance of slurry pumps, like the key components of a precision instrument, directly affects the production rhythm and final benefits of coal preparation plants. The primary prerequisite for ensuring the stable performance of slurry pumps is their correct use. From equipment selection to daily operation and maintenance, every link is crucial and determines whether the slurry pump can operate continuously and efficiently in the production line of coal preparation plants.

 

I. Precise Selection: Laying the Foundation for Efficient Operation

Selecting a slurry pump is like custom - making a suitable tool for the production process of a coal preparation plant, which requires comprehensive consideration of several key factors. Head, flow rate, and shaft power are the three core elements of pump selection. They are interrelated and jointly determine whether the slurry pump can adapt to specific working conditions. The production scenarios in coal preparation plants are complex and changeable, and different coal washing links have different requirements for slurry pumps. For example, in the coal slime transportation link, the slurry pump needs to have sufficient flow rate to meet production efficiency and an appropriate head to overcome pipeline resistance; when transporting clean coal, the reasonable matching of shaft power can effectively avoid energy waste.

 

However, in the actual selection process, in addition to the above - mentioned core elements, there are some key parameters that are easily overlooked. Each slurry pump has limitations on the maximum weight and concentration of the slurry it can transport, as well as the characteristics of the maximum particles. Taking the coal slime transportation in coal preparation plants as an example, if the transportation concentration is too high, the resistance in the feed pipe will increase sharply, just like a road blocked by a large amount of debris, making it difficult for vehicles to pass. The increase in this resistance will not only reduce the pump's transportation efficiency but may also cause damage to individual pump parts due to excessive pressure. When the transported particles exceed the maximum value allowed by the pump, these "uninvited guests" will block the impeller flow passage, just like foreign objects stuck between machine gears, causing abnormal vibrations of the pump body and then causing irreversible damage to the flow - through components.

 

Therefore, when selecting a slurry pump for a coal preparation plant, a comprehensive and detailed analysis must be carried out in combination with specific working conditions. It is possible to draw detailed process flow diagrams according to the production requirements of different workshops in the coal preparation plant to clarify the flow rate, head, and other parameters required for each link. At the same time, fully consider the characteristics of the coal slurry, such as concentration and particle size, and select a matching slurry pump model. In addition, a grid that meets the particle - passing requirements of the pump can be set in the pump inlet sump, which is like setting a safety line for the pump body to prevent oversized particles from entering and ensuring that the slurry pump can operate safely and efficiently.

 

II. Standardized Operation: Ensuring Stable Equipment Operation

 

(I) Comprehensive Inspection Before Initial Operation

Before the slurry pump is put into operation for the first time, a comprehensive and detailed inspection is essential, just like a rehearsal before an important performance. First of all, carefully confirm whether the rotation direction of the motor is consistent with the specified rotation direction of the pump. This operation must be carried out strictly in accordance with the instructions of the corresponding model. When testing the rotation direction of the motor, the motor should be separated from the pump for individual testing. It is absolutely prohibited to test the two connected at the same time to avoid damage to the pump body due to the wrong rotation direction.

 

The coupling, as a key component connecting the motor and the pump, must have a complete and correctly installed elastic pad. Otherwise, abnormal vibrations and noises will occur during operation, affecting the stability and service life of the equipment. At the same time, ensure that the motor shaft and the pump's rotation are concentric, which is like making two gears mesh precisely. Only when they are concentric can the smooth transmission of power be guaranteed. When manually turning the pump (including the motor), it should feel light and smooth, without tightness or friction. If there are any abnormalities, the root cause of the problem needs to be investigated in a timely manner.

 

The bearing box is the "lubrication heart" of the slurry pump. Appropriate - type bearing oil should be added to the position indicated by the oil level gauge to provide a good lubrication environment for the bearings and reduce friction losses. Before starting the pump, the shaft seal water (cooling water in the case of mechanical seals) should be turned on in advance, which is like turning on the "cooling system" for the equipment to prevent damage to the sealing components due to excessive friction heat. At the same time, open the pump inlet valve, close the pump outlet valve, and check whether the valves are flexible and reliable, and whether the anchor bolts, flange gaskets, and bolts are firm to ensure that the entire pipeline system is correctly installed and stable.

 

(II) Precautions for Daily Start - up and Operation of the slurry Pump

The start - up process of the slurry pump needs to follow specific operating specifications. Before starting, open the pump inlet valve, close the pump outlet valve, and then start the pump. After the pump is started, slowly open the pump outlet valve. The size and speed of valve opening should be such that the pump does not vibrate and the motor current does not exceed the rated current. This process is like accelerating a car slowly; excessive or too - fast operations may cause impacts on the equipment.

 

For slurry pumps used in series, the start - up process is slightly different. After starting the first - stage pump, the outlet valve of the last - stage pump can be opened slightly (it is appropriate when the current of the first - stage pump motor reaches about 1/4 of the rated current), and then start the second - stage, third - stage, and finally the last - stage pump in sequence. After all the series - connected pumps are started, gradually open the outlet valve of the last - stage pump. Also, pay close attention to the vibration of the pumps and the current of each pump motor to avoid equipment failures caused by improper operation.

 

During daily operation, special attention should be paid to avoiding running the pump when the high - pressure air duct is not closed. High - pressure air ducts are usually installed on the feed pipes of slurry pumps in coal preparation plants near the feed sump. Their function is to stir up the settled materials after the pump stops to prevent blockages at the feed inlet. However, if the high - pressure air duct is not closed or not tightly closed when the pump is running, high - pressure air will mix into the materials. These gases expand in the low - pressure area at the pump inlet and then violently impact the volute and liner in the high - pressure area, like a strong airflow constantly hitting the inner wall of the equipment, accelerating equipment wear. In severe cases, it may even cause the volute or liner to break.

 

Most slurry pumps in coal preparation plants are installed in a flooded suction mode. When a centrifugal pump is working, the absolute pressure of the water flow at the pump inlet will decrease, and the minimum pressure area is near the inlet edge of the impeller. When the pressure in this minimum pressure area drops to the saturated vapor pressure of the critical water pressure value, cavitation will occur. The generation of a large number of bubbles will block the impeller flow passage, disrupt the continuity of liquid flow, resulting in a significant decrease in the pump's head, power, and efficiency, and even a broken flow condition where normal operation is impossible. Therefore, during actual operation, closely monitor the flooded suction height of the pump relative to the free liquid surface in the suction sump to avoid cavitation problems caused by insufficient flooded suction height.

 

It is crucial to install flow meters and pressure gauges in the operation monitoring system to keep track of the running status of the slurry pump in real - time. The flow meter can intuitively reflect whether the pump's transportation flow meets the production requirements, and the pressure gauge can monitor whether the pressure at the pipeline outlet is up to standard. At the same time, always pay attention to the current of the motor to ensure that it does not exceed the rated current. In addition, monitor the operation status of components such as oil seals and bearings in real - time. Once abnormalities such as oil leakage, overheating, or abnormal noises are found, deal with them in a timely manner. Before stopping the pump, close the feed gate first and let the pump run with clean water for a period of time to discharge all the materials in the pipeline to prevent the materials from settling in the feed pipe and volute. Settled materials will not only make it difficult to start the pump again but also cause the pump to shake violently when starting due to the generation of eccentric force and even block the inlet pipeline, affecting the normal use of the pump.

 

The correct use of slurry pumps in coal preparation plants is a systematic project. From precise selection to standardized operation, every link is closely connected. Only by strictly following these usage points can the performance advantages of slurry pumps be fully utilized, ensuring the efficient and stable operation of the production process in coal preparation plants and creating greater economic and environmental benefits for enterprises.

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