In modern industrial production, material conveying is a crucial link, and screw conveyor, as an efficient and practical conveying equipment, is widely used in various industries. From the inter-process transfer of grain and flour in grain processing, to the continuous supply of raw materials to the kiln or mill on the cement production line; from the transmission of all kinds of materials between reactors in the chemical industry, to the waste treatment of waste efficiently sent to the treatment equipment, the figure of the screw conveyor is ubiquitous, which greatly improves the production efficiency and reduces the labour intensity .
Screw conveyor is mainly composed of screw shaft, screw blade, bearing and transmission device. When the motor drives the screw shaft to start rotating, the screw blades act as diligent porters, pushing the material slowly from the inlet and conveying it forward along the conveying pipeline. In this process, the material seems to be given forward momentum, driven by the spiral blades, moving forward towards the discharge port in an orderly manner. Moreover, through the clever adjustment of the spiral chamber pitch, inclination angle and other parameters, it can also be flexibly adapted to different materials and conveying needs.
However, although the screw conveyor for industrial production has brought a lot of convenience, but in the process of long-term operation, but also inevitably encountered a variety of failures. Next, let us understand the common faults of screw conveyor.
一.Common faults and solutions
1.Plugging dilemma
Screw conveyor plugging is one of the more common failures, and its causes are manifold. Improper selection of parameters may be the main reason, if the rotational speed of the screw conveyor is too fast, the material will be quickly thrown to the trough wall in the conveying process, and it is difficult to convey forward smoothly, which leads to the accumulation of materials. And in terms of operation, non-standard operation will also trigger the problem of material blocking. Start with a load when starting, or in stopping the material is not unloaded on the stop, as well as conveying the process of material input is not uniform, discontinuous, may make the material in the trough gradually build up, and ultimately lead to clogging. The characteristics and condition of the material itself should not be ignored. When the material contains debris, or conveying a large number of fibrous materials, these debris and fibres are prone to intertwine with each other, impeding the normal flow of materials, which in turn triggers the blockage. For example, in the grain processing process, if the grain is mixed with sisal rope, stones and other debris, it is very likely to lead to screw conveyor plugging.
For the plugging problem, we can start from many aspects. In the parameter selection, we should fully consider the characteristics of the material and conveying requirements, and reasonably determine the rotational speed of the screw conveyor and other parameters to ensure that the material can be transported smoothly. Strictly comply with the operating procedures is essential, when starting must do no load start, to avoid the motor to withstand excessive starting current; feeding process to ensure continuous and uniform, can be installed vibrating feeder to assist in achieving this goal. In the feeding, should gradually increase the amount of material, slowly reach the rated conveying capacity, to prevent all of a sudden fierce feeding lead to blockage and equipment wear. Increase the discharge port or lengthen the end of the chute, can also effectively solve the problem of poor discharge and too late to discharge the material. Install a small section of counter-rotating blade at the end of the trough of the discharge port, which can prevent the end of the blockage. Necessary cleaning of the material entering the conveyor is equally critical, to remove large or fibrous impurities in advance, to avoid their entry into the machine caused by clogging.
2.Motor failure
Drive motor as the power source of the screw conveyor, once the failure, the conveyor will fall into the ‘strike’ state. Motor burnout is a more serious failure, there are two main reasons. When the material is mixed with hard lumps or small iron, these foreign objects will jam the reamer, so that the motor instantly withstand huge resistance, the current increases sharply, thus burning the motor. The incoming material is also an important cause of motor burnout, when the amount of incoming material exceeds the load capacity of the motor, the motor will heat up due to prolonged overload operation and eventually burn out. In the cement production line, if a large number of limestone and other raw materials suddenly flooded into the screw conveyor, it may make the motor overwhelmed.
In order to protect the motor from being burned, first of all, we should prevent foreign objects such as small iron pieces from entering the conveyor, so as to avoid them from jamming, resulting in a sharp increase in the motor current. In the process of equipment operation, we should always pay attention to the situation of the material, once found that there are foreign objects mixed in, should immediately stop to clean up . Ensure balanced feeding is also the key to avoid too much incoming material, such as motor overload operation. You can install flow control device to precisely control the amount of feed to ensure that the motor is always working within the rated load. Before shutting down, be sure to send the material to finish, to prevent the accumulation of material in the machine, to the next start-up difficulties, but also to reduce the start-up load of the motor.
3.Shaking of the casing
When the screw conveyor is running, sometimes the case is seen to be wobbling, which is because the centre line of each spiral section is not adjusted to a concentric state when it is installed. When the screw shaft rotates, the eccentric part will produce friction with the inner wall of the casing, which leads to casing shaking. The casing wobble will not only affect the stability of the equipment, but also may increase the wear and tear of the casing, shortening the service life of the equipment.
If the casing is found to be wobbling, it needs to be reinstalled to find the correct centreline. In the installation process, use professional measuring tools, such as latitude and longitude, level, etc., to ensure that the centre line of each spiral section is precisely concentric . At the same time, check the connection parts between the spiral joints to ensure that the connection is firm and there is no looseness or misalignment. In routine maintenance, it is also necessary to regularly check the stability of the casing, timely detection and treatment of potential problems, to avoid greater damage to the equipment caused by the shaking of the casing.
4.Bearing heating
The suspension bearing plays an important role in connecting and supporting the screw shaft in the screw conveyor, however, it sometimes experiences excessive temperature rise. This is mainly due to improper location installation, resulting in material stagnation in the connection during the conveying process, increasing the pressure of the connection, and under the load condition, the bearing will heat up. Hard and large objects mixed into the machine is also one of the causes of high bearing temperature rise, these foreign objects will produce abnormal friction when passing through the suspension shaft connection, which will increase the bearing temperature. If not dealt with in time, the bearings may be damaged, affecting the normal operation of the screw conveyor.
When the temperature rise of the suspension bearing is too high, it is necessary to adjust the position of the suspension bearing in time so that it is installed correctly and the retention of materials in the joint is reduced. In the adjustment process, it is necessary to operate in strict accordance with the installation instructions of the equipment to ensure the positional accuracy of the bearings. Cleaning up foreign objects is also an essential step, to carefully check whether there are hard and large objects mixed in the machine, if so, it should be cleaned up immediately, and then test run until normal. When cleaning up foreign objects, pay attention to safety to avoid injury to equipment and personnel.
5.Material overflow
Overflow is also one of the common failures of screw conveyor, and high moisture content of material is an important reason. When the moisture content of the material is too high, the moisture will collect on the screw hanging bearing and gradually thicken, making it difficult for the incoming material to pass through, just like a water pipe being blocked, and the material will overflow at the inlet. The debris in the material makes the screw bearing clogged, which will also lead to the material can not pass smoothly, and then overflow. Transmission device failure, not found and dealt with in time, will also make the material in the machine accumulation, and ultimately overflow. In some material conveying process, if there is no strict control of the moisture of the material, or not clean up the debris in the material in a timely manner, it is easy to machine overflow.
For the overflow problem, first of all, we should strengthen the drying of raw materials, reduce the moisture content of the material, to avoid the moisture in the spiral hanging bearings set, affecting the passage of the material. You can use the dryer and other equipment to pre-treat the raw materials to ensure that the moisture of the material meets the transport requirements. Shutdown to clear the machine debris is also very important, we should regularly check whether there are debris in the material, once found, should immediately shut down to clean up, to prevent debris clogging the spiral hanging bearing. When the transmission device is out of order, it is necessary to stop the machine in time to repair, to avoid the accumulation of materials in the machine overflow. When repairing the transmission device, select professional maintenance personnel, use the appropriate tools and accessories to ensure the quality of repair.
6.Input shaft section fracture
The fracture of the input shaft section of the spiral shaft is mainly caused by the excessively poor coaxiality during installation, or the low safety factor when selecting the shaft. When the coaxiality is super poor, the input shaft will be subjected to extra torque and stress during operation, which will easily lead to fatigue fracture of the shaft. The low safety factor when selecting the shaft means that the bearing capacity of the shaft is insufficient, and when it encounters a larger load, it is prone to fracture.
For the problem of fracture of the input shaft section of the spiral shaft, it is necessary to adjust the coaxiality and adopt the method of stop positioning to ensure that the bearing boxes on both sides of the cylinder are concentric. In the installation process, the coaxiality error should be strictly controlled to ensure that the input shaft is uniformly stressed during operation . The material of the shaft head should be selected as high-strength material to improve the bearing capacity and anti-fatigue performance of the input shaft. Suitable high-strength alloy steel or other high-performance materials can be selected according to the specific working conditions and load requirements of the equipment. In routine maintenance, the operation of the input shaft section should be checked regularly, and potential problems should be found and dealt with in time, so as to avoid the serious impact on the equipment caused by the fracture of the input shaft section.
Screw conveyor plays an indispensable role in industrial production, however, its common failures such as material blockage, motor burnout, casing shaking, etc., will adversely affect the productivity and equipment life. By deeply analysing the causes of these failures and adopting targeted solutions, such as reasonable selection of parameters, strengthening equipment maintenance, strict compliance with operating procedures, etc., the occurrence of failures can be effectively reduced to ensure the normal operation of the screw conveyor.
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