Analysis of the wear of the bearing position of the roller press and online repair technology exchangeDate: 2019-07-04 Views:
The roller press is one of the important equipments in the cement production process. It is mainly used for the rolling of cement clinker. Some cement companies also use roller presses instead of cement vertical mills for rolling limestone. Once the roller press fails, the impact on the entire cement production line is very large, which will cause huge economic losses to the enterprise.
In the failure of the roller press, the bearing wear of the roller press is one of the most common problems, and it is also the most difficult problem for the enterprise to solve. Because the weight of a single roller of a roller press is often between 30-50T, it is very difficult to disassemble and transport, which is very time consuming, and the comprehensive cost of offline repair is generally not less than 200,000 yuan. The repair cycle is also relatively long, generally no less than 15 days of repair cycle. If the repair work is carried out during the maintenance period, the impact on the company will be relatively small, but if it occurs in the normal production stage, the impact will be very large. So how to solve the problem of bearing wear in the field with high efficiency and high quality is very important.
After the emergence of Sole carbon nano-polymer material repair technology, it solves the problem of on-site repair of the bearing position of the roller press. It does not require a lot of disassembly, only the bearing seat and the bearing need to be disassembled, and the whole repair cycle It will be completed within 24 hours.
1. So why is there any wear on the bearing position of the roller press? What is the root cause?
For the reason of the bearing wear of the roller press, I will introduce a case to you. From this case, you may see some fundamental problems:
An engineer from Sole Industry went to a state-owned cement group to solve the bearing wear problem of the 1800-1600 roller press in Hefei. The main parameters of this equipment are 1:12 taper shaft, the bearing position is small neck size 900mm, the wear width is 500mm, and the bearing wear depth is 4-5mm.
At the scene we found a phenomenon where two employees used tools to clean the mud in the bearing housing (mixture of grease and clinker powder), and a trolley was parked next to the bearing housing. After about 1 hour, the mud of the entire bearing housing was cleaned. Clean, and the amount of sludge that was cleaned up was amazing, a whole cart. How did these sludges form? After careful inspection, it was found that the seal of the bearing housing was completely damaged, and the sealing groove was worn out so that a large amount of clinker dust entered the bearing housing and mixed with the lubricating grease to form a large amount of sludge. The CEOs who were present at the time were shocked and engaged in the cement industry for the first time in decades. In the on-site communication, our engineers learned that the company needed to replace the new bearings every year, but never changed the retaining plates and seals. Barrier failure and seal failure are the root causes of bearing damage.
The bearing position of the roller press is generally 1:12 cone or 1:30 taper shaft, and the bearing position of a small number of roller presses is a straight shaft. Most of the bearings used are 2 series double row self-aligning bearings, and N series cylindrical roller bearings are used in a small number of parts. The friction coefficient of the bearing itself is very small. When the bearing is in normal operation, the shearing force in the circumferential direction of the mating surface of the bearing inner ring and the bearing position is relatively small, but an abnormal situation occurs between the bearing ball, the cage and the roller table. Then, the shearing force in the circumferential direction of the mating surface of the inner ring of the bearing and the bearing position will increase instantaneously. When the shearing force is greater than the pre-tightening force between the inner ring of the bearing and the bearing position, then the relative movement between the bearing inner ring and the bearing position occurs, resulting in the wear of the bearing position of the roller press.
After years of repairing the bearing wear of the roller press, we summarize the following reasons for your reference:
(1) Roller end face baffle scouring wear: In order to prevent the clinker or raw meal powder from entering the bearing in a large amount during the normal operation of the roller press, a baffle plate is arranged at both end faces of the roller. After the surface of the baffle is worn and washed by long-term dust, the perforation will be damaged. This will cause a large amount of dust to flow into the seal of the bearing end cap, and the wear of the end cap seal will be invalid, so that the dust enters the bearing from the seal, resulting in A series of problems such as increased friction coefficient between the balls, the cage and the roller table, poor bearing operation, increased running resistance, and bearing heat generation occur. As the amount of dust increases continuously, the friction between the inner part of the bearing is greater than the pre-tightening force between the inner ring of the bearing and the bearing surface of the bearing, which causes the inner ring of the bearing to rotate, causing the bearing position to wear and the bearing in a short time. Damage
(2) Seal failure: The sealing form of the roller press is generally a rubber ring seal. The position near the shaft head is generally a seal, and the seal on the rear shoulder is generally two seals. The sealing ring is in direct contact with the rear shoulder seal ring and is lubricated by grease to reduce the friction coefficient. Therefore, once dust or other foreign matter enters between the sealing ring and the sealing ring joint surface, the two-way wear of the sealing ring and the sealing ring will result, and finally the sealing gap will increase, the sealing will fail, and a large amount of powder is poured into the bearing;
(2) The pressure plate is not fastened for a long time: the inner ring of the roller bearing and the bearing are generally matched by a taper surface. The common taper is mainly in the form of 1:12 and 1:30. The excellent taper fit is easy to disassemble and mount the bearing, especially for large equipment such as roller presses. However, the taper fit has certain defects. During the running vibration of the equipment, the taper mating surface is easy to loose and the pre-tightening force is reduced. Therefore, if the inner ring of the bearing cannot be tightened in time or periodically, the pre-tightening amount between the mating surfaces will eventually disappear; therefore, it is necessary to periodically tighten the bearing to lock the platen. It can be tightened to the specified torque each time, and cannot be blindly fastened;
(3) The bearing is in long-term operation and cannot be replaced in time: the bearing will be used for a long time, and its running clearance will increase continuously. When the clearance increases to a certain extent, the vibration of the equipment will also increase. Increased vibration of the equipment will also have a devastating effect on each part, thus entering a vicious circle. Therefore, it is very important to periodically check the bearing running clearance and develop a reasonable bearing replacement cycle;
(4) Overload production: The cement market is very good in 2018, and the benefits are objective. Some enterprises will overload production in order to increase production. For example, a daily production capacity of a 5000T production line will increase to more than 6000T, which will inevitably increase the load of the equipment, even exceeding the performance specifications of the equipment design. The failure rate of the equipment will increase continuously over time;
(5) Metal fatigue wear: metal fatigue wear is a metal characteristic, this phenomenon cannot be avoided, and the cycle of fatigue wear can only be extended by reasonable use and maintenance;
(6) Design problem: The roller press that we came into contact with, the worn bearing position is mostly 1:12 cone, and the small part is 1:30 taper axis. This is definitely not an accidental phenomenon. We believe that in addition to the above analysis reasons, taper design is also one of the inevitable factors affecting the use of bearing positions. The 1:30 taper ratio is smaller than the 1:12 taper, so that the bearing is easier to tighten in place, and the pre-tightening force between the inner ring of the bearing and the shaft mating surface is also larger. At the same time, the bearing position of the 1:30 cone is matched with the bearing, and the inner ring of the bearing is not easy. Loose. The bearing position of the 1:12 cone is matched with the bearing, and the bearing is prone to looseness.
2. How to judge the bearing wear of the roller press during the operation of the roller press?
(1) The radial displacement and axial displacement of the roller bearing housing increase, even offset, accompanied by severe vibration, at which time the bearing position is worn or the bearing is damaged;
(3) Mark the pressure plate and the inner ring of the bearing, and check the relative position of the two marks regularly. Once the position changes relatively, it indicates that the inner ring of the bearing is loose or worn and needs further treatment.
(4) Abnormal bearing temperature: the bearing temperature continues to rise, the cause of bearing wear occurs, the bearing inner ring and the bearing position directly slide and friction cause the temperature to rise continuously; the cause 2 bearing lubrication problems; the cause of the three bearing damage; The water cooling system has failed;
3. Then, after the bearing position of the roller press wears, how to carry out online repair work?
We believe that the online repair roller press bearing position must first ensure the following data:
(1) Concentricity: The repair of any shaft ensures that the concentricity after repair is essential. If the concentricity deviation is too large, it will cause equipment vibration, which will reduce the service life of the repaired part and cause serious impact on the bearing and other parts of the equipment.
Our method of ensuring concentricity is to use the front and rear shoulders of the roller press as a basis for repair, and to process the sample ruler according to the original drawings of the equipment. The sample ruler is processed by the wire cutting process, so the overall error is small; the sample gauge is used as the standard gauge to measure the specific wear dimension of the bearing position, then the spot is welded on the surface of the shaft, and the height of the anchor point is found through the template ruler. The positioning points are evenly distributed in the circumferential direction, so as to ensure that the positioning points after positioning of the bearing are used to position the concentricity. Because it is on-site repair, there will always be some error in accuracy, and the overall deviation of concentricity will not exceed 0.2mm. The rotation speed of the roller press is generally between 100r/min and 200r/min, so the deviation within 0.2mm does not affect the normal operation of the roller press;
(2) Complete taper surface: Before we used the sample ruler and the positioning point to locate the concentricity, then we use the bearing inner ring as the repair tool to complete the repair of the bearing taper surface. Sole carbon nano-polymer material SD7101H is a paste, which has good thixotropic properties and is easy to form. In this way, the mating surface of the mating surface and the inner ring of the bearing can be 100%. The larger the matching area, the more uniform the force is, and the effect is better;
(3) Pre-tightening amount: The pre-tightening amount is reserved for the bearing position of the roller press. According to different journals and different taper, the pre-tightening amount is usually between 10-20mm. The pre-tightening amount is generally between 5-10 mm. This not only ensures the pre-tightening force when the bearing is installed, but also leaves a certain margin for the later tightening of the bearing;
(4) Pre-tightening force: The new roller bearing is fastened by means of a hydraulic system to open the inner ring of the bearing and then to the shaft. However, once the bearing position wears out, the hydraulic mounting system can no longer be used because there is a gap between the mating surfaces, and the holding pressure cannot be achieved. After the repair of Sole carbon nano-polymer material is completed, the previous bearing assembly method should be changed, and the inner ring pressure plate and bolts of the bearing should be used for fastening. Of course, the fastening process should be tightened according to certain rules, and the pre-tightening force should be Depending on the play, not on the design torque;
(5) Bearing clearance: The bearing clearance can be viewed in the national standard. We recommend that the clearance after tightening be larger than the value specified by the national standard.