Analysis of the cause of twin-screw pump failure, sincere help!
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The P37101C screw pump plate in the heavy oil tank area pump room does not move. 1. Basic equipment conditions and performance parameters of P37101C: The pump feeds material from the storage tank and loads the tank truck through the screw pump. It operates intermittently and has no filter at the inlet. model: 2RLG178 * 80-1.7-A1-1000 rated power: 110KW rated speed: 1000r/min medium: Asphalt temperature: 130~150℃ outlet pressure: 1.7MPa flow rate: 120m3/h. The gap between the shell and the screw sleeve is 0.2mm. It is a built-in twin-screw pump. The synchronization gear is in the middle and the bearing is built-in and lubricated by the medium. 2. The last failure occurred on September 26, 2018. The screw pump needed to be disassembled and inspected because the disc did not move. Returned to the factory for repair, the cause of the failure was that hard metal particles in the tank entered the bearing and the gap between the screw sleeve and the wall panel, causing damage to the bearing and wear of the horizontal surface of the screw sleeve and the wall panel. On November 8, the pump was turned and stuck again. After disassembling the pump and inspecting it, it was found that the phenomenon was consistent with the previous failure. (1) The inner ring of the coupling side support bearing NU214 (NSK) is severely worn, as shown in Figure 2, and the rolling elements are severely worn. (2) The bearing positions on the main and driven shafts have varying degrees of wear, and the wear on the coupling side of the driven shaft is more serious. See Figure 4. The bearing position on the non-coupling side of the driving shaft is slightly worn, as shown in Figure 5. Check that the spindle runout value at the positioning ring is 0.10mm, which does not meet the requirements of the Maintenance and Inspection Regulations for Screw Pumps SHS01016-2004 that the spindle runout should not be greater than 0.05mm. Other runout values meet the requirements. (3) The screw sleeve and cylinder liner are rubbed. See Figure 6, the shell bushing is adhered and worn, see Figure 7, the screw sleeve is adhered and worn. (4) Conduct a metal magnetism experiment on the remaining asphalt blocks in the pump cavity to see if they can be adsorbed on magnets. (5) Conduct spectral analysis on the adhesion and unworn parts of the screw sleeve respectively. See Figures 9 and 10. The adhesion is iron alloy and the shell is ht250. It cannot be judged whether it is welding slag. The unworn part is nitride steel 38CrMoAl, which is consistent with the material of the screw sleeve marked on the manufacturer's drawing. (6) Carry out hardness testing on two bearings respectively (one set of bearings with macroscopic visible wear, and one set of bearings with no obvious macroscopic wear). The test results are shown in Figure 11 and Figure 12. The Rockwell hardness is approximately HRC45-HRC57, which does not comply with the general technical rules for rolling bearings GB307.3.: Ordinary bearing hardness requires that the hardness of the bearing outer ring, rolling elements, and bearing inner ring be HRC61-HRC 65.
This post was last edited by CHANGBAISHI on 2018-11-22 09:49 Failures of this type of pump are mostly caused by bearing damage. If there is no other reason to replace the bearings. In addition, it is best to install a filter with a larger filtration area. This part of the gear mesh is a vulnerable part. Turning the car does not move, disintegration is necessary no matter what.
This post was last edited by 1070273960 on 2018-11-22 10:09 Hello, we are a manufacturer of twin-screw pumps. First, confirm whether the transported materials are clean? Then analyze the cause of the pump. But judging from your reaction. The biggest problem is the built-in bearings and gears, so even if the bearings are replaced, it can only be dealt with for a period of time. An external bearing pump should be used.
1. The inlet filter cannot be missing； 2. This is the first time I have seen the built-in setting of the synchronization gear. I don’t know what the manufacturer’s considerations were for this design.
The bearings are placed inside, the gears are placed inside, and only one set of mechanical seals can be used.
The media is too dirty, causing the bearings and transmission teeth to wear!
Mainly there is no filter. Considering the transportation of asphalt, it is recommended not to use a screw pump. Is it better to use a centrifugal pump?
On the surface, the built-in bearing gear only requires one set of mechanical seals to facilitate maintenance. However, the bearing gear must also be considered. Ensuring the normal operation of the bearings and gears has always been the priority of each pump (unless the medium is very clean and the lubricity is very good, and the built-in type can be used). It is better to use four sets of mechanical seals with slight leakage than to put the bearing gear in a dangerous situation and cause damage to the pump, which will cause greater losses to production and maintenance.
study* Yes, the plan has changed next year. I wonder if the centrifugal pump can be used to pump asphalt? Or use an external screw pump?
This post was last posted by 3983596_FPPZ edited on 2018-11-24 09:04 It is strongly not recommended to use centrifugal pumps with this viscosity of asphalt. Once the asphalt solidifies when shut down, it will become a pile of scrap metal. It is better to find solutions to the problems that occur with the screw pump.