Study On The Erosion Form Of The Nitrile Rubber Based On The Screw Pump

At the beginning of the screw pump's operation,in order to ensure the volumetric efficiency the interference fit was set between the rubber stator and the metal rotor caused large extrusion.In the running process,Metal rotor carrying crude oil with sand wore with rubber stator.With the wear of rubber stator the interference between the stator and the rotor reduced,then the interference fit was changed to the clearance fit gradually.In the clearance fit,the rubber stator was worn and the volumetric efficiency was decreased because of the cutting effect of the sand.When the rubber wear to a certain extent and the displacement did not meet the requirements,the screw pump was scrapped.In the process of interference fit-clearance fit-screw pump was scrapped,its life and rubber's wear resistance were closely related.At this stage,people have carried out the two body wear and three body abrasive wear of the rubber seal,the development of rubber seal's formula,and made a lot of research results.But there is no abrasive erosion of rubber stator based on failure process of screw pump.In this paper,the abrasive erosion behavior of nitrile-based stator rubber is studied under different interferences and clearances with self-developed friction and wear testing machine.The effects of different interferences,clearances and sands on the impact of rubber erosion are investigated and the surface morphology of rubber is observed.The results showed that as the interference increased,the friction temperature and wear loss of NBR are increasing,and the time required for the frictional torque to reach stabilization increases first and then decreases and reaches a peak at 0.6 mm.The friction is relatively flat when the interference is small and increases sharply when the interference is large.The reason for this is that the contact pressure of the rubber surface is large,the friction heat softens the rubber,the adhesive wear occurs and the gluing phenomenon occurs.In the crude oil medium containing sands,friction and wear of NBR are reduced first and then stabled with the increase of interference.The sands in the crude oil produce the plowing effect on the surface of rubber,forming scratches and pits on the surface.In the clearance fit,the friction and wear loss of NBR are reduced sharply first and then stabled with the increased of clearance.With the increase of the sands' size in the crude oil,the contact area between the sands and the rubber surface increases,and the friction and wear loss of NBR are increasing.In the clearance fit,the wear loss with sharp sands under the crude oil medium is greater than that with round sands.The reason is that the sharp sands have more cutting edges,which are more easily pressed into the rubber surface,and the cutting effect on the rubber surface is obviously.The research in this paper not only has important research value to the development of the theory of rubber abrasion,but also has practical significance to improve the useful life of the liquid transportation equipment such as the screw pump.