With the rapid development of modern industry, more and more special conditions & structures appeared, various non-standard bearings are needed due to the restriction in special circumstances. Bearing for crank arm of mud pump is a kind of special structure designed by our company. The mud pump drives the crankshaft to rotate through gear, meanwhile drive the piston to make reciprocating movement through the connecting rod of crankshaft and pistion, thus to achieve the pump’s work.
１　Crankshaft bearings
　　It can be seen from Picture 1, there exists larger radial impact load when the piston is making reciprocating movement , so the crankshaft adopts cylindrical roller bearing which can withstand greater radial impact load. Due to the limitaions of crankshaft structure, the overall bearing can not be installed, it requires to use split structure or bearing with adapter sleeve structure. From Picture 1, there is no positioning device in the bearing fit, it is difficult to locate & tighten the bearing, thus adopts four-row cylindrical roller bearing. Increasing the size of bearing inner bore, meanwhile design it into the taper structure which is easy to install. The adapter sleeve is a two-body structure, putting the bearing assembly into the crankshaft, then putting two half adapter sleeve sets into crankshaft bearing’s inner bore taper surface, afterwards, tightly locking the nut and fixing bearing on the crankshaft, this is easy to install.

Picture 1
　Bearing structure on the crankshaft

1.rotation center；2.cylindrical roller bearing with the tapered bore；3.bearing；4.connecting rod
　　The adapter sleeve and bearing inner bore surface will produce meshing after the mud pump has worked for a period of time, bearing removal is quite difficult when repairing or replacing bearing for equipment. Thereby, when design adapter sleeve, adding oil on it (Picture 2), then high pressure oil pressed from the oil inlet to form hydraulic oil film on the fit surface of bearing through oil passage, thus the friction resistance of the contact surface reduced, bearing removal become much easier, in this way, adapter sleeve can also be used as withdrawal sleeve.

Picture 2 Adapter sleeve

　　At the connection point of piston and connecting rod (Picture 3), the radial cross-section is smaller, which not only requires the bearing can bear greater radial load, but also requires its structure is simple, compact, and easy for mounting & dismounting, so four-row cylindrical roller bearing is the appropriate choice. From Picture 3, we can see that the outer ring and roller is the outer component, cylindrical pin as bearing’s inner ring, so as to save space, increase the diameter of rolling element, meanwhile to improve bearing’s load capacity. At the same time, the friction coefficient for cylindrical roller bearing is low while the manufacturing accuracy is high, thus it is easy for mounting & dismounting, besides, also easy for maintenance and replacement.

Picture 3　

1.connecting rod；2.four-row cylindrical outer component；3.cylindrical pin；4.piston housing；5.piston connecting rod
　　As the bearing working environment seriously polluted, thus to install dust cover at the two ends of the bearing to form closed seal to prevent silt & dust entering the bearing to affect service life, on the other hand, it can also ensure the normal operation of the bearing.

　　Users actual application results show that these two types of bearings are in line with on-site condition with good reliability, which can meet production requirements.