Questions regarding bearing temperature and lubricant grade
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Recently, the bearing on the non-drive side of a multi-stage pump (Sulzer) used in our company reached a temperature of 76 degrees Celsius. We were using 46# lubricant; now we want to switch to 68# lubricant. Will this yield good results?
What is the temperature at the site? If it’s high, considering using oil grade 68 might be a good option
When the bearing temperature of a multi-stage pump is high, other factors also need to be taken into account. Using lubricant with a high viscosity will increase the bearing temperature further; simply replacing the lubricant without identifying the root cause will not solve the problem. In multi-stage pumps, the bearings at the non-driving end are generally positioning bearings; sometimes a thrust disc is also installed. During operation, together with the balance disc and balance pipes, these elements are used to balance the axial forces. If the clearance of the balance disc is too large or too small, the axial force that can be balanced by the balance disc decreases, while the axial force that needs to be balanced by the positioning bearings increases. As a result, the axial load on the positioning bearings rises, which in turn causes an increase in their temperature. It is recommended to check the clearance of the balance disc and adjust it accordingly. Check the clearance of the bearing shells at the drive end; too small or too large a clearance can also lead to high temperatures
Agree with the comment above. A higher label viscosity increases the load-bearing capacity but is not conducive to cooling.
That’s the case with Sulzer’s multi-stage pumps: the axial force is high, and the bearings have to bear too much of this axial force, which is why the temperature rises. It is recommended to replace the balance mechanism; if that doesn’t work, install water cooling for the housing! Simply change the balancing mechanism to a combination of discs and drums!