As a result further investigation should be done to eliminate other causes

As a result further investigation should be done to

This preview shows page 5 - 6 out of 12 pages.

As a result, further investigation should be done to eliminate other causes before concluding that the radial loads are excessive [11]. Most failures that are a result of excessive radial thrust occur when the pump is operating at low flow rates. As a result, radial loads can be reduced by operating the pump at higher capacities or by installing a bypass from the pump discharge back to the pump suction or suction source [11]. 2.4 Axial Thrust Axial thrust is imposed along the shaft axis, either in the inboard or outboard direction. The thrust is usually a result of a dynamic cyclic component, which is superimposed on a steady-state load in either direction. Increasing the dynamic load on the shaft may impose excessive stresses, which could ultimately lead to metal fatigue. The static, steady-state load may impose an excessive load on the bearing, which may increase the temperature to an unacceptable state and lead to a short bearing life. The majority of thrust bearing failures are fatigue failures due to the dynamic cyclic axial loads on the bearing components [11]. Bearing damage is caused by both static and dynamic axial thrust. Heavy static thrust will cause cracking in the balls or rollers, and in the race of the rolling element bearings, and in the metal scoring of the shoes in the tilting-pad bearings. Excessive dynamic loads which surpass the bearing ratings will result in fatigue failures of the balls or rollers, and raceways in the rolling element bearings. In order to determine which of the two types of loads caused the failure, one would have a close examination under the microscope. Fatigue failure from dynamic loading will show a hammering effect caused by the points of impact. Fatigue failure from static loading will show metal fatigue without the hammering effect of the impact loading. Rolling element bearing failures can be addressed in large, between bearing pumps by substituting a tilting-shoe type of thrust bearing. The high cyclic axial forces are better absorbed in the oil film of the tilting-shoe bearing than in the rolling element bearing [11]. Shaft failure is mainly due to the high cyclic loading induced on the shaft when the pump is partially recirculating its output. In this case, axial cyclic stresses can be reduced by increasing the pump output, or by installing a recirculation line to bypass sufficient flow to move the pump total flow rate beyond the critical point. If this is not possible, then the shaft failures can be reduced by substituting a shaft material of higher endurance limit [11]. Depending on the location of the axial thrust, different instrumentation would be used to determine its magnitude. Proximity-type sensors should be used to determine the axial movement of the shaft relative to the bearing housing. Deflection of the thrust-bearing housing can be obtained using seismic instruments. Finally, axial loading of the tilting-shoe type of thrust bearing can be monitored by a load cell permanently installed in the levelling plate [11].
Image of page 5
Image of page 6

You've reached the end of your free preview.

Want to read all 12 pages?

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors