Centrifugal pumps are among the most prevalent types of industrial equipment, with many facilities employing hundreds or even thousands of these machines. Frequently, redundant backup pumps are kept on hand, which can lead to a lack of concern about emergency breakdowns. However, significant costs can still be incurred if a pump fails.
While there are many areas where you can concentrate your reliability efforts, such as installation, alignment and balancing, the lubrication of the pump is one of the most important and often missed or misunderstood factors. If you fail with this step, all your other efforts will be a waste, and the pump will still fail.
First, you must select the correct lubricant and additive package to use on the pump. If the pump is under high loads and temperature, you may want to consider extreme-pressure (EP) or anti-wear additives. These additives will add protection to the bearing surface when the bearings are under a high load. If the system is operating in high humidity or a wet area, it may require an anti-rust or anti-corrosion additive. These additives provide a protective barrier to keep moisture from attacking internal machine surfaces.
Viscosity is the next important factor. If using a mineral-based lubricant, you must consider the temperature or ambient conditions in which the pump is operating. If the area or the process is very hot, you may need a higher viscosity lube oil.
If the pump is operating in a very cold environment, a lighter ISO grade oil may be necessary. High-speed pumps will require a lighter viscosity lube so the lubricant can flow into the high-speed components. The original equipment manufacturer (OEM) may not understand your specific applications, so you may have to change viscosity based on the operating conditions.
Moisture is the No. 1 destroyer of lubricating oils and must be controlled. Desiccant breathers may be needed. Having proper sealing systems for the environment is also key. Pumps can be ordered or fitted with labyrinth seals, which will reduce the amount of moisture and particles entering the component’s bearing area.
They also can keep your lubes from leaving the pump. Be sure your lube transfer process is satisfactory and that you have dry lubes to put into the pump when topping off or changing lubricants.
How much foreign material is in the lubricant that is inside the pump? Sometimes it is not cost-effective to pull oil samples on small pumps, so you must inspect and keep the oil clean. If you verify that the lube added to the pump is very clean, it can add many years to the life of your bearings. I always recommend at least an ISO code of 16/14/12 or better for any pump lube oils.
Remember, lubrication is the key to long centrifugal pump life, so keep your lubes clean, cool and dry.
This article was previously published in the 2018 Machinery Lubrication Conference Proceedings.