CONSTANT OIL LEVEL
By PumpWorks Engineering Team / February 26, 2021
Horizontal Pump Bearing Housing Lubrication Method
Whether horizontal pump shafts are supported by rolling element bearings, journal bearings, or a mixture of both, lubrication is critical for maintaining their reliability. This discussion will not focus on lubricating quality (viscosity, type of lubricant, contamination, etc.), but rather on lubricating levels and more specifically, maintaining a constant level.
I recall a conversation with an engineer from a major rolling element bearing supplier…
“Users of oil rings are my best customers” – i.e. many bearings are prematurely killed by improper use of oil rings.
When pressed on this, the comment was further explained…
“Wrong level and even more emphatically inconsistent level.”
I will admit that wrong level and inconsistent level are inextricably linked. The topic of the proper oil level for effective and reliable operation will be left to another time.
Very often maintaining oil level is left to pump operators directly or at best managing automatic devices for oil level control.
There are two broad categories of devices used to gauge level:
- Visual indicators
- Constant level oilers
Constant level oilers generally possess some aspect of visual indication as well as an automatic control function.
The visual indication method can and often does lead to erroneous oil levels; generally manifesting itself in overfilling, which results in overheating and ultimately bearing failure. Try overfilling your car’s crankcase!
The use of constant level oilers does increase the likelihood of consistent correct level but does not guarantee success. Unfortunately, the major drawback of constant level oilers is the high probability of incorrect level settings or changing level settings inadvertently by the very component tasked with their proper operation – humans.
Types of Constant Level Oilers
From the major supplier of constant level oilers, there are two basic types:
- The pure vertical adjustment type that allows some measure of vertical flexibility on how the oil is added by “breaking” the liquid seal or meniscus.
- The more common type that contains an adjustable mechanical device that breaks the meniscus.
Both devices are effectively designed to connect to existing NPT connections on reservoirs. The pump operator then makes the internal adjustments to the control level.
Failure Points of Constant Level Lubrication Systems
There are often several breakdowns with the use of these devices. They range from lack of knowledge as to their true function to how do you replenish the reservoir when required.
The most egregious error is often adding lubricant directly to the reservoir and thusly bypassing the true function of the constant level oiler. In this method, the pump operator is often deceived by the level indicator on the constant level oiler. The pump operator has crossed over into the overfilling region. Failure is imminent.
Unfortunately, I have found the best solution to this perplexing problem is to effectively eliminate the human element in the daily management of level consistency control. I am somewhat uncomfortable with recommending reaching for the lowest common denominator. Follow-up pump lubrication training is critical. Unfortunately, you cannot train everyone who will potentially touch the pump.
I have found the best solution is to select a constant level oiler that is non-adjustable. This type of constant level oiler requires that the oil ring details and the required oil level are well known (It is difficult to separate level consistency and oil level). I would highly recommend that bearing housings that are to be modified should be done by a well-established OEM or independent repair center. Clear instructions and inspection by the pump owner or owner’s representative are imperative (I am effectively avoiding the somewhat more tenuous topic of correct level).
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