Pumps & Systems, September 2007
In the past, the nuclear power industry has experienced equipment failures due to improperly set oilers. There was never a precision tool available to help ensure the level was being properly set on a typical oiler . . . until now.
The nuclear power industry has long realized the importance and benefit of lessons learned from operating experience (OE) that continually helps improve the nuclear safety, performance, and reliability of its plants. This awareness comes from openly sharing operating experience and knowledge between all the nuclear sites.
A few years ago, I attended a presentation at a pump conference that discussed the problem of accurately being able to set the oil level on pumps that use a typical style constant level oiler. Shortly after the conference, I was reviewing OE notices and saw that a control rod drive pump at a nuclear site had experienced a catastrophic failure due to an improperly set oiler. OE data also revealed where a nuclear plant had discovered after inspection that over 30 percent of the oilers were improperly set.
This sequence of events caught my attention because here at the Oconee Nuclear Station we use constant level oilers. We recognize the importance of being able to correctly set and accurately maintain the oiler's oil level on a pump or other piece of rotating equipment.
Proper oil level is essential for the life of both the lubricant and the equipment. If a critically low oil level condition exists, the rotating equipment bearings will not receive enough lubricant necessary to maintain proper film strength, which results in surface contact and eventual failure. Without enough oil to prevent excess friction, thermal runaway can quickly occur and lead to a rapid catastrophic failure.
Churning of the oil will also occur if a critically high oil level condition exists. This accelerates the oxidation rate as a result of excess air and elevated temperatures. Too much oil will also lead to oil leaks and can affect the proper operation of oil rings and flingers.
This critical oil level range - between the low and high level - can be extremely narrow for rotating equipment with small bearings. In smaller equipment, setting the oil level so that it is accurately maintained within its critically low and high level range becomes even more imperative. (Note: The equipment manufacturer should always be consulted for the recommended oil level.)
The industry OE data I reviewed not only exposed that equipment failures had happened due to improperly set oilers, but that users could easily set a constant level oiler incorrectly by using conventional setup techniques. The typical method for setting an oiler involves using a straightedge and level and transposing the mark from the oil sump to the oiler, thus placing a mark on the oiler that corresponds to a mark on the oil sump.
The accuracy of this method depends entirely upon the experience of the user and how accurately they can visually sight the scale between the oil sump and the oiler - which becomes more difficult as the distance between the two points of reference increases. The greater the distance the oiler is from the housing, the easier it is to make a mistake setting the oiler adjustment using this conventional technique.
At that time, there was not a precision tool available that ensured the level was being properly set on a typical oiler. We needed a tool to improve the method of setting the oil level on a constant level oiler that provides greater accuracy than conventional techniques.
Consequently, Oconee Nuclear Station developed a laser guided oil level setting tool.1 This tool uses a laser to transfer the oil level setting from the adjusting arm in the oiler onto a reference mark on the bearing housing (oil sump) that represents the correct oil level for the equipment bearings.
More specifically, this tool provides a first portion that is configured to extend into the base of the constant level oiler and into engagement with the adjustable element. It also provides a second portion that is disposed exteriorly of the base to indicate visually, by laser beam, the disposition of the adjustable element relative to the oil containing sump.
The laser beam is equipped with a line generator which projects a red line against the pump bearing housing, rather than just a red dot.
Thus, as the elevation of the adjustable element of the oiler is moved upwardly and downwardly during the setup process, the oil setting tool provides a visual reference, via the laser, at each step in the adjustment process. This accurately sights the position of the adjustable element relative to the oil sump from outside of the oiler, greatly improving the ability of the technician to ensure the most precise positioning of the adjustment element in relation to the oil sump.
This tool becomes particularly useful when an oiler is positioned three or more inches away from the oil sump housing. The laser guided oil setting tool eliminates the need for a straightedge, level, marking pen, and possibly a flashlight due to the laser's red line, which is precisely projected from the oiler's setting to the oil sump, whether it is three inches or three feet away.
This laser guided oil setting tool is small enough to carry in your pocket and has a built-in level to help ensure the most accurate settings are made. This tool is quick and easy to use and ideal for those areas where lighting may be less than adequate.
To our knowledge, this laser guided oil setting tool is the first of its kind. By significantly improving the technician's ability to more precisely set the oil level on an oiler, it greatly reduces the possibility of inaccurate measurements caused by human error when using conventional techniques.
This tool ensures that the equipment's oil level has been correctly set and helps improve the reliability of rotating equipment using these types of oilers.
Special thanks to the Oconee Rotating Equipment Team #221 and Laseraim Tools Inc. for their assistance in the development of this tool.
1Duke Energy has applied for a patent for this tool.