Flagging Limits
What Are Flagging Limits?
Proper flagging limits are the foundation of any successful oil analysis program. They alert you when something is abnormal and assign a severity rating of Reportable (yellow), Unacceptable (orange) or Severe (red) to individual data points. The flagging limits applied to your Fluid Life analysis reports can originate from Fluid Life Global Limits, Original Equipment Manufacturer (OEM) recommendations or customer specific customized limits. Combinations of all three flagging types are possible as well and not uncommon for mature oil analysis programs.
Where Do They Come From?
Fluid Life Global Limits
Fluid Life uses relevant historical data to create histograms (distribution plot analysis) and global flagging limits. Historical oil analysis data from different users is assigned to a histogram based on component type, equipment manufacturer, equipment model, oil type (manufacturer, brand, and grade), industry, and equipment application. Fluid Life’s Global Flagging Limits are applied as a default to oil analysis reports if the other two types below are not requested by the user.
Original Equipment Manufacturer Recommendations
Most major OEMs have some type of oil analysis flagging limit recommendations. Some may be model/brand specific while others might be general guidelines for a certain fleet or oil grade. Oil manufacturers are more likely to provide some flagging limit guidance on analysis results such as viscosity, additives, oil degradation (oxidation, acid number) while heavy equipment manufacturers are more likely to provide limits on oil cleanliness (particle counts, contamination concentrations, water) and wear metals. Contact your OEM or equipment/oil vendor representatives to inquire about OEM specific flagging limits. If you have OEM limits that you’d like to include in your oil analysis program, contact your Fluid Life representative.
Customer Specific Flagging Limits
Some oil analysis users will forgo global flagging limits and OEM flagging recommendations to implement their own. This typically happens when a user routinely has too many flags or is using oil analysis to support a continuous improvement project or specific maintenance practice (Oil Drain Extension, Component Life Extension, Condition Based Oil Changes, Improved In-Line / Off-Line Filtration, etc.). A customer is free to request flagging limits on individual results that can be applied across the board on all active units, on a certain fleet type, certain component type, make/model type, or on individual units, components and sampling locations. If you aren’t happy with your current limits but don’t know what to apply as an alternative, you may want to consider flagging optimization product where Fluid Life’s reliability department will help your site apply statistical, engineering and application based flagging logic to better your oil analysis program.
Why Is Sample Information So Important?
Sample information is very important towards the application of proper oil analysis flagging limits as it lets the lab know what limits are best to apply to your results. Especially for Fluid Life Global Flagging Limits. See below for the difference in flagging limits for Iron (ppm) when sample information is optimized vs. when sample information is vague. With flagged results being one of the main driving forces to influence the decision-making process during data interpretation, it’s important to get the best flagging possible applied to your results.
- Hydraulic, Caterpillar 797B, Mining Surface Fleet, Oil Sands
- Reportable (yellow) = 10ppm
- Unacceptable (orange) = 12ppm
- Severe (red) = 16ppm
- Hydraulic, No Equipment/Industry/Application Info
- Reportable (yellow) = 20ppm
- Unacceptable (orange) = 31ppm
- Severe (red) = 52ppm