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Knowledge Center Bearing Lubrication Procedures: Part 7 – Sampling Procedure for Grease Analysis

Part 7 of our 9-part series on bearing lubricating procedures on sampling procedures for grease analysis.

Monitoring grease condition is an important step in maintaining and tracking equipment reliability. It can detect lubricant break-down and aid in identifying potential problems before they occur. Corrective actions can be taken before other signs of deterioration begin to show, such as increases in operating temperatures, noise, and vibrations. By tracking the condition of grease in an application, it can provide important information on the quality of the grease, how it is performing and help adjust relubrication intervals.

The following is a general guideline to follow when removing samples from a piece of equipment or component to increase the accuracy of the analysis. Please contact your local Klüber Sales Engineer with any questions or concerns regarding this process.

Caution: Personal care must be taken when sampling from equipment. It is up to the user to determine the safest way to obtain a sample.

Sampling Containers
Ensure the material of the container will not interact with the material being sampled. Crushproof plastic or glass bottles are typically acceptable and preferred. Plastic bags can be used, but may interfere with analysis of grease consistency. Rags and other absorbent materials should be avoided. The size of the container should be selected to ensure sufficient sample quantity so that all of the intended analyses can be completed.

Cleanliness
To minimize potential contamination of a grease sample, the following precautions should be followed:

  • Gloves should be worn for personal protection and to minimize sample contamination.
  • Visually inspect and clean sampling containers and sampling equipment if needed.
  • Clean the component to be sampled from dirt, dust and any other contaminants that may affect the results of the analysis.
  • Once the sample is taken, the container should be capped or sealed to prevent leaking or further contamination.
  • It is always good practice when shipping multiple samples to also seal each container in a separate airtight bag to prevent leakage and possible cross-contamination.

Sample Labeling
Proper labeling is of the utmost importance to ensure that the analysis is completed properly. Each component and piece of equipment should be given a unique identification for tracking and trending purposes. The samples should be taken one at a time and labeled immediately upon collection. As a minimum, the following information should be written on each sample bottle:

  • Sample Date and Time – when the sample was physically taken from the component
  • Equipment Description – brief summary of the facility and equipment, including the location, make, model, machine number, etc.
  • Run time of the current grease
  • Name of the baseline grease
  • Contact information, including facility location and who took the sample

Procedure

Spatula Extraction
When the component is open and the grease is accessible, a spatula may be used to extract the sample.

  1. If applicable, while the piece of equipment is still running, relubricate with the appropriate amount of fresh grease. Allow time for the freshly added grease to displace the used, in-service grease.
  2. Shut down the piece of equipment and place it in a safe condition (i.e., lock out, tag out if necessary).
  3. Use a spatula to clean the outermost layer of grease that has been contaminated by the environment. Discard this grease and thoroughly clean the spatula if it will be used again in the sampling process.
  4. Using a clean spatula, take the sample of grease from the component. If removing from a bearing, the sample should be taken from the area closest to the rolling elements and cage. Open the sample bottle and scrape the grease into the bottle by using the side of the bottle, avoiding any outside contaminants from entering the bottle or coming into contact with the grease.
  5. Seal the bottle and ensure that it is appropriately labeled as previously outlined. If available, place the sample bottle in its own Ziploc bag for shipping to prevent leakage or cross-contamination.

Vacuum Tube (Syringe) Extraction
When the grease in a component is inaccessible (sealed, within a housing, etc.), a syringe with a length of plastic tubing can be used to extract a sample from an inspection port, fill port or drain port.

  1. Obtain a piece of plastic tubing that will assist in taking a grease sample from a point that is not reachable by means of a spatula. The minimum ID of the tube should be 1/8”.
  2. Cut a length of tubing that will allow easy access into the component. Ensure that the inside and outside of the tubing is clean and free of any dust, dirt or chemicals that could contaminate the grease sample. Be careful to avoid contamination when cutting the tubing with tools and ensure that there are no burrs left on the cut end of the tube that could fall into the grease lubricated component or contaminate the grease sample.
  3. Clean any dust, dirt or debris from the access point to prevent any foreign material from getting into the component.
  4. Shut down the piece of equipment and place it in a safe condition (i.e., lock out, tag out if necessary).
  5. Remove the access port, and insert the plastic tubing into the component far enough so that the tubing is extracting grease that is in direct contact with the component (i.e., between the rolling elements and cage of a bearing).
  6. Draw the plunger on the syringe to extract the grease sample. Do not contaminate the syringe with grease; stop filling the length of tube with grease approximately two inches before the grease reaches the syringe.
  7. Remove the tubing from the component and clean the outer surface of the tube. Open the respective clean sample bottle and inject the grease into the bottle. Try to avoid any outside contaminants from entering the bottle or coming into contact with the grease.
  8. Steps 5 through 7 may have to be repeated several times to obtain an adequate amount of grease to be analyzed.
  9. Seal the bottle and ensure that it is appropriately labeled as previously outlined. If available, place the sample bottle in its own Ziploc bag for shipping to prevent leakage or cross-contamination.

Once samples are properly contained and labelled, they should be adequately prepared for shipment to ensure that they arrive without damage. It is important to include the appropriate SDS with any grease shipment.

Read Part 6 on how to use a grease gun.

What bearing lubrication challenges do you face? Let us know in the comments below.

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