The 5 Telltales of a Looming Pitman Failure | Telsmith

The 5 Telltales of a Looming Pitman Failure

There are many methods for determining that the time has come to recondition your Telsmith swing jaw assembly. It has brought you through the busy and slow times in your operating seasons, now it’s time to evaluate it for the 5 telltales of an impending pitman failure.  Confirming you have any 3 of these conditions usually gives you enough time to react and acquire necessary parts and start planning on repairs.  Use this information wisely as it can help you make informed decisions on your crusher and revenue streams.

1.Oil or grease analysis with an escalation in high internal bearing component contamination findings

Organic (from within) contamination would include Fe (Iron), Cu (Copper) and Pb (Lead) as these are the primary elements found in the bearing race and rollers (Fe) and in many spherical bearings that have Brass (Cu + Pb) cages for aligning the rollers.  As these begin to wear these components increase the component elements in the oil or grease.  High or increasing levels of concern would include:

  • Iron (Fe) above 150 ppm
  • Copper (Cu) above 200 ppm
  • Silica (Si) above 150 ppm
  • Water greater than 0.5 ppm

Phosphorus (P) lower than 200 ppm (Phosphorus is the EP or extreme pressure additive required in many crushers). When this Phosphorus level decreases it indicates that the oil no longer has the load-bearing characteristics needed to protect your crusher bearings. Verify you are sourcing an EP gear oil with your oil supplier. Silica levels above 150 ppm indicate a potential dirt entry source, verify the breathers are good and that all tank seals are intact. Water should be 0 ppm so higher levels may indicate condensation issues maybe a result of breather issues or reservoir or crusher seals might be permitting that water entry. Be sure to sample each bearing location so that you can identify the potential source of the contamination whether it be organic or external.

2.Decreasing coast downtime

Hopefully, you’ve been logging the machine coast downtime which is the time it takes the crusher to stop rotating after you power off (with the lubrication system running of course).  You should start measuring this from day one.  The coast downtime depends upon the size of the crusher and the bearing condition so having this information right from the start when you commission the crusher is clearly helpful. Logging the coast downtime helps you recognize when there are issues and confirms when there is a looming issue.  Sometimes a decreased coast downtime may merely indicate debris is stuck where it shouldn’t so always perform a good inspection of the feed, chamber and discharge areas for any buildup of debris stuck between the cheek plates and the pitman die on a jaw crusher as an example.  Clear this debris and you should get a better coast downtime.  If you are noticing a gradual (several months) consistent loss in your coast downtime take a close look at the other telltales.

3.Bearing temperature variations that don’t make sense

Monitoring or logging the bearing temperatures again gives your informed telltales about the condition of the bearings. Look at the swing jaw bearing housings and the mainframe bearing housing separately as a Swing jaw bearing and mainframe bearing typically have a larger difference in temperatures.  Compare swing jaw bearings and note any big differences in temperature (15 – 20oF difference) can help identify issues. Sometimes the side with the sun shining on it can make these temperatures different so logging these temperatures helps get you some averages to look at.  If you are lucky enough to have built-in temperature sensors, your PLC might be logging these for you.  If you do have higher temperatures between like bearings inspect the jaw centering in the frame.  Verify the grease amounts and grease purging requirements if this is a grease-lubricated model.

4.Bearing Internal noises

These can be audible or detected by vibration analysis tools. Compare swing jaw bearings to each other and compare the mainframe bearing areas together.  For both audible and vibration analysis being consistent on the location at the component or for audible the distance, you are measuring the decibel level can be helpful.  Logging these values consistently over time helps to make those tough decisions on repair now or wait to repair.

5.Higher crusher motor amperages empty or spikes during operation

Higher than normal motor amperages when running the crusher empty can indicate that there is a possible bearing issue looming. If this is a grease unit be sure to verify the grease is not excessively filled or over greased.  If so try purging the grease.  You can contact us to discuss this further. If you have high motor amperage spikes occasionally during operation combined with any noises this is a good indication there might be a roller element or cage getting ready to bind up.

Understanding these 5 telltales better and using them to your advantage can really help you make better decisions on when to pull the pitman for repairs and hopefully before it locks the bearings up causing more repair expenses.

Contact your local service representative with any questions or for help on preparing for repairs here:

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