Hello everyone, I have a conveyo

[bamia]

Hello everyone,

I have a conveyor that is supposed to run 24/7, though it is now running nor more that 10 hours per day, and I would like recommendations for monitoring and maintaining two Plummer blocks with roller bearings (I believe shaft size is 70mm). There are grease nipples, so that's something but part of the check list requires taking heat measurements and my question is where would the best area be to measure the temperature. I downloaded a .pdf showing the structure of the block and the bearing appears to be mounted in the middle with seals on both ends of the block. I elected to measure at the seal because the shaft transmits the heat from the gear box which gets quite hot.


SNHF 516 instruction manual

Thank you.

 

[TugboatEng]

Closest to the bearing is the best place to take the measurement. What are you using? Are you going to install a thermometer in the housing or use a non-contact method? The non-contact method isn't precise so it doesn't matter much where you take the reading, just try to get it in the same spot every time.

Why are you only getting 10 hours of operation? Is the bearing overheating?

In all reality, you should remove the grease nipples. Too much temptation for someone to over grease or use the wrong grease.

 

[3DDave]

I've come to dislike grease as a lubrication method, particularly with an eye to adding more. Unless the thickener from the original grease installation is completely removed before putting in more grease, then eventually bad things happen. For sealed, one time use or for cases where oil absolutely cannot be contained then there isn't a choice, but it seems like it would be so much better to put fittings at the desired oil level - one for input, one for out, and push clean, filtered, and continuously replenished oil.

But I don't sell bearings.

I'd expect the main relation between temperature and re-greasing interval is due to higher migration rate of the lubricants from the thickener with increased temperature, so it's really the bulk temperature that matters - whatever temp the housing should be sufficient, but if you are also adding a lot of heat through the shaft, then measure the shaft temperature.

You might also add a static shield to divert radiated heat from the gearbox away from the bearing block.

 

[dvd]

Most bearing manufacturers have options for condition monitoring - talk with your bearing supplier, they usually have opinions and recommendations

SKF Plummer Block Condition Monitoring

 

[TugboatEng]

Bearings in this application don't usually require a lot of observation or maintenance, that's why I'm curious about the 10 hour bit. If properly packed with a polyurea grease these bearings could run for many years without a thought.

 

[romke]

I am somewhat amazed over the manufacturers instructions. They supply a lot of detail about mechanical things like mounting etc, but seem to fail to give realistic instructions about lubrication of the bearings.

OK, they tell you how much grease should be in the bearing. However - they do so using the wrong dimension. The amount of grease should not be recommended by weight; the amount of grease should be recommended by volume. Neither do they specify the type of grease their recommendations are based upon. There are quite a lot of different greases out there that differ in properties and some would be quite a bit more suitable given the operating conditions then others.

As far as operating temperature measurement is concerned: the rule of thumb is that based on a assumed standard operating temperature of 70 degrees C the regreasing interval should be halved for every 15 degrees C higher and should be doubled for every 15 degrees C less then 70 degrees C, for a standard lithium grease. When using a better quality grease, the regreasing interval probably could be doubled.

As for temperature measurements I would suggest to measure the temperature of all the bearings for a certain amount of time after say 5 hours of continues running. That will give you an idea about the average operating temperature of the bearing of the grease and might also tell you whether all bearings more or less give the same reading or that they differ depending on location or bearing "health". From that moment on you have a baseline value that can serve as a guide for future maintenance.

Basically a bearing filled with the right amount of grease of suitable quality does not need frequent regreasing. One interesting method of checking whether there is sufficient grease in the bearing is to use a "ultrasound grease gun". That is a grease gun that is capable of measuring the sound spectrum produced in the bearing - and can let you hear whether more grease leads to more noise or less when regreased. Regreasing should be done in such a way that the amount of noise measured should reach the lowest sound level attainable and in future the bearing should be checked regularly and only be regreased when the sound level has increased clearly. Such a kind of grease gun is pricey but most likely you will learn you that frequent checking of bearings and regreasing can be reduced quite bit. Most bearings fail prematurely due to too much grease...

 

[bamia]

Thank you everyone.

@TugboatEng , we are using Fluke thermometer.
The machine has been recently commissioned and they're still ironing out few bugs so the conveyors (3 for now and one coming online soon) are running only when the machine runs.

 

[bamia]

Romke, do you have recommendation for ultrasound grease gun; specific make that has good track record.

Thanks

 

[Tmoose]

Many manual grease guns list the "delivery" in ounces per number of strokes of the lever.

Product # Description Pressure Delivery Cylinder Capacity
500 Lever Gun 10,000 psi 1 oz./21 strokes 16 oz.

Number of strokes is the probably the handiest or maybe the only practical useful reference for the millwright/mechanic out re-greasing bearings.

Gotta think for most greases fluid ounce measurements and actual weight in ounces are within 5-10% of the same thing.