Beariing temperature

[stratford]

Hello to all. On site we have a 6.3kV motor with Drive end bearing D625-6322-C3. On this bearing we experience temperatures to 61 oC. Is this normal wroking temperature? The protection relay of the motor trips at 70 oC. I think this is a little bit more sensitve than usuall. In other applications we have motor tripping at 90-100 oC temperature of bearings. Can you help on this? Also i want to ask how can i understand the type of bearing from the part number.

 

[ischgl99]

I assume you are measuring the bearing temperature with a probe on the outer race?

Allowable temperature will depend on the application, is this grease or oil lubricated? What kind of grease are you using, brand, product name, etc?

For the bearing part number, not sure what the D625 is, 6322 is the bearing series indicating a deep groove ball bearing medium series with a bore of 110mm and the C3 is the clearance class between the balls and the race.

Do you know the manufacturer of the bearing? That would help to indentify the D625 prefix.

 

[stratford]

mbensema I measure the temperature with RTD, the motor is greased. Unfortunately i dont have motor catalogue either bearing manufacturer.
Can you rpopose trip limit for dip groove ball bearing?

 

[Tmoose]

Although motor housing over the windings are often rated 40 degree rise over ambient, I'd be concerned if a bearing housing got nearly that hot.

I'd consult the manufacturer. Every one is on the Internet.

Running hotter than planned can use up bearing clearance, age the grease at a much faster rate, or be a sign of a mechanical problem, or simply too much grease, which can be terminal too.

 

[ischgl99]

Stratford, is this the peak temperature you are seeing,a constant temperature, has it been gradually rising?

After the bearings are regreased, there will be a rise in the temperature for about an hour or two while the new grease is worked into the bearing and the excess expelled. This is normal and nothing to be concerned about unless the bearing is being greased too often and is always at the higher temp.

Another cause of high temperature is the incorrect grease being used, or the grease could be depleted and you are seeing high temperatures due to damage to the bearing.

61C seems a bit high to me for a greased bearing, but Tmoose is correct, you need to consult the manufacturer of the equipment or a bearing application engineer to be certain. The bearing application engineer will need to know the operating conditions of the equipment, ambient temp, speed, etc. It would be helpful to know when it was last greased, how often, what kind of grease, etc.

 

[jmoritz]

61 C is not a high operating temperature for a bearing, especially in an electric motor. 90 C is not unheard of.

The OEM has probably tested or theorised that the operating temperature would be around 60 and therefore set the problem alarm to 70 C. A 10 degree rise in temperature, not after regreasing or start up, would indicate a problem with the bearing may be beginning.

The other motors may equally have been proven by testing or through theory that the operating temperature would be around 80 and therfore set alarms at 90 C.