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new motor getting overheating

new motor getting overheating

new motor getting overheating

(OP)
Hi expert engineer,, could you please help me for my issue below :
We commissioned a new pump with new electric motor (315 kw, 546 A, 2985 RPM, 50 Hz), but we have get rising in temperature (overheating) in the MTR DE bearing crazily during first four hours reach to 107 °C, so we stop the motor immediately and the problem still come after run the motor (for two days), so we have decided for opening its shield bearing housing cover (single type) to inspect bearing greasing (proper initial quantity , proper distributed, over greasing or lack of greasing), but we found the bearing greasing well also the initial quantity of grease good also,, for satisfying we have greased the bearing by hand in the some gaps between the balls, after that we run the motor again ,, but the rising of temperature problem @ bearing still (same as before). We have check motor vibration and bearing shock pulse by spatial device we found the motor in perfect condition (max vibration reading reached to 1.8 mm/s and Carpet value -5 & max value 4)

So your help required plz to solve this issue and my questions:
1. Is this rising in the temperature normal for new motor? (Bearing type TKN 6317 C3).
2. Are there other reasons than those related to greasing?
3. Are there any related to motor Hz in bearing overheating ( max. Hz reached 46 Hz )?
4. Practical solution for solving the problem


RE: new motor getting overheating

How are you monitoring bearing temperature?
I'd calibrate the sensors by some method.

Then I'd run the motor solo ( uncoupled) and monitor the bearing temperature.

What is the installed axial gap of the coupling ? Are the coupling hubs installed flush with the ends of the motor and pump shafts, or however the coupling manufacturer specifies ?
If the gap is insufficient, then the motor can become the thrust bearing for the pump, or the pump and motor thrust bearings can fight each other, to the death.

Is your vibration analysis gear capable of taking spectra to 600 kcpm and beyond, or "demodulated" measurements, like Spike Energy ? Spike energy is pretty good at detecting the crazy high frequency screeches and other cries for help that an axially loaded bearing emits. Sensor mounting becomes much more demanding for those type measurements.


RE: new motor getting overheating

Quote:

1. Is this rising in the temperature normal for new motor? (Bearing type TKN 6317 C3).
It doesn't seem normal to me, especially if you have verified there is not excess grease, and you have run the motor for two days.

Quote:

2. Are there other reasons than those related to greasing?
Some possibilities that come to mind: Wrong grease. Too much axial or radial load imposed by driven equipment (due to belt drive, gear drive, or misalignment of coupled machine). Lack of loading causes skidding. ODE and DE bearings are not coordinated properly to accomodate thermal growth. Loss of internal clearance of ode bearing as a result of differential thermal expansion of shaft above housing and/or excessive interfence at shaft fits and low clearance of housing fit.

Less likely possibilities but included for brainstorming: inner ring spinning on shaft or outer ring creeping in shaft (usually would show up on vibration, but you never know). Severe contamination of the lubricant is causing increased friction (again typically should show on vib). Something is causing rotor to heat and that heat is being transmitted by bearing to the housing.

Quote:

3. Are there any related to motor Hz in bearing overheating ( max. Hz reached 46 Hz )?
In general as you increase speed, the bearing gets hotter. However there may be an exception for VSD motor driven very slow, let's say 25% speed. In this case as you decrease speed you are decreasing cooling flow from the attached fans but you are not necesssarily decreasing generated heat by the same proportion. In this case I would expect the entire motor frame to run hot (you don't tell us the temperature in the middle of the motor frame).

Quote:

4. Practical solution for solving the problem
I don't know. Is the motor TEFC? Is motor vertical or horizontal? If vertical, is there a wavey washer. Is it a coupling or belt drive? Was the driving equipment connected during the run? What is the loading level? Do you know what type of grease? Do you have a thermal image?... image would give an idea of the rest of the motor and the shaft and may provide some clues.

=====================================
(2B)+(2B)' ?

RE: new motor getting overheating

(OP)
Dear Tmoose.

Many thanks for your kind replied,,
1- we monitored the temp. by temp. gun, unfortunately no sensor has been installed yet..
2- First we will check axial gap of the coupling ( if insufficient we will correct as per manufacturer specifies)
3- Then we will run the motor solo ( uncoupled) and monitor the bearing temperature.

Yes I agree with you For (If the gap is insufficient, then the motor can become the thrust bearing for the pump, or the pump and motor thrust bearings can fight each other, to the death ).

4- Unfortunately currently we have vibration tool/pen for taking the reading, I can't do analyzing or check high frequencies by this device.

Many thanks again

RE: new motor getting overheating

(OP)
Dear electricpete,

I appreciate your kind replied ,,

1- Regarding to motor arrangement is Horizontal (multi stage pump) & Type of grease Mobilux EP3
2- The winding temp. very normal ,,, NO thermal imager we have ,but the hotter zone is the MTR DE bearing housing Zone especially upper place..

thank you

RE: new motor getting overheating

(OP)
Here I have question to you ( Mr. Tmoose & Mr. electricpete)

IF there is too much axial load imposed by driven equipment or insufficient gap of the coupling , usually would show up on vibration (external), but our readings are very perfect For : V = 0.47 H = 0.48 A = 0.54


waiting your reply Please

RE: new motor getting overheating

(OP)
vibration unit mm/s for above readings

RE: new motor getting overheating

(OP)

Vibration readings for pump DE
V = 1.16 mm/s H = 0.73 mm/s A = NA


RE: new motor getting overheating

In theory, incorrect coupling gap can in theory give a static force (no time variation), which can give a static response (no vibration). What type of coupling?



=====================================
(2B)+(2B)' ?

RE: new motor getting overheating

Slipping caused by an UNLOADED bearing can be an issue to. Make sure the bearing carries sufficient load.

RE: new motor getting overheating

hi

My question is the motor loaded when it over heats? If so is the motor capable of handling the pump load?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

RE: new motor getting overheating

(OP)
Dear Expert,,

Today I have run our motor solo (uncoupled) as your recommended to me with full Hz & RPM (50, 2999),
The temperature in the DE bearing & NDE was 59 °C & 48 °C (Because still hot from the last running before shutdown),,
The test run was one hour only (readings taken every 10 min.)
Time DE NDE
00:00 59 48
00:10 64 44
00:20 70.9 43.6
00:30 77.4 43
00:40 80.6 42.5
00:50 82.8 40.4
01:00 83.4 40.3

We observed the temp. of motor shaft near to seal reached to 95 °C.
Total rising in one hour = 24.4,, but when the motor coupled motor temperature rising from 37 °C to 75 °C (38 diff).

** Coupling gap reduced to 198.8 mm (200 mm as per design), because thermal expansion .. type Flexible Disc Coupling**

NOW ,,
- Is this rising in the temp. with solo test normal?
- Are there any effect with the shaft expansion (1.2 mm) on the this coupling type (the flexibility good in this type)
- If do solo test morning @ 37 °C the diff. in one our will be 24.4 i.e. the temp. will become 61.4°C or will be 75 °C as every day.
- Any problem with motor bearing or Not?
- Are there any direct related if the motor designing NOT capable of handling the pump load (Motor big than pump or Not fully loaded )

@ rob768 & desertfox
Regarding to motor loaded when the bearing overheated ,, today morning we have observed our pump reached to 170% than its capacity while the motor still not reached to full load in Hz & Amperage??!
Also we have old backup pump (still operating) its motor capacity 200KW, but the new pump motor 315KW while the two pumps same in designing capacity

RE: new motor getting overheating

(OP)
Hi guys,,

Any reply

RE: new motor getting overheating

(OP)
Are there any related between bearing spacer & shield bearing housing ,,, we have observed this zone hotter than other and some scratching/polishing @ top surface which it touch with each other
it is possible to be the heating source due to friction ???!!

RE: new motor getting overheating

Are you using an infrared measuring device? I'd confirm its accuracy by getting an RTD or thermocouple or something else in there. Maybe you've already done that and have faith in your measurements.

RE: new motor getting overheating

I have seen two instances where the motor repair shop accidentally installed both drive-end and non-drive-end bearings in the fixed configuration. Normally the DE bearing would be fixed and the NDE would be floating. As the rotor heats up and grows, the bearings are overloaded.

Johnny Pellin

RE: new motor getting overheating

That seems like an unusual bearing and grease combination for a horizontal motor. I would expect a heavy duty thrust bearing with extreme pressure grease in a vertical motor direct coupled to a pump with very high thrust load. For a horizontal motor coupled with a flexible coupling to a pump that has its own thrust bearing, this seems a poor choice. I would expect a radial bearing (6200 series) and a polyurea based grease like Polyrex EM.

Johnny Pellin

RE: new motor getting overheating

(OP)

Today I have do these activities :

1- Run the motor solo w/out shield bearing housing (after see some polishing on the spacer rim) --- Result temp. constant @ 57
2- Grind bearing spacer rim by using sand paper & motor running
3- Run our motor solo (uncoupled)& bearing covered with full Hz & RPM (50, 2999) for 3.5 Hrs --- Result Temp. rising from 31 C to 80 C then decreasing from 80 C to 66 (coutenouse decreasing), but we stop the motor.
4- after that we run the motor coupled with full pump load --- Result temp. rising from 60 C to 117 C , then we stop the motor..

--Please your suggestion required after these observations--

RE: new motor getting overheating

Hi

The pump load to great for the motor?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

RE: new motor getting overheating

What are you referring to as "shield bearing housing" and "spacer rim?" What parts are these? Can you provide a drawing?

Johnny Pellin

RE: new motor getting overheating

(OP)
I mean by shield bearing housing = housing cover
and spacer rim = bearing stopper ring side face

RE: new motor getting overheating

(OP)
Are the motor Bearing Clearance Class caused bearing overheating in sometime Or Not?


In other words, If I have bearing C3 ,then I want to change its clearance class to C4 ,, Is this effective to reduce the bearing temp. If I know that the cause of overheating is due to this class???

RE: new motor getting overheating

No. I would not expect the bearing class (C3 or C4) to explain the overheating. The note about removing some material from the spacer ring seems to me to be the key. I would suspect one of two potential causes:

The bearing which is overheating is being crushed axially within the housing. The fixed bearing needs to be constrained from axial movement. But, it should not be axially crushed. I am not a motor expert. But, we would normally want this bearing to have 0.002 to 0.004 inch axial clearance between the outer races and the housing.

Both drive and and non-drive-end bearings are fixed axially. Thermal growth of the rotor in service is overloading the bearings in thrust.

Johnny Pellin

RE: new motor getting overheating

(OP)

Quote (The bearing which is overheating is being crushed axially within the housing. The fixed bearing needs to be constrained from axial movement. But, it should not be axially crushed. I am not a motor expert. But, we would normally want this bearing to have 0.002 to 0.004 inch axial clearance between the outer races and the housing.)

Regarding to axial gap/movement there is enough gap available for free movement,,, we have run motor solo, but the problem still ??!!

RE: new motor getting overheating

(OP)

Quote (Thermal growth of the rotor in service is overloading the bearings in thrust.)

if we run motor solo, no way to say there is thermal expansion there .. is it right?

RE: new motor getting overheating

Even running solo, the motor is pulling amps and generating heat. As I understand it, the bearings heated up more slowly running solo and did not get as hot. But, they still heated up. Is that not correct?

Johnny Pellin

RE: new motor getting overheating

(OP)

Quote (Even running solo, the motor is pulling amps and generating heat. As I understand it, the bearings heated up more slowly running solo and did not get as hot. But, they still heated up. Is that not correct?)

Yes,, that was our wondering,, you know motor ampere was 15A during solo test

RE: new motor getting overheating

Hi
What I understand ,I think the problem reside in many points that you have to verify.
- quality & ORIGINALTY of the bearing.
- seals shaft contact .
- grease quantity and type and if it is not mixed.
- type of cooling fan of the motor
- alignement

RE: new motor getting overheating

(OP)

Quote (Hi What I understand ,I think the problem reside in many points that you have to verify. - quality & ORIGINALTY of the bearing. - seals shaft contact . - grease quantity and type and if it is not mixed. - type of cooling fan of the motor - alignement)


Many Thanks (32c4) for your replied,,

Regards To :
(1)& (2) We have replace the old bearing by new one (SKF) & New shaft contact seal before a few days,, Problem Still.
(3) First we have working with recommended grease Mobilux EP 3, problem still ,,, then we use Mobilith SHC 100 spatial for higher speed bearing applications, such as electric motors,but problem still,,
(4) built in cooling fan (fixed with shaft)
(5) Alignment is perfect , no high level vibration (all readings under 1 mm/s),, also we have run motor in each time with solo (uncoupled), but still the problem !!!!!

wondering issue!!

RE: new motor getting overheating

"New shaft contact seal"\\

Is the contact seal part of the OEM motor design?
What is the OEM seal number, and what is the number of the replacement seal?
Is the cavity between the seal lips being well greased at installation?

Do you have special requirements making a contact seal necessary?
Typical Contact seals have a service life measured in 1000s of hours.

I am assuming the shaft diameter under the seal is about 2.375" or 60 mm.
3000 would result in a surface speed of around 1900 fpm (15 m/s), which is below the very general limit of 3000 fpm for A typical seal design in NBR material.

I'd remove the contact seal and run the motor solo to see what temperature results.
I'm expecting the temperature to stay low.
If so, I'd work with the OEM to reconsider the true sealing requirements, fully expecting to go back to a non-contact seal design, perhaps with an additional flinger. Options also exist like removing the garter spring from the well lubricated contact seal, substituting a Forsheda V-ring , or even ( grrr [flame]) bearing isolators.

RE: new motor getting overheating

(OP)
Hi Tmoose,, thank you for your help & reply,,

1- Is the contact seal part of the OEM motor design?
Yes the contact seal part of the OEM motor design , its number (H218 ID 85, OD 110, TH 12 )
2- Is the cavity between the seal lips being well greased at installation?
I'm not sure I contact my partner, He was there that time.
3- Do you have special requirements making a contact seal necessary?
No

4- shaft diameter 85 mm

So, now we will check the cavity between the seal lips being well greased at installation OR NOT!!
And we will remove the contact seal and run the motor solo to see what temperature results!!

We will see ,, hope good result
thank you again

RE: new motor getting overheating

(OP)
ear All,,
Hi Tmoose,,
First of all we inspect the shafts for both direction after dismounting the bearing shield housings,, we found some marks on the shafts under due to lip seal friction,, (see pic attached)
we have run the motor solo w/out motor cooling fan & bearing shield housings with its seals. It is clear from the all readings of temp. (max. reading was 50 C for one an hour),, the temp. of both DE & NDE bearing is NORMAL..with it without cooling fan..

@ Tmoose,,,
you suggest to us :
1- To reconsider the true sealing requirements
2- OR go back to a non-contact seal design
3- OR removing the garter spring from the well lubricated contact seal and we see the result
But what do think ?

Our lip seal (H218 ID 85, OD 110, TH 12 ) contact type

thanking you all

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