When the system was designed was the KW requirement for thermal capacity checked vs the mechanical KW requirements. Some designers overlook this requirement and it can be very critical especially in very rugged and hot ambient applications.

Your readings are not excessive but they are relatively high. You need to verify the specifications of the oil being used and at what temperature does that oil start to break down. Has the oil been analysed since start-up to see if it is not contaminated? Typically it is a good practice to change the oil after a certain numbers of operating hours - that interval is typically provided by the manufacturer.

Does your reducer have the ability to install a fan on it? Some reducers even have the ability to have 2 fans installed. Without knowing has this reducer is mounted I am assuming that there is a coupling of some sort either high speed or low speed or both. Have the coupling(s) been recheck for alignment?

You can also look at synthetic oils that will run at higher temperatures.

You have not giving us much information as to your application and if the reducer met the design requirements for the load to be applied. ■

I have had large boxes run hot for a very long time and never had a problem. As long as you monitor it and do not see any major changes than it should not be an issue.

An option you can try is a viscosity index improver additive to the oil, or switch to an HVI PAO which has a higher viscosity at 100 deg C than the standard PAO.

Another couple of checks I just thought of is the vent. Be sure that the vent is located properly and is installed. Also check that the reducer is level. ■

Dear Roland,

Looking at the temperature reading, I notice that at full load, the temperature rise is approx 7 degrC per hr with no indication of reaching an equilibrium as you mentioned.

I would say that the temperature did not go higher, because the installation did not continue to run under full load.

I consider the oil temperature of 94 degC. rather high and considering that the oil temperature is not the highest temperature in the gearbox, I understand your concern. What happens when the gearbox has to run 24 hrs?

Using the temperature readings, it must be possible to calculate the relevant heat parameters.

F.i.

From the cooling curve at no load, it must be possible to calculate the cooling heat flow.

(The cooling temperature curve is an exponential e-function)

Then using a warming up curve, it must be possible to calculate the heat generation, also taking into account the cooling heat flow at the same time.

The outcome of these calculations should then be compared with the design calculations.

In addition, it might be recommendable to manually measure the temperatures from the bearing housings or at least as close as possible to the bearings.

Is the gearbox equipped with splash lubrication or with a lubrication pump.?

In case of splash lubrication, the gears must be picking up oil, but the oil level should not be too high.

In case of a forced lubrication, the gears should run above oil level and the oil pressure must be set at the required value to have proper spraying. At the same time the spring loaded overflow valve should not release too much oil, because that overflow is unnecessary heat generation.

In case of forced lubrication with an oil pump, it gives you the opportunity to add an extra oil/air cooler

Quote:

That's also the last word from the supplier

Unquote

That is a shocking experience.

Success

Teus ■

Dear Roland,

That the temperature during the performance test was higher than calculated can have at least 3 reasons:

-The calculations are wrong

-The conditions during the test were different from the assumed calculation conditions

-The gearbox is not properly mounted or improper components are used.

Your suggestion of some bearings sitting “stiff” can be checked by listening with a stethoscope (or just a big screw driver against your ear) or a vibration analysis.

One can imaging that the expansion of the shaft due to an increased temperature causes the bearings take increasing axial loads, although the design must prevent that.

Are the proper bearing tolerances used?

When you change the seals, you can also measure some bearing tolerances by lifting the shafts.

If the problem gets worse, there is of course a possibility to mount an external cooling system with a belt driven circulation pump and air/oil cooler.

I still do not understand the attitude of your supplier, apart from money reasons, of not supporting you with technical advices and cooperation.

Stay calm

Teus ■

Dear Roland,

I assume that the power to mass index is very high instead of low as you say, as the temperature is also high.

The gearbox heat dissipation capability of 7.6 kW, is that calculated under the same conditions as measured during the test? At least the temperature difference on which the heat dissipation capability is based must be given.

As a technician, the best way to survive is not to interfere with the $$people.

It gives you headaches, bad sleep and a troublesome installation.

Next time, just order an oversized gearbox, still wrongly calculated, but operating in the field under partial load and therefore without, at least, heat problems.

-Supplier happy, because he sold a more expensive gearbox. (I suppose they are cheap anyway due to the low mass to power index)

-You happy, because your installation runs trouble free.

-$$people happy , because everybody is happy and they take the credit for the wise decision.

You catch more flies with honey than with vinegar.

If you can’t beat them, join them.

Take care

Teus ■

Dear All

Greatings

This problem happened to me where the units have been converted from dual drive to single drive, by giving up of one gear boxes 320 kw . To get rid of the problem of high temperature was the work of the following: -

Change the type of oil from VG 320 TO VG 460

Increase the speed of wind

I used agear drive with the same number of rotation and convertion ratio but with half pwore (According to publicly available at the time ) and linked to drivin roller ( belt conveyor ) Still this is a successful period of its use since 5 years ago

By the way the ambint temp 55 deg .

Changed the fluid coupling to delay champer type D Voith coupling

Best regards

Ali ■

Dear Mr.Ali,

I feel that - When you change the oil from VG 320 to VG 460 oil temperature may increase due to higher internal friction of oil. Request to confirm.

Regards, ■

Dear friend

The application i had mentioned it in my answer is work efficiently and without any significant problems, can you remember me specification gearbox and the type of application . and picture if any .

Thank you

Ali ■