Heating elements 300°C in lubricating oil.

Dear Gilles,

You are right. You have a severe thermal cracking of the oil. You should retrofit the system for having indirect heating. We have experience on that kind of retrofit.

If you send to me an email to schmid@sicelub.com, we could help to you.

Thanks in advance,
Cristián Schmid

quote:

Originally posted by Gilles Van Mol:
Hi,


I have a 6.000l oil reservoir with 18 x 1000W electrical heating elements in the reservoir. The temperature of the elements is 300°C. I think this temperature is much to high and we will change the way of heating the oil (Shell Omala 220 SP2).



Oil analysis: PQ index = 2 (low) and spectrometical analysis (ICP): 1 ppm Fe. Viscosity = 86 cSt!! due to thermical cracking 300°C I think.
Analysis of the hard material around the heating elements (photo): 15.000ppm Fe, PQ index = 1170.

Is there a reason why the ferro magnetic elements like iron agglomerate around these elements?


Kind regards,

Gilles

Hi Gilles,
Shell Omala has a light EP package that will activate @ 300°C,
Why are they having to use Shell Omala rather than a heat transfer fluid like Mobiltherm 605??

If we heat damage heat transfer fluid the system is exceeding the Watts Density of the fluid being heated.
Water has a specific heat value of 100,
Oil has a specific heat value of around 5,
Water conducts heat very efficiently whereas oil does not and although heat is being applied to oil the other side of the reservoir could be cool if no mechanical circulation,
If we force oil to heat faster than the fluid can conduct the heat away the temp of the fluid will increase until the fluid cracks with the heavier ends carbonising with the fluid viscosity reducing and carbon content increasing.
If we increase the area of the heat source the likely hood of “burning” the fluid reduces accordingly,
Your system has pipes with the element inside which does increase the surface area so maybe we have a rogue element with hot spots that is burning the fluid, a check of the elements powering up from cold in an empty reservoir with a thermal camera may indicate any hot spots from faulty elements.
The agglomeration of the ferrous wear debris is most likely due to the magnetic field around the heating elements lightly magnetising the element pipes plus the energy field around the element when operating.
The amount of metallic wear debris in the reservoir appears significantly excessive, we would be inclined to complete a Wear Debris Analysis on the wear debris so the wear mode causing the wear is known and once the wear mode is known the abnormal wear can usually be corrected,
What does the system do??
Thanks
Rob S

Thanks for the reply's!

I suppose the excessive wear debris is from de gears. The viscosity was reduced to 86 cSt!

It's a reservoir connected to 9 gearboxes. I think the best solution is to connect a heater to an offline filter unit. Normally there are 20 shutdowns a year, so with this solution there will be no problem to heat the oil continuously.

I will check the surface temperature of the original heating elements and other oil paramaters like MPC.

Kind regards, Gilles

Dear Gilles, you are right.

This is one of the possible solutions. The other is to make the heating in an indirect way.

I will send to you some information by email.

Regards

quote:

Thanks for the reply's!

I suppose the excessive wear debris is from de gears. The viscosity was reduced to 86 cSt!

It's a reservoir connected to 9 gearboxes. I think the best solution is to connect a heater to an offline filter unit. Normally there are 20 shutdowns a year, so with this solution there will be no problem to heat the oil continuously.

I will check the surface temperature of the original heating elements and other oil paramaters like MPC.

Kind regards, Gilles

Hi Gilles, the viscosity you mention is @ 40°C,
The viscosity should rechecked at the operating temperature and the current viscosity and oil film thickness rechecked back to the gearbox spec to check if the hot oil viscosity is adequate for the drive design, my concern is the amount of wear debris re back to my suggestion a Wear Debris Analysis be performed on the oil sample as that will indicate whether the wear id abrasive from fine hard particle ingress or adhesive from inadequate lubrication film, the drop in viscosity is expected when lubricants are over heated as the heavier ends carbonise first leaving the lighter ends, another area for you to consider is the flash point of the fluid will have reduced to 50-60°C as well causing some safety concerns, if heat transfer fluids are accidentally released the fluids don’t usually ignite but produce significant amounts of white smoke, I don’t think the current lubricating fluid is best for the operation but the current wear mode should be diagnosed before any changes are made. Thanks Rob S

If we increase the power of the heat source the likely hood of “burning” the fluid reduces accordingly,
Your system has pipes with the element inside which does increase the surface area so maybe we have a rogue element with hot spots that is burning the fluid.