Gearbox oil decreasing pressure during summer

[npower0073]

On site we have 10 cooling tower fans, driven through eelctric motors , long shaft and gear box.
We have experienced two issues upt o now, after 3 years of operation:

1) Ringing on the gears of the gearboxes, the most probable cause is the direct on line start of the motors
2) During summer, the oil , loses its pressure, when it orks in 1.5 bar during other times, in summer it goes to 0.7 bar. THe lowest allowable limit is 0.5 bar.

Can you assist on that issues?

 

[Matt51]

"Ringing on the gears" - do you mean noise from resonance?
Second problem, oil viscosity is thinner in the summer?
What oil are you using in the gearboxes?

 

[diskullman]

With current energy costs, I'm surprised everyone does not switch to synthetic oils that maintain viscosity better.

Russell Giuliano