AGITATOR GEARBOXES FAILURE

Vibration.

Thanks

Please give more infos like:

Where the failure reoccurs? Did you said the blades get loosen?

How are the blades fixed with shaft?

Is the shaft hanging? Bottom supported?

What are speeds?

Is GB, worm and worm wheel? GB output shaft directly coupled with agitator shaft? What coupling?

Please elaborate the failure and failure mode which are very important to address the condition that need to be monitored.

Hi, the failure reoccurs on gears and bearings once the blade comes off the shaft. The shaft is suspended in a CIL tank with slurry bolted with 6 blades. The shaft is bolted to the press fitted coupling attached to gearbox. Gearbox speed is 25RPM Ratio 58.82

I need to be able to protect the gearbox as soon as the blade is gone. Loosing one blade causes misalignment and vibration which are among the reasons for the gearbox failure.

"Loosing one blade causes misalignment and vibration which are among the reasons for the gearbox failure."

You have the clear 'failure mode', 'blades get loosened'.

1. Why blades get loosen?

1.1 Speed or angle of twist more. Changing the speed would be difficult, so review the twist angle.

1.2 Air vertex forms and leads to irregular loading of blades. Consider vertex breaker (might lead to increased power consumption).

1.3 Too long/slender blades leading to high vibration. Consider reinforcing/inter connecting blades to increase the rigidity/shorter but wider blades.

2. Prevent blades getting loosened.

2.1 Review the using different lock washers/lock nuts

2.2 Even 'tack welding' the nuts with bolts might.

Gearbox failure to excessive vibration [caused by severe imbalance from blade loss] CAN be stopped with a vibration sensor/switch mounted on the gearbox-to kill the power when vibration starts. However, it is far better to permanently fix the root cause---mixer blades coming loose.

There is something fundamentally wrong with the mixer blade arrangement. Lightning or Chemineer (only 2 of the may mixer manufacturers) can provide technical assistance for resolving the mixer design/operation problem. In my 40 years of practice, never have had a mixer blade come off.

I've seen this we solved are case by double nutting and lock washer,use 316 stainless steel hardware. Then drill and wire your bolts for added protection. Do not be afraid to put a wrench on them during routine maintenance

Good day all ,

I am new on this forum and i like it very much it is very helpfull in engineering matters.

Please can you assist me with our agitator gearbox having a High load problem?.What is the rootcause of this load?

At the density of 30% load rise up to 110%

Agitator shaft have six blades with 16rpm.

Thank you all.

Dear Mr.KADETE,

You have not mentioned the type of failure of Gear Box. Is it

1. Bearing Failure,?

2. Is it Gear Failure.?

Bearing failure is due to excessive vibration, lub.oil leakage, Gear Failure may be due to Less Service Factor, Wrong Application Factor which should be considered at the time of design/placing order etc.

You have mentioned that blades got loosened - hence it is a Problem relating to VIBRATION.

Pl. furnish more details on this problem. Also inform this Forum what was the problem and how it is solved.

DHAYANANDHAN.S