@Walt Strong posted:

So I guess you are trying to identify whether the jamming fault initiated in the rotor lobes or the timing gears? I vote for the rotor lobes!

Walt

I agree with Walt.  Since about half the teeth seem to be fine the timing gear damage seems to be a secondary failure.  Having said that, as you rebuild the machine, I’d be carefully reviewing the drawings to make sure the lock nuts are anchored properly.

Dear Gentlemen,

more finding in picture bellow, rub in lob, both lobs have same marck but only one point. 

 

its mean the cause of failure was the lobs started to touch each other, and secondary the teeth in timing gear began to damage. 

is it correct? 

no other abnormality were found in the others componentes.

I will wait for your coments.

regards.. 

 

 

 

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@ramonruiz posted:

Dear Gentlemen,

more finding in picture bellow, rub in lob, both lobs have same marck but only one point. 

 

its mean the cause of failure was the lobs started to touch each other, and secondary the teeth in timing gear began to damage. 

is it correct? 

no other abnormality were found in the others componentes.

I will wait for your coments.

regards.. 

 

 I would agree with this.  One thing I would be doing as well is double checking on the suction side equipment; things like a suction line filter is you have one.

An unusually small rub area that possibly indicates debris entered the mesh zone; instead of timing gear slip. Check suction upstream for loose/missing fasteners and broken components in filter and muffler/silencer.

You did inspect for rotor lobe tip rubs on casing?

What was the condition of the four bearings?

Understanding the root cause and correcting it could avoid a repeat failure!

Walt

@ramonruiz posted:

Dear Jhon,

Thanks for your prompt response, next step is to check the suction pressure. 

regards.

RR

I suspect to check pressure you would run the machine, or possibly check operating logs.  As I said, and Walt also, pull every screen and filter on the suction side and examine them before running again.  In light pf your statement "because the blower worked only few days" this is critical.  New installations (assuming it is new) frequently have debris in them.

Looks like the most significant rub was in axial direction between the rotors and end plate. These rubs may have stopped the rotation. I was standing next to a 2-lobe 600-hp blower when a severe axial rub occurred. It looked like a welder's cutting torch sending sparks out the NDE (timing gear end). The case iron case turned cherry red before the E-stop was pressed! If axial clearance is too tight and allows a minor rub, then the rotor can heat faster than casing and the expansion rate of rotor increases the rub; leading to spectacular failure!

Walt

@Walt Strong posted:

Looks like the most significant rub was in axial direction between the rotors and end plate. These rubs may have stopped the rotation. I was standing next to a 2-lobe 600-hp blower when a severe axial rub occurred. It looked like a welder's cutting torch sending sparks out the NDE (timing gear end). The case iron case turned cherry red before the E-stop was pressed! If axial clearance is too tight and allows a minor rub, then the rotor can heat faster than casing and the expansion rate of rotor increases the rub; leading to spectacular failure!

Walt

we faced one issue before (2 month ago) with excessive axial float, like you are telling, is the next picture similar to the case you faced before?  it looked like a welder's cutting torch on timing gear..

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@ramonruiz posted:

we faced one issue before (2 month ago) with excessive axial float, like you are telling, is the next picture similar to the case you faced before?  it looked like a welder's cutting torch on timing gear..

Keep in mind that when you have extreme distress in the timing gear, as shown by the previous pictures, you will also have extreme high axial force developed since your timing gears are single helical.  This might explain why the left rotor (as shown in the picture) seems to exhibit more damage than the right rotor.

Last edited by John from PA

John stated: "This might explain why the left rotor (as shown in the picture) seems to exhibit more damage than the right rotor."

It would be good to know whether drive or driven rotor had the greater axial rub.

Regarding the "welding torch sparks" comment; I do not recall if I saw the timing gears, since the blower was sent quickly away to shop. I do recall that the blower was a rebuild, and it failed during first plant run after less than 1-hour.

Is the OP blower a new design or rebuilt or just new from OEM?

Checking rotor axial clearance can be tricky, because of temperature and bearing axial movement. The correct bearing type and installation procedure should be checked and verified, even though bearings showed no signs of a fault.

A torsional resonance can initiate or add to rotor lobe tangential contact and axial force on timing gears; because of helical gear type. I have measured torsional vibration on these type of blowers and found poor selection of shaft coupling that required a coupling element change. I have seen blower foundation resonance that require structural modifications (steel and epoxy grout). I have also seen blower soft foot that required oversize shims for correction. Obviously some or none of these issues could be related to the OP failure.

Walt

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