Bearings practices vs. shipping damage? 1

[objengrs]

I'm involved in some tests to see if a large industrial assembly can be safely delivered by rail and/or truck. (The few motors & gearboxes have rotors in the 1000-3000 lb. range, and spherical or cyl. roller bearings. Mostly they will later end up in rather slow speed rotation (<100 rpm), although a a couple components are geared up to >1500 rpm.

Some vendor's limits on shock and vibration levels during this transit are quite low, 1 to 2 g. Well, low compared to what truck & train makers design their vehicles for.

Anyway, they don’t want the bearings blocked (restrained) during transit. (Instead they seem more interested in rotating the whole drivetrain a a little bit every few minutes with an idler motor.)

Does anyone have a general rule-of-thumb about what size equipment gets bearing lock-ups or supports before transporting? (train, truck, forklift?)

Or, do you know of any industry standards or handbooks that address how fragile typical big machines are while transporting?

 

[waross]

The lower limit of lock up for shipping would by computer floppy drives and washing machines. It may not be as much a question of size as a question of an ability to withstand shipping shocks.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[starkopete]

Hi,
For what it is worth, I know that a major motor manufacturer blocks the motor shafts on all 440 Frame and above motors and on 2 Pole motors 400 frame and above. (The frame sizes are NEMA).

Thanks

 

[Adalius]

In my line of work as a major machinery mover I've dealt with machines from 2000# to 250000# coming in on common carriers or being shipped out on my company's trucks. Some come in on trains, some on trucks, some on ships. I have to admit, amongst all that, I see *maybe* 1 item in 10 blocked out from the manufacturer, but rarely does it appear to be to prevent bearing damage.

Typically, what I see is shafts restrained from turning freely, for instance in the case of 5000+ HP motors which is usually done by an endplate which bolts to the housing. They don't seem to concerned about the shaft 'bouncing' on the bearings being an issue.

Its similar for both small and large machining centers, typically they'll have the head blocked out and/or restrained with strapping to prevent it from sliding sideways or moving up and down in the event that something gives, but again, nothing is isolated from the bearings to stop any shock loads.

Depending on what the assembly actually is there's a good chance I've moved one and I can give you some more specific information as to what was done to it if you'd kindly mention what this assembly is/does. That is to say, if you tell me its a VTC, HTC, mill, casting machine, whatever, I can (usually) tell you how we'd block it out for transport.

 

[electricpete]

Often blocking is applied by wedging timber between coupling hub and bottom or inboard end of the motor frame. If coupling hub removed, then fasten a T-bar to the bottom/end of the shaft using drilled hole which was hopefully provided there, and wedge between T-bar and bottom of motor.

EPRI has several publications which specify shaft blocking for shipping of any motor big enough to be rewound/refurbished. (in other words, both their form-wound and random wound motor rewind/refurbishment spec specifies blocking).

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[edison123]

As a motor repair man, I would say that only those motors with white metal (babbitt) bearings need to be locked. I have not seen any motors with anti-friction bearings being shaft locked.

 

[electricpete]

EASA AR-100 states: "Packing and transport should be as arranged with the customer. Blocking of the shaft is recommended, depending on the type of machine, mode of transport and the distance to be traveled."





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[electricpete]

Our practice is to require for all large motor repairs (not just sliding bearing). That is based on EPRI requirements. I personally believe it is more important for vertical motors than for horizontal.

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[MotorVib]

Blocking the shaft is normal on motor, but on generaters we would often just leave them free to spin. But the we didn't push the bearings when compeared to the bearing C and Co value.

Chris

"In this house, we obey the laws of thermodynamics." Homer Simpson