Which one better? Horizontal or vertical storage of spare rotor of compressors? 2

[Sabergg1981]

Hi all
I want to know about advantages and disadvantages of horizontal storage of spare rotor from point of maintenance, balancing ...
Is there any preference when selecting one of these two method?
Is there any criterion about size, weight,... To choose one of these 2 methods?

 

[JJPellin]

We currently require vertical storage for all multi-stage compressor and turbine rotors. We also store multi-stage pump rotors vertically, when practical. The risks of horizontal storage have to do with run-out more than balance. A long thin rotor with multiple interference fit parts can bow in horizontal storage. This bow might straighten out when the machine runs. But, that is a high risk to take.

As much as orientation, storage in a controlled environment is very important. Our storage canisters are all set up for nitrogen purge to prevent corrosion.

I have granted exceptions related to vertical storage in a few cases. For barrel machines with full internal bundles, the weight of the diaphragms between stages may be a problem in a vertical orientation. For a few of these, I have approved horizontal storage. These internal bundles can still be stored vertically, but the canister may need to support the diaphragms separately so that this weight does not hang on the impellers. For a bare rotor, vertical is always better. The support should be at the top so that the rotor is hanging. If this is not practical, the rotor could be supported from the bottom, in compression rather than tension. This is not preferred, but is still better than horizontal storage.


Johnny Pellin

 

[CaracasEC]

Vertical storage is preferable. However if for some reason, the storage will be horizontal, it needs maintenance such as turning 2 & 1/4 turn every week to avoid permanent sagging.Mr. JJpelin has very good explanation...

 

[Sabergg1981]

Thanks you both

 

[elbrownos]

I have often wondered why a rotor will bow in horizontal storage.
Doesn't this suggest room-temperature creep exists in stainless steel?
I'm pretty sure it doesn't.

 

[JJPellin]

I don't believe that the bowing of these rotors requires a belief in low temperature creep. As I mentioned in my first post, these rotors often have many parts (impellers and sleeves) mounted to the shaft with an interference fit. Uneven stresses in the interface between the shaft and the mounted parts could account for the bow.

As it happens, a few weeks ago, we pulled out a long thin rotor for a multi-stage pump (10 stages) that had a substantial bow when it was removed from the storage canister. We mechanically straightened the rotor before installation. It is up and running well. If the bow was just a result of unevenly distributed stresses under the interference fit impellers, there is a chance it would have straightened out once it was in service. But, I could not afford to take that chance.


Johnny Pellin

 

[elbrownos]

Thanks, that's a much more believable explanation.
What's the basis of 2.25 turns per week?