Cryogenic cleaning of motors & generators 5

[edison123]

Anyone have any experience with cryogenic cleaning of electrical machines with dry ice ?

How effective is the cleaning especially, the normally inaccessible areas like in-betwwen layers of the winding, ventilation ducts etc. ?

Does the winding have condensation film after the cleaning due to exposure to the extremely temperatures ?

 

[tld11]

Yes we (2 coal units/1 gas fired Combined cycle unit) use dry-ice blasting equipment for periodic cleaning of various motors:

- It works extremely well on dirt/dust type contaminants, especially in stators where there is ample room to direct the spray and blow the loose materials out.

- In tighter areas where there is no path for the loose material to exit the process works well for loosening the material, but we still need to follow with blowers or vaccums.

- Occasionally there is a small film of condensation; we do use a gentle heat to dry the areas we blast.

- Our experience has been that the ice blasting does NOT work well at all if there is oil in the contaminants you’re trying to remove.

 

[edison123]

Thanks tld11. I am planning to buy some dry-ice cleaning equipment for my shop. Can you recommend any OEM names ?

 

[tld11]

Cold Jet is the OEM for the equipment we have experience with (

http://www.coldjet.com).

The equipment is easy to use and we've never had any trouble, I should note though that we rent the equipment when we need it from a local outfit so we haven't had to maintain it. It's proven useful enough though that we're planning to purchase our own set up next year.

I guess one other minor thing to note as a lesson learned - make sure that you have whatever your sites chemical handling processes require (MSDSs, material handling procedures, etc.) before you bring in the dry ice.

 

[edison123]

Thanks tld. I will be contacting them soon.

I like the idea of making your own dry ice.

 

[TIMMAAYY]

There are several manufacturers of dry ice equipment. Shop around and do some price checking. It's not rocket science... only one or two moving parts on a machine. Some of them have gimmicky nozzles and make claims about being able to adjust CFM on the fly, etc., which is just a marketing gimmick.

If you're using plant air, you might get some moisture in the air, which will lead to even more condensation on the surface you are cleaning, but it quickly evaporates. Many of the manufacturers also have a switch right on the gun that allows for "air only", which lets you blow air on the surface to speed up drying. If you have an aftercooler on your air compressor system, you shouldn't see a lot of condensation, unless you're doing this outside on a hot humid day.

 

[aolalde]

Hi Edison123.
We have recently blasted a ball mill synchronous motor 3000 HP 32 poles. the rotor was partially removed to reach the windings.
Dry ice blasting cleaned nicely the areas reached by the blasting but did not well at the hidden areas between top and bottom conductors.
The extreme low temperature generated a lot of water condensation (Florida). The winding required drying to restore the Insulation Resistance and PI into acceptable levels.

 

[electricpete]

We've occasionally had that done on some of our motors for various reasons although not enough to form a personal impression. What I hear from people in shops is similar to what said above: Works very well with minimal cleanup but some areas by their nature are hard to get at and it doesn't do well for oily areas.

A recommendation for customers considering this is that the people who do it should be familiar with motors/generators. Lots of people advertise the dry ice cleaning service but may not be specialists in motors. (Obviously that doesn't apply to edison's original post)

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[edison123]

Hello Alex. Nice to hear from you. Thanks for confirming my worst suspicions - ineffective cleaning between layers and condensation. And what exactly happens to all that dirt and grease ? Do they just vanish ?

There is a misconception about the condensation part since many are led to believe that dry ice is all CO2 and hence there won't be any moisture by using it.

I have put my plans of buying one on hold for now given the economy.

Thanks pete for driving those points in with more validation.

And thank you TIMMAAYY for reviving a dead thread of mine.