What is best solvent ( environmentally safe) can be used for big generator (stater & rotor) contaminated by oil? what is the standard amount required per area?
Not sure exactly what you mean by "big generator", this procedure from CAT (attached) I have used on several occasions, usually in remote areas or when we needed to get a machine back up and going ASAP after a flood or similar situation. In most cases a field cleaning effort worked ok, sometimes the generator was just too far gone.
I did field cleaning on two 1MW generators that were oil soaked from rear seal failures late last year, using Zep Industrial Purple Degreaser (can't use anything really good in California). Used hot water from a standard hot water heater at about 120 degrees F, applied the soap with a hose end sprayer, let it stand about 10 minutes, rinsed with hot water, blew out free water with compressed air, dried overnight with a couple of large forced air heaters, then ran them with the generator output leads shorted and a power supply on the field. Took two days to get decent readings, but overall got them back in service way quicker than a clean dip and bake. They were retested last month, still ok, but they also run all the time so they stay relatively warm and dry.
Have had mixed results with dry ice cleaning, really depends on how much oil and grease you have on the windings and for how long.
Oil easily gets yanked out of the generator windings when you wash with detergent soap and pressure wash with steam.
Your big problem will then be drying the windings in such a way that you won't generate too much steam when trapped water inside windings expand!
thanks all
my generator is 26 MW Brush type , due to some reason sealing failed and lot of oil entered the generator housing and due to heat oil spread over all winding , walls and ceiling , everywhere inside housing. I want to pull out rotor from stator and do thorough cleaning .
who has such experience and advice me.
I'll reiterate with Parchie said. Steam (or sometimes water) spray followed by bake cycle is how machines are usually cleaned in repair shops. It is probably the "best" of all the options available if you have ability to get the stator to a shop where it can be baked. But if you're trying to do it in the field, then you have to figure out how to dry it since you can't throw the whole stator in the oven.
Dry ice cleaning has been discussed before - has the advantage of very little cleanup since the CO2 pellets disappear (sublimate). But it's not known to be great for removing oil.
I have experience with attempting to clean a stator in place on a horizontal sleeve bearing motor 2500hp with oily/dirty stator windings. Rotor was removed and citrosol was sprayed (low flow rate and low velocity from handsprayer) and some handwiping was done. It seemed to do a good job where we could easily access for example the outside of the knuckles. It seemed relatively effective in removing the film that could be seen/felt. But there were a lot of inaccessible places and I also couldn't shake the feeling that we were just washing a lot of the dirt into the crevices.
If this is a DAX series machine then check the bearing vent / pressure equalising hoses from the bearing pedestals to the plenum. At one point in time Brush used a spiral-reinforced hose not dissimilar to Kopex flexible conduit and it used to harden and fracture resulting in oil seepage from the bearings. Might have a photo or two somewhere - my PC is in pieces right now so will have a look when I get things sorted out.
