How To Seal 3 Phase Motors From Water Intrusion?

Look at the ingress protection rating of the motor and check that it is suitable. If not, then replacement of any leaking terminal box seals, or even the whole motor, is the way to go.

http://www.protectingpeople.co.uk/fire_tech/ip_explained.htm

At our hydroelectric plant, the terminal box is filled with a high viscosity silicon gel. It's a pain when you have to disconnect the motor, but it is very effective. You might also try converting to watertight plugs.

As for the shaft end, you could add a sheet metal baffle around the shaft end to reduce the spray velocity before it reaches the seal. I suspect the shaft seal was not designed to handle that type of pressure/velocity. It would be difficult to design a seal which could keep out a direct spray of that magnitude while still allowing free rotation of the shaft.

<the terminal box is filled with a high viscosity silicon gel>

Does this affect the original equipment manufacturer's warranty at all?

This is actually the manufacturer's recommendation. The entire plant was build in France by Alsthom Atlantique and shipped to the US on 2 barges. All of the motors were already installed with the gel inside the terminal boxes.

Could you contain the motor (with all its protective circuitry) in an IP rated box having the shaft end extend out of the box via an appropriate shaft seal? You could mount on the outside all the IP rated switches for the machines operation! Or is this OTT?

Get in IP67/IP68 rated motor is the best way!

Best way to solve is referred to enclosure standard such as IP or IEC, chosing the motor application appropiate to its standard code.

But traditionally, for junction box it need to be modified so that the cover is sealed from outsider by adding rubber for instant.

For infiltration from shaft, it need to be modified its bearing housing by adding seal nozzle but this difficult to do.

Do not know anything about junction boxes, but for shaft ends there are many manufacturers of "bearing protectors". A simple search should find manufacturers. One of the best designs that I have seen is either MagTecta or the LabTecta made by AESSEAL (and no I do not work for them).

It will be very difficult to make nonwashdown motor "sanitation proof", make the offending parties bag all vunerable equipment & charge for ant start up failures.

Just make sure you have some sort of bellows to allow for expansion and contraction of the air inside the motor during changes in temperature. If you don't do that you will suck moisture into the motor when the motor cools off.

I fully agree with this statement. Have you thought about the little nooks and crannies everywhere on the motor and the mount? The water, if it is water we are talking about, will attack this poor motor everywhere and that means NOT ONLY AT THE JUNCTION BOX OR SHAFT END!

I am afraid that converting a normal motor to work under these conditions will be more expensive than using one designed for the job. If you do not take all these in account, including the heat it produces and the electromagnetic field it will have, you will end up with a motor that is going to rot away while you wait.

I also am in a similar environment. We use both manual and CIP sanitation methods with high pressure, real hot water, and Zep chemicals. When I first took over maintenance in this plant 5 years ago they were doing everything from smearing RTV all over to wrapping things with garbage bags. EMT and flex were all over in places that should be sealed rigid. And of course they were killing lots of motors and frapping lots of wires. You can put in the best motors and if the rest is crud...well you know...

I standardized on Baldor and I'm extremely pleased with their washdown motors. Stainless housing with welded on peckerhead. TEFC or TENV. Hard to kill. Good quality.

One thing to be aware of...Washdown motors do not shed heat as well and run a little hotter. If your application does alot of normal start stop motion then you need to leave the motor run continuous and use a Warner clutch/brake(or whatever brand you prefer) to control movement. Simple to apply.

Kinda late contribution but on vehicle washing plant I used a small quantity of dry compressed air fed via a needle valve to a connection tapped into the terminalbox lid.

Special motors with potted terminal boxes needed air connections into an end shield.

The air needed is just a whisper not sufficient to blow out shaft seals,and avoid grease being pushed out of bearings.