Need Help on Seawater Seals for a shaft

[GFS666]

Hi All,
I need help in finding a seawater seal. I have a unique application where I have two filtered (to 10 microns) seawater filled chambers. A shaft turning at 3000 RPM runs between the two chambers. Chamber #1 will vary in pressure from ambient to 750 psi. Chamber #2 will have a pressure either equal or less than chamber #1, with minimum pressure in it being ambient. I need a seawater seal for the shaft going between the two chambers so that seawater doesn't flow between the two. Does anyone have a recommmendation for a seal that would do the job? And would anyone have a recommendaton on the shaft material? I'm assuming a Stainless Steel shaft would work well in this application, but anyone's experience would gladly be appreciated..

Gordon

 

[Heckler]

Bal Seal Engineering, Inc is a great start for your seal research.

http://www.balseal.com/products/index.php

Heckler
Sr. Mechanical Engineer
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[Scipio]

That's unique alright, am I reading right that it's separating the two flooded chambers and the intent is the seal is wetted on both sides, and the differential across the seal can be anywhere from 0 (both chambers same pressure) to 750 psi (chamber 1 full pressure, chamber 2 atmospheric)?

As for shaft material, some sort of stainless, yes, but you have to be careful. Depending on your temperatures, some stainless materials don't react well with the chlorides in sea water. Unless you're running cold I'd avoid austenitic stainless, martinsitic might work though. Or you could look at marine grade shaft material like aqualloy.

 

[EdStainless]

You will need a high alloy shaft material, otherwise you will get crevice corrosion under the seals.
Historically Monel 400 or K-500 was used depending on strength needed. You could use a 6%Mo superaustenitic stainless, but this would be almost as expensive as Monel these days.

Your best bet might be a duplex. You could look at 2205. It will not be immune to corrosion in this application, but it should work.

Try John Crane for seals. The metal parts will all need to be Ni alloy.

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[zeusfaber]

AES seals is worth a look too - lots of experience with funny pressure seawater work.

A.

 

[RotEquipEngr]

I would recommend either Chesterton or Flowserve seals. Chesterton had a pump and seal line that was designed exclsuively per U.S Navy specs. to be used aboard naval vessels, so they will have a lot of know how and expertise dealing with sea water applications. I believe that one of their designers was an engineer on a submarine in the Navy. My contact for engineered solutions for mechanical seals is Mike Ellsworth at 318-470-0716 in Shreveport, La. He can get you headed in the right direction.

 

[JP01]

The corrosion rate of Seawater is affected by air (oxygen) present, the temperature and sodium concentration, therefore the area and sea which you are working in will determine the corrosion rates.
Stainless steel is generally not recommended but Duplex materials are very common for cast and machined parts in cartridge mechanical seals. However Monel is safer but very expensive (with the multi-springs in Hastelloy).
If you want further good application data, you can look on

http://www.aesseal.com

 

[unclesyd]

I would use Aqualloy 22 or Aquamet 22 for the shaft. You can get TGP and straightened in about any size you want. There are tables that the load carrying capacity all mapped out.

I would give these people a call.

http://www.wbmetals.com/shafting.asp#22