Choosing rotating shaft seal for submerged water application

Choosing rotating shaft seal for submerged water application

Choosing rotating shaft seal for submerged water application

abeschneider

(Mechanical)

(OP)

28 Nov 06 00:38

Hi,
I'm trying to specify seals for an application as follows:
- submerged, freshwater (river water; not many particulates; some chance of suspended sand)
- max pressure: 3 psi
- max vacuum: 8 psi
- shaft speed: 520 RPM, continuous, single-direction (non reversing)
- surface speed: 1.4 m/s (4.5 ft/s)
- shaft hardness: 25-27 Rc
- desired life: at least 2 years continuous operation

I'm having trouble figuring out what seal to choose; it seems a mechanical seal is overkill given the low pressure and speed.  Packing is leaky and maintenance-heavy. I've heard O-rings "are not good in dynamic situations".  And lip seals damage the shaft and wear very quickly.

What is a good suggestion for the main shaft seal?

By the way, the shaft bearings (ball) are on the "dry" sides of the shaft (think of the application as a shaft going through a box filled with water under the above pressure).  Should I specify both shaft seals at the "box walls" as well as bearing isolators?

Thanks for your help.

P.S. I posted this in the "Mechanical Seal Engineering" forum a few days ago, but haven't received any replies.  Sorry if I offended anyone by re-posting in this forum.

RE: Choosing rotating shaft seal for submerged water application

eromlignod

(Mechanical)

28 Nov 06 10:12

How about a lip seal with a wear band under it?

Don
Kansas City

RE: Choosing rotating shaft seal for submerged water application

Philrock

(Mechanical)

28 Nov 06 11:06

You might also consider a pre-seal - a seal whose main purpose is to protect the main seal.  I often use an o-ring as a pre-seal and a fluoropolymer u-cup as the main seal.

Since you have bi-directional pressure, you may need 2 seals at each sealing point.

By far your best resource for information on this will be seal manufacturers such as Parker or Bal Seal.

RE: Choosing rotating shaft seal for submerged water application

Heckler

(Mechanical)

28 Nov 06 14:36

I would contact http://www.balseal.com/index.jsp . Lip seals have to create a wear surface on the shaft. I did a miniature pump for a remote sensor application. Seal drag was very critical since this pump was solar powered. One thing we tried with great success is coating our shaft with NP3 (EN w/teflon codeposit) http://www.coatingtechnologiesinc.com/services_plating.htmlThe teflon codeposit really helped with reducing friction and bedding in of the seal.

Best Regards,

Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
XP Pro SP2.0
NVIDIA Quadro FX 1400
      o
  _`\(,_
(_)/ (_)

Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login