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RE: [PSUBS-MAILIST] Great link page - mechanical seals

Hi Doug,
 
I didn't know you were building an ROV! I have a number of hobby servos of the largest model produced lying around from an earlier project -- let me know if they'd be of any use to you. As hobby servos go, they're monsters almost the size of a pack of cigarettes.
 
I've had a quite frustrating time researching seals, so appreciate the information below. It sounds like they had someone knowledgeable to speak to, and I'll give him a call. In general I've found vendors have organized their offerings centered on pump brands and models. If I were to call asking for a seal for pump XYZ they'd know exactly what I need. But ask them for a 500 psi seal for a 1" shaft, and they don't know how to find it.
 
So far, the seal that seems to do the job for me is John Crane's type 9B. However, since it's about $650 I'm still doing a little research on alternatives. MSC sells very cheap "type 21" seals and in their catalog specifies they are good for 250 psi unbalanced, and something like 600 psi unbalanced. Problem is, there is no balanced/unbalanced choice in their part numbers when ordering. The balanced/unbalanced feature is a function of the seal geometry, not installation. And other vendors list the type 21 at only 250 psi. MSC gave me the contact information for the supplier, but it turned out to be the wrong company, and even though I went back to MSC a second time that's who they had in their database. So my conclusion is their catalog is simply in error on those specs.
 
thanks,

Alec

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of djackson99@aol.com
Sent: Thursday, March 29, 2007 7:47 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Great link page - mechanical seals

Vance, thanks for continuing to bring this point up, and David and Alex; thanks for the leads.

I talked to an engineer with Parker about their FlexiSeal products:
http://www.parker.com/packing/cat/english/5315_FlexiSeal.pdf

Regarding a seal was for a 1/4" stainless steel drive shaft in sea-water.  He said I want the smallest cross-section seal possible, with the lightest spring load, and then the the breakout torque
from the seal will reach 5 in oz at approximately 350 psi, requiring 0.003 hp.  At 1500 psi the torque
is around 25 in oz, or .012 hp.  With a "back seal" or a second harder material seal behind the primary seal to prevent it from exturding between the housing and the shaft, these seals can be used to 3000 psi!  But why before that point the entire lip of the seal will be smashed against the shaft and sucking away more torque as the pressure increases.

Specs:
Material:  Graphite filled PTFE
High Pressure: Extended Heel Option
Lip Style: Chamfered ID & OD
Spring: Stainless / canted coil / Light Load
Part Number: 0149 FH x 062 00250 140 SVM -010

I am planning on using hobby motors for positioning thrusters (ROV Not Sub) so the torque requirements are very important since these little motors don't have much to spare.  The loading on a trolling motor shaft will be higher due to the fact that most trolling motors have 3/8 inch shafts and not 1/4 inch, but they also have a lot more hp to spare.  Based on these numbers, I would not bother oil compensating a trolling motor unless it was going below 1000 ft and a hobby motor unless it was going below 400 ft.

The part that is missing here, is we don't know how much HP we will give up to oil compensation of a specific motor.  It is a balancing act between torque lost to the oil and current loss between the brush and the commuter (if there are brushes), the oil possibly reacting with the wire insulation and the torque lost to the seal.

The FlexiSeals come in so many sizes, it would like not even be necessary to machine the housing.  And if you went with the small cross-section seal you might be able to easily fit two so you have one as a backup if the frist fails.

I would really appreciate some feedback. 

Alex:  Did you get any details from John Crane?  

I tried AESSEAL and this is the contact info and what they recomended:
USA Component Seal Sales Enquiries Contact:  Chris Rehmann
Telephone:  +1 865 531 0192 Email:  chris.rehmann@aesseal.com
http://www.componentseals.com/
Part:B04  3/8 inch: 75 psi  Starting Torque:  Unknown  Running Torque: Unknown   $15-$28 each

Best Regards
Doug Jackson
Tulsa, OK
www.submarineboat.com

 
 
-----Original Message-----
From: david@ryma.com.au
To: personal_submersibles@psubs.org
Sent: Thu, 8 Mar 2007 11:22 PM
Subject: RE: [PSUBS-MAILIST] Great link page - mechanical seals

John Crane have a type 2100 seal that could meet trolling motor requirements.  They are available from 3/8” or 10mm up to 290 psi (20 bar).
 
Regards
 
David Paget
 
-----Original Message-----
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of djackson99@aol.com
Sent: Friday, 9 March 2007 2:55 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Great link page - mechanical seals
 
A tolling motor has a shaft size of 1/4, maybe 3/8 inch; and I don't see any mechanical face seals for less than 1/2". 

The high pressure seals tend to be cartridge units like this one: http://www.klozure.com/ViewProduct?product=52&region=1

Does anyone have a manufacture recommendation?

I do have a call into a local company regarding Parker Flexseals.  It's hard to believe but they have a max of 10,000 psi:   http://www.parker.com/packing/cat/english/5350_11.pdf

This is the starting page for the complete rotary seal product line:
http://www.parker.com/packing/cat/english/5350_0.pdf

Please let me know what you think.

Thanks -Doug J
www.submarineboat.com

-----Original Message-----
From: vbra676539@aol.com
To: personal_submersibles@psubs.org
Sent: Thu, 8 Mar 2007 8:49 AM
Subject: Re: [PSUBS-MAILIST] Great link page - mechanical seals
Ceramic pump seals--don't know which one, but it shouldn't be all that hard to find. Did you ask Crane's tech staff? Vance
 

-----Original Message-----
From: Alec.Smyth@compuware.com
To: personal_submersibles@psubs.org
Sent: Thu, 8 Mar 2007 9:26 AM
Subject: RE: [PSUBS-MAILIST] Great link page - mechanical seals
Vance, what was it they'd done to those Minnkotas again? I remember they'd 
replaced the lip seals on the shaft, but was it with ceramic seals? Because if 
they go to 1,200 feet, I'm interested!
 
I'm been spending way too much time trying to source ceramic seals. There is a 
ubiquitous and cheap seal from John Crane called a Type 21, which in the MSC 
catalog is listed as "650 psi balanced / 250 psi unbalanced". Now, all my 
research so far indicates that whether a mechanical seal is balanced or not 
depends on the shape of the seal, and they offer only one shape, so I don't know 
what MSC is talking about. 
 
John Crane claims only the 250 psi figure, and their seals for 500 psi cost 
about 20 times as much.
 
 
thanks,
 
Alec
 
________________________________
 
From: owner-personal_submersibles@psubs.org on behalf of Joseph Perkel
Sent: Thu 3/8/2007 9:05 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Great link page
 
 
 
Vance,
 
The Minn Kotas are impressive!...I've seen enough now to stop worrying about 
thrusters. 
 
Nice photos of PC 1401. Of real interest to me are the saddle tanks (appears to 
be welded sheet metal), and the forward view port.
 
From what I can see so far, for my boat, the fore and aft MBT's along with the 
fairings, can be standard mold / plug / glass construction. But the saddle tanks 
have a shape more conducive to sheet over frames.
 
So my question to you is, what gauge sheet do you suppose this is, and what 
should the interior surfaces be coated with? Once sealed, these would not be 
opened again.
 
Joe
 
 
 
    
________________________________
 
    From: vbra676539@aol.com
    Reply-To: personal_submersibles@psubs.org
    To: personal_submersibles@psubs.org
    Subject: Re: [PSUBS-MAILIST] Great link page
    Date: Wed, 07 Mar 2007 15:36:12 -0500
    
    
    Re: 1401. Do you guys remember the discussion we had about Minn-Kota 
thrusters modified to sustain up to 1200 feet without compensation? Well, there 
they are. Vance
     
     
    -----Original Message-----
    From: MerlinSub@t-online.de
    To: personal_submersibles@psubs.org
    Sent: Wed, 7 Mar 2007 3:28 PM
    Subject: [PSUBS-MAILIST] Great link page
    
    
    http://www.modell-u-boote.de/links/links_originale/links_originale.html
    
    http://www.modell-u-boote.de/originale/perry_1401/perry.html
    
    http://www.modell-u-boote.de/originale/marder/marder.html
    
    http://www.modell-u-boote.de/originale/holland/holland.html
    
    regards Carsten
    
    
    
    
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