Author Topic: Silicone Grease  (Read 6684 times)

a1v1n

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Silicone Grease
« on: 02 Nov 13, 21:02 »
just wondering if there is any specific type of silicone grease for greasing of o-rings for dive torch/uw casing? i'm seeing many different types being sold whether in shops or online.

thanks in advance!

discoburg

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Re: Silicone Grease
« Reply #1 on: 03 Nov 13, 07:27 »
Whats the reason for greasing o-rings?
just wondering if there is any specific type of silicone grease for greasing of o-rings for dive torch/uw casing? i'm seeing many different types being sold whether in shops or online.

thanks in advance!
I do agree that the Mola-Molas are a MYTH!

BareBear

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Re: Silicone Grease
« Reply #2 on: 05 Nov 13, 14:36 »
I think as long as it says silicone grease, and does not contain any petroleum products, it should be fine.

Buy them in grease form instead of spray form, the grease form will be more tacky and form a physical barrier against water seepage.

The reason silicone grease is used is because greases made from crude-derived products will cause rubber to deteriorate over time.

discoburg

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Re: Silicone Grease
« Reply #3 on: 05 Nov 13, 16:42 »
Why not just replace the o-rings over a period of time? Safer. By the way grease will not form a physical barrier against water seepage.
I think as long as it says silicone grease, and does not contain any petroleum products, it should be fine.

Buy them in grease form instead of spray form, the grease form will be more tacky and form a physical barrier against water seepage.

The reason silicone grease is used is because greases made from crude-derived products will cause rubber to deteriorate over time.
I do agree that the Mola-Molas are a MYTH!

grbenji

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Re: Silicone Grease
« Reply #4 on: 05 Nov 13, 18:34 »
Why not just replace the o-rings over a period of time? Safer. By the way grease will not form a physical barrier against water seepage.

Grease reduces friction, especially for those covers/ports that close by twisting/turning.

lybc

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Re: Silicone Grease
« Reply #5 on: 06 Nov 13, 09:56 »
Why not just replace the o-rings over a period of time? Safer. By the way grease will not form a physical barrier against water seepage.

Agreed. The grease doesn't block the water. It is to maintain the "quality" of the O-ring. Gievn the cost factor, I would choose preventive maintenace over corrective maintenance anytime.  ;D

bighead

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Re: Silicone Grease
« Reply #6 on: 06 Nov 13, 11:49 »
Rubber (or elastomers) will harden over time and degrade. In such cases, the rubber will lose it elasticity and crack easily. Hence, grease is usually needed to keep them SOFT so that it can conform to the space needed for proper sealing. Most of the O rings used are made of NBR. Hence, using silicone grease will not be an issue. If you are not sure, you can get the grease from Andrew at S&S.

Replacing the O rings is definitely much better as rubber has a shelf life. Most important is to bring the O ring and housing down to the shop so they can do a test on the spot to check if it fits well.

siaokao

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Re: Silicone Grease
« Reply #7 on: 06 Nov 13, 14:45 »
It seems like there are many different views to this issue.  I like to contribute my take as follows:

1.  Why apply Silicon Grease onto O-rings? We apply grease onto o-rings to ensure the o-ring sits properly into its place.  When we close covers for strobes, torches or camera housings, there will be movement of the o-rings.  Compression movement (think camera housing), twisting movement (think torches), sliding movement (think S&S Strobe covers).  In fact, most devices or ours will subject our O-rings to several or ALL of the above movements.  Eg.  Ikelite S90/95 housing back cover hinged to one side, in this example, there will be a combination of all 3 movements. Sliding the O-ring into front housing, and because the cover is hinged on one side, side near the hinge will have different travel movement than the side further away thus creating twisting movement and finally, compression as the cover is finally closed and back cover compresses the O-ring onto the walls of the housing.  in all these movements, if the O-ring is not able to slip into place and gain traction on any part of the housing, you will ended up with O-ring not properly seated.. meaning poor seal.. which also means leak. 

Siaokao ans in short:  Grease is to ensure O-ring can slip into place, not twist, slide or compressed into a wrong position thus compromising the seal.

2.  Does the Silicon grease form a physical barrier to prevent water seepage? As explained above, no.  But it does play an important role to help O-ring get into place and keep water out.

Siaokao ans in short: NO

3.  Silicon grease condition the o-ring? Most modern underwater housing/torches uses silicon O-rings which have excellent resistance to weathering and ageing.  Therefore in my humble opinion, there is no need to keep them greased to 'condition them'.  In fact, some article even suggest silicone O-rings have poor resistance to chemicals and that includes silicon oil!  However, if you do have rubber or other elastomer based O-rings, you may like to perform that task.  Again, IMHO just forget abt this, just change them to better O-rings when you think ur current ones are 'harden'.. they cost only a few cents.

Siaokao ans in short: Why bother?

4.  Should we grease the O-ring then?  Refer to point 1.  But do not over do it as excessive grease will trap sand/dirt etc and that will be deadly for your equipment.

Siaokao ans in short:  Yes.  Just enough to lub the O-ring

Above are strictly my own opinion, you are encouraged to research into it and understand for yourself if the above make sense.  Disagree with me?  Share them, its a forum afrerall!  :)
« Last Edit: 06 Nov 13, 14:48 by siaokao »
So they call it a 'FACT' coz someone made some statements on a 'FACT SHEET'? hummm...

discoburg

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Re: Silicone Grease
« Reply #8 on: 06 Nov 13, 16:12 »
I agree and this is the only use for grease on a o-ring.
Siaokao ans in short:  Grease is to ensure O-ring can slip into place, not twist, slide or compressed into a wrong position thus compromising the seal.
I do agree that the Mola-Molas are a MYTH!

bighead

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Re: Silicone Grease
« Reply #9 on: 06 Nov 13, 16:18 »
First point is wrong. Can the o ring still be placed in the groove if its not greased ? I think its still possible. The o ring works by deforming in a predictive manner. As long as it sits in the groove properly, it can do the sealing job. Maybe the link will explain it better.

http://en.wikipedia.org/wiki/O-ring