o-ring vs gasket?

[gcbryan]

Regarding keeping water pressure from getting past the lens any thoughts/facts on what is more effective, using properly sized o-rings or using either silicone sealant or underwater putty epoxy to just seal up the area?

In a manufacturing sense (assembly line) I can see that an o-ring is speedier. For a home build curing time isn't a factor.

O-rings and silicone sealant would both allow some flexing which might keep the stresses on the lens down a bit. Epoxy would require the lens to take all of the stress.

From a logical point of view silicone sealant just seems like liquid o-ring material that can provide a custom fit.

Any thoughts or experience in this matter?

 

[steve6690]

If you need to get it apart again at some time in the future I'd say a properly-sized o ring is the way to go. My own dive light has a single o ring and can do 300m. They use o rings in critical applications such as rebreathers so I would tend to trust the science behind them.

 

[gcbryan]

Good points.

I do trust the science behind them. In certain cases though it's possible to convert non-dive light to dive lights. If you don't have a lathe or the ability to control the size of the gland or if there is no gland then it seems that silicone sealant is a pretty good option. It should be reversible also.

Epoxy wouldn't be of course.

I'm trying to learn more about o-rings at the same time that I'm experimenting a bit with silicone sealant and just read the post on here where someone used epoxy putty as well.

 

[H20doctor]

I have used JB weld to seal up the front of a lens... and I have also used 100% silicone also... i did this on lights where i new there were never going to be serviced, and if they broke or flooded then they went into the trash..... gaskets and gasket fits are almost always hand cut , and that means time , and trial and error... it would be nice though to use a gasket type of seal on a light

 

[gcbryan]

I have used JB weld to seal up the front of a lens... and I have also used 100% silicone also... i did this on lights where i new there were never going to be serviced, and if they broke or flooded then they went into the trash..... gaskets and gasket fits are almost always hand cut , and that means time , and trial and error... it would be nice though to use a gasket type of seal on a light

Have you found that silicone worked better than JB weld or did the both just work?

I figured that JB weld would work unless you missed a spot and then it would be impossible to fix. With silicone it's flexible and in most cases you could get back in there if you had to. Just curious.

 

[Packhorse]

Here is how I see it and I am not expert, but...

Gaskets have pressure applied on a greater surface area meaning it spreads the load more which may not give a good as seal as a O ring.

JB Weld has no give. Although very strong it might crack under pressure.

Silicon sealant will not stick all that well and also there is no compression to aid in sealing.

Simple fact is O rings work really well. When the design is right the higher the pressure the better the seal. Sure other methods may work, but they are not optimal.

 

[gcbryan]

Here is how I see it and I am not expert, but...

Gaskets have pressure applied on a greater surface area meaning it spreads the load more which may not give a good as seal as a O ring.

JB Weld has no give. Although very strong it might crack under pressure.

Silicon sealant will not stick all that well and also there is no compression to aid in sealing.

Simple fact is O rings work really well. When the design is right the higher the pressure the better the seal. Sure other methods may work, but they are not optimal.

I think I agree with you in general but if you are talking about a lens with silicone on both sides and where the lens is also pressed against a hard surface I would think the silicone must compress a bit just like a silicone o-ring.

 

[Packhorse]

If you half did the thread up and let the silicon set then did it up a bit more then maybe. But you may run the risk of splitting the silicon.

But if you put silicon on it and do it up then there will no compression.

 

[gcbryan]

If you half did the thread up and let the silicon set then did it up a bit more then maybe. But you may run the risk of splitting the silicon.

But if you put silicon on it and do it up then there will no compression.

I was experimenting with a light that wasn't designed to be a dive light. On a well designed dive light is there generally an outer o-ring, then the lens, and then an o-ring behind that?

There would have to be that inner o-ring right...otherwise there would be no compression. Mine only had the first o-ring.

 

[Packhorse]

It all depends on the design.
Some have a O ring then the lens and then another Oring that doesnt do the sealing but pushes the lens on to the 1st Oring to seal.
Other designs like the Mag light use a threaded bezel that screws down pressing the lens and O ring together.
The Mag is a bad example as the sealing O ring is on the outside of the lens and the deeper it goes the more likely it is to leak. It also requires a second O ring on the circumference before the thread. It is much better to have a O ring behind the lens. In which case the front O ring isnt so much for sealing but just an interface between the bezel and lens.
Having said that, I have built a dozen or so can lights based on maglights with no mods to the lens sealing except a thicker lens and thicker O rings. Never had one fail.

Anyway it both designs the O rings are compressed.

 

[gcbryan]

It all depends on the design.
Some have a O ring then the lens and then another Oring that doesnt do the sealing but pushes the lens on to the 1st Oring to seal.
Other designs like the Mag light use a threaded bezel that screws down pressing the lens and O ring together.
The Mag is a bad example as the sealing O ring is on the outside of the lens and the deeper it goes the more likely it is to leak. It also requires a second O ring on the circumference before the thread. It is much better to have a O ring behind the lens. In which case the front O ring isnt so much for sealing but just an interface between the bezel and lens.
Having said that, I have built a dozen or so can lights based on maglights with no mods to the lens sealing except a thicker lens and thicker O rings. Never had one fail.

Anyway it both designs the O rings are compressed.

I see, thank. The light I tested had the Mag type of construction.

When you replace o-ring are you measuring them and then just ordering online or locally based on your measurement or do you take the existing o-rings out and take them to a local o-ring supplier and have them give you something similar but thicker.

I'm not clear on how people do this. Do you just get a bunch of different o-rings and try them until one fits? Do you use Nitrile or stay with silicone with a higher durometer?

 

[Packhorse]

It all depends on the application. If its a dynamic O ring there will be a optimal size.
For static like the Mag light bezel I use the next size up. Truth be told you will probably be OK with the stock ones....maybe.
I always use 70 duro nitrile. More due to availability than any thing.

With the W200's I modify I replace with the same size but change out the poor quality 60 (?) duro ones for 70 duro.

Take into account I am not engineer or O ring expert. But I have found this is what works for me.

 

[Delphinus]

I guys I don't know the correct word for it but the torches that I sell from Scubalight have a variation of the 2 o-rings seal that works very well.

The front glass has an o-ring under it that makes the seal and the glass is kept in place not with another o-ring but with a ring made of Derlin or similar, if you want I can take a picture of it.

 

[Codiak]

I've found JB-Weld work great for metal to metal bonding when I don't want things to move, period, ever....

For smooth, regular surfaces O-Rings work well

For irregular surfaces or things I want sealed with potential access I use Liquid Gaskets of fish tank Silicon Sealant.


keep in mind, to get a epoxies to bond on a maglite you really need to remove the aniodizing

 

[Delphinus]

I've found JB-Weld work great for metal to metal bonding when I don't want things to move, period, ever....

For smooth, regular surfaces O-Rings work well

For irregular surfaces or things I want sealed with potential access I use Liquid Gaskets of fish tank Silicon Sealant.


keep in mind, to get a epoxies to bond on a maglite you really need to remove the aniodizing

I never used JB-Weld and I don't recommend a hard material to seal water, underwater it may work but if a cave diver or a boat man let the lamp became hot the different dilatation coefficient will make it leak, believe me I have here several resin potted led lamps state of the art many ago that flooded even being full potted.

 

[350xfire]

Regarding keeping water pressure from getting past the lens any thoughts/facts on what is more effective, using properly sized o-rings or using either silicone sealant or underwater putty epoxy to just seal up the area?

In a manufacturing sense (assembly line) I can see that an o-ring is speedier. For a home build curing time isn't a factor.

O-rings and silicone sealant would both allow some flexing which might keep the stresses on the lens down a bit. Epoxy would require the lens to take all of the stress.

From a logical point of view silicone sealant just seems like liquid o-ring material that can provide a custom fit.

Any thoughts or experience in this matter?

O-ring... gaskets tend to "walk" when cranked down. You can put a bit of silicone if you want along with the o-ring.

 

[Packhorse]

O-ring... gaskets tend to "walk" when cranked down. You can put a bit of silicone if you want along with the o-ring.

Not when its designed right.
I can assure you there is no silicon sealant with O rings on the space shuttle! :naughty: No silicon lube either. Im sure its all Tribolube.

 

[350xfire]

Not when its designed right.
I can assure you there is no silicon sealant with O rings on the space shuttle! :naughty: No silicon lube either. Im sure its all Tribolube.

I didn't realize we were building space shuttles here.. lol
Main reason why I use a bit of silicone on the head is to keep water from pooling in the space between the aluminum housing and the lens.

 

[Packhorse]

I didn't realize we were building space shuttles here.. lol

You wouldnt believe some of the projects I have on the go

 

[350xfire]

You wouldnt believe some of the projects I have on the go

Hmmmm, do tell us!