cannister lid seal type??? please help!!!

[hilk]

hi .. to DIYER....

please help to guide me for tyhe cannister lid seal ???
below attchement which picture...

i don know which one is the best O ring seal for cannister lid....please guide, thanks

type A : o ring grove & o ring at cannister

type B : o ring grove & o ring at lid

type C : only o ring at lid

type D : o ring grove & o ring at both lid and cannister

thanks

mervyn

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[dannobee]

Well, I'm no engineer, but I do know that my UW video housing has two o-rings on the lid, much like "D," except there are two parallel grooves and two o-rings in the lid. And it's rated for 200 ft, and it's never flooded in 7 years.

 

[waynne fowler]

I am not an engineer either but I'd opt for a combination of C & D.. using both of the lid O-Ring systems... on sitting like the lid ring on IMG C and the other grooved into the lid as in IMG D... it would have to leak thru both systems... the face (IMG C) being a very robust sealing surface as it is under quite a bit of compression. You'd have to be careful I'd think about making this (IMG C) seal so tight that it deforms the O-Ring and compromises the seal.

 

[oxyhacker]

There is absolutely no advantage to either A or B over C for a divelight canister - notice that virtually all the commercial cannisters use C. Recessing the face seal O-ring is not necessary, as the water pressure will keep in in position, and trying to machine seats for it greatly increases the chance of screwing up. KISS!

Type E (type C face seal with a recessed barrel seal as type D) was popular in the early days, but was gradually abandoned by most commercial light builders as just not worth the extra trouble since, among other things, it meant each lid must be precisely fitted to the canister. Another problem is that if the cylinder did leak, pressure would get trapped inside and could blow off the lid violently when the latches were released if one did not take precautions.

Camera cases are another situation, since the value of the contents is so much greater it can be worth taking extra precautions, so E might be appropriate there. Do note that one of the reasons why C is so popular is that it does not require any great skill or care in machining, while a barrel seal O-ring requires a very precisely dimensioned gland in order to be of any benefit. You can build a type C canister that will stay dry hundreds of feet down with nothing but hand tools, while the others all require a lathe or mill.

 

[mddolson]

I'm a belt and suspenders kind of guy. Knowing that murphy works overtime, I use both C and D. Knowing that it only takes one grain of sand or salt crystal on an o-ring to make it leak, I use both C and D in my cannister.

MIke D

There is absolutely no advantage to either A or B over C for a divelight canister - notice that virtually all the commercial cannisters use C. Recessing the face seal O-ring is not necessary, as the water pressure will keep in in position, and trying to machine seats for it greatly increases the chance of screwing up. KISS!

 

[hilk]

to mddolson and oxyhacher:

is this the seal that you all mean ??

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[mddolson]

Seal type.

Hilk, my lid is essentally what hou have in your type E drawing/sketch.
However I did not put a groove in the top face of the cannister as your drawing shows.
I saw no need for it. The oring is trapped against the verticle wall of the lid, and compressed between the top of the cannister and the T or flange face of the lid.

Mike D

 

[hilk]

hi.. sorry the type E seal i post picture is wrong....
below is the right one which from mddolson idea...

 

[hilk]

hi,, sorry type E seal i post is a wrong picture...

i repost againt the right one below ... which is according to mddolson idea for cannister lid seal...

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[mddolson]

right type E seal..

Yep that's it.

Just had to laugh by the way.
Take a look at the bottom of your cannister drawing . LOL
That is one tuff joint to make!

Mike D