Gaskets Vs. O-rings for sealing

AM

Hi

I am not suggesting gaskets are better than o-rings or vice versa but interested in hearing other views regarding which is best and why for gas/pressure applications.

Regards

AnneMarie

UKSteve

Hi ..what kind do you have in mind? Ones that require differential pressure to energise or just flat rubber?

My experience of gaskets (and for that matter, lip seals, P/T/L seals etc ) comes from wellhead equipment with much higher pressure ratings.. but I could envisage gaskets being ok for static seals (i.e. ones you make up once / seldom) but not ideal for service with repeated makeup (scrubber head for example). With a gasket would you not need a lot more sealing surface to be in good condition and stay that way? Also gaskets tend to need more preloading and so beefier material on the item being sealed to energise the seal than an oring.

Steve

lizardland

I suppose the big obvious advantage of gasket seals is that you'll never be stuck for a spare. You can cut improvised gaskets from sheet rubber or inner tube (or a tube of instant gasket paste) which you can't do with an o-ring.

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David Pye

Also, with a gasket you can have a mating face with a larger surface area, making it less prone to leaks.

As an o-ring has a comparatively small sealing area, if you scratch it, then you are in leak city...

David

Drmike

orings for high pressure ap
field repair likely
freq dismantled part

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AM

David

I just realised you own my old KISS No. 69!! I hope Chiseller gave you the extra delrin parts that I gave him when I sold it. I also just noticed you have that terrible Paragon still on there, sling that in the bin and get something decent Do you dive with Alan Lopez? Tell him I still think his food is deadly and I'll see him later in the year :-)

To clarify, I am talking about a small flat sealing area, static...and a sheet gasket, i.e. rubber, but one that will be removed/refitted relatively frequently. Definitely not a gasket for the scrubber housing!!

Regards

AnneMarie

Dave Sutton

AM,

For what you describe, a gasket is fine, and in fact is easier to repair/replace in the field as one can be made with manicure scissors and a drill in an emergency. It's actually a good solution and requires less precise manufacture to make it work. I would have no concerns with it.

Just as a data point, the Russian stuff all uses gaskets, and I have never seen an O-Ring on any sort of access plate (static seals) on any of their kit. We have routinely replaced perished ones with rubber cut from tyre innertubes with perfect success. Simple = Good when it comes to field repairs. The reusability of the gasket is based on it's material, but good quality gaskets can be used many times with confidence.

Dave

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AM

It's probably not the done thing to hijack your own thread but...I wasn't asking for advice on a specific seal for a specific design. I was inviting commentary on the pros and cons of each.

My phone is running out of battery power so I can't post or read replies until later, replies on the merits of either seal type appreciated!

Regards

AnneMarie

jmhardingjr

Dave,

That old SeaLab Emerson scrubber (fiberglass) uses a flat gasket to seal. That one was tested how deep?

For those who aren't familiar with this rebreather, it's scrubber has got a hard rubber gasket that's about 1/2" wide and the scrubber lid is held on with only two bolts to compress the seal on a 4" diameter cylinder. Worked for the US Navy.

So, as far as pros and cons to sealing methods:

Okay, the gasket is sensitive to foreign particles, scratches, deformation, degradation . . . basically everything the o-ring is. The pro is that the sealing surface is usually wider and can thus be more tolerant of the above issues because more area of the sealing surface has be compromised for it to fail. But, if it's a completely flat gasket, then it needs a more significant load to hold high pressure. However, if you have a shaped gasket (ie-with a raised center ridge) or a shaped sealing surface (ie-a raised relief on one surface and a depressed groove in the mate surface) than you get the benefits of both a gasket and an o-ring.

Just my two cents.

Jay

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David Pye

Hehe, no, he didn't actually ;-) Was still worth buying it, as I am a member of the Uni club and the innuendo I can generate from owning 69 makes it quite worthwhile!

I have ditched the Paragon and went with the Mares Proton (which is much nicer and easier to get serviced!) I still have the Inspiration hose towers on it as they seem to work quite nicely! Hasn't done anything too mean to me yet, apart from the MAV o-ring shredding, upping the O2 rate quite rapidly!

Funnily enough I dived with Alan this evening (Chandris *again* sigh.. - not really his fault, other people wanted to do it..) and passed on your message! He said he wasn't sure whether your intent to dive off his boat again soon was a threat or a promise!

David