UK source of very soft 'O' rings?

Most commonly available 'O' rings are about 70 Shore hardness but I need some softer ones (about 40 Shore I think). They are for a static seal so silicone would be fine but I am open to any suggestion. They will be used in seawater and the size is 6.5" ID x 0.139" section. (BS260)

I have done umpteen online searches but not found anything suitable. I just thought someone here might know where I could try.

Ian P

that

Welcome to my world.

I usually make my own as the type and composition of O rings I need are either unavailable, horrendously expensive to make or cost two pence and thirty pounds postage!

Anyway, I buy most of my Viton run-of-the-mill stuff from Simply Bearings, all my Polyurathene from McMaster Carr and I buy material from Batchelor Poly in Birmingham who can also manufacture to your own specification and if you want a number of them they are not that expensive.

O rings are, in my experience, much worse for diverse specification than 36tpi threads

graham.

Martins Rubber - Southampton

Graham

I have never made my own rings. Whilst I have had brilliant results gluing rubber with cyanoacrylate type adhesives they have been outnumbered by the failures, so never had any confidence that one could put £10,000s worth of video gear in and enclosure and know it would be stay dry.

Are DIY rings reliable and an approach I should investigate? In this case I definitely need something really soft.

Rod

The person I spoke to just now at Martins could only offer standard 70 hardness but I have bookmarked them. Thanks for suggesting them though.

Ian P

I use O rings in extremely high pressure, Air, CO2 and mixed gas applications and rarely have a failure. I spent a great deal of my time underwater and my suggestion is to contact Kirby Morgan in the US or Siebe Gorman in the UK for advice. I used to know someone in the R&D department at Desco (their "Pot" was hilarious, survive using one of those and you can survive anything, spun brass) but he was killed experimenting with Trimix. It happens.

They may be more approachable than you think. If you are determined to use 40 Durometer material I would really suggest you get them made. We used to use anything we had to hand and amazingly I survived a good many years using this "wat u got?" method. Bummer when they leak though and if you have paid for the kit yourself that is double bad! A crazy suggestion, but one we used in emergencies was a tube of silicone sealer and loose assembly then when nearly cured nip it up. Worked for us (on occassion)

graham.

Edited By Oompa Lumpa on 10/04/2014 13:55:02

Hi

We uses a manufacturer called Superior Seals to supply us with nitrile o-rings

May be worth making an enquiry

http://superiorltd.com/contact/

regards

Lee

Could try Simrit. Colin

Ian,

Have you seen Precision Polymer Engineering, Aberdeen

They list a 40 shore as one of their materials available but I have no idea what form they offer it in,
They do have design services and consultancy so may be worth talking to.

Bob D

Graham

'Rarely have a failure'!

That's far too often for me!

Whilst there is no human life at risk here, there is tens of thousands of poundsworth of video equipment and I would not want to be held responsible if it got wet.

The possibility of using soft 'O' rings was because that is what one camera housing manufacturer uses. Probably though they use the same ring in a number of products so they can purchase in quantity.

Today I got a quote from a well respected supplier (Barnwell). The cost shocked me! The best price was £14 each but I have to buy 100. (£1420+VAT etc) Cheapest outlay is £200+VAT for 5 off). Since my application is a one-off and only want 2 seals I think I will have a rethink.

Colin, Bob, Lee, Thanks. I will try those tomorrow.

Ian P

Ian

Another you might try turned up on a search Polymax **LINK**. They list a BS260 ring in silicone at about £0.75!

According to their site they do rings from 40 Shore so could be worth talking to.

Never had any contact with them so no idea what they are like.

Good luck

Keith

I frequently get seals from Polymax and think I did try them a few weeks ago but I think the ones I wanted had to be special order and long delivery so ended up very expensive.

Ian P

"

'Rarely have a failure'!

That's far too often for me!"

Sorry, I need to qualify that. The failures, seldom, are always from re-using O rings and not replacing with new. Not the actual material itself. The word "Challenger" springs to mind.

graham.

Hi Ian

The O-rings used in screw-on buoyancy-tank hatches for sailing dinghies are a soft porous rubber with a skin.

Any sailing shop would supply, I would think. About the size you need, too.

Jim

Could You revise the groove and use a square section ring You can make Yourself?

If your having to use sub 70 shore theres something seriously wrong with the design and application. Because theres not much pressure 1.5 cross section more than adequate which will take in excess of 4000psi and seal at zero. Have a look at the design

70 shore and Viton 75 shore order tomorrow you will get Tuesday from Sealforce via the bay. Beats minimum order at most places.

"70 shore and Viton 75 shore order tomorrow you will get Tuesday from Sealforce via the bay. Beats minimum order at most places."

Thank you for that, very useful thing to know.

graham.

I am not going to rise to the bait on the 'something seriously wrong' with my design.

Why would anyone manufacture sub 70 hardness rings if they were never needed?

Ian P

Lots of applications in industry for sub 70 durometer rings and seals. Lots of places in home and workshop they are needed, too.

Silicone rubber seals and o-rings are available down to 30 +/-5 durometer range commercially and probably even lower for a special. Very high heat rating too. Quite a handy seal material.

All seal and o-ring suppliers sell several hardnesses of elastomers.

No idea what prompted the "seriously wrong with design" comment.

Good luck JD

**LINK** for any information on orings. IBCO Bournemouth are the people I use at work for orings.

Andy.

Very interesting Andy thanks. I wonder if the Dupont Kalrez seals will withstand high pressure CO2? I will give them a ring in the morning I think.

graham.