O-ring material selection
O-ring material selection
(OP)
Hi,
I'm new to this forum stuff and I'm not sure if this is the right place to ask, so if you could kindly read on and if this is not the right place, could you possibly point me in the right direction?
I'm in the process of designing a water diverter valve for use in a domestic product that will divert water flow (max pressure 5 bar) from one port to another, and want to use o-rings for sealing purposes.
Basically my design comprises of 2 parts (intended to be injection molded plastic parts) in a piston/internal bore configuration with the o-rings seated radially in grooves externally on the piston part. It is intended that the valve be hand operated over a quarter turn, and this is where I need some help ... My concern is, if I do not specify the right o-ring material and groove dimensions, the piston part will 'stick' in the internal bore and will not be able to be operated by hand, which will defeat the purpose of the design! (and it's got to be watertight!)
I have done some extensive research, using various o-ring design guides available on the internet, but my application seems to fall between the accepted applications of 'static' and 'dynamic' sealing methods ... So, any suggestions would be greatly appreciated.
Thanks for your time..!
I'm new to this forum stuff and I'm not sure if this is the right place to ask, so if you could kindly read on and if this is not the right place, could you possibly point me in the right direction?
I'm in the process of designing a water diverter valve for use in a domestic product that will divert water flow (max pressure 5 bar) from one port to another, and want to use o-rings for sealing purposes.
Basically my design comprises of 2 parts (intended to be injection molded plastic parts) in a piston/internal bore configuration with the o-rings seated radially in grooves externally on the piston part. It is intended that the valve be hand operated over a quarter turn, and this is where I need some help ... My concern is, if I do not specify the right o-ring material and groove dimensions, the piston part will 'stick' in the internal bore and will not be able to be operated by hand, which will defeat the purpose of the design! (and it's got to be watertight!)
I have done some extensive research, using various o-ring design guides available on the internet, but my application seems to fall between the accepted applications of 'static' and 'dynamic' sealing methods ... So, any suggestions would be greatly appreciated.
Thanks for your time..!





RE: O-ring material selection
That's what I use, pretty extensive. Don't know if you've been through that or not yet.
James Spisich
Design Engineer, CSWP
RE: O-ring material selection
Dan
www.eltronresearch.com
Dan's Blog
RE: O-ring material selection
Apart from the O ring grooves etc, you will have to consider the effect of the plastic body/O ring combination. Fortunately, acetal is a popular choice for potable water under continuous pressure due to it's good long-term creep behaviour. It is also a good material for other polymers to slide against.
www.tynevalleyplastics.co.uk
RE: O-ring material selection
I have read the Parker guide, but couldn't identify a suggested method of sealing for my application. I think 'dynamic' sealing is the closest, but in my application the part is not reciprocating.
Pud ... Are you suggesting that the plastic molded parts be made of acetal, or is that the o-ring material?
RE: O-ring material selection
Dynamic would be moving during operation.
James Spisich
Design Engineer, CSWP
RE: O-ring material selection
O-ring material would probably be a viton or a buna-n material (most prevalent).
James Spisich
Design Engineer, CSWP
RE: O-ring material selection
I've done a bit more research on the internet, and the o-ring seal I'm trying to accomplish is referred to as an 'oscillating' seal (eg. faucet valve). The general consensus being use the same design guidelines as for a 'reciprocating' seal.
I intend to use an o-ring with a cross section size of 3mm and according to the design guidelines the groove needs to be 2.6mm deep and 3.9mm wide. Although I have read somewhere that it might be advisable to reduce the 'squeeze' on the o-ring to reduce friction.
Which is why I'm concerned about material choice for the o-ring, as I don't want the two parts being sealed together to 'stick'. Would lubrication of the 0-ring at installation alleviate this?
Any suggestions welcomed...
RE: O-ring material selection
In this case, a fingerprint's worth of silicone grease would probably be sufficient.
Mike Halloran
Pembroke Pines, FL, USA
RE: O-ring material selection
The body - not the O rings.
Ticona (used to be Hoescht (sp?)) have had water valves on continuous pressure test for over 20 years in Germany (just to make sure, they say). They will tell you all you need to know about water valves and their like.
Not sure where in the World you are, but Ticona have Technical Support in most places on the planet.
H
www.tynevalleyplastics.co.uk
RE: O-ring material selection
Ed Danzer
www.danzcoinc.com
www.dehyds.com
RE: O-ring material selection
Even with the guidance you will need to plan for testing and iterations to refine the design. Make you mold dimensions "steel safe" so it if things change you can do it by removing steel instead of adding it.
P.S. if you use someone's design guides specify them as the brand of the seal or material.
RE: O-ring material selection
RE: O-ring material selection
Ted
RE: O-ring material selection
After considering all the design requirements for o-rings and the close tolerances that are needed (that I'm sure will be difficult to attain with plastic molded parts), I have decided to use a 'T' shaped rubber extrusion to create the seal between the parts used in my design.
Again, thanks for your time!