O-RING

I have a basic doubt that you understand what is an O-ring

I think its the o-ring you need to design first considering the pressure,temperature and mating diameters involved. although i am no expert on this, my logic is you design a television and then design the box it fits into?

Hi NickName,

it was not necessary for you to be so blunt. This is a forum where you can ask questions. and that is what that person has done. If you are an expert in o-rings,please help him or else do not comment.There are other people who will answer.

Who did answer ?

Till now, as far as I can see, nobody.

The process to design an O-ring is quite complex and to day the geometry is almost all over the world standardized since the forms to produce o-rings are very expensive. I know it because a long time ago I was obliged to design o-rings and had to find solutions for the problems I met. At that time there was no software able to do a finite element analysis for elastomers and even the linear small deformation FEA was difficult to use, not usual and not always accessible due to high cost. So that all design was based on good sense, series of experiences and the few books where some limited informations were available.

Now o-rings are not any more "designed", they are chosen in catalogues and only the material is some time different from the standard choice (very broad)according to the specific requirements of the application.

Dimensions are related to each other so that as well the torus mean diameter as the torus section diameter are defined at same time. The problem this type of seal has to fight with is the extrusion in the gap at higher pressures. The value of "high" is relative and to avoid it the Shore hardness is adapted to the pressure range. But the higher the hardness the higher the permanent set and thus the higher risk of leaks at low pressure. This is the reason why anti extrusion rings have been developed in order to combine the low hardness of the o-ring which gives a good sealing at low pressure with the low risk of extrusion of the added rings at high pressure.

Now this is a VERY short presentation of a few o-ring related aspects.

If you want to go into more details then you should download the o-ring book from the parker -hannifin site and study it. It also not complete there are several aspects (detail aspects) not described since they are related to very specific and seldom met applications.

Satisfied ? If yes ok, if not ask again but more specifically and also explain the basics of the question.

Nick Name

hi

what is the formula for calculating gland fill. I read value of gland fill should be ideally 75-80% to accomodate various expansions(thermal,etc) but in AS568A standards for a particular o-ring cross-section dia , the gland height and width is always lesser. This leads to gland fill being more than 100%
What mistake am i making. Please guide

Have you followed the indications and downloaded the Parker O-Ring manual?

Instead of asking questions as you do it is for you better to look in this booklet and understand the O-ring related problems. I do not know the standards you mention if you look in the booklet you will find yourself where the error is.

To your information the temperature is not the principal reason for an expansion reserve, it is mostly the fact that under the effect of the fluid the compound does change its volume.