Some time ago we spoke about the O-Rings and how good they were when a risk of extrusion from the housing could exist. The O-Rings create the seal effect pressing against the housing parts that hold it, but the capacity of the ensemble depends basically on these three factors: (1) the correct choice of the O-ring, (2) the surface finishing of the housing and (3) the play between the elements.
When the O-Rings are called to exercise the seal in circuits in which the pressure reaches high levels, one of the risks to be considered is that of the ring extrusion from the housing. Such a risk is increased when the O-Ring compound is soft.
In order to avoid this risk we may rely on back-up rings (BUR), also known as anti-extrusion rings. The back-up rings are designed to guarantee a high level of seal performance in contact with the O-Ring. Otherwise said, they aim to protect the O-ring so that it may develop its task.
The choice of the right back-up ring lies in the following points which should be born in mind:
• The compounds chosen for the back-up rings must meet all of the compatibility requests of the fluids requested of the O-Rings.
• The hardness to support the other pressure loads must be suitable.
• The resistance to the usage and ageing must be high, to guarantee good performance for the entire life of the O-ring to which they are required to protect.
• The measure of the back-up ring, of course, must go with the O-ring that protects.
If the choice is the correct one the back-up ring will provide an excellent performance, as a back-up element for the piston and shank seals that may be generally found in hydraulic static circuits and hydraulic dynamic circuits. The back-up ring could be located in the rear or under the pressure of the sealing element which is holding, although there could also be different housings that hold two back-up rings, each from a different side of the O-ring.
At JIOrings we have NBR90 back-up rings according to the Parker® Standard:
From: -006 to -460 (ø3,56mm to 394,31mm).
Thickness: 1,14/1,24 1,14/1,35 1,02/1,27 1,52/1,93 2,44/2,97.
* Under request, we may provide different measures and other materials.
If you want to purchase them in our online store you can find them by product (BUR or Back-Up Ring) and size. You can also take the British Standard number that the O-ring has as a reference (for example, BS211) to search in the “Description”.
|Check stock in real time|
|Back-up rings||NBR||≤400||-20º to +100º|
Office: Polígono Erletxe,
Plataforma H, Edificio 2, Nº 5
48960 Galdakao (Bizkaia)
43º 14′ 06″ N
02º 47′ 27″ O
Telephone: 94 401 44 20