An O-ring is a simple and versatile ring-shaped packing and sealing device with a circular cross section. It functions as a compact and reliable sealing device by absorbing the tolerance stack-up between closely mated surfaces in both dynamic and static applications. They are commonly used in machine design because they are low-cost, easy to produce and have simple mounting requirements. Characteristics of O-rings
- They can seal over a wide range of pressure, temperature and tolerance
- Ease of service, no smearing or retightening
- No critical torque on tightening, therefore unlikely to cause structural damage
- O-rings normally require very little room and are light in weight
- Can be reused, and advantage over non-elastic flat seals and crush-type gaskets
- The duration of life in the correct application corresponds to the normal aging period of the O-ring material
- O-ring failure is normally gradual and easily identified
- They are cost-effective
- Where differing amounts of compression effects the seals function, an O-ring is not affected because metal to metal contact is generally allowed for.
- O-ring compounds can be selected to resist most environmental extremes
For demanding sealing applications when customers require the very best, Kalrez® parts manufactured only by DuPont Performance Elastomers, are the elastomer seals of choice. Supplied in standard O-rings or custom shapes, Kalrez® resists over 1,800 different chemicals while offering the high temperature stability of PTFE (327°C). Types Available:
- Slabs and Sheets
- Custom Parts and Shapes (Rod, tubing etc)
Kalrez® Compound Available (Click on each of them for more informations):
An encapsulated O-ring is a two-component circular seal with a round cross section. The elastomers impart memory to the seal and are encapsulated in a teflon jacket. The encapsulation protects the elastomer from hostile environments.
Advantage of using Encapsulated O-Rings:
- Corrosion Resistant
- Low absorption
- Uniform dimensions
- Low Ovality
- Excellent Resilience
- Enclosed Core
- Live Seal
- Abrasion Resistant
- Chemically Inert
- Impact Strength
- Smooth surfaces
- No Swelling
Back-up rings help prevent extrusion in high pressure service or compensate for loose fitting parts. The use of loose fitting parts makes for cost reduction in the machining of unit components.
The 90 durometer curve may be used to find the maximum recommended clearance at a given pressure for temperatures up to 74°C. In using these curves, it must be remembered that cylinders tend to expand when pressurized. The extrusion curves can be used in 2 different ways to reap the benefits of backup ring, depending on the application. In low pressure seals, the curves will indicate wider permissible clearances than those given in the design charts. Tolerance on these can be opened up until they permit these larger clearances to occur, resulting in substantial machining economies. When tolerances are increased, however, one must check to be sure that squeeze values cannot become too high or too low.
In high pressure applications, the curves will indicate whether adding a backup ring will permit the use of standard catalog gland dimensions or whether the clearance will need to reduced further.
In double acting seal assemblies, a backup ring is required on both sides of the O-ring. It is cheap insurance to use 2 backup rings even in single acting installations.
Quad-rings are four lipped seals with a specially developed sealing profile. It has a double sealing function as compared to O-ring. A wide range of elastomer materials for both standard and special applications allows practically all liquid and gaseous media to be sealed. The choice of a suitable material is determined by the temperature, pressure and media. They are vulcanized as a continuous ring. Quad-rings are supplied to the American Standard AS 568 A.
Advantages of using Quad-ring:
- Avoid twisting in the groove.
- The seal does not tend to roll in the groove during reciprocating movement.
- Low friction. It requires less radial squeeze than a comparable O-ring.
- Less squeeze mean less friction, less wear, and thus a longer service life
- Very good sealing efficiency. Due to it special profile, a high sealing effect is achieved.
- A lubricant reservoir formed between the sealing lips improves start up
30 sizes of O-rings in a handy storage case.
This convenient O-ring kit contains 30 of the most popular sizes, for a total of more than 400 O-rings, in one convenient kit. It is really to use and will give you easy access and storage to whatever size you need.
O-ring cord is used instead of an O-ring in certain cases. It is only applicable as a static seal. They are made from extruded strips, and the joint is either by vulcanization or an adhesive. They are the most versatile and economical form of seal to be used today and are accepted by engineers as an essential item in hydraulic and pneumatic equipment.
O-ring cords are available in NBR and Viton.