Notices for operation with O-ring

O-ring sealing Mechanism
O-ring seals by using 2 main forces.
  • 밀봉
    ① Repulsive force-based o-ring compression SEAL If O-ring is pressed and transformed, it generates a repulsive force. Sealing is performed as O-RING groove intervals disappear.
  • 밀봉
    ② Fluid pressure-based o-ring transformation SEAL Used fluid (liquid or gas such as oil, water, air, etc.) generates pressure to transform O-Ring. Sealing is performed as O-Ring groove intervals disappear.
cmp 의미
  • 밀봉
    Compression ratio refers to O-RING compression ratio at grooves. Lower compression ratio does not give sufficient repulsive force to cause poor sealing. On the contrary, higher compression ratio is likely to damage O-RING.(see the formula below)
  • 밀봉
    Filling ratio refers to the calculated value of O-Ring cross-section area to groove cross-section area. (see the formula below) Lower filling ratio could cause a problem as O-ring can move inside grooves. On the contrary, higher filling ratio could damage O-RING by pushing it out from grooves or provides insufficient compression to cause poor sealing.
How to use o-ring for movement and fixing (lateral compression)
For movement, operation,rotation
for movement, operation,rotation
For fixing,(lateral compression)
for fixing,(lateral compression)
In this operational condition, sometimes o-ring sticks out. Please refer to the followings to deal with such sticking out.
O-ring standard   thickness d Groove height (D-d)/2 Groove width G
No Back up ring 1 Back up ring 2 Back up rings
1.9 1.5 2.5 3.9 5.4
2.4 2.0 3.2 4.4 6.0
3.1 2.5 4.1 5.6 7.3
3.5 3.0 4.7 6.0 7.8
5.7 5.0 7.5 9.0 11.5
8.4 7.5 11.0 13.0 17.0
화살표
Examples of cross-section standard of cylindrical face fixing/movement grooves (reference standard) Set the groove internal diameter at an almost same value (stretches by 0.2~0.3mm) as o-ring internal diameter(ID number). Thickness 4.0, 6.0, and 10.0 are for V series (for vacuum). No setting value for cylindrical face fixing/movement groove designing.
Stick-out measure (decide whether to use Back up ring)
Stick-out point. O-ring sticks out of the groove and is damaged.
Cylindrical face fixing/movement grooves have gaps in its design structure. Depending upon groove design (max diameter groove, housing interval), used fluid pressure, o-ring hardness, etc., stick-out could take place. Stick-out is assessed based on the following graph In the case of stick out, the following measures could be considered; Choose an appropriate one according to situation
  • · O-ring hardness change (from 70 to 90 degrees)
  • · Design change (narrower groove gaps)
  • · Back up ring addition (need to change groove design)
오링의 경도 압력 및 틈의 관계
Please note that the values in the Figure does not reflect the housing expansion caused by fluid pressure. (In general, it is recommended to consider such expansion and design gaps not exceeding 75%.)
  • pic
  • pic
A gap (max diameter gap) exists between outside cylindrical surface(housing) and inside cylindrical surface(rod or piston). If the gap is empty, o-ring sticks out to cause damage or leak.
  • 삐져나옴 발생
    The vertical axis represents fluid pressure; horizontal axis, groove max diameter gap (housing gap). Each serves as a stick-out measurement in the cases of using hardness 70,80, and 90, and back up ring. For instance, in the Figure on the right side, if hardness is 70, the color indicates stick-out existence.
Used for flat surface(flange) fixing
pic
  • 밀봉
    for internal pressure(high pressure)
  • 밀봉
    For external pressure (vacuum,decompression)
Other groove design (Triangular groove, Other groove)
pic
  • 밀봉
    Triangular groove · Standard A is 1.3~1.4 times of o-ring thickness · 45° angle
  • 밀봉
    Other groove · No groove standard · Standard and shape change depending upon how to use.

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