DIRECTIONS ON USE OF RK 'O' RINGS

One Single 'O' Ring per sealing point is enough to seal against vaccum and pressures over 15000 PSI, so long as suitable materials, correct dimensional and installation tolerances and selected.

'O' Rings are used especially for static application and also suitable for dynamic sealing. 'O' Rings can also be used for slow turning movements. Their use in the case of High Peripherical Velocities is however, not recommended.

ABOUT RECIPROCATING SEALS

• Not less than 30 cm. per minute when the pressure difference across 'O' Ring is less than 25 KG/SQ. CM.
• Lack of lubrication will result in excessive wear. Metal plated smooth surface will be preferred.
• Squeeze of more than 8% on cross section on long stroke application will be prone to spiral failures.
• The back - up Rings provide extra lubrication on the return stroke which helps to prevent spiral Failures.

ABOUT ROTARY SEALS

• Rotary seals for shaft seals, & similar applications. The maximum speed Recommended is 450 meters per minute.
• Shaft material should be hardened steel having 55 rockwell hardness
• 'O' Ring clearance, side thrust and end plate are very critical Rotary seals.
• Most elastomers under elevated temperatures will contract due to this reason. The 'O' Rings should never be under permanent stress conditions.
• The friction between the 'O' Ring and the Rotary shaft results in heat evolution. Hence dimensional tolerances should be maintained critically.

ABOUT OSCILLATING SEALS

• A speed of not more than 60 meters per minute is not recommended.

SPECIAL CHARACTERISTIC OF 'O' RINGS

"RK" 'O' Rings can give leak-proof sealing in static applications even at very high pressures. The pressure may be constant or variable. The maximum pressure recommended for the softer materials in dynamic applications is 18 Bar, and in the case of harder grades 70 Bar. For dynamic seals at higher pressures, O-Rings have to be used together with Back Up Rings.

Though 'O' - Rings offer a reasonable approach to the ideal hydraulic seal, they should not be considered the immediate solution to all sealing problems. There are certain definite limitations on their use i.e. high temperature, high rubbing speeds, cylinder ports over which seals might pass, surface finish of parts in contact and large shaft clearance. Disregard for these limitations will result in poor seal performance. All the types of "RK" O-Rings stated above have their advantages in sealing designs, but where the design, specifications permit the proper use of 'O' Rings, they will be found to give long and dependable service.

COMPATIBILITY

The fluid or fluids with which the 'O' Rings will be used is one of the first considerations. If the fluid will have an adverse effect chemical reaction resulting in surface destruction, loss of strength, dissolution or marked change in physical properties immediately or so as to give short life. There is little advantage in proceeding with the design until the problem is solved. If more than one fluid is involved both the sequence and time of contact with the 'O' Ring need to be considered.