O-Ring Seals

OTHER COMMON O-RING SEAL CONFIGURATIONS
Aside from reciprocating seals, there are other types ol motion where an O-ring seal may be utilized. For example.

OSCILLATING SEALS, in which the inner or outer member of the assembly moves in an arc relative to the other, rotating one of the members in relation to the O-ring

ROTARY SEALS, where an inner or outer member of the sealingassemblyrevolves aroundthe shaft axisinonlyone direction. The direction may be reversed. It there are multiple brief arcs of motion, the designer should refer to parameters for oscillating seals.

SEAT SEALS, utilize an O-ring to close a flow passage by distorting the face of the O-ring against the opposite contact face Closing the passage distorts the seal element to create the closure.

CRUSH SEALS, a variation of the static seal. literally "crushes" an O-ring into a space with a cross section different from the standard gland. Although often an effective seal. the O-ring is permanently deformed and must be replaced if the unit is opened.

PNEUMATIC SEALS, may be any of the previously described types but are given a different classification because they seal a gas or vapor as opposed to a liquid Thus. other design factors, such as adequate lubrication (for dynamic seals), temperature increases due to compression of gasses and permeability of the seal element must be considered when the application is pneumatic.

VACUUM SEALS, also may be any of the foregoing types (except pneumatic) and are classified separately because of special design considerations and the unusually low leakage requirements of vacuum systems.

LIMITATIONS OF O-RING USE
Although the O-ring offers a dependable and reasonably economical approach to hydraulic sealing, they are not a "universal" seal. applicable to all sealing problems Certain limitations must be imposed upon their use. among them, high temperatures.high f notional (rubbing) speeds, cylinder ports over which the seal element must pass and excessive clearances. 0-rings therefore, may beconsidered for just about all sealing applications except:

1. Rotary speeds exceeding 1500 fpm contact speed.
2. Environments (temperature and media) incompatible with any elasto-meric material.
3. Insufficient structural support for anything but a flat gasket.

Given the above, and with a reasonable amount of care upon installation, the Parker O-ring will perform the job it was designed to do.

CONCERNED ABOUT QUALITY....
Relax, we are too The quality assurance group at Parker is one of the toughest in the business. Parker's reputation for the production of quality products was earned the hard way. by years of attention to detail and conformance to both our own rigid internal QC specifications and those of our customers.

The Parker quality assurance program utilizes seven major stages of control, listed below in the same sequence as they occur during the manufacturing process:

1. Raw Materials
2. CBI (see below)
3. Compound
4. Pro-Forms
5. Tooling
6. Molded Parts
7. Finished Parts

CONTROLLED BATCH IDENTIFICATION
Another Parker exclusive is the availability of CONTROLLED BATCH IDENTIFICATION or CBI. This internal 0.A. system, developed by Parker in 1961 , allows for complete traceability of the O-rings you purchase at virtually any time during their life cycle. This unique service, available at no charge to users of Parker 0-rings allows for the retrieval of data on the physical properties of any given lot of Parker O-rings from compounding to finished product. Traceability includes information on:

• HARDNESS
• TENSILE STRENGTH
• ULTIMATE ELONGATION
• SPECIFIC GRAVITY

By furnishing Parker with the CBI serial number (when requested with your initial order), actual test values for that specific lot of Parker O-rings can be placed at your disposal. As more and more specifications

are requiring traceability, the availability of CBI will assist you in maintaining your own product quality. Another good reason to specify Parker O-rings.

HOW TO SPECIFY AND ORDER PARKER O-RINGS
When you order an O-ring, the manufacturer needs to know the inside diameter (I.D.), the cross sectional diameter (W), and the compound (elastomer formula) from which it is to be made. These three pieces of information are sufficient to describe the O-ring completely. Alternately, you may find the Parker part number which conforms to the desired I.D. and cross section and specify this number followed by the Parker compound number.

EXAMPLE: 2-010 N674-70 Parker Seal has three O-ring size series available: the 2-, 3- and 5- series.

PARKER PARBAKS . . . FOR HIGH PRESSURE OR LOOSE TOLERANCE APPLICATIONS
The Parker Series 8-xxx N300-90 Parbak is a unique hard rubber anti-extrusion device. It is used to reduce the clearance gap on the low pressure side of the O-ring seal. An O-ring and Parbak combination will withstand much higher pressures than an O-ring alone.

Parker Seal's unique Parbaks are outstanding for several reasons. The Parbak is molded in one continuous circle, yet it can be streched easily into place. Because they are not split or skived, Parbaks do not pinch or cut the O-ring seal. The Parbak is uniforrn in material and size. Parbaks are available for use with all Series 2-xxx O-ring sizes except 2-001 through 2-003. Specify the same Series 8-xxx number as the Series 2-xxx O-ring with which they wiN be used. The Standard Series 8-xxxN300-90 Parbak is suitable for a temperature range from -65°F to +250°F Other materials are offered for more specialized applications. Parker 8-xxx V709-90 Parbaks are available for continuous temperatures up to 400 "F For phosphate ester service, 8-xxx E652-90 Parbaks are recommended.

PARBAK HINTS

1. Wherever possible use two Parbak rings, one on each side of the O-ring.
2. If only one Parbak ring is used it should be placed so that the O-ring is between it and the pressure.
3. Parbaks may be installed with the contoured face either against the O-ring or against the side of the groove.
4. Packer's Parbaks will not "collapse" or cold flow if used with proper groove designs.
5. Use groove widths given in Gland Dimension Tables