Seal Kit Installation Guidelines

Sun Hydraulics cartridge seal kits require normal precautions when being installed. Do not use any sharp edged tools that may cut the seal. Care should be taken to minimize the stretch on the seal during installation. Special consideration should be given to any sharp or rough surfaces that the seal must pass over. O-ring installation tools are commercially available from many seal manufacturers and tool suppliers. Screwdrivers and awls are not appropriate installation tools.

Note that the seal materials must be compatible with the hydraulic fluid and assembly lubricants used in the system. If in doubt, consult one of the many seal handbooks available on fluid compatibility. Cartridges cannot be converted to a different seal materail by simply changing the external seals. Most cartridge valves incorporate internal seals which can only be replaced by first disassembling the valve. Contact your local Sun Distributor if such a conversion is required.

Back-up Rings

Most of the back-up rings used by Sun Hydraulics are rectangular in cross-section and have no installation orientation requirements. Use the same techniques and care used to install o-rings. When replacing spiral back-up rings, take special care that the spiral is wound like a left-hand thread so that the back-up ring will follow the cartridge into the cavity properly when being assembled.

Back-up ring material is Hytrel® with Buna-N seals (as shown in the last 3 digits of the Sun Seal kit part number: 990-***-007 kits) which is compatible with most petroleum based fluids, and Viton® with Viton seals (990-***-006). For detailed material information, refer to our Materials of Construction page under Technical Resources.

Glyd® Rings

The GLYD® rings used by Sun are Teflon® based and require special care to install properly. Specialized tooling may be needed to properly stretch and then re-size these rings without damaging them. In the absence of these tools, careful use of the cartridge (to stretch) and the cavity (to resize) may enable these seals to be successfully installed.

Industry Standard O-Ring Reference

Sun part numbers for most o-rings include the AS568A (ARP568) Uniform Dash Number as part of the numbering system. For field repair when Sun Service kits are not readily available, this information may prove useful.

O-ring part numbers are typically a nine-position code, where the 4th position indicates the type of seal material (see below). The 7th, 8th and 9th positions indicate the AS568A Uniform Dash Number when within -004 through -284 range. With the last three digits falling outside of this range, the part number is unique to Sun Hydraulics and bears no reference to the AS568A standard.

Note: O-ring codes with a "5" in the fifth position (e.g. 500-051-590), the cross sectional width is .050" and the last three digits represent the nominal o-ring I.D.