Sun offers cartridges with EPDM (Ethylene Propylene Diene Monomer) seals for use with phosphate ester fluids. EPDM seals provide compatibility with Type 4 and 5 fluids such as Skydrol®, Fyrquel®, HyJet™ and Pyrogard™ 53 and offer high stability over wide temperature ranges.

These cartridges are factory tested with Skydrol 500B-4 hydraulic fluid and are intended for use in systems such as test stands and aircraft ground support equipment. As with any Sun products, they are not intended for installation on aircraft.

EPDM O-Rings (no limited shelf life)

  • 80 durometer EPDM rubber o-rings; Parker Compound; E0893-80
  • Manufacturer's temperature range rating: -70 to 250°F (-60 to 120°C)
  • O-Rings are purple in color
  • Cartridges configured with EPDM seals will also contain the following seal material: PTFE (Teflon®, product of E.I. DuPont Co.) back-up rings and/or Teflon cap seal, product of Parker Seal Division

Exposure Concerns

  • Exposure to petroleum-based fluids, greases or lubricants will damage EPDM material seals
  • Residual Skydrol 500B-4 fluid will remain in cartridge after factory test. Make sure application fluid is compatible.
  • See www.skydrol.com for safety and environmental information.

Circuit & Application Concerns

The various grades of Skydrol, (500B-4 and LD4), have lower viscosity than common mineral oil-based hydraulic fluids.

The spool leakage in non-seated pressure control and directional control valves using Skydrol 500B-4 could be as high as five times the published leakage based on standard ISO 32 hydraulic oil.  The Skydrol 500B-4 technical data sheet offers additional information on the properties of this fluid.

  • On PSDT, PSFT, PSHT, and PSJT valves, with fluid at 100°F, one can expect a 10% difference between the reduced pressure and the applied pilot on these valves due to the viscosity of Skydrol® 500B-4, and leakage can also be five times the leakage of the same valves on ISO 32 hydraulic oil
  • Non-sealed pilots counterbalance valves may experience five times the pilot leakage (consider using a sealed pilot version counterbalance)

Consult the factory for applications with Skydrol or low-viscosity fluids where excess leakage could be of concern. 

Performance Data

All Sun cartridge performance data is derived using Chevron Rando HD ISO 32 viscosity grade oil having a specific gravity of 0.85. Fluids with a different viscosity and specific gravity will result in different performance characteristics. Tests are conducted at 110°F (42°C). Leakage is often specified in drops per minute. For reference, when Sun uses drops as a unit of measure for leakage, 250 drops equals one cubic inch (16 cc). The performance data provided is developed in Sun's R&D laboratory.  

Packaging and Installation

Cartridges with EPDM seals are individually packaged in sealed plastic bags at the factory to properly protect the seals from incompatible chemicals such as petroleum-based products. These cartridges are not available from the factory as part of a cartridge/manifold assembly. Care must be taken to ensure there are no petroleum-based products present during installation. Sun ductile iron manifolds are shipped from the factory coated with dewatering oil for corrosion protection. These manifolds must be properly washed to remove the dewatering oil prior to installation of cartridges with EPDM seals.