High Pressure O-Rings

High Pressure O-Ring Materials:

Polyurethane (AU)
PTFE
Specialty Products
Parker Parbaks®
Disogrin Backup Rings

The system operating pressure is always a consideration as it effects the choice of seal materials in several ways.

Hardness (Durometer)

First is hardness, as may be required to resist extrusion in dynamic designs or where there is a large gap between sealed members in static applications. At very low pressures, proper sealing may be more easily obtained with lower durometer hardness (50-60 shore A). With higher pressures, the combination of pressure and material shore hardness determine the maximum clearance that may safely be tolerated.

Second is at-rest vs operating conditions and requirements for “leakless” at rest conditions which would suggest due consideration be given to the long-term compression set properties of a given material.

O-ring Extrusion

Extrusion of O-rings may also be prevented by the use of anti-extrusion (back-up) devices. These are thin rings of much harder material fitted into the gland between the seal and the clearance gaps, which essentially provide zero clearance. They are available in hard elastomer compounds, leather, PTFE, Nylon and other similar materials. Parker Parbaks® are elastomer back-up rings and are generally recommended based on their proven functional superiority. The exact point at which it becomes necessary to use anti-extrusion devices will depend on the pressure, type of elastomer being used, its Shore hardness, the size of the clearance gap, and the degree of “breathing” of the metal parts which will be encountered.

*chart courtesy of Parker O-Ring Handbook (ORD 5700)

Parker Urethane (AU) O-Ring Compound:

General AU Information

Brand	Parker Compound Number	Datasheet	Hardness (Shore A)	Low Temp	High Temp	Color	Recommended For
Parker	P0642-70		70 +- 5	-40	180	Black	Drive Belt Applications, Millable

High Pressure PTFE Materails:

Material	Description	Service Temp °F	Tensile Strength at Break (psi)	Hardness Shore D
Virgin PTFE	Excellent for Cryogenic applications. Good for gases	-425 to 450	4500	60
Modified PTFE	Lower creep, reduced permeability and good wear resistance.	-320 to 450	4600	60
Mineral Filled PTFE	Excellent low abrasion to soft surfaces & improved upper temperature performances. FDA Materials.	-360 to 550	4070	65
Fiberglass Filled PTFE	Excellent compressive strength and good wear resistance.	-200 to 575	3400	67
Fiberglass & Molly Filled PTFE	Excellent for extreme conditions: high pressure & temperature & for longer wear life on hardened dynamic surfaces	-200 to 575	3100	62
Graphite Filled PTFE	Excellent for corrosive service. Low abrasion to soft shafts. Good in unlubricated service.	-250 to 550	3200	60
Carbon-Graphite Filled PTFE	Excellent wear resistance and reduces creep.	-360 to 575	2200	64
Bronze Filled PTFE	Excellent extrusion resistance and high compressive loads.	-200 to 575	3200	63
Carbon Fiber Filled PTFE	Good for strong alkali and hydrofluoric acid. Good in water service.	-200 to 550	3200	60
Aromatic Polyester Filled PTFE	Excellent high temperature capabilities & excellent wear resistance	-200 to 575	2500	61