Section E – Technical Information

Leak Rate Information

Seal Type
Spring
Lower Unpolished Polished Plated Polished & Plated Higher
Energized without
Load Bare Seal Plating Load
C-Ring

Lower Polished
C-Ring Unpolished Bare Seal without Plated Polished & Plated Higher
Load Plating Load

Polished Polished
O-Ring Lower Unpolished Bare Seal without Plated & Higher
Load Plating Plated Load

Wire Lower Unpolished Bare Seal

Higher
Ring Load Load

Lower Higher
U-Ring Unpolished Bare Seal Polished without Plating
Load Load

Lower Polished without Plating Higher

E-Ring Load Load

10 3 10 2 10 1 10 0 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13
Typical Helium Leak Rate ( mbar - liter per mm circumference)
sec
Equivalent leak rates for other gases: Multiply the helium leakage rate by the following factors to obtain the leakage rate of the following gases.

Oxygen: 0.35 Nitrogen: 0.37 Hydrogen: 1.42 Air: 0.37

The graph above shows typical ranges of

leakage rates that may be expected with
Leak Rate Equivalents
various types of seals. Testing was per- Approximate
formed using helium mass-spectroscopy cc mbar – liter Torr – liter Pa – m3 Approximate 1mm3 Bubble
leakage detection. A standardized condition sec sec sec sec Equivalent Equivalent
of 1 atmosphere differential pressure at 1 1.01 7.6x10-1 1.01x10-1 2x10-3 SCFM Steady Stream
70°F was used in all cases. Test procedures
and installation parameters were in 1x10-1 1.01x10-1 7.6x10-2 1.01x10-2 1 cc every 10 seconds Steady Stream
accordance with the recommendations 1 cc every 100
given in this design guide including a 1x10-2 1.01x10-2 7.6x10-3 1.01x10-3 10 per second
seconds
surface roughness of 16-32 µ inch Ra.
1x10-3 1.01x10-3 7.6x10-4 1.01x10-4 3 cc per hour 1 per second
The widths of the horizontal bars indicate
the spread of leakage values that may be 1 every
1x10-4 1.01x10-4 7.6x10-5 1.01x10-5 1 cc every 3 hours
expected depending on the specific plating 10 seconds
selection and surface condition. (It should
1 every
be noted that these results are not directly 1x10-5 1.01x10-5 7.6x10-6 1.01x10-6 1 cc every 24 hours
100 seconds
applicable to liquids, since the much higher
viscosities and surface tension will generally 1x10-6 1.01x1-6 7.6x10-7 1.01x10-7 1 cc every 2 weeks 3 per hour
prevent leakage entirely).
1x10-7 1.01x10-7 7.6x10-8 1.01x10-8 3 cc per year
As a service to our customers, we are
pleased to offer specific seal performance 1x10 -8
1.01x10 -8
7.6x10 -9
1.01x10 -9
1 cc every 3 years
Bubbles too
testing and analysis for unusually challeng- 1x10-9 1.01x10-9 7.6x10-10 1.01x10-10 1 cc every 30 years infrequent to
ing and “mission critical” applications. Testing observe
can be set up to reproduce the actual 1x10-10 1.01x10-10 7.6x10-11 1.01x10-11 1 cc every 300 years
conditions expected in service. Please 1x10-11 1.01x10-11 7.6x10-12 1.01x10-12 1 cc every 3000 years
contact your local Parker representative.

Parker Hannifin Corporation • Composite Sealing Systems Division

E-78 Advanced Products Business Unit • 33 Defco Park Road, North Haven, CT 06473
Phone: 203 239 3341 • Fax: 203 239 4409
www.parker.com