|
Test Type |
Temperature,
°C (°F) |
Oxygen Pressure, MPa (psi) |
Impact Energy,
J (ft-lb) |
Test Result |
|
Ignition in gaseous oxygen 1 |
400 (752) |
13 (1,886) |
-- |
No Ignition |
|
Pressure drop in gaseous oxygen bomb 2 |
99 (210) |
0.7 (100) |
-- |
No Pressure Drop after 600 hr |
|
Mechanical impact in liquid oxygen |
Ambient |
-- |
98 (72) |
No reaction in
20 trails 3,4, 5 |
|
Mechanical impact in liquid oxygen |
Ambient |
-- |
122 (90) |
No reaction in
20 trails 1 |
| Mechanical impact in liquid oxygen |
Ambient |
-- |
736 (543) |
No reaction in
20 trails 6 |
1 British Specification 3100.
2 American Society for Testing and Materials 0942.
3 Marshall Space Flight Center Specification 106B.
4 National Aeronautics and Space Administration Handbook, 8060.1B, Test 13, Part 1.
5 American Society for Testing and Materials 02512.
6 West German Federal Institute for Materials Testing (BAM), 8104-411. |
Viscosity
Viscosity Units
Viscosity is a measure of a fluid's resistance to flow when subjected to external forces. Viscosity expressed in this brochure is kinematic viscositythe ratio of dynamic or absolute viscosity to density-at the same temperatures. Kinematic viscosity is the value usually measured, but is easily converted to dynamic viscosity as follows:
| centistoke x density = centipoise cSt x glcc = cP |
Because of the high density of Krytox® fluids, the dynamic viscosity is almost double the kinematic.
Grease Viscosity
Typically, greases are compared based on the viscosity of their base oil. Because greases are thickened, they have a viscosity that is much higher than the base oil. The grease viscosity is affected by temperature, hardness grades, and base oil viscosity. Values for Krytox® GPL 205 are about 9000 cSt at 25°e (77°P) and 6000 cSt at lOOoe (212°P). The viscosity varies with shear rate.
Speed Factor
The speed factor (DN) indicates the permissible speed range for a grease in a rolling bearing. The DN value is the inner race ID in mm x rpm. DN values of 100,000-400,000 and higher have been achieved at temperatures of 204-260°C (400- 5000P) in actual field service using Krytox® greases.
The speed factor is affected by the base oil type, in addition to viscosity and thickener type, and is a measure of the lubricant's internal friction. The limiting speed for grease-lubricated rolling bearings is dependent on the type of bearing, its load, speed, precision, and lubrication system.
Electrical Properties
Krytox® oils are good insulators. The electrical properties of additive-free Krytox® greases approach those of the oils; however, incorporation of some additives may significantly alter these values. In fact, the conductivity of the grease may be increased, if desired, by incorporating a conductive additive, such as powdered copper metal.
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