Lubricants for Oxygen Use
|Publication Date:||1 October 1997|
This SAE Aerospace Information Report (AIR) describes two classes of lubricants which, when properly applied, can be used in oxygen systems and components.
Lubricants covered by this document are classified as follows:
Class I Fluids and greases
Class II Solids and dry films
Field of Application:
The major requirement established is that lubricants must be primarily
non-reactive, in all
expected use conditions, to gaseous oxygen (GOX) and liquid oxygen
(LOX). The emphasis on oxygen
compatibility confines the choice of the components making up the
formulation to non-reactive
fluids, thickeners, powders and binders. These are typified by the
fully fluorinated fluids -
In selecting lubricants for oxygen systems, not only oxygen compatibility has to be considered but also their toxicity property. A toxic chemical, even if it is oxygen compatible, should not be used in oxygen systems.
Oxygen compatible lubricants are safer in oxygen systems only in the sense that the energy required to initiate a reaction is higher than that of conventional materials. Under appropriate conditions, all such materials are combustible in oxygen.
Prior to application of any lubricant, all components which come in contact with oxygen must be cleaned for oxygen service and thoroughly dried.
Fluids and greases will not function as lubricants at LOX temperatures − 183 °C (−297 °F). Only solid or dry film lubricants can be used at these temperatures.
Fluoro and chloro-organic compounds are capable of reacting with aluminum and magnesium, even in the absence of oxygen, when the metals are subjected to conditions of high shear or galling, as is the case with pipe threads.
Bonded solid lubricants do not provide corrosion resistance. The metal substrate must be protected or be a corrosion-resistant material prior to the application of the solid film.