NATO APP-11(B) PDF

INTRODUCTION

GUIDANCE

1. Lubricants must be carefully selected for safe operation of equipment in oxygen-enriched environments.

2. Oxygen compatible lubricants are safer in oxygen systems because the required energy for ignition is greater. It is standard practice to lubricate the joints and threads of pipe, tubing and fittings to avoid seizing and to assure a tight connection.

3. None of the fluids or greases tested would function as lubricants at LOX temperature (-297°F) though they are considered safe to use in gaseous oxygen systems. At LOX temperature only solid or dry-film lubricants can be used (SAE-AMS-M-7866, MIL-PRF-81329).

SELECTION OF LUBRICANTS FOR OXYGEN SYSTEMS

Lubricant should be selected for oxygen-enriched environment service through qualification tests. The qualification tests should be more severe than the actual operating conditions. The selection should be from several types of materials found from experience to be suitable for use in oxygen systems. Use only lubricants that have been qualified for oxygen service and use them sparingly. The limits of temperature and pressure for their application must be specified and observed.

PRECAUTIONS IN USING OXYGEN COMPATIBLE LUBRICANTS

1. Many LOX compatible halogenated hydrocarbons used as lubricants have low threshold limit values (TLV) and their decomposition products are, in most cases, very toxic and corrosive. The only practical solution is to assess the hazards associated with any particular chemical application and to take adequate precaution to insure the safety of the operation.

2. Lubricants such as Fluorolube, Halocarbon, and Krytox should not be used with aluminum and light alloys under high shear; a serious explosion could result even in the absence of oxygen.

LIMITATIONS OF OXYGEN COMPATIBILITY TESTING

1. No single test can qualify materials for safe application under all conditions encountered in oxygen systems. Conditions for testing are quite specific and actual operating conditions may be quite different from test conditions. Test data serves only as a guide in selecting alternative materials for oxygen service to meet different conditions.

2. Non-homogeneity of compounding formulas by processors makes batch testing almost imperative. Care must be exercised in identifying the composition of a product. A common chemical name should not be used to designate different products with different compounding ingredients.

3. According to NASA TM X-67953, Lewis Research Center, material compatibility constitutes only 20% of the causes of mishaps with liquid oxygen and 36% with gaseous oxygen. Procedural deficiency causes the largest number of mishaps, closely followed by design deficiency.

NAEC MISC REPORT 92-0354 (REVISION A) COMPATIBILITY OF MATERIALS WITH OXYGEN

1. Many tables and figures given in NAEC MISC Report 92-0354 Revision A are not reproduced in this report. References to the above report only are given. NAEC MISC Report No. 92-0354 Revision A can be obtained from the Naval Air Warfare Center Aircraft Division, Code PD34, Lakehurst, NJ 08733, USA.

DEFINITION OF OXYGEN RICH ENVIRONMENT

1. For the purpose of this document, an oxygen rich environment is defined as an environment in which the concentration of oxygen exceeds 23.5 percent by volume.