ISO 22538-3:2007 宇宙システム—酸素の安全性—パート3：酸素システムおよびコンポーネント用の非金属材料の選択 | ページ 2

3.1 用語と定義

このドキュメントでは、次の用語と定義が適用されます。

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 22538-3 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee SC 14, Space systems and operations.

ISO 22538 consists of the following parts, under the general title Space systems — Oxygen safety:

• Part 1: Design of oxygen systems and components
• Part 2: Selection of metallic materials for oxygen systems and components
• Part 3: Selection of non-metallic materials for oxygen systems and components
• Part 4: Hazards analyses for oxygen systems and components

The following parts are under preparation:

• Part 5: Operational and emergency procedures
• Part 6: Facility planning and implementation

Introduction

Polymers, although used extensively, are flammable in oxygen. The ignitability of polymers varies considerably, but the risk associated with the flammability of polymers can be minimized through proper selection combined with proper design. When selecting polymers for high-pressure oxygen systems, the susceptibility to ignition of the polymer and the possible ignition sources in the system are given equal consideration with the structural requirements.

The most common cause of ignition of polymeric materials in high-pressure systems is probably adiabatic compression heating of oxygen in the system by rapid pressurization. For this reason, it is important that oxygen systems containing polymers be pressurized slowly. Mechanical impact is rarely a credible ignition source in high-pressure oxygen systems because the level of mechanical impact to which polymeric materials are now exposed is normally well below the energies required for reaction. However, mechanical valve actuation, which has been largely eliminated from current designs, can cause impact loading of valve seats or other detail parts resulting in failure of the parts or mechanically induced ignition of polymeric materials.

Other mechanisms for ignition of non-metallic materials are considered although test data may not exist. Ignition of polymeric materials by impact of metallic and non-metallic particulate is probably feasible, although no conclusive studies have been conducted. Ignition of polymeric materials by burning contaminants has not been studied experimentally, but the use of incompatible oils and greases (especially hydrocarbon greases) is one of the most common causes of oxygen-system fires. Improper component design or installation can result in extrusion of polymeric materials with insufficient mechanical strength for the pressure application. The fresh, fine, extruded surfaces are far more ignition-susceptible than the undamaged polymer. Polymer extrusion has been blamed for some fires, but no formal ignition studies have been performed.

1 Scope

This part of ISO 22538 describes a process for the selection of non-metallic materials for oxygen systems and their components. This part of ISO 22538 applies equally to ground support equipment, launch vehicles and spacecraft.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

3 Terms, definitions and abbreviated terms

3.2 Abbreviated terms

Bibliography