Design Integration

The success of the coupling in limiting leakage depends on its capability for providing the necessary seal contact. The interface requirements involve the seal housing, surface finish, machine lay, and surface flatness and waviness. A summary of the surface finish and flatness requirements for aerospace-type seals is included in section 2.5 (table I). The sealing ability of the coupling is directly related to the flange surface condition, since a surface that is smooth and approaches a true...

Brazed Joints

Brazing is a thermal process of joining metal parts by diffusion bonding with a metal filler that has a flow point over 800 F but less than the melting point of the parts to be joined. Brazing generally is used when welding is not desirable or practical or when minimum distortion or minimum residual stress is required. Brazed joints are an acceptable method for making fixed joints in many propellant systems for example, in the Apollo spacecraft, over 770 brazed joints were used on the various...

Dynamic Seal Configuration

Dynamic seals are mechanical devices used to minimize or reduce to an acceptable level leakage from one region to another when there is relative motion at the sealing interface. Relative motion, either sliding or rotary, generally occurs between a static or stationary interface and a moving interface. In sliding motion, the direction of motion is perpendicular to the seal interface, with the contact surface continuously changing location. In rotary motion, the direction of motion is in line...

Static Seal Configuration

Diametral Clearance Ring Size

Static seals are devices used to limit or control leakage of fluid in a separable connector in which there is no relative motion of the mating surfaces other than that induced by changes in the operating environment. The present basis for successful static-seal design is a complete analysis of the leakage requirement and the integration of the seal into the coupling. This analysis takes into consideration the fluid, environments, loads, and the seal requirements imposed on the coupling design....

Foreword

NASA experience has indicated a need for uniform criteria for the design of space vehicles. Accordingly, criteria are being developed in the following areas of technology Guidance and Control Chemical Propulsion Individual components of this work will be issued as separate monographs as soon as they are completed. This document, part of the series on Chemical Propulsion, is one such monograph. A list of all monographs issued prior to this one can be found on the final pages of this document....

Welded Joints

Welding is one of the common methods for joining tubular components in a propellant system. Welded joints normally exhibit mechanical properties and environmental- and propellant-compatibility characteristics similar to those of the components being joined. A welded joint can be constructed so that it contributes little or nothing to system contamination. Welded joints can be made at a subassembly stage on a bench or they can be made as final installation joints in the propellant system. The...

Radial Or Toggle Seals

The radial seal concept fig. 26 is based on converting an axial load to a radial interface load through a toggle action within the seal structure. The coupling flanges are designed to confine the outer diameter of the seal such that radial interference occurs and plastic flow of the seal takes place when an axial load is applied during installation. Because of the plastic flow, the seal is not reusable however, the flanges are reusable with new seals. The axial load required to install this...

Seal Protector

Seal barriers are structures that protect the seal and coupling. Seal applications in hot-gas systems are the most troublesome because of loss of material properties and the thermal effects on the coupling components. At the annealing temperature of the metal, the seal loses most of its initial preload and will leak. Also, at these temperatures the flanges are less rigid and warp. A large number of hot-gas couplings are in exhaust systems for solid propellants, and solid combustion products may...