Pressure sealing closure Final report, 15 Mar. 1963 - 28 Feb. 1966
Mechanically operated pressure sealing closure for space suits
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Membrane Switches Check Seal Pressure
Array of flexible membrane switches used to indicate closure of seal. Switch membrane responds to pressure exerted by rigid surface on compliant sealing medium and provides switch contacts monitored electronically. Membrane switches connected in series and placed under seal. When all switches are closed lamp or LED lights up, indicating requisite seal pressure has been realized at all switch positions. Principle used to ensure integrity of seals on refrigerator and oven doors, weatherstripping, hatches, spacecraft, airplanes, and submarines.
Hodgetts, P. J.↗
Flexible heat-and-pressure seal
Device withstands both heat and pressure and accomodates relative motion between seated surfaces. Seal consists of flexible tube filled with thermally insulating material and coated with pressure resistant materials.
Bellavia, J., Jr.↗
Hand-tightened, high-pressure seal
To provide flared tubing and hose connections for high-pressure hand tightened cryogenic service, a 1/4-inch male AN seal was modified by machining to receive a special, double-truncated-cone-shaped Kel-F washer between it and the flared flex hose connector.
Meyer, W. A.↗
Pressure-Sealing Optical Coupling
Light signals passed out of high-pressure cryogenic environment. Optical coupling passes signals in fiber-optic channels across pressure-and-temperature barrier. Coupling made in different configurations and modified to suit requirements of different cryogenic instrumentation systems.
Irvin, Timothy B.↗
High-pressure cryogenic seals for pressure vessels
This investigation of the problems associated with reliably containing gaseous helium pressurized to 1530 bars (22 500 psi) between 4.2 K and 150 K led to the following conclusions: (1) common seal designs used in existing elevated-temperature pressure vessels are unsuitable for high-pressure cryogenic operation, (2) extrusion seal-ring materials such as Teflon, tin, and lead are not good seal materials for cryogenic high-pressure operation; and (3) several high-pressure cryogenic seal systems suitable for large-pressure vessel applications were developed; two seals required prepressurization, and one seal functioned repeatedly without any prepressurization. These designs used indium seal rings, brass or 304 stainless-steel anvil rings, and two O-rings of silicone rubber or Kel-F.
Buggele, A. E.↗
Self-aligning, low-pressure sealing poppet valve
Design and characteristics of poppet valve operated by very low differential pressures to control fluid flow are described. Valve is used to control flow of petroleum, chemical, and aircraft hydraulics where low leakage rates and activation at low pressures are required.
Gonzalez, R.↗
High-pressure cryogenic seals for pressure vessels
Problems associated with maintaining high pressures at cryogenic temperatures in pressure vessels are investigated. The goals were to identify the appropriate materials and design for a seal intended for cryogenic applications at pressures up to 4,080 bars (60,000 psi), and to examine the factors affecting the seal performance. The method employed and the apparatus used in a series of experimental seal system tests, and the test results are described in detail. It is concluded that the common seal designs and extrusion seal-ring materials such as Teflon, tin, and lead are not suitable. However, new seal systems developed using indium seal rings, brass or 304 stainless steel anvil rings, and two 0-rings of silicone rubber or Kel-F did prove suitable.
Buggle, A. E.↗
Research study to develop means of manufacturing bonding clips, brackets and joints, and pressure sealing joints with uniform stress distribution Final report, 29 Feb. 1968 - 1 Jul. 1969
Uniform adhesive shear stress distributions in double-lap bonded joints and joint design criteria
Evensen, H. A.↗
Electrically-conductive Low-Permeability Pressure Seal
Metal-plated butyl rubber seal has been devised for enclosures of electronic equipment that must be maintained under dry, inert atmosphere. Seal prevents gas leakage over prolonged periods, while conductivity suppresses electromagnetic emissions from sealed equipment. Seal is formed by depositing aluminum or gold onto molded-in-place butyl rubber gasket and surrounding areas of flange.
Krieg, H. C.↗
Long-Lived, Replaceable Low-Pressure Seals
Simple units operate by metal-spring and elastomeric compression. Ring-shaped gasket has rectangular cross section from which paired cantilever spring arms extend in K-shape. In unassembled state, arms hold elastomeric jackets lightly but securely. Assembled between flanges, arms and jackets become compressed and form airtight seal on both flanges. Suitable for use on hatches and windows; combines advantages of low leakage, long life, and easy replacement.
Weddendorf, Bruce↗
Eccentricity and misalignment effects on the performance of high-pressure annular seals
Annular pressure seals act as powerful hydrostatic bearings and influence the dynamic characteristics of rotating machinery. This work, using the existing concentric seal theories, provides a simple approximate method for calculation of both seal leakage and the dynamic coefficients for short seals with large eccentricity and/or misalignment of the shaft. Rotation and surface roughness effects are included for leakage and dynamic force calculation. The leakage calculations for both laminar and turbulent flow are compared with experimental results. The dynamic coefficients are compared with analytical results. Excellent agreement between the present work and published results have been observed up to the eccentricitiy ratio of 0.8.
Chen, W. C.↗
A Balanced-pressure Sliding Seal for Transfer of Pressurized Air Between Stationary and Rotating Parts
A combination sliding-ring and pressure-balancing seal capable of transferring pressurize air from stationary to rotating parts was developed and experimentally investigated at sliding velocities and cooling-air pressures up to 10,000 feet per minute and 38.3 pounds per square inch absolute, respectively. Leakage of cooling air was completely eliminated with an expenditure of balance air less than one-fourth the leakage loss of air from labyrinth seals under the same conditions. Additional cooling of the carbon-base seal rings was required, and the maximum wear rate on the rings was about 0.0005 inch per hour.
Curren, Arthur N↗
Measurement component technology. Volume 1: Cryogenic pressure measurement technology, high pressure flange seals, hydrogen embrittlement of pressure transducer material, close coupled versus remote transducer installation and temperature compensation of pressure transducers
The results are presented of an investigation into the availability and performance capability of measurement components in the area of cryogenic temperature, pressure, flow and liquid detection components and high temperature strain gages. In addition, technical subjects allied to the components were researched and discussed. These selected areas of investigation were: (1) high pressure flange seals, (2) hydrogen embrittlement of pressure transducer diaphragms, (3) The effects of close-coupled versus remote transducer installation on pressure measurement, (4) temperature transducer configuration effects on measurements, and (5) techniques in temperature compensation of strain gage pressure transducers. The purpose of the program was to investigate the latest design and application techniques in measurement component technology and to document this information along with recommendations for upgrading measurement component designs for future S-2 derivative applications. Recommendations are provided for upgrading existing state-of-the-art in component design, where required, to satisfy performance requirements of S-2 derivative vehicles.
Hayakawa, K. K.↗
Inflatable Perimeter Seal
Effective, inexpensive pressure seal between two flat surfaces formed from silicone rubber tubing. Resembling refrigerator seal, pressure seal especially useful where shape of sealed region irregular or subject to change. Unlike gaskets and O-rings, tubing seals require no machined grooves or custom-made parts and not adversely affected by warpage of sealed surfaces.
Shepherd, Clayton C., Jr.↗
A generalized theory for eccentric and misalignment effects in high-pressure annular seals
High-pressure annular seal leakage and dynamic coefficients vary with eccentricity and misalignment. Recent seal leakage data with both concentric and fully eccentric alignments support the seal leakage model with surface roughness and eccentricity effects included. In this paper, the seal dynamic coefficient calculation has been generalized and allows direct calculation of the seal dynamic coefficients at any circumferential location. The generalized solution agrees with the results obtained by using the calculated values of an earlier paper and performing a coordinate transformation. The analysis results coincide with the measured data in showing that the stiffness and damping matrices of seal coefficients are not skew symmetric, and the main diagonal seal coefficients are not equal. The measured direct stiffnesses were found higher than predicted by the concentric seal theory, but this may be explained by the presence of eccentricity in the test operating mode.
Chen, W. C.↗
Low-Stress Sealing of Pressure Transducers
Compliant washer seals high pressures without excessive compressive stress on transducer. Conformal washer serves as effective seal for transducer passing through walls of pressure vessel. Washer makes it unnecessary to tighten mounting nut to high torque, which could damage transducer or adversely affect accuracy. Washer also used to seal mountings for temperature sensors and other devices.
Kroy, R. E.↗
Pressure-Energized Seal Rings to Better Withstand Flows
Pressure-energized seal rings intended to withstand flows better than do conventional pressure-energized seal rings have been conceived. The concept applies, more specifically, to seal rings used on some valve stems, pistons, and the like. A conventional pressure-energized seal ring generally has a U-shaped cross section and consists of an elastomer or other suitable polymer with an embedded metal energizing spring (see Figure 1). The working fluid from the high-pressure side that one seeks to seal is allowed into the U-shaped cavity, so that the pressure pushes the sides of the seal ring tighter against the gland and body sealing surfaces, thereby increasing the degree of sealing. Unfortunately, when the seal ring is exposed to flow of the working fluid, under some conditions, the flow grabs the lip of the U-shaped cross section and ejects or deforms the seal ring so that, thereafter, a proper seal is not obtained. Figure 2 depicts one of several alternative seal rings according to the present concept. One element of the concept is to modify the U-shaped cross section from that of the corresponding conventional seal ring to eliminate the exposed lip and prevent entry of the working fluid into the U-shaped cavity. Unlike in the conventional seal, pressurized fluid would not push the seal ring directly against the both gland and body sealing surfaces. Instead, the pressure would directly push the seal ring against a gland sealing surface only. In so doing, the pressure would squash the seal ring into a smaller volume bounded by the gland and body sealing surfaces, and would thereby indirectly press the seal ring more tightly against the body sealing surface. To enhance the desired squashing deformation, a spring having an approximately parallelogram cross section would be embedded in the modified U-shaped cavity. As the pressure pushed two corners of the approximate parallelogram closer together along the axis of the seal ring, the other two corners of the approximate parallelogram would be pushed farther apart along a radius of the ring, thereby causing the polymeric ring material to push radially harder against the body sealing surface. From the radially innermost corner of the approximate parallelogram, the spring material would extend radially, then axially into recesses in the seal gland. These extensions would help to restrain the seal ring against ejection. A seat retainer would hold the sealing ring in the gland and form a mechanical compression seal to prevent or at least reduce leakage of pressurized fluid into the cavity behind the seal. However, because there would likely be a little leakage, the cavity behind the seal should be vented to the low pressure side to prevent buildup of pressure in the cavity over time; otherwise, the built-up pressure could cause ejection of the seal ring when the pressure on the high-pressure side was reduced. Polymeric seal-ring materials may not be able to withstand working conditions in applications that involve abrasive and/or hot working fluids. For such applications, all-metal seal rings may be preferred. The bottom part of Figure 2 shows one example of an alternative gland configuration with an all-metal seal ring.
Farner, Bruce↗