Metallic gaskets

Lead 500 Good chemical resistance. Best couformability of metal gaskets. 

With metal gaskets and moderate bakeout, turbo pumps can reach pressure below 10-9 torr without traps. They can be started at a pressure up to 1 torr. The time required to reach full pumping speed ( lmin) is much shorter than for diffusion pumps. Also these pumps must be backed by a primary pump. 

In ultralow (p < 10-7 torr) vacuum, metallic gaskets are used. 

Metallic Gaskets for Pipe Flanges — Ring-Joint Spiral Wound, and Jacketed Nonmetallic Flat Gaskets for Pipe Flanges Buttwelding Ends Steel Line Blanks... 

When aggressive gases or vapors have to be pumped, valves made of stainless steel and sealed with VITILAN sealant are usually used. For nuclear technology, valves have been developed that are sealed with special elastomer or metal gaskets. We will be pleased to provide further design information for your area of application upon request. 

V-Clamp Joints These joints (Fig. 10-143) are attached to the pipe by butt-weld or expanded joints. Theoretically, there is only one relative position of the parts in which the conical surfaces of the clamp are completely in contact with the conical surfaces of the stub ends. In actual practice, there is considerable flexing of the stub ends and the clamp also complete contact is not required. This permits use of elastomeric gaskets as well as metal gaskets. Fittings are also available with integral conical shouldered ends. 

In a diamond cell, the sample volume is sacrificed for the sake uf higher pressures, and hence, all operations connected with (he cell have lo be performed under a microscope. In preparing the DAC for an experiment, the first step is to indent Ihe metal gasket (hardened stainless steel strip nr Inconel strip) with the anvil diamonds to the correct thickness (5(1 to UK) micrometers) and then drill a IOO- to 200-micrumeter hole as close lo the center of the indentation as possible. The gasket is seated on the face of one of the diamonds in the same orientation as it had when the indentation was made. The sample material and a small chip of ruby for pressure calibration are (lien placed in the hole. Finally, to maintain hydrostatic pressure the hole is tilled with a tiny drop of fluid from a syringe and then (he hole is quickly sealed by (he diamond fucus before Ihe fluid evaporates. 

Fig. 10.1. Some common high-pressure tank fittings. The seal in the top three fittings is made by contact between the nipple in the connection and the seat in the outlet. Note the cone-shaped, round, and bullet-shaped nipples for (a), (b), and (c) respectively. The bottom connection (d) is sealed by means of a flat soft-metal gasket. Never attempt to mix outlet and connections between the various designs. Note the grooves on the connection nuts for connections (b), (c), and (d). This groove indicates a fitting with left-handed threads. (Reproduced by permission of the copyright holder, Mathe-son Gas Products, Inc.)...

Fig. 10.11. Metal gasket sealed bolted flange closures. A soft metal gasket, generally made of aluminum or copper, is clamped between knife edges (ci) or stepped flanges (b).

Fig. 10.7. Flange tubing connectors, (a) Cajon VCO O-ring sealed Fitting (b) Cajon VCR metal gasketed flange fitting. (Reproduced by permission of the copyright holder, Markad Services Co.)...

Calibration of the pressure is best accomplished using the Ruby scale. Generally this is done using a metal gasket between the two diamond windows surrounding the sample in which a liquid (such as Nujol or Teflon oil) is added to produce hydrostatic pressure. The technique measures the pressure dependence of the sharp Ruby Ri fluorescence transition at 692.8 nm, although the R2 band at 694.2 nm can also be used. The Ruby fluorescence is induced by the blue excitation of the Ar+ (488.0 nm) or the He- C d (441.6nm) lasers. 

Lead Tin 500 Good chemical resistance. Best conformability of metal gaskets. Good resistance to neutral solutions. Attacked by acids, alkalies. 

To be referred to next is the most modem diamond anvU type, generating pressures of order of 10 -100 GPa. The cell illustrated in Figure 6(e) consists of two gem diamonds with optically flat surfaces, between which a sample confined in a drilled hole of a thin metal gasket is sandwiched. To attain isostatic compression an inert gas or an organic liquid, like a 4 1 volume mixture of methanol and ethanol, is contained with the sample. The generated pressure is measured directly from the pressure shift of the fluorescence line of mby powder mixed with the sample. Temperatures to 5000 K can be obtained by laser heating. The quantity of sample confined in a typically 0.1-mm-wide hole is extremely small, just a few microcrystals. At present, research has focused on in situ observations using X-ray and other optical methods, rather... 

Figure 11 The diamond-anvil cell has emerged as the dominant and most versatile tool for achieving high pressures (up to millions times of the atmospheric pressure). It uses two diamond anvils, which exert pressure and serve as windows on the sample. A metal gasket confines the sample and supports the anvils. Because diamond is the strongest material known and is transparent over a wide range of the electromagnetic spectrum, various high-pressure experiments are performed using synchrotron radiation...

A low-temperature reaction chamber has been built which can employ lithium fluoride, barium fluoride, or sapphire windows mounted to a metal cell by means of metal flange fittings, indium metal gaskets, and Teflon pressure rings. This cell has been used for the study of low-temperature infrared spectra of HCl in liquid xenon and of CH4 in liquid argon. It has been more fully described in a recent paper (29). 

ASME B16.20-1998(R2004) Metallic gaskets for pipe flanges—ring-joint, spiral-wound, and jacketed (ASME International). 

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