Double walled vessel

The U.S. military specification, M1L-P-27201B, requires 95% para content, 99.995% minimum hydrogen by difference, 50 vppm maximum total imputities, 9 vppm maximum combined nitrogen, water, and volatile hydrocarbons, 1 vppm maximum combined oxygen and argon, 39 vppm maximum helium, 1 vppm maximum carbon monoxide and dioxide, and a 10/40 micrometers nominal /absolute particulate filtration level. Liquid hydrogen is stored in double-walled vessels with evacuated pedite or multilayer insulation and transported in similarly insulated 50,000-L trailers or 900,000-L barges. 

The body of the reactor is a double-walled vessel A (o.d. 5 cm) with two... 

Tests at 1000°C. After 1 hour of pumping the apparent leak rate of a mullite double-walled vessel is 1.7 X 10 8 l.-mm. of mercury per second or 2 X 10-8 cc. (N.T.P.) per second. In terms of permeability rates this value is equivalent to 3 X 10-10 cc./sq. cm./second/mm./cm. of mercury. Roeser (28) has studied a number of refractory procelain tubes from several manufacturers. His permeability values vary from 8.3 X 10 10 to 5 X 10-8 cc./sq. cm./second/mm./cm. of mercury. We have studied two double-walled vessels. These two tubes give nearly identical apparent leak rates although one is constructed of mullite and the other from zircon. It may be possible that more sensitive tests would show up differences in apparent leak rates. 

Cryogenic [-273 to -101°C (-459 to -150°F)] High Vacuum This technique is based on the Dewar flask, which is a double-walled vessel with reflective surfaces on the evacuated side to reduce radiation losses. Figure 11-66 shows a typical laboratory-size Dewar. Figure 11-67 shows a semiportable type. Radiation losses can be further reduced by filling the cavity with powders such as perlite or silica prior to pulling the vacuum. 

The copper calorimeter works on the principle of the mixture calorimeter in place of the calorimetric liquid there is a copper block with good thermal insulation, provided with an axial cavity for receiving the warmer or cooler substance under investigation. The change in the temperature of the block is measured with the aid of thermocouples the good thermal conductivity of copper ensures that all parts of it are always at practically the same temperature. With a view to the best thermal in-FlG 3- sulation, it is contained in a double-walled vessel which is evacuated and silvered. 

While it is important to take proper precautions (see Appendix 2), properly built equipment offers few hazards if relatively small quantities of liquids are used under pressure. The energy stored in a compressed liquid is of the order of 0.2-0.5 kJ mor kbar" this is much less than in a gas. In the event of the catastrophic failure of a vessel, only around 10 per cent of the liquid would need to escape to reduce the pressure to the atmospheric value, and double-walled vessels are unlikely to suffer a failure of both cylinders. The author has experienced the failure of a piston-cylinder apparatus which led to nothing more than a sudden depressurization. On the other hand, hazards may arise from the low-pressure side, which is likely to be carrying oil at 500 bar or more a pin-hole jet at this pressure can penetrate the human body. The valve threads may become worn and the stems may then be forcibly ejected. So hose connections should be inspected and renewed regularly and, where possible, they should be shielded from personnel, the valves should be mounted with the stems pointing away from the operator, and the guidelines set out in the code of practice (see Appendix 2) should be followed. 

Fig. 2.14 Schematic view of the insulated double wall vessels filled with tubes (left) and tube-and-plate assemblies (right), showing the space lost due to the manifolding and insulation...

Chlorine transport wagons usually are not externally insulated. Such insulation, particularly if wet, can be a source of corrosion, and it impedes inspection. The standard containers therefore are double-walled vessels with insulation between the two bodies. 

In double wall vessels and tanks the inner wall is subjected to the low temperature and the material required must correspond to that temperature. The outer vessel shell is used to support the insulation, contain the vacuum, if required, and support the total weight of the tank, contents and insulation. The outer vessel may be ordinary carbon steel, since it is a structural part only. The outer vessel does not need to be ASME Code stamped unless requested. 

The starting material for all experiments was a gel, being the source for Si, A1 and Na, prepared by mixing a Ni SiOs-solution with a solution containing NaOH and Al-nitrate at 20°C. The Si/Ai atomic ratio was varied between 5.67 and 39.0. This gel was suspended in an excess of demineralised water at 90 C in a double-walled vessel equipped with baffles, and vigorously stirred at 1500 tpm [6J. The temperature was controlled by circulating... 

A double-walled vessel is used to prevent loss of coolant accidents a free convective flow of air is organized in the annular gap between the walls, which in normal operation facilitates formation of a thin layer of slag lining on the inner surface of the vessel ... 

Cryogenic containers are of special construction, intended to hold liquids at very low temperatures from about -130°F down to absolute zero. These are double-walled vessels, with the annulus evacuated and filled with insulation. Venting of small amoimts of vapor provides some autorefrigeration to dissipate heat. 

A double-wall vessel containing insulatioi under vacuum in which the vacuum casing forms the outer skin of the vehicle. 

A double-wall vessel containing insulation under vacuum with a removable vacuum support. 

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