Multilayer pressure vessels

The term solid-wall or monobloc vessel is applied to all components where the cylindrical wall consists of a single layer. Solid-wall vessels are suitable for all types of pressure vessels, in particular for those operated under high temperatures. Thermal stresses arising during heating or cooling are smaller than in multilayer vessels because of the good thermal conduction across the wall. Therefore solid-wall vessels are especially suitable for batchwise operation. 

Fig. 4.3-19. Different kinds of flanges of multilayer high pressure vessels [34]. a, forged flange shrunk onto the multilayer vessel body b, forged thinner flange ring shrunk onto the multilayer vessel body c, flange made out of the same material as vessel body d, forged flange ring welded directly to the inner liner of the multilayer vessel.

Figure 1. Insulation design for pressure vessel. The figure shows a vacuum space for obtaining good performance from the multilayer insulation, instramentation for pressure, temperature and level, and a vapor shield for reducing hydrogen evaporative losses.

Nozzle attachments to high pressure vessels are almost always made through the heads, or end closures, rather than through the shell as is done in common pressure vessels. This is primarily due to the thickness of the shells and the fact that multilayered vessels are common in high pressure systems. Nozzles through multilayer vessels, while not impossible, are discouraged. 

Laminated pressure vessels with thin-walled layers may be produced by a technique devised by the A.O. Smith Co. of Milwaukee USA and subsequently used by the Struthers Wells Co. This and similar techniques (Krupp, Coillayer and Plywall) are illustrated in the bottom three diagrams in Table 8.2. The shell of the multilayer system consists of concentric cylinders, each of which is itself built from three segmented layers with longitudinal seams. The segments are staggered and on one side welded to the previous layer by three-plate welding (Figure 8.2). 

The multilayer design has the further advantage that a postweld heat treatment (PWHT) for stress relieving is not required due to the low thickness of each layer. For multiwall design, PWHT is typically required. The multilayer design has therefore some advantages for high-pressure vessels that may have to be delivered in several parts as no PWHT is required at site. 

The addition of HC1 to 1,3-butadiene in the gas phase at total pressures lower than 1 atmosphere and at temperatures in the range of 294-334 K yielded mixtures of 3-chloro-l-butene and ( )- and (Z)-l-chloro-2-butenes, in a ratio close to unity44,45. Surface catalysis has been shown to be involved in the product formation (Figure 1). The reaction has been found to occur at the walls of the reaction vessel with a high order in HC1 and an order less than unity in diene. The wall-catalyzed process has been described by a multilayer adsorption of HC1, followed by addition of butadiene in this HC1 layer. This highly structured process is likely to involve near simultaneous proton and chloride transfers. 

In Tsai [7], an elasticity solution for stresses in a pressurized thick cylindrical vessel is presented. In this analysis, the longitudinal bending deformation due to end closures is neglected, the formulation of the elasticity problem then reduces to a generalized plane strain analysis. The effects of material selection, layup sequence, and winding angles on the burst strength of thick multilayered cylinders are also addressed. 

Fig. 4.3-4 (ABC) gives the superimposed stress distribution in the walls of a two-layered vessel under internal pressure. It can be clearly recognized that the compressive tangential prestresses by shrink-fitting (Fig. 4.3- 4B) are decreased at the inner layer and increased at the outer layer towards a more even stress distribution (Fig. 4.3- 4 C) compared to that for a monobloc cylinder (Fig. 4.3- 4A). The theoretical fundamentals for the dimensioning of shrink-fit multilayer cylinders can be taken from [2][8][9].

In NRH, the liver is interspersed with numerous diffuse nodes, which are 1-3 mm in size (occasionally up to 3 cm) and yellow to yellowish brown in colour with blurred boundaries they consist of hyperplastic hepato-cytes. No fibroses or perinodal connective tissue septa are evident. The multilayered, disordered trabeculae do not have a lobular structure. (66, 69) CD 8" cytotoxic T cells infiltrate the acinus. The nodes lack central veins and bile duct proliferations. The intemodular parenchyma becomes atrophied due to pressure. It is possible by means of reticulin staining to demonstrate the nodes with the irregular trabeculae, whereas the altered vessels are best shown using elastica staining. The liver surface is smooth. (78) In the course of disease, presinusoidal, and later sinusoidal, portal hypertension with hepato-splenomegaly and oesophageal varices are usually observed. (64, 65, 67) (s. fig. 36.4)... 

The DAVINCH is a double-walled steel chamber. The replaceable inner vessel is made of armor steel and the outer vessel is made of multilayered carbon steel plates with a corrosion- and stress-crack-resistant inner plate made of, for example, stainless steel, Hastalloy, or a similar material. The chambers are separated by air. Owing to its double-wall design and the materials of construction, the DAVINCH has the ability to confine high-pressure detonation gases, eliminating the need for an expansion tank to contain them following a detonation. 

A multilayer insulation consisting of a reflective foil fixed on the outside of the inner vessel is usually chosen to minimize the transport of radiation heat With increasing number of radiation shields, however, additional heat transfer is introduced due to conduction via physical contact An optimal number is between about 60 and 100 layers [51]. The whole remainder of the intermediate space, in larger vessels about 1 m in thickness, serves as a vacuum jacket to avoid heat transport by convection or residual gas conduction. A typical pressure value in this space is < 0.013 Pa. Appropriate getter materials help maintain the vacuum over longer times. 

The stratification test program described here utilized a 70-ft vacuum-jacketed test vessel. The test vessel was a 4-ft-diameter x 6-ft-long stainless steel inner tank supported within a 6-ft-diameter outer tank by means of four legs, several tie rods, and a sway bar. The inner tank was designed for a working pressure of ISOpsig at liquid-hydrogen temperature. Its upper and lower domes w ere insulated with 1 in. of multilayer insulation to minimize inadvertent heat leak to the test fluid. Removal of the outer tank dome (Fig. 2) provides ready access to the inner tank. A 14-in. manhole in the upper dome of the inner tank provides access to the tank interior. 

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