Dished end

Old vessels may not be as cheap as they seem at first sight. Nozzles and manways are often in the wrong plaee, and the eost of modifying them may make the vessel more expensive than a new one. A designer who was persuaded to use an old cylindrical pressure vessel ended up using the two dished ends and nothing more ... 

Receivers are commonly made of steel tuhe with welded dished ends, and are located horizontally. Small receivers may he vertical, for convenience of location. The liquid drain pipe from the condenser to the receiver should he amply sized, and any horizontal runs sloped to promote easy drainage. Shut-off valves in this line should not he in a horizontal outlet from the condenser, since their slight frictional resistance will cause liquid hack-up in the condenser. Oudet pipes from the receiver may he from the bottom or, by means of an internal standpipe, may leave at the top. A valve is invariably fitted at this point. 

A typical fermenter is a closed, vertical, cylindrical, stainless steel vessel with eonvexly dished ends and of 25-250 capacity. Its height is usually two to three times its diameter. Figure 7.2 shows such a vessel diagramatically, and Fig. 7.3 gives a view inside an actual vessel. 

Hemispherical, ellipsoidal and torispherical heads are collectively referred to as domed heads. They are formed by pressing or spinning large diameters are fabricated from formed sections. Torispherical heads are often referred to as dished ends. 

Standard torispherical heads (dished ends) are the most commonly used end closure for vessels up to operating pressures of 15 bar. They can be used for higher pressures, but above 10 bar their cost should be compared with that of an equivalent ellipsoidal head. Above 15 bar an ellipsoidal head will usually prove to be the most economical closure to use. 

In recent years much attention has been paid to the use of explosives for the shaping and working of metals. Figure 14.12 illustrates a simple application of the process for forming a dished end of a vessel. A flat metal blank is placed over a suitable mould and the space between them evacuated. Above the blank is water and in this a suitable explosive charge is fired. The metal takes the form of the mould with little or no spring-back and usually does not require further treatment. The process is particularly... 

Brittle failure of the dished end of a 50 ton horizontal pressure vessel released anhydrous ammonia vapors which caused the explosion to occur. 

Figure 6.7 Dished ends, conical bottoms and flat bottoms.

Dished ends, conical bottoms and flat bottoms of the tanks should be provided as shown in figure 6.7 above. 

Figure 10.1 3 m x 8 m Autoclave Foreground-rubber lined and painted ducts with dished ends. 

Cylindrical pipe with dish end and bottom orifice... 

For a particular reactor volume and operating pressnre, the thicknesses of shell and dished ends were calculated. Knowing the density of the material, the weight of the shell was estimated. An extra 50% was added for the nozzles, supports, shaft, impellers, agitator drive, and so on. In addition,... 

The simplest typa of fixed bed is shown in Fig. 13.3-3 which is illustrative of a mudem large plnot for water purification. The vessel is of a conventional dished-end pressure construction with supports and an access manhole. Construction malaria Is for the vessel are umally mild steel with a lining of rubber or plastic. Susnless steel is sometimes used and smaller vessels are made of reinforced plastic. The depth of settled resin bed is seldom more then about 1 m but the vessel must allow freaboard of about another meter above the upper surface of resin for expansion during fluidization to clenn ntbhish out of the bed. 

When the drum is horizontal and the incoming stresun is all liquid, it is best to enter the feed near one dished end, and use an internal pipe terminating with a bend or a baffle that points the entering liquid jet at the dished end. This breaks the incoming liquid jet and minimizes turbulence and disturbance to any liquid-liquid separation. 

Larger capacity storage vessels are basically the same double-walled containers, but the evacuated space is generally filled with powdered or layered insulated material. For economic reasons, the containers are usually cylindrical with dished ends, approximating the shape of a sphere, which would be expensive to build. Containers must be constructed to withstand the weights and pressures that will be encountered and adequately vented to permit the escape of evaporated gas. Containers also should be equipped with rupture discs on both inner and outer vessels to release pressure if the safety relief valves should fail. 

The normal direction of flow in such a bed is downward so that the resin acts as a packed bed without any relative movement of particles. The bed of resin can be supported by various means. The simplest is to fill the vessel to cover the lower dished end with coarse sand in which distributor manifold pipes are buried. This can create problems because the volume of liquid trapped in the voids of the sand can cause cross-contamination between cycles of operation. An internal false floor with distributor cups of plastic screwed into place on a grid pattern overcomes this problem. Such constraction is more expensive and has to be supported structurally to take the entire pressure thrust on the bed during flow. Some plants use an elaborate manifold of distributor pipes laid against the lower dished end which is itself filled with resin. 

A.1.1.1 The Tank or Vessel The most common version of the tank or vessel is a vertical cylindrical tank with a dish end at the bottom. In exceptional cases (mostly old designs), the bottom may be conical. In this latter case, there is always the danger of inadequate mixing in the conical part. If a solid phase is an integral part of the... 

Rewatkar et al. (1989) have reviewed the literature on solid suspension in two-phase systems. Subsequently, a large body of information has been generated, which rationalizes the earlier data as discussed earlier. It should be noted here that most investigators (e.g., Rewatkar et al. 1989 Nikhade and Pangarkar 2005) used vessels with flat bottoms. In such vessels, fillets of solids tend to form at the vessel wall base comers. For larger vessels with dish end bottoms, these fillets are found predominantly below the impeller or halfway between the vessel axis and periphery. 

The values for the flat bottom vessels are typically 10-20% higher than those for vessels with dish ends. Thus, predicted from correlations of data in flat bottom vessels are conservative (Jafari 2010). 

A jacketed stainless steel vessel without any sharp comers. Sharp comers facilitate growth/fouling, which is difficult to remove. Standard flanged dish ends are used as a cover with provision for agitation assembly, feed/outlet nozzles, etc. as per the requirement of the process planned. The relevant details are provided in Section 7B.16. 

Calculation of working volume for a horizontal cyhndrical vessel is more complex. Firstly we have to calculate the volume (Vq) between the bottom of the vessel and the 0 % level indication. The length of the vessel (1) is that measured between tangent lines - the point where any dished ends are welded to the vessel. The last term in Equation (4.3) determines the volume of Hquidheld in the dished ends. It assumes a 2 1 ratio between drum radius and depth of each dish. It should be omitted if the vessel has flat ends. 

The working volume (V) may then be derived (again omitting the term for the dished ends if not required). 

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