Quick-opening closures

Unstayed flat heads and covers can be designed by very specific rules and formulas given in this subsection. The stresses caused by pressure on these members are bending stresses, and the formulas include an allowance for additional edge moments induced when the head, cover, or blind flange is attached By bolts. Rules are provided for quick-opening closures because of the risk of incomplete attachment or opening while the vessel is pressurized. Rules for braced and stayed surfaces are also provided. 

With apparatus designed for maximum operating pressures of 200-350 atmospheres the reactor head is generally bolted to the tank with the high pressure seal made with a compressible gasket. Other versions of autoclaves have quick opening closures that can be used to pressure maxima around 100-125 atmospheres. 

Quick-opening closures - Many of the vessels and heat exchangers within the system will operate in batch mode. Frequently it will be necessary to remove the top head of a vessel for introduction of the feed material or removal of the spent residue, or for cleaning and inspection of the surfaces in contact with the botanical. Several quick opening closure systems are currently available to accomplish this, but care must be taken to insure that the system chosen is best for the intended use. 

Closures at the ends of vessels may be permanent, removable, serewed or flanged. The type of closure at the end of a pressure vessel depends on the frequency of opening, the size of the vessel, the temperature of the vessel, the corrosive conditions, openings and nozzles through the closure and the type of access provided by the removable head. Quick opening closures are available up to about 20,000 PSI. 

Quick Opening Devices. Breech block, tapered or interrupted thread, or pinned closures are often used when an end cover has to be removed quickly, as with some isostatic presses (126,136), or to enable the end cover to be removed easily after the vessel has been heated to high temperatures. 

Pechacek, R. "High Pressure, Quick Acting Closure for Large Diameter, Full Opening Nuclear and Petro-Chem Pressure Vessels". The American Society of Mechanical Engineers New York. ASME 78-PVP-74 1978, p. 2. 

The nonlubricated plug valve may be successfully used in refinery loading services in 2-inch, 3-inch, 4-inch sizes rated at 300 psi. The advantages of using this type of valve are bubble-tight closure, easy repair by replacing the slips and compact size with relatively quick opening action. 

One of the more common types of closures for pressure vessels is the unstayed flat head or cover. This may be either integrally formed with the shell or welded to the shell, as shown in Fig. 10.1 or it may be attached by bolts or some quick-opening device as shown in Fig. 10.2. It may be circular, obround, square, rectangular, or some other shape. Those circular flat heads that are... 

Where quick opening is less important than fatigue life, the internal thread closure can also be used with a continuous thread (see Figure 12.5a). Also, frame-supported end closures (Figure 12.8) can be operated quickly, although the manipulation of heavy parts is required (vessel or frame). 

Exposure of sulfolane 261 to sodium azide and mesylation regioselectively afforded mesylate 262, which was transformed into aziridine 263 by a three-step sequence involving azide to amine Staudinger reduction, acetylation, and ring closure. The trans 1,2-diamino derivative 264 was quickly obtained from 263 by azide opening of the aziridine ring, followed by reduction. 

Finally, in addition to the proven quick-release clamp closure, the finger-pin closure and the segment-ring closure have proved themselves with an opening and closure cycle of less than 5 minutes in large-scale plants. 

Low bulk d islty, often difficult to handle solid feeds may require use of pre-loaded baskets. Full bore openings are used on vessels with quick, hi pressure closures. 

It is not considered economically convenient to place the turbine with the reactor in a containment building (although in the past, small reactors with this characteristic have been buUt). Isolation of the reactor cooling system from the outside is by means of quick isolation valves. Inherent in this feature are the problems of their rehabdity in closure and their leakproof characteristics (to the point that some experts say, but without sufficient reason, that BWRs have to be considered substantially open towards the outside environment). On the other hand, no problems have been attributed to the steam generators. 

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