High-Pressure Monobloc Vessels

Deigning high-pressure equipment presents naany facton and. conditions to be taken into consideration. Tp mentioi onl a few, the following may be listed  

Available materials, their physical properties anc cost. 

Among these the operating condition.s are the ittbsnmpor tant since other factors rjCjgp pfaat vari 

Elastic failure of a given material may be considered t occur when the elastic limit of the material is rewihed Beyond this limit the specimen is permanently deformed o ruptured. Of the various thet ries developed to accoun for elastic failure, four are of s pecial interest. 

According to Lame and Claj)eyron (189), it was sufficien to find the greatest principal stresses in order to defermiin when the elastic limit, was reached. Siuut-Vemml (148 considered that the cia.sl,ic limit was raaclied when ttu 

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Fig. 4.3-7. Comparison of different design strategies of high pressure cylindrical vessels A, Monobloc (eq. 4.3-9) B, Two piece shrink fit Rm = M-, R0 (eq. 4.3-12) C, Partially autof-rettaged cylinder (eq. 4.3-13) D, collapse pressure (pCOmPi. pi) of a Monobloc (eq. 4.3-10) a0,2 yield strength p imposed internal pressure, Rm radius of the shrink fit.

HPR monobloc (Fig. 3.8) For applications at high pressure, the HPR monobloc is available. This tool features six 100 mL PTFE-TFM vessels fixed in a strong casing, serving operation limits of 300 °C and 100 bar. 

Flat end pieces (plates) are frequently chosen for production reasons. For monobloc forgings of high pressure vessels or welded on end pieces it is important to avoid stress risers at the transition locations. For conical transition the stresses yield only slightly larger than those in the cylindrical wall (Fig. 4.3-8). 

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. 

As decribed in Chapter 4.3.2, it is increasingly common to design and manufacture such apparatus as monobloc reactors. Furthermore with modem testing facilities with, for example, ultrasonic methods it is possible to check the finished apparatus up to wall-thicknesses of 350 mm. These developments are an excellent contribution for the safe operation of high-pressure vessels. 

Motoihaga H, Tahara T. Manufacturing monobloc ultra high pressure vessels. High Pressure Technology, PVP-Vol. 344, ASME 1997. 

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