Heads, vessel

The critical buckling pressure for a sphere subject to external pressure is given by (see Timoshenko, 1936)  

This equation gives the critical pressure required to cause general buckling local buckling can occur at a lower pressure. Karman and Tsien (1939) have shown that the pressure to cause a dimple to form is about one-quarter of that given by equation 13.59, and is given by  

A generous factor of safety is needed when applying equation 13.60 to the design of heads under external pressure. A value of 6 is typically used, which gives the following equation for the minimum thickness  

Any consistent system of units can be used with equation 13.61. 

Torispherical and ellipsoidal heads can be designed as equivalent hemispheres. For a torispherical head the radius Rs is taken as equivalent to the crown radius Rc. For an ellipsoidal head the radius can be taken as the maximum radius of curvature that at the top, given by  

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Vessel heads can be made from explosion-bonded clads, either by conventional cold- or by hot-forming techniques. The latter involves thermal exposure and is equivalent in effect to a heat treatment. The backing metal properties, bond continuity, and bond strength are guaranteed to the same specifications as the composite from which the head is formed. AppHcations such as chemical-process vessels and transition joints represent approximately 90% of the industrial use of explosion cladding. 

Flanged joints are used for connecting pipes and instruments to vessels, for manhole covers, and for removable vessel heads when ease of access is required. Flanges may also be used on the vessel body, when it is necessary to divide the vessel into sections for transport or maintenance. Flanged joints are also used to connect pipes to other equipment, such as pumps and valves. Screwed joints are often used for small-diameter pipe connections, below 40 mm. Flanged joints are also used for connecting pipe sections where ease of assembly and dismantling is required for maintenance, but pipework will normally be welded to reduce costs. 

Heat may be lost due to condensation at the reactor vessel head, but this can be minimized through appropriate insulation. 

In the case of pressure vessels when attaching the dished heads to the sidewall of pressure vessel head the surface of the dished head need to be machined to accommodate the thickness transition, as shown in Figure 1.54. 

Vessel diameter Volume of cylindrical vessel Depth and volume of vessel head ... 

Calculate the liquid levels. Liquid level is usually measured from the center of the bottom of the vessel head. So, the head volume must be subtracted from the total volume to calculate the straight-side liquid level then the head depth must be added to the straight-side liquid level. 

Table 6.5 Summary of Equations for Sizing Accumulators Subscripts L = liquid — HV = vessel head V = 2VL ts ts = 5 to 10 min...

Select a vessel head. If the internal pressure is 150 psig (10.3 barg) or less, select a torispherical head. If the internal pressure is above 150 psig (10.3 barg), select a 2 1 ellipsoidal head. 

Depth of fluid in the vessel head over rectangnlar weir... 

Flanged joints are used for connecting pipes and instruments to vessels, for manhole covers, and for removable vessel heads when ease of access is required. Flanges may... 

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