Stiffeners location

The ends of the vessels will stiffen the shell if the position of the saddles is less than D/4 from the ends. Ring stiffeners, located at the supports, are used to stiffen the shells of long thin vessels. The rings may be fitted inside or outside the vessel. 

Frequently cost savings for cylindrical shells can result from reducing the effective length-to-diameter ratio and thereby reducing shell thickness. This can be accomplished by adding circumferential stiffeners to the shell. Rules are included for designing and locating the stiffeners. 

The peripheral stiffening zone (tray ring) is generally 25 to 50 mm (1 to 2 in) wide and occupies 2 to 5 percent of the cross section, the fraction decreasing with increase in plate diameter. Peripheiy waste (Fig. 14-28) occurs primarily with bubble-cap trays and results from the inabihty to fit the cap layout to the circular form of the plate. Valves and perforations can be located close to the wall and little dead area results. Typical values of the fraction of the total cross-sectional area available for vapor dispersion and contact with the liquid for cross-flow plates with a chord weir equal to 75 percent of the column diameter are given in Table 14-6. 

Figure 4.17 Locations of the nine sensors monitoring position of the resin front viscosity and degree of cure in the T stiffened panel...

The location of the glass transition temperature will depend on the nature of the polymer. Generally, a plastic differs from a rubbery material due to the location of its glass transition temperature. A plastic has a T above room temperature, while a rubber has a Tg below room temperature. As previously mentioned the flexibility of the chain will affect the value of T. Flexible groups will tend to lower the T, whife stiffening groups will act to increase it. Side groups can also affect the value. The... 

A vessel supported on two saddles can be considered as a simply supported beam, with an essentially uniform load, and the distribution of longitudinal axial bending moment will be as shown in Figure 13.22. Maxima occur at the supports and at mid-span. The theoretical optimum position of the supports to give the least maximum bending moment will be the position at which the maxima at the supports and at mid-span are equal in magnitude. For a uniformly loaded beam the position will be at 21 per cent of the span, in from each end. The saddle supports for a vessel will usually be located nearer the ends than this value, to make use of the stiffening effect of the ends. 

If material is located away from a neutral axis, the part can be stiffened. This technique increases the moment of inertia of the cross section [14], Basically, this relationship is... 

Stiffeners should never be located over circumferential weld seams. If properly spaced they may also double as insulation support rings. Vacuum stiffeners, if combined with other stiffening rings, such as cone reinforctunent rings or saddle stiffeners on horizontal vessels, must be designed for the combined condition, not each independently. If at all... 

No credit has been taken for stiffness due to proximity of lugs to heads or stiffening rings however, such location may be advantageous. 

Whenever possible, shipping saddles should be located adjacent to some major stiffening element. Some common stiffening elements include stiffening rings, heads (both internal and external), or cones. If necessary, temporaiy internal spiders can be used and removed after shipment is complete. 

The stresses in the vessel shell should be determined by standard Zick s analysis. The location of shipping saddles should be determined such that the bending at the midspan and saddles is not excessive. Also, the stresses due to bending at the horn of the saddle is critical. If this stress is exceeded, the saddle angle and width of saddle should be increased. Also, move the saddle closer to the head or a major stiffening element. 

Figure 16.17 Impact identification on stiffened composite panel using a system ID approach, (a) Impact locations (b) impact localization spread (c) force reconstmction [35].

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