Shear clips

Underneath the tray, where the tray panels are bolted together, there is a narrow vertical strip of steel which is called the integral truss. This truss is not connected to the tray ring. Referring to Fig. 8.4, 

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Fulminatin (Ger). Mixture of NG 85 wool shearings (clippings) 15% proposed by Fuchs of Alt Berau, Silesia... 

Effective drainage of the entire plane structure is important in preventing fluids from becoming trapped in crevices. The entire lower pressurized fuselage is drained by a system of valved drain holes. The fluids are directed to the drain holes by a system of longitudinal and cross-drained paths through the stringers and frame shear clips. 

To avoid this problem of intrinsic tray weakness, the support lips (also called "integral trusses") are attached to the vessel wall. As shown in Figure 3-5, a bracket is welded onto the vessel wall below the ring. The support lip is attached to this bracket with a "shear clip." Now tlie trays integral truss is attached to the vessel wall. 

The shear clip must be designed to break away from the vessel wall at some predetermined stress. Otherwise, a powerful pressure surge could deform the wall of the vessel itself. However, if the shear clips can be designed to be strong enough to withstand a AP across the tray deck of about 0.6 psi (i.e., about 2 ft of hydrocarbon liquid) the downcomers would blow clear before the shear clips would fail. Hence, the downcomers would act as a partial safety bypass and protect the tray decks from damage. 

Shear clips Weld the shear clip to the underside of the tray as shown in Fig. 5.8, but certainly not to the tray ring. 

Figure 9.4 Shear clips improve the mechanical integrity of the tray deck.

The shear clips can be cut from an ordinary 0.25-inch carbon steel plate. 

Bolt the trays to the tray ring, or use back-to-back trays with shear clips (see my book. Process Design for Reliable Operations, for mechanical details). This will help to avoid tray failures due to pressure surges caused by high liquid levels. 

Figure 8.4 Shear clips Improve the mechanical Integrity of the tray deck.

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