Hold-down plate

D. Hold-Down Grid (see Figure 3). According to Strigle, Normally, the upper surface of the packed bed is at least 6 in. below a liquid distributor or redistributor. The bed limiter or hold-down plate is located on top of the packed bed in this space. It is important to provide such a space to permit gas disengagement from the packed bed. Such a space allows the gas to accelerate to the velocity neces-... 

Adsorbers, distillation colunuis, and packed lowers are more complicated vessels and as a result, the potential exists for more serious hazards. These vessels are subject to tlie same potential haz. uds discussed previously in relation to leaks, corrosion, and stress. However, llicse separation columns contain a wide variety of internals or separation devices. Adsorbers or strippers usually contain packing, packing supports, liquid distributors, hold-down plates, and weirs. Depending on tlie physical and chemical properties of the fluids being passed tlirough tlie tower, potential liazards may result if incompatible materials are used for llie internals. Reactivity with llie metals used may cause undesirable reactions, which may lead to elevated temperatures and pressures and, ullinialely, to vessel rupture. Distillation columns may contain internals such as sieve trays, bubble caps, and valve plates, wliicli are also in conlacl with tlie... 

Figure 9-15A. Hold-down plate for packed tower. Used by permission of U.S. Stoneware Co. (now, Norton Chemical Process Products Corp.).

Figure 9-15B. Typical metal hold-down plate for use with ceramic or carbon packing. Note It rests directly on top of the packing bed-limiters are similar in design in metal or plastic, bolted to column wall above packing. Used by permission Norton Chemical Process Products Corp., Bull. TA-80.

Figure 1335. Packed column and internals, (a) Example packed column with a variety of internals [Chen, Chem. Eng. 40, (5 Mar. 1984)]. (b) Packing support and redistributor assembly, (c) Trough-type liquid distributor, (d) Perforated pipe distributor, (e) Rosette redistributor for small towers. (0 Hold-down plate, particularly for low density packing.

Figure 11.56. Hold-down plate design (Norton Co.).

In the first molding step, half of the fluoroplastic resin was charged into the mold. Next, the bearer and core assembly was set in the mold. Then the other half of the resin was dispensed into the mold. The hold-down plate was used to compress the contents of the cavity while the mold was heated to a temperature above the melting point of the fluoroplastic resin. After cooling, the part can be removed and machined to the required specifications. 

Figure 2.11. Hold-down and retainer plates (a) Retaining plate. (6) Hold-down plate, (c) Hold-down plate. (Courtesy of Koch Engineering Co.).

Hold-Down Plates and Bed Limiters (Retaining Devices)... 

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