Dock levelers

The engineer must decide whether warehouses should be at ground level or at dock level. The latter facilitates loading trains and trucks, but costs 1520% more than one placed on the ground. It is usually difficult to justify the added expense of a dock-high warehouse. 

Where loading docks are used, they should be provided with dock levellers and if the trucks need to drive onto the vehicle, the condition of the platform should be checked and the vehicle wheels chocked. When loading or unloading from the ground, adequate space should be allowed between and around vehicles Figure 27.3). 

Flush Docks. These are constructed flush with the warehouse floor and with the outer wall of the building. This type of dock is generally built at a height above the outside grade level to accommodate the height of the vehicles to be serviced. Where the terrain is flat, ramps down to the docks are usually provided. This type of dock is normally provided with dock seals for weather protection. Also typical are dock leveler installations to accommodate minor differences in the heights of vehicle load beds. 

Dock Levelers and Dock Boards. These provide a bridge between the delivery or shipping vehicle and the dock (Fig. 4.58). They also serve to accommodate differences in height between vehicles and the dock. Dock levelers are typically installed to be flush with the floor of the dock when retracted. Models which attach to the outside of the dock as a retrofit are also available. The levelers are activated or retracted by spring pressure or hydraulics. Dock boards are reinforced steel plates which are manually lifted into place to form the bridge. 

Factors used in selecting the appropriate dock leveler or board include the weight of the heaviest load and materials-handling vehicle combination to cross it, the distance which the unit must span for bridging, and the combined width of the load and materials-handling vehicle. Manufacturers of this equipment offer a wide variety of weight capacities and sizes. 

FIGURE 4.58 Types of dock levelers and dock boards. (Reproduced with permission from Material Handling Handbook and Directory, 1977/1978, published by Material Handling Engineering magazine, Cleveland, Ohio.)... 

Dock levelers are another aspect that must be planned properly. The length of the dock leveler is important. The usual guideline is that the longer they are, the longer the life of the unit. Dock levelers should be planned for a minimum lifespan of ten years. Lengths of dock levelers range for 2 feet 4 inches to 12 feet. Most are 8 feet in length. 

Dock leveler widths, for recessed levelers, are usually in three basic widths 6-foot, 6-foot 6 inches, and 7-foot. The 6-foot leveler width allows for access by 40-inch pallets on an 8-foot-wide trailer. The 6-foot 6-inch-wide leveler can accommodate 40-inch and 48-inch-wide pallets in an 8-foot or 8-foot 6 inches trailer. Seven-foot-wide levelers allow for two 48-inch side-by-side pallets in an 8-foot or 8-foot 6-inch trailer. If a 6-foot wide leveler is used for an 8-foot 6-inch trailer, a drop-off is created at the edge of the leveler. This can be hazardous to operators because it would be difficult to properly lift 48-inch pallets within these dimensions. 

Cross-traffic over dock levelers should be prohibited. A lift truck could easily fall through the... 

Safety stops are another feature of dock levelers, to keep the ramp from free-falling in case a trailer separates unexpectedly from the dock. Lift trucks crossing an unsupported platform can fall to the bottom of the leveler and possibly off the dock. Safety stops limit the free fall of the platform. 

Is forklift cross traffic over dock levelers restricted ... 

What-if produces a table of narrative questions and answers suggesting accident scenano.s. consequences, and mitigation. Table 3.3.2-1 shows a typical What-If analysis for the Dock 8. < in the left in the line above the table is indicated the line/vessel that is being analyzed. To the right is the date and page numbers. The first row in the table contains the column headings beginning with i ie what-if question followed by the consequences, safety levels, scenario number and comments. 11C comments column may contain additional descriptive information or actions/ recommendations. 

Painted metal exposed at coastal areas, ports and docks often suffers most from such hazards, which may be aggravated by high levels of u.v. radiation and the erosive action of blowing sand. Such conditions can prevail up to approximately 3 km inland. 

The NHR contains also the conserved Calcineurin docking site, PxlxIT, required for the physical interaction of NEAT and Calcineurin. Dephosphorylation of at least 13 serines residues in the NHR induces a conformational change that exposes the nuclear localization sequences (NLS), allowing the nuclear translocation of NEAT. Rephosphorylation of these residues unmasks the nuclear export sequences that direct transport back to the cytoplasm. Engagement of receptors such as the antigen receptors in T and B cells is coupled to phospholipase C activation and subsequent production of inositol triphosphate. Increased levels of inositol triphosphate lead to the initial release of intracellular stores of calcium. This early increase of calcium induces opening of the plasma membrane calcium-released-activated-calcium (CRAC) channels,... 

The pump will be placed on a floating dock that is just a few feet above the river level, so that the net positive suction head (NPSH) will be adequate. The maximum height from the bottom of the barge to the pump will be 20 ft. 

Figure 21.2 Conceptualized construction of an A-B subunit protein toxin (left). The B chain contains a binding region for docking onto cell surfaces, while the A chain contains a catalytic site that produces cytotoxic affects intracellularly. The two subunits are joined by a disulfide bond that is reductively cleaved at the cellular level to allow the A subunit to affect cell death. A molecular model of ricin is on the right.

Again, detailed structural information at a molecular level was the key. Once these pictures were available slight chemical differences between the COX-1 and COX-2 isoenzymes could be seen COX-2 had a side pocket while COX-1 didn t. This meant that a molecule that could dock into the COX-2 side pocket (binding site) but not into COX-1 would specifically block COX-2 without touching COX-1. In 1999 this hope was realized with the availability of COX-2 selective anti-inflammatories such as Rofecoxib and Celecoxib that can be as much as 50-fold selective for the target. 

Finally, the wrangle is halted. The audience in the gallery settles down. Above the level of the fury and bias, the defendants dock faces the bench. By the strange convention of juridical architecture, height stands for both despair and dispassionate judgment. 

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