Self-supporting stack

Self-Supporting Stack - This type of unit is designed so that the flare riser pipe has no lateral strucmral support. For short flares, this type is the least expensive to erect and maintain. 

Used lumber must have all nails removed before stacking. Lumber must be stacked and leveled on solidly supported bracing. The stacks must be stable and self-supporting. Stacks of loose bricks should not be more than 7 ft (2.1 m) in height. When these stacks reach a height of 4 ft (1.2 m), they should be tapered back 2 in. (51 mm) for every foot of height above the 4-ft (1.2-m) level. When masonry blocks are stacked higher than 6 ft (1.8 m), the stacks should be tapered back one-half block for each tier above the 6-ft (1.8-m) level. 

However, the mechanical self support of cells is basically provided by the thickest PEN layer either one of the electrodes or the electrolyte (Sulzer Hexis, MHI, RR, CFCL). Thick porous ceramic (RR, MHI) and metallic substrates and interconnects (Ceres Power) onto which a thin PEN is applied have also been suggested to provide the mechanical support required. The electrolyte and anode supported cells are nowadays preferred in tubular and planar stacks. 

The cheapest and least durable chimney is the guyed steel stack. Self-supporting metal stacks and those of reinforced concrete come next. Radial and hollow brick stacks, properly designed, are cheaper than those of common brick of equal excellence. 

A self-supporting SOFC-based power plant system, HEXIS (Heat Exchanger Integrated Stack), using circular planar elements has been developed by the Sulzer company in Switzerland for natural gas as a fuel and a power of up to 7 kW [26]. Field tests have started in summer 1997 commercialization is planned for the year 2002. The development goal is the construction of small-size systems in the power range of 1 - 200 kW. 

UF membranes are made commercially in sheet, capillary, and tubular forms. Sheet membrane is used in plate-and-frame devices, stack devices, and spiral elements. Capillary membranes are generally 0.4-1 mm diameter, are self-supporting, and are pressurized from inside. Usually, drey are made with a skin on both inside and outside surfaces so that they can be pressure reversed for cleaning. Tubular devices ate cast on supports and ate generally in the 10-25 mm diameter range. 

Materials which are piled, grouped, or stacked near a roof edge must be stable and self-supporting. 

Sealless planar Electrochemical cells made up of electrolyte, cathode, and anode are stacked with metal interconnects without using sealing materials. For example, disk-type planar sealless stacks have been constructed by Mitsubishi Materials Corporation. For this purpose, fuel and air are introduced through the central part of the respective cells. Outside the cells, the remaining fuel becomes combusted with air. Self-supporting cells are usually used for this design. 

The high conductivity of LSGMC makes it possible to fabricate self-supported cells and operate them at intermediate temperatures this in turn makes it easy to fabricate cathode and anode on the LSGMC electrolyte. A sealless stacking method is adopted electrochemical cells are stacked with metal interconnects using current collectors for cathode and anode sides. Because of this simple configuration and materials, their stack performance is similar to the sum of respective cell performance. In other words, loss in stacking is very small. 

Semi-submersible rigs are often referred to as semis , and are a floating type of rig. Like the jack-up, a semi is self contained. The structure is supported by large pontoons which are ballasted with water to provide the required stability and height. The rig is held in position by anchors and mooring lines or dynamically positioned by thrusters. A large diameter steel pipe ( riser ) is connected to the sea-bed and serves as a conduit for the drill string. The blowout preventer (BOP) is also located at the sea-bed ( sub sea stack ). 

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