Buoys

Ship-shaped FPSOs must be designed to weather vane i.e. must have the ability to rotate in the direction of wind or current. This requires complex mooring systems and the connections with the well heads must be able to accommodate the movement. The mooring systems can be via a single buoy or, in newer vessels designed for the harsh environments of the North Sea, via an internal or external turret. Figure 10.33 shows a schematic of the Shell-BP Foinaven FPSO. 

The raw ROM (run of mine) ore is reduced in size from boulders of up to 100 cm in diameter to about 0.5 cm using jaw cmshers as weU as cone, gyratory, or roU-type equipment. The cmshed product is further pulverized using rod mills and ball mills, bringing particle sizes to finer than about 65 mesh (230 p.m). These size reduction (qv) procedures are collectively known as comminution processes. Their primary objective is to generate mineral grains that are discrete and Hberated from one another (11). Liberation is essential for the exploitation of individual mineral properties in the separation process. At the same time, particles at such fine sizes can be more readily buoyed to the top of the flotation ceU by air bubbles that adhere to them. 

Buoyancy. The low density, closed-ceUed nature of many ceUular polymers coupled with their moisture resistance and low cost resulted in their immediate acceptance for buoyancy in boats and floating stmctures such as docks and buoys. Since each ceU in the foam is a separate flotation member, these materials caimot be destroyed by a single puncture. 

In the United States, other experimental wave-energy systems have been investigated in California and Hawaii, including a 30-MWe heaving-buoy... 

The marine environment is highly aggressive. Materials in marine service are constantly exposed to water, corrosive salts, strong sunlight, extremes in temperature, mechanical abuse, and chemical pollution in ports. This climate is very severe on ships, buoys, and navigational aids, offshore stmctures such as drilling platforms, and faciUties near the shore such as piers, locks, and bridges. 

Nonuniform corrosion or pitting corrosion frequently occurs on steel structures in seawater and in soil. Nonuniform and pitting corrosion easily lead to damage in tanks, pipelines, water heaters, ships, buoys and pontoons, because these structures lose their functional efficiency when their walls are perforated (see Chapter 4). 

The fourth source type option in SCREEN is for volume sources, which is selected by entering V or V for source type. The volume source algorithm is based on a virtual point source approach, and may be used for non-buoy ant sources whose emissions occupy some initial volume. The inputs requested for volume sources are as follows ... 

This pressure variation can be considered as the transfer of a pressure wave in space. In the same w ay, w hen a stone is thrown into a lake, the ripples generated move radially from the point of entry of the stone. But this observation is only apparent, because a floating buoy will stay in the same horizontal position. It does not move radially in the space the perturbation, however, moves. 

G. Daien (Stockholm) invention of automatic regulators for use in conjunction with gas accumulators for illuminating lighthouses and buoys. 

Auftriebt m, buoyancy upward thrust lift plankton, -mittel, n. buoying agent swelling agent. 

Auftriebskraftt /. buoyant (or buoying) force, lifting force. 

It should be noted that if this cementing operation were to be carried out using an inner drillpipe string to place the cement in the annulus, the above force of buoyancy would be reduced by the buoyed weight of the drillpipe. However, unless very heavy drillpipe were used, the casing and drillpipe would still float on the cement slurry. 

Figure 9.1 Id illustrates a simple model of bonding in metals known as the electron-sea model. The metallic crystal is pictured as an array of positive ions, for example, Na+, Mg2+. These are anchored in position, like buoys in a mobile sea of electrons. These electrons are not attached to any particular positive ion but rather can wander through the crystal. The electron-sea model explains many of the characteristic properties of metals ...

This frontier s practical opportunities were first developed with submarines, which until the nuclear ones were limited to depths of only a few hundred feet. Many thousands of feet can now be navigated. The crushing pressures below the surface, which increase at a rate of about V2 psi per foot of depth, make corrosion a major threat to the operation and durability of many materials. For example, the life of uncoated magnesium bolts in contact with steel nuts is less than seventy-two hours, aluminum buoys will corrode and pit after only eleven months at just four hundred feet, and low-carbon steel corroded at a rate one-third greater than in surface waters. 

Tests on plastics in deep water have been extremely successful. As an example filament-wound RP cylinders and PVC buoys retained their strength. PVC washers and the silicone-seating compound used in steel-to-aluminum joints helped prevent their corrosion. Black twisted nylon and polypropylene... 

Leisure Flotation devices Marine buoys Sailboards Toys Canoes/kayaks Low temperature, impact strength cost, weatherability Low temperature, impact strength cost, weatherability Low temperature, impact strength cost, weatherability Low temperature, impact strength cost, weatherability Low temperature, impact strength cost, weatherability... 

AB diblock copolymers in the presence of a selective surface can form an adsorbed layer, which is a planar form of aggregation or self-assembly. This is very useful in the manipulation of the surface properties of solid surfaces, especially those that are employed in liquid media. Several situations have been studied both theoretically and experimentally, among them the case of a selective surface but a nonselective solvent [75] which results in swelling of both the anchor and the buoy layers. However, we concentrate on the situation most closely related to the micelle conditions just discussed, namely, adsorption from a selective solvent. Our theoretical discussion is adapted and abbreviated from that of Marques et al. [76], who considered many features not discussed here. They began their analysis from the grand canonical free energy of a block copolymer layer in equilibrium with a reservoir containing soluble block copolymer at chemical potential peK. They also considered the possible effects of micellization in solution on the adsorption process [61]. We assume in this presentation that the anchor layer is in a solvent-free, melt state above Tg. The anchor layer is assumed to be thin and smooth, with a sharp interface between it and the solvent swollen buoy layer. 

Thus, the spacing of the chains relative to the neutral, free, swollen size of the buoy blocks is, for a given chemical system and temperature, a unique function of the solvent-enhanced size asymmetry of the diblock polymer and a weak function of the effective Hamaker constant for adsorption. The degree of crowding of the nonadsorbing blocks, measured by a decrease in the left-hand side of Eq. 28, increases with increasing asymmetry of the block copolymer. 

Figure 7 shows the results of measurements of adsorption density by Parsonage, etal. [77] on a series of eighteen block copolymers, with poly(2-vinylpyridine) [PVP] anchors and polystyrene [PS] buoys, adsorbed from toluene (selective for PS) of variable molecular weight in each block. The results are presented as the reciprocal square of Eq. 28, that is, as a dimensionless number density of chains ct (d/Rg A)-2. For all but the copolymers of highest asymmetry, Eq. 28 is in good agreement with the data of Fig. 7. The high asymmetry copolymers are in the regime of the data of curves (a) and (c) of Fig. 3 where the large relative size...

FIGURE 16.11 In the froth flotation process, a stream of bubbles (white circles) is passed through a mixture of ore (orange circles), rock (brown rectangles), and detergent. The ore is buoyed up by the froth of bubbles and is removed from the top of the chamber. The unwanted gangue is washed away through the bottom of the container. 

---