Marine environment, simulations

Wiggins et al. [456] used neutrons from the thermal column of a 10 kW pool-type research reactor and from a 120 pg Cf source to study the prompt photon emission resulting from neutron capture in magnesium nodules (ter-romanganese oxides) from the ocean floor. Spectra were recorded with a Ce(Ii) detector and a 1024-channel analyser. Complex spectra were obtained by irradiation of seawater, but it was possible to detect and estimate manganese in nodules in a simulated marine environment by means of the peaks at 7.00, 6.55, 6.22, and 6.04 pV. 

Current process equipment technology has kept abreast of the oil Industry s requirements of producing high specification products on floating production systems in hostile marine environments. Extensive research and development work involving motion simulation and analytical modeling has now provided process equipment designs to match the performance levels of fixed platform equipment. 

For special purposes, more complex equipment is occasionally used (not covered by 4665) which additionally attempts to simulate corrosive or polluted atmospheres. There is an ISO standard for plastics for a salt spray exposure test93 which could in principle be applied to rubber should such an exposure be needed. Cyclic exposure to corrosive atmosphere could be more representative of service94,95. One particular circumstance is exposure to a marine environment and there is an ISO standard covering this for plastics96. 

If suitable field sites are not available or lack controlled conditions, then corrosion tests must be conducted in the laboratory. Cabinets are constructed in which the atmosphere is controlled and high humidity and temperature can be used to help accelerate the tests. Marine environments are simulated by salt spray and industrial environments by sulphur dioxide or nitrogen dioxide. Figure 18 shows a salt-spray cabinet and the arrangement of test panels. Periodic changes of temperature within the cabinet can be used to simulate night and day. Addition of other aggressive salts or acid into the sprayed solution is further used to accelerate the test. 

M.A. Matin, E. Hoque, J. Khatoon, Y.S.A. Khan, M.M. Hossain, A.J. Mian. Distribution and Fate of C-DDT in Microcosm experiments simulating the Tropical Marine Environment of the Bay of Bengal, in Proceedings of a Symposium Environmental Behavior of Crop Protection Chemicals, IAEA-SM-343/15, Vienna, Austria, 1997, pp. 279-287. 

The results (28) of simulations of an algal bloom in a marine environment such as the coastal ocean are presented in Figure 10. The vertical flux of particulate nitrogen leaving the mixed surface layer by sedimentation is plotted as a function of time after a pulse input of nitrate from the bottom waters stimulates algal growth in surface waters. 

Mathematical Model for Simulation of the Fate of Copper in a Marine Environment... 

A mathematical model is formulated to describe the first-order kinetics of ionic copper released into a marine environment where sorption on suspended solids and complexation with dissolved organic matter occur. Reactions are followed in time until equilibrium, between the three copper states is achieved within about 3 hr (based on laboratory determinations of rate and equilibrium constants). The model is demonstrated by simulation of a hypothetical slug discharge of ionic copper, comparable to an actual accidental release off the California coast that caused an abalone kill. A two-dimensional finite element model, containing the copper submodel, was used to simulate the combined effects of advection, diffusion, and kinetic transformation for 6 hr following discharge of 45 kg of ionic copper. Results are shown graphically. 

Figure 4. Finite element network for simulation of fate of copper in the marine environment...

Simulation of the fate of copper after injection into the marine environment is illustrated by Figures 5, 6, 7, and 8. 

Fig. 1.9 Pits on 304 stainless steel after exposure to simulated marine environment (3.5 g/L NaCI) [27].

Fig. 1 Methane hydrate, which is stable belou- and to the left of the phase boundary line. Also shovra is the geothermal gradient in permafrost as well as marine environments. Where the curves intersect, natural methane hydrate is stable. Natural methane hydrates are found in the lightly shaded region. BSR labels the "bottom-simulating reflector." an unexpected interface found by sonic exploration techniques and usually associated with the interface between sediments with and without hydrate. View this art in color at...

Corrosion study The corrosion behavior of carbon composite fibers was studied to simulate the effects of galvanic interaction on damage to composites in the marine environment [196]. 

Another oxidation/sulfidation test to assess the performance of gas turbine alloys is the burner rig test A schematic of the burner rig is shown in Fig. 6. Here a jet fuel is burned in a combustion chamber with an air-fuel ratio of 30 1. The flame jrasses down a tube at the end of which are the samples to be evaluated, mounted in a rotating platen. The samples are in the form of pins. The jet fuel normally contains a certain amount of sulfur. There are provisions to add additional sulfur in the form of volatile sulfur compounds. In addition, seawater can be added into the gas stream to simulate a marine environment. The setmples are typicaDy exposed to the flame temperature for 58 min and cooling air for 2 min in a 1-h cycle. The test is typiccJly conducted for about 500 h. 

Automobiles and mUitaiy equipment frequently are exposed to marine environments and road salt. Beach test sites are available, but simulations in the laboratory are convenient. The ASTM B 117, Method of Salt Spray (Fog) Testing, has been widely used for this purpose to evaluate rusting, pitting, and SCC. Martensitic stainless steels and maraging steels have been exposed to salt spray (and other NaCl environments) to evaluate resistance to SCC prior to use in military equipment and fasteners. Ferritic and austenitic stainless steels have been tested to evaluate resistance to rusting prior to use in automotive applications. 

J. E. A. Storms, Event-based stratigraphic simulation of wave-dominated shallow-marine environments. Marine Ceol. 199(3-4), 83-100 (2003). 

PCBs and DDTs were absorbed on polypropylene and polyethylene in high concentrations in a simulated marine environment (Mata et al. 2001). 

This test method establishes the procedures, equipment, materials, and conditions to measure the degree and rate of biodegradation of plastic materials under aerobic mesophilic marine water conditions. This test method is designed to produce repeatable and reproducible test results under controlled test conditions that simulate the marine environment. 

Field studies (exposure tests) in marine or simulated marine environments demonstrated the much better corrosion resistance of stainless steels in concrete. After 4.5 years in natural marine conditions no cracking and no pitting corrosion occurred on an Fe-11% Cr alloy (Hewitt and Tull-min, 1994). Under accelerated chloride ingress the same alloy showed some pitting corrosion after one year, whereas specimens with plain carbon steel had already cracked. A 9.5 years exposure program on steels embedded in concrete containing up to 3.2% chloride additions with respect to the cement content showed that ferritic stainless steel with 13 % Cr showed corrosion at chloride levels over 1.9% (Treadaway etal., 1989). 

Salt-spray testing The salt-spray test, which was originally designed to test coatings on metals, has been widely used to evaluate the resistance of metals to corrosion in marine service or on exposed shore locations [19 20]. However, extensive experience has shown that, although salt-spray tests yield results somewhat similar to those exposed in marine environments, they do not reproduce all the factors causing corrosion in marine service. Salt-spray tests should thus be considered to be arbitrary performance tests and their validity dependent on the extent to which a correlation has been established between the results of the test and the behavior under expected conditions or service. Despite the current widespread use of continuous salt-spray methods, their unrealistic simulation of outdoor environments is a serious shortcoming. 

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