Simulative Laboratory Testing

Often it is desirable to perform screening tests on candidate materials. From the previous discussions of the influence of mating geometry on contact stresses and thermal considerations, it should be obvious that any laboratory test that is not an exact physical duplicate of the application will be a compromise on some aspect. The primary purpose of simulative laboratory tests is to rank candidate materials as they would rank in the application. A secondary purpose is to predict the absolute magnitudes of friction and wear in the application. The only reason that this is secondary and not primary is that is seldom possible to translate laboratory tribology tests directly to absolute performance in the application. 

While it is typically possible to control the environmental temperature, due to frictional heating it is virtually impossible to control the interfacial tanperatures. Slight changes in coefficient of friction can result in significant temperature rises (10-20°C). The environmental temperature is usually set and the surface or subsurface temperatures are monitored throughout the test. Since many of the materials (e.g., nylon) are sensitive to humidity, control of humidity will enhance the quality of the results. 

Typically, the tests fall into the following categories of which there are often commercially available testers. 

Unidirectional or oscillatory slip with thrust washer 

Pure rolling, rolling/slip with cylinder-on-cylinder 

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Sequestration of CO2 in a Depleted Oil Reservoir. This project will investigate down-hole injection of CO2 into depleted oil reservoirs in New Mexico. It will conduct a comprehensive suite of computer simulations, laboratory tests, field measurements, and monitoring efforts to understand the geomechanical, geochemical, and hydrogeologic processes involved. It will also use the observations to calibrate, modify, and validate the modelling and simulation tools. 

An assessment of drop-impact damage risks can be made by direct observation, self-contained instruments (within packs), and special recording instruments to identify how simulated laboratory tests can ultimately be substituted for travel tests. Data loggers are now capable of recording temperatures, RH, impacts and vibrations. 

Warehousing and distribution hazards include impacts, compression and vibration. One or a combination of these may distort the container, loosen or tighten the closure, and cause deterioration to the decoration. Thus any of these aspects may have to be tested by simulated laboratory tests or actual warehousing/travel tests. 

The materials listed in Table 21 were investigated by simulating laboratory tests under operating conditions and exposure tests in waste water evaporator units of flue gas desulphurisation plants and waste incineration plants [64]. It was confirmed that only an approximate resistance can be estimated for the metallic materials in these plant sections. Precise material resistance data can only be determined for actual plants. The mass losses determined for alloy C-276 and alloy 59 after an exposure time of 9 months was only 0.053 mm/a (2.09 mpy) and 0.045 mm/a (1.77 mpy), respectively, with respect to the term of exposure. Therefore, they do not have technical significance. This results in the following proposal for materials for pipelines and tanks of waste water evaporator units of flue gas desulphurisation plants... 

Effectiveness of these EP oils can be evaluated by a number of laboratory test units such as those shown in Figure 4. While the American Society for Testing and Materials (ASTM) procedures describe a number of standard test procedures (10), the operating conditions and test specimen materials should be chosen to simulate as nearly as possible those in an appHcation. 

Any of the three RS is adequate to derive a time history of an earthquake to simulate test conditions in a laboratory. This, however, being a complex subject, assistance must be obtained from experts in the field for constructing an RS for laboratory testing, preparing... 

Materials evaluation should be based only on actual data obtained at conditions as close as possible to intended operating environments. Prediction of a material s performance is most accurate when standard corrosion testing is done in the actual service environment. Often it is extremely difficult in laboratory testing to expose a material to all of the impurities that the apparatus actually will contact. In addition, not all operating characteristics are readily simulated in laboratory testing. Nevertheless, there are standard laboratory practices that enable engineering estimates of the corrosion resistance of materials to be evaluated. 

As the seale of operation inereases, the effeet of the heat eonsump-tion by the plant typieally deelines. Therefore, the extent to whieh the kineties of the runaway reaetion is influeneed by the plant is redueed. For plant seale vessels, the ([t-faetor is usually low (i.e., 1.0-1.2) depending on the heat eapaeity of the sample and the vessel fill ratio. Laboratory testing for vent sizing must simulate these low ([t-faetors. If the laboratory ([t-faetor is high, several anomalies will oeeur ... 

The phenomenon and mechanisms of cavitation-erosion have been considered in Section 8.8 and here it is only necessary to consider laboratory test methods that have been designed to simulate conditions that prevail in practice and which may be used to evaluate the performance of materials. 

Although laboratory tests (NACE TMO 169-76, and Reference 313) are obviously of value in selecting materials they cannot simulate conditions that occur in practice, and although an initial sorting may be made on the basis of these tests ultimate selection must be based on tests in the plant. This is particularly important where the process streams may contain small concentrations of unknown corrosive species whose influence cannot be assessed by laboratory trials. Testing is also important for monitoring various phenomena such as embrittlement, hydrogen uptake, corrosion rates, etc. which are considered in Section 19.3. 

Laboratory tests used in the development of inhibitors can be of various types and are often associated with a particular laboratory. Thus, in one case simple test specimens, either alone or as bimetallic couples, are immersed in inhibited solutions in a relatively simple apparatus, as illustrated in Fig. 19.34. Sometimes the test may involve heat transfer, and a simple test arrangement is shown in Fig. 19.35. Tests of these types have been described in the literatureHowever, national standards also exist for this type of test approach. BSl and ASTM documents describe laboratory test procedures and in some cases provide recommended pass or fail criteria (BS 5117 Part 2 Section 2.2 1985 BS 6580 1985 ASTM 01384 1987). Laboratory testing may involve a recirculating rig test in which the intention is to assess the performance of an inhibited coolant in the simulated flow conditions of an engine cooling system. Although test procedures have been developed (BS 5177 Part 2 Section 2.3 1985 ASTM 02570 1985), problems of reproducibility and repeatability exist, and it is difficult to quote numerical pass or fail criteria. 

The problems that have been experienced in the recirculating rig test are indicative of those often met in performance testing. Attempts to reproduce the service conditions in a laboratory test inevitably involve attempting to reproduce each of the controlling conditions that exist in the real situation. Variations, which may be relatively small, in these simulations can lead to significant differences in test results. There is therefore much to be said for keeping test conditions as simple as possible rather than attempting to reproduce accurately the conditions in practice. A balance between reproducibility and realism has to be struck. 

Modeling. There is as yet no rapid simulated laboratory aging test for catalysts that is recognized as a good predictor of catalyst aging in the vehicle. 

The wear resistance of rubber compounds is of great practical importance for tires, but the mechanisms involved in tire wear are multiple and may vary depending on the vehicle, the driving conditions, and other extraneous variables. Many attempts have been made to develop laboratory test methods to simulate tire wear under various conditions. Whilst none can fully replicate road wear, various laboratory abrasion tests can be used to provide an indicator of wear resistance of tires under certain conditions. 

Laboratory tests on samples exposed to actual plant liquids or simulated environments should be done only when testing in the actual operating environment cannot be done. When MIC is a factor in the test, microbial communities from the actual environment of interest must be used. Pure cultures of single types of microbes cannot provide conditions present in the actual operating environment. 

Pilot plant tests, and laboratory corrosion tests under simulated plant conditions, will help in the selection of suitable materials if actual plant experience is not available. Care is needed in the interpretation of laboratory tests. 

A primary advantage of laboratory tests is that they are less expensive and so more of them can be performed. Also, certain conditions can be simulated in a lab that cannot be duplicated in the field. One can saturate the soil fully in the laboratory, getting rid of all the gas. One can also vary the overburden stress in the lab, which cannot be done conveniently in the field. Finally, in the lab, actual waste liquids can be passed through a column of material for testing, a condition that could not be duplicated in the field. 

The objective of this work is to study the possible influence of the crude oil composition on the amount of coke deposit and on its ability to undergo in-situ combustion. Thus, the results would provide valuable information not only for numerical simulation of in-situ combustion but also to define better its field of application. With this aim, five crude oils with different compositions were used in specific laboratory tests that were carried out to characterize the evolution of the crude oil composition. During tests carried out in a porous medium representative of a reservoir rock, air injection was stopped to interrupt the reactions. A preliminary investigation has been described previously (8). 

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