Testing laboratories

Comparative testing in the beakers of a particular jar test apparatus is, however, vahd due to the identity of stirring conditions. So the effects of various doses of flocculating chemicals, of different pH conditions, and of different types of chemicals (e.g. indifferent electrolytes, aluminium or ferric salts, various polyelectrolytes) can be determined. Usually, an optimum is required and this relates to the formation by flocculation of a separable suspension. 

Frequently, the first assessment is visual, looking for the appearance of visible floes (which normally is greater than about 100 pm) and their growth to sizes of about 1 mm with clear liquid between. As flocculation is a prior step to some solid-liquid separation processes, an assessment is required of their settling, filtration or flotation behaviour. 

Flotation of floes by air bubbles can be tested by using jar test beakers which have a false bottom diffuser plate so that after flocculation by stirring, diffused air can be released through the suspension to form a floe froth scum on the surface. Such a modified jar test apparatus has been designed by the UK Water Research Centre. Similarly, if dissolved air flotation is of interest then compressed air can be released into the bottom of the beaker to float the flocculated particles. Obviously in flotation it is the clarity of the bottom liquid which is important and sampling near the bottom is required for turbidity or particle count measurements. 

Comparisons of different jar test apparatuses can be made by estimating the mean velocity gradient (G value) using equation 4.46  

V is the volume of the stirred beaker P is the power transferred from the stirrer to the suspension. 

The process starts with a database search to determine whether human health information, ecological toxicity data, or chemical data exist on the C R material of interest (Fig. 7). If data are unavailable, the user requests toxicity screening tests (algae and daphnia were the primary aquatic indicators used in this study). If the test results show no toxicity, no further investigation is required. If the screening tests results show toxicity, the user requests tests for evaluating the source strength and effects of reference environments on toxicity response, and chemistry. 

Whenever possible, standard test procedures and means of evaluation provided by organizations such as ASTM, NACE, or SSPC should be consulted and followed. Only in this manner can correlation with the results of other workers be established. SSPC and NACE certified coating/corrosion professionals are trained to investigate paint failures and know which analytical technique or investigation method may provide the most useful information. 

Use of Tooke gage for measurement of paint layers. (Courtesy of KTA-Tator, Inc.) 

The number and t5rpes of tests that can be conducted in the laboratory are almost limitless. Table 14.9 lists some of the ASTM tests relevant to protective coatings. Because field testing of coatings is so costly in time, labor, and facilities, it has been the persistent aim of formulators, raw materials producers, and users of coatings to establish meaningful accelerated tests. These may involve a wide variety of comparatively simple, as well as highly sophisticated procedures. 

These tests can define certain characteristics of a coating system. This discrimination usually is specific to the type of accelerated test, and frequently does not indicate in advance how a given coating will perform in service. However, the tests are invaluable when developing coatings or appraising new concepts in coatings application or use. 

General immersion tests General immersion tests can be as simple as the standard saltwater immersion test for coatings to be used in the atmosphere, or as complicated as cold wall effect immersion tests for heavy coatings to be used constantly in immersion service. It is essential to reproduce the anticipated conditions of the field exposure as dosely as possible when evaluating coatings for immersion service. 

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David, P G.l. Brown and E.W. Lehman (1993), SFPP - A new laboratory test for assessment of low temperature operability of modern diesel fuels". CEC 4th International Symposium, Birmingham. 

If oil and water are mixed as an emulsion, dehydration becomes much more difficult. Emulsions can form as oil-in-water or water-in-oil if mixed production streams are subjected to severe turbulence, as might occur in front of perforations in the borehole. Emulsions can be encouraged to break (or destabilise) using chemicals, heat or just gentle agitation. Chemical destabilisation is the most common method and laboratory tests would normally be conducted to determine the most suitable combination of chemicals. 

Possible water sources for injection are sea water, fresh surface water, produced water or aquifer water (not from the producing reservoir). Once it has been established that there is enough water to meet demand (not an issue in the case of sea water), it is important to determine what type of treatment is required to make the water suitable for injection. This is investigated by performing laboratory tests on representative water samples. 

Laboratory tests indicated that gamma radiation treatment and cross-linking using triaHylcyanurate or acetylene produced a flexible recycled plastic from mixtures of polyethylene, polypropylene, general-purpose polystyrene, and high impact grade PS (62). 

In laboratory tests, appHcation of DMAC to the skin of pregnant rats has caused fetal deaths when the dosages were close to the lethal dose level for the mother. Embryonal malformations have been observed at dose levels 20% of the lethal dose and higher. However, when male and female rats were exposed to mean DMAC concentrations of 31,101, and 291 ppm for 6 h per day over several weeks, no reproductive effects were observed (6). 

Health and Safety Factors. Boron trifluoride is primarily a pulmonary irritant. The toxicity of the gas to humans has not been reported (58), but laboratory tests on animals gave results ranging from an increased pneumonitis to death. The TLV is 1 ppm (59,60). Inhalation toxicity studies in rats have shown that exposure to BF at 17 mg/m resulted in renal toxicity, whereas exposure at 6 mg/m did not result in a toxic response (61). Prolonged inhalation produced dental fluorosis (62). High concentrations bum the skin similarly to acids such as HBF and, if the skin is subject to prolonged exposure, the treatment should be the same as for fluoride exposure and hypocalcemia. No chronic effects have been observed in workers exposed to small quantities of the gas at frequent intervals over a period of years. 

Flammability. The results of small-scale laboratory tests of plastic foams have been recognized as not predictive of their tme behavior in other fire situations (205). Work aimed at developing tests to evaluate the performance of plastic foams in actual fire situations continues. All plastic foams are combustible, some burning more readily than others when exposed to fire. Some additives (131,135), when added in small quantities to the polymer, markedly improve the behavior of the foam in the presence of small fire sources. Plastic foams must be used properly following the manufacturers recommendations and any appHcable regulations. 

Miscellaneous chemicals are used to modify the final properties of rigid polyurethane foams. Eor example, halogenated materials are used for flammabihty reduction, diols may be added for toughness or flexibiUty, and terephthalate-based polyester polyols may be used for decreased flammabiUty and smoke generation. Measurements of flammabihty and smoke characteristics are made with laboratory tests and do not necessarily reflect the effects of foams in actual fire situations. 

A number of laboratory tests are used to predict chemical stabihty. The amount of existent gum in a gasoline is determined by ASTM D381. This method involves evaporating a sample by a jet of heated air. The residue is weighed, solubles are extracted with / -heptane, and the sample is reweighed. 

Most hafnium compounds requite no special safety precautions because hafnium is nontoxic under normal exposure. Acidic compounds such as hafnium tetrachloride hydroly2e easily to form strongly acidic solutions and to release hydrogen chloride fumes, and these compounds must be handled properly. Whereas laboratory tests in which soluble hafnium compounds were injected into animals did show toxicity, feeding test results indicated essentially no toxicity when hafnium compounds were taken orally (33,34). 

Test salons are often used to evaluate hair fixatives. Half-head studies are performed, with the test product appHed to one side of the head and a control product to the other in reaHstic use amounts. Similar properties as desctibed in laboratory tests are measured. Finished products are often sent to testers homes where they have an opportunity to evaluate the products in real use situations for extended pedods. 

Thus the Brinell test in its original manifestation is a laboratory test in which cut pieces are brought to it for testing. The lack of portabiUty spawned several modifications to achieve that property. 

Quality Control and Testing. Control of inks is done by examining their color strength, hue, tack, rheology, drying rate, stabiHty, and product resistance. Elaborate control equipment and laboratory testing procedures are employed to test the finished inks. Weather-Ometers,... 

The sound-absorbing properties of acoustical materials also are influenced by the manner in which the materials are mounted. Standard mounting methods for use in laboratory testing are specified in ASTM E795-92 (2). Unless noted otherwise, pubflshed data for acoustic ceiling materials are for Mounting Type E-400, for which the material being tested is suspended 400 mm below a hard surface. 

L bor toiyMethods. The laboratory test method for determining the sound-transmission loss performance of constmctions is defined in ASTM E90-90 (11). The sample is installed in an opening between two highly reverberant rooms that are acoustically well isolated from each other. 

Elame-spread and smoke-density values, and the less often reported fuel-contributed semiquantitive results of the ASTM E84 test and the limited oxygen index (LOI) laboratory test, are more often used to compare fire performance of ceUular plastics. AH building codes requite that ceUular plastics be protected by inner or outer sheathings or be housed in systems aH with a specified minimum total fire resistance. Absolute incombustibHity cannot be attained in practice and often is not requited. The system approach to protecting the more combustible materials affords adequate safety in the buildings by aHowing the occupant sufficient time to evacuate before combustion of the protected ceUular plastic. 

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. 

Resistance is iadicated by yes, ie, laboratory tests have shown enough promise to warrant test under actual service conditions. 

Sohd materials, such as gilsonite and asphalt, and partially soluble sulfonated asphalt may also be added to plug small fractures in exposed shale surfaces and thereby limit water entry into the formation (105,124). The asphalts are oxidized or treated to impart partial solubiUty. These materials may be softened by the downhole temperature, causing them to deform and squeeze into small openings exposed to the borehole. Laboratory tests designed to evaluate shale-stabilizing muds have confirmed the beneficial action of these materials (125) (see also Soil STABILIZATION). 

An alternative to this process is low (<10 N/m (10 dynes /cm)) tension polymer flooding where lower concentrations of surfactant are used compared to micellar polymer flooding. Chemical adsorption is reduced compared to micellar polymer flooding. Increases in oil production compared to waterflooding have been observed in laboratory tests. The physical chemistry of this process has been reviewed (247). Among the surfactants used in this process are alcohol propoxyethoxy sulfonates, the stmcture of which can be adjusted to the salinity of the injection water (248). 

Uniform, rehable flow of bulk soflds can allow the production of quaUty products with a minimum of waste, control dust and noise, and extend the hfe of a plant and maximi2e its productivity and output. By conducting laboratory tests and utili2ing experts with experience in applying soflds flow data, plant start-up delays that can impact schedule and cost can be eliminated. 

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