Tracer methods

Flow measurements using tracers are performed in all piping systems carrying oil, gas or water including separators, compressors, injector systems, and flares. Calibration of elsewhere difficult accessible flow meters is regularly performed by the tracer methods, which are based on international standards. Tracer flow measurements are also well suited for special purposes... 

The gaseous tracer method yields the equivalent piston flow linear velocity of the gas flow in the pipe without any constraints regarding flow regime under the conditions prevailing for flare gas flow. 

Figure 2. Principle of 3 phase flow measurements by the continuous dilution tracer method.

Leaking fi om process flows may pose operational risks and cause environmental problems as well as economic losses. Two examples of tracer methods for testing, localising and quantifying leaks are given below. 

Generally, however, the application of tracer methods remains a rarity compared to methods which directly exploit the motion sensitivity of the NMR signal. The detection of motion is based on the sensitivity of the... 

Tracer Type. A discrete quantity of a foreign substance is injected momentarily into the flow stream and the time interval for this substance to reach a detection point, or pass between detection points, is measured. From this time, the average velocity can be computed. Among the tracers that have historically been used are salt, anhydrous ammonia, nitrous oxide, dyes, and radioactive isotopes. The most common appHcation area for tracer methods is in gas pipelines where tracers are used to check existing metered sections and to spot-check unmetered sections. 

Tracer methods involving chemical markers injected into the contents of the tank may be used. Instmmentation capable of picking up the chemical marker can then determine the presence of a leak caused by seepage of the tracer into the ground. This, like the hydrocarbon sensing method, is genericaUy referred to as soil vapor monitoring. This method suffers the same weaknesses that have to do with undertank soil permeabUities. 

European Standard EN 1093-4. Safety of machinery—Evaluation of the emission of airborne hazardous substances. Part 4 Capture efficiency of an exhaust system— Tracer method. 1996. 

Tracer methods are not as well standardized as some of the conventional methods. One standard is available, but it comprises radioactive tracers only, which are perhaps not the best alternative for measurements in buildings. In principle, at least three different measurement methods are available the... 

ISO 4053-1 1977. Measurement of Gas Flow in Conduits—Tracer Methods—Part 1 Cjcncrai. International Organisation for Standardisation, 1977. 

It has been shown by employing the radioactive tracer method with C-labeled carboxylic acids [79] and with rotating disc electrode experiments [80] that carbo-xylates are adsorbed at the anode surface. 

Despite the advantages that sand-based systems provide for estimating rhizodeposition, studies in soil are still required. These are far more technically demanding and are heavily biased toward the use of radioactive tracer methods. 

Applications Radiotracer measurements, which combine high sensitivity and specificity with poor spatial resolution, have been used for migration testing. For example, studies have been made on HDPE, PP and HIPS to determine effects of manufacturing conditions on migration of AOs from plastic products into a test fat [443]. Labelled antioxidant was determined radio-analytically after 10 days at 40 °C. Acosta and Sas-tre [444] have used radioactive tracer methods for the determination of styrene ethyl acrylate in a styrene ethyl acrylate copolymer. 

Tracer methods can also be used, in which tracers such as freon, fluorescent materials, and isotope-fuel are added to a tank, and are then detected externally. An analogy of tracer methods includes pressurizing the tank with a noble gas, then detecting the gas if it escapes from the tank through cracks or holes. 

S. Heavens (33) hat mit einer radioaktiven TRACER-Methode gezeigt, daB selbst dann, wenn die Dampfdrucke von Verdampfer und Ver-dampfungsgut weit auseinander liegen (W und Ge) in dem aufgedampften Film Spuren des Verdampfermaterials nachweisbar sein konnen. 

In an earlier presentation, we reported on a deuterium tracer method for investigating the mechanisms of coal liquefaction Q). 

Two significant results of that investigation were that deuterium incorporation was found to vary with product fraction and that preferential incorporation of deuterium was found in benzylic structural positions. The purpose of this research is to extend the use of the deuterium tracer method to donor solvent reactions. 

R. P. Skowronski, J. J. Ratto and L. A. Heredy, "Deuterium Tracer Method for Investigating the Chemistry of Coal Liquefaction", Annual Report, 1977, Rockwell International,... 

Since the discovery of the first noble gas compound, Xe PtF (Bartlett, 1962), a number of compounds of krypton, xenon, and radon have been prepared. Xenon has been shown to have a very rich chemistry, encompassing simple fluorides, XeF2> XeF, and XeF oxides, XeO and XeO oxyf luorides, XeOF2> XeOF, and Xe02 2 perxenates perchlorates fluorosulfates and many adducts with Lewis acids and bases (Bartlett and Sladky, 1973). Krypton compounds are less stable than xenon compounds, hence only about a dozen have been prepared KrF and derivatives of KrF2> such as KrF+SbF, KrF+VF, and KrF+Ta2F11. The chemistry of radon has been studied by radioactive tracer methods, since there are no stable isotopes of this element, and it has been deduced that radon also forms a difluoride and several complex salts. In this paper, some of the methods of preparation and properties of radon compounds are described. For further information concerning the chemistry, the reader is referred to a recent review (Stein, 1983). 

As mentioned earlier (see p. 122) the previously postulated dioxetane intermediate in firefly bioluminescence has been challenged as no 180 is in-corporated in the carbon dioxide released during oxidation of firefly luciferin with 18C>2. In view of the crucial significance of the 180. experiments De Luca and Dempsey 202> rigorously examined the reliability of their tracer method. They conclude from their experiments that all available evidence is in favour of a linear, not a cyclic peroxide intermediate — in contrast to Cypridina bioluminescence where at least part of the reaction proceeds via a cyclic peroxide (dioxetane) as concluded from the incorporation of 180 into the carbon dioxide evolved 202,203). However, the dioxetane intermediate is not absolutely excluded as there is the possibility of a non-chemiluminescent hydrolytic cleavage of the four-membered ring 204>. 

A disadvantage of tracer methods is the frequent presence of exchange processes which are difficult to account for. This hampered Happel s work with 180 (30) and complicated the interpretation of the work of Conner and Bennett (34), who used pulses of tracers and a qualitative interpretation of their data on CO oxidation over NiO. 

Dlldukovic, M.P. (1985), Tracer Methods in Chemical Reactors Techniques and Applications, NATO Advanced Study Institute Conference, June 2-12, U. Western Ontario, London, Ontario. 

Thus, if m = 10 2 mol l"1, and if all the monomer is polymerised, and if all kinetic chains are started by addition of AlX+2 to monomer, there will be 10"4 mole of Al-C bonds per base-mole of monomer. For reactions in a hydrocarbon solvent, where kp is of the order of 10s 1 mol 1 s 1, and tV2 appreciably greater, [Pn+] is correspondingly smaller and the whole task much harder. Further, before the C-Al bonds can be identified, they must be converted into a stable, analysable species by unambiguous reactions and these must be such that the products formed from the unreacted AlBr3 during the conversion do not interfere with the subsequent analysis. It is evident that radioactive tracer methods offer the best hope of solving this problem. 

W. A. L. David,2 using radio-tracer methods, has determined the concentration of ( undecomposed ) O.M.P.A. necessary to give a complete kill of Aphis fabae on beans. He gives a figure... 

Such a mechanism is not incompatible with a Haven ratio between 0.3 and 0.6 which is usually found for mineral glasses (Haven and Verkerk, 1965 Terai and Hayami, 1975 Lim and Day, 1978). The Haven ratio, that is the ratio of the tracer diffusion coefficient D determined by radioactive tracer methods to D, the diffusion coefficient obtained from conductivity via the Nernst-Einstein relationship (defined in Chapter 3) can be measured with great accuracy. The simultaneous measurement of D and D by analysis of the diffusion profile obtained under an electrical field (Kant, Kaps and Offermann, 1988) allows the Haven ratio to be determined with an accuracy better than 5%. From random walk theory of ion hopping the conductivity diffusion coefficient D = (e /isotropic medium. Hence for an indirect interstitial mechanism, the corresponding mobility is expressed by... 

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