Loop test loops

Loop Tests Loop test installations vary widely in size and complexity, but they may be divided into two major categories (c) thermal-convection loops and (b) forced-convection loops. In both types, the liquid medium flows through a continuous loop or harp mounted vertically, one leg being heated whilst the other is cooled to maintain a constant temperature across the system. In the former type, flow is induced by thermal convection, and the flow rate is dependent on the relative heights of the heated and cooled sections, on the temperature gradient and on the physical properties of the liquid. The principle of the thermal convective loop is illustrated in Fig. 19.26. This method was used by De Van and Sessions to study mass transfer of niobium-based alloys in flowing lithium, and by De Van and Jansen to determine the transport rates of nitrogen and carbon between vanadium alloys and stainless steels in liquid sodium. 

Open-loop testing with air or with the specified gas is relativcls straightforward, but there are difficulties in carrying out closed-loop (l sk with equivalent gases. 

Class I includes all tests made on the specified gas (whether treated as perfect or real) at the speed, inlet pressure, inlet temperature, and cooling (if applicable) conditions for which the compressor is designed and is intended to operate, that is, an air machine or a gas-loop test on the specified gas within the limit set by Table 10-3. 

Classes II and III include all tests in which the specified gas and/or the specified operating conditions cannot be met. Class II and Class III basically differ only in method of analysis of data and computation of results. The Class II test may use perfect gas laws in the calculation, while Class III must use the more complex real gas equations. An example of a Class II test might be a suction throttled air compressor. An example of a Class III test might be a CO2 loop test of a hydrocarbon compressor. Table 10-4 shows code allowable departure from specified design parameters for Class II and Class III tests. 

Because of safety concerns, all combustible and/or toxic gases must be used in outdoor test loops or in a special indoor test building with the required safety monitoring equipment. The gas cost factor makes the problem even more difficult. The problem of known gas properties adds another complication. Despite all the negative aspects just mentioned, most performance tests are closed-loop tested. 

Figure 10-2. Schematic of a typical shop test-loop arrangement.

Another method of test is to test all sections simultaneously. In this method, the weight flow through each section is maintained in the same proportion. A separate gas cooler is required for each stream and the loop must have sufficient capacity to enable stable conditions to be obtained. In this system, the machine is tested as fully built but requires extensive shop test space to accommodate the multiple gas coolers and large test-loop piping required, if there are several sidestreams. 

Loop testing the sidestream compressor is probably the most difficult, if more than two sidestreams are involved. Reviewing the sidestream problem should give an insight to the various configurations and the test arraiigeiueut. 

Lissajous figure. 378 Loop testing, 417 Lube and seal system specification information, 449... 

Oil film seals, 304 On stream, 144 Open-loop testing, 417 Operation... 

To determine the appropriate injection rate, a field test should first be performed at one of the industry-sponsored full-scale loop test facilities. The optimum mixture, its injection rate, and location of injcciioii points will be a function of flow geometry, fluid properties, pressure leinpcrature relationships, etc., that will be encountered in the actual field application. The appropriate injection rate and location of injection jii iiiis can be determined from this test by observing pressure increases, which indicate that hydrate plugs are forming. 

The CREDO data base contains data from The Fast Flux Test Facility in Richland, Washington, The Experimental Breeder Reactor - II in Idaho Falls, Idaho, The test loops of the Energy Technology Engineering Center (ETEC) in Canoga Park, California, The JOYO Liquid Metal Fast Breeder Reactor at the 0-Arai Engineering Center (OEC) in Japan, and the test loops of OEC. 

Table 7.36 Results in thermal convection loop tests of material in contact with molten lead...

Three different forms of EPR test can be employed, designated as the single loop, double loop and reactivation ratio methods in Figure 19.20. 

Pitting caused by the dissolution of non-metallic inclusions can increase the value. Consequently, the microstructures of specimens with a high value must be examined to identify the source of the elevated value. In general, P values below 0-10 are characteristic of unsensitised microstructures, while sensitisation is indicated if P, exceeds 0-4. Single loop tests are sensitive to mild degrees of sensitisation but do not readily distinguish between medium and severely sensitised materials. 

Reactivation Ratio EPR Test (Fig. 19.20c) This is a simpler and more rapid method than the single or double loop tests, and depends on the fact that the value of determined during the anodic scan of a double loop test (which produces general dissolution without intergranular attack on sensitised material) is essentially the same for all AlSl Type 304 and 304L steels. 

Evaluation of loop-test results Although the thermal loop test approximates to the conditions which obtain in a dynamic heat-transfer system, in evaluating the results it is necessary to be aware of those aspects in which the test differs from the full-scale unit, as otherwise unwarranted confidence may be placed in the data. Assuming that adequate attention has been paid to the purity and condition of components, etc., the following factors will, according to ASTM G68 1980, influence the observed corrosion behaviour ... 

Under development are intelligent vehicles for crack detection. An elastic-wave version (developed by British Gas and the Harwell Laboratory) is currently being evaluated in a test-loop. This vehicle has successfully detected stress-corrosion cracks in the test-loop. The Gas Research Institute (USA) is sponsoring development work with intelligent vehicles at the Battelle Columbus Division (Ohio). Facilities for testing vehicles were commissioned in 1991... 

Fig. 11. Test loop for investigating the effect of inlet throttling on burn-out [from Styrikovitch et al. (SI 7)].

Data are available for metallic impurities in the primary coolant of in-pile test loops at MOL which uses I.C.l. Na, and from Degussa Na which is used as the... 

The PBL reactor considered in the present study is a typical batch process and the open-loop test is inadequate to identify the process. We employed a closed-loop subspace identification method. This method identifies the linear state-space model using high order ARX model. To apply the linear system identification method to the PBL reactor, we first divide a single batch into several sections according to the injection time of initiators, changes of the reactant temperature and changes of the setpoint profile, etc. Each section is assumed to be linear. The initial state values for each section should be computed in advance. The linear state models obtained for each section were evaluated through numerical simulations. 

ENA was recently used for remote on-line corrosion monitoring of carbon steel electrodes in a test loop of a surge water tank at a gas storage field. An experimental design and system for remote ENA and collection of electrochemical impedance spectroscopy (EIS) data (Fig. 13) have been presented elsewhere. In the gas storage field, noise measurements were compared with electrode weight loss measurements. Noise resistance (R ) was defined as... 

Figure 14. Representative noise data as monitored for steel electrodes exposed in a test loop at a gas storage field (a) o V(r). (b) o l(r), (c) Rn, and (d INT, .

T. Palermo, A. Sinquin, H. Dhulesia, and J. M. Fourest. Pilot loop tests of new additives preventing hydrate plugs formation. In Proceedings Volume, pages 133-147. 8th Bhr Group Ltd et al Multiphase 97 Int Conf (Cannes, France, 6/18-6/20), 1997. 

The open-loop test response fitted to a first order with dead time function GPRC can be applied to other tuning relations. One such possibility is a set of relations derived from the minimization of error integrals. Here, we just provide the basic idea behind the use of error integrals. 

As far as we are concerned, using the error integral criteria is just another empirical method. We are simply using the results of minimization obtained by other people, not to mention that the first order with dead time function is from an open-loop test. 

A. Tuning relations based on open-loop testing and response fitted to a first order with dead time function... 

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