Loop-test installations

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. 

The loop test results should be recorded (a sample instrument loop check sheet has been provided for reference purposes in Appendix 23D) and included with the site test records. Checks for mechanical/electrical completeness are recorded using the upper section of the sheet and the dytramic loop test results are recorded on the lower section. The test results sheets will provide the documentary evidence essential for Installation Qualification (IQ). Representatives from the installation contractor and/or the customer will witness the final loop tests and countersign the test sheets. Any tests not witnessed must be accompanied by written confirmation from the customer that witnessing has been waived. 

The primary element may be installed within a continuous section of pipe flowing full or at the inlet or exit of a pipe or a plentun chamber. Orifice and venturi tube are installed within the pipe in a closed-loop test. The flow nozzle may be installed within, at inlet, or at outlet of the pipe. 

It is normal practice to use a venturi tube installed within a continuous section of pipe in piunp-acceptance tests and a flow nozzle at the exit of the discharge pipe in compressor-acceptance tests. More closed-loop testing has recently been required in compressor testing. Industry normally uses the nozzle configuration shown in Fig. M-26 with a closed loop. The construction of the primaiy elements and examples of their installation are given in the following paragraphs. 

Fig. 3. Comtrack 921 pipe prover. Liquid flow through the Comtrak s closed loop is created by the movement of a sealed piston. Flow meters being tested are installed in the loop upstream from the piston. As the piston advances, the caUbration fluid travels through the meters and returns to the back side of...

Early in the program, critical components (e.g.,the turbomolecular pump) and circuit boards were tested for their ability to survive neutron and gamma irradiation rates and doses similar to those that would be received from exposure to the detonation of a tactical nuclear device. All components were powered up at the start of the gamma irradiation tests but not during the neutron irradiation tests. Circuit boards were protected by circumvention circuits that powered down critical circuits in 10 to lOOps upon detecting radiation. All components survived the nuclear radiation tests. This unusual performance was noted with positive commendations by the staff at the White Sands Missile Range, where the tests were performed. Tests of the fully integrated CBMS II system, installed in a reconnaissance vehicle, will be conducted in the future. 

A typical test loop includes a pump capable of pressure development to 1000 psig and sufficient valving and piping to permit multistation installation of fiber samples. Feed solutions are delivered from reservoirs which are thermostated and isolated in order to maintain constancy of temperature and composition. The facility is so established that both permeate and concentrate are returned continuously to the reservoir. 

The level of site acceptance testing should be such as to demonstrate satisfactory operation of the system functions in conjunction with the manufacturing process equipment and may involve control loop tuning. Site acceptance testing in its basic form should include installation checks, power-up, diagnostic checks, and commissioning of process and safety-related operational I/O, controls, sequencing, interlocks, alarms, and reports. 

Outside of the occasional system calibration and model verification tests, the routine maintenance burden of a Raman system is quite low. Optical windows may need to be cleaned, though automatic window cleaning systems can be implemented if it is a known issue. The most likely maintenance activity is laser replacement. Some systems have a backup laser that turns on automatically if the primary laser fails. This lessens the impact of a failure if the unit is being used for closed-loop process control. With a quality instrument and well-developed models, process Raman installations need less maintenance than many competing techniques. 

The pre-op team steam tested the equipment with up to 50 psig (345 kPa gauge) steam to check for any system leaks. Prior to the steam test, temporary piping 8 inches (20 cm) in diameter was installed to the pre-engineered 24-inch (61 cm) vent to release the steam to the atmosphere. The A Unit and the B Unit coker shared a common vent line to the atmosphere. Unfortunately, the design of the piping modification created a loop that could collect water as the steam condensed. 

All conductors are part of three closed current loops with impressed currents which are kept constant, and a three-phase high voltage system enables simultaneous PD measurements in the three conductors (Fig. 8.9). The complete test circuit is installed in a shielded cabin as a Faraday cage, all power lines enter this cage via filter banks to suppress unwanted signal transmission to the internal test circuit. The main parts of the test circuit are ... 

Start with one isolated unit operation. Get its control system installed, tuned, and tested for closed-loop stability and robustness. Then move on to the next unit and repeat. Build up the entire plant... 

The calibration procedures adopted on-site must be agreed on with the customer and conform to recognized industry instrument calibration standards and the supplier s instructions. These procedures must be applied to all in-line instrumentation, loop instrumentation, local controllers, analyzers, and so on. Where the control and monitoring instrumentation is integrated with a computerized control system and where factory tests have been carried out, the installation calibration procedure should be agreed on with the customer. 

The following test procedure should be carried out in order to test the correct operation of field instrumentation and equipment installed in a control loop, and to provide the necessary documentary evidence (test records) to satisfy the requirements of the IQ protocols ... 

As for the control technology, JAEA proposed to use SG as the thermal absorber, which is installed downstream the chemical reactor in the secondary helium gas loop, to mitigate the temperature fluctuation of the secondary helium gas. By the simulation test with the mock-up test facility, it was confirmed that the SG could be used as tlie thermal absorber. 

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