An Evaluation of Pressure Measurement Technology and Operating Performance Using Sandia's Molten Salt Test Loop

Sandia National Laboratories has recently completed the design, construction, commissioning, and initial operation of a Molten Salt Test Loop (MSTL) facility in Albuquerque, NM, USA. MSTL provides three parallel test loops for customers to evaluate new and existing technology in flowing molten nitrate salt at plant-like conditions of up to 70 kg/s flow rate, 40 bar pressure, and 300-585 °C temperature. The test loop furnace contains 40metric tons of 60% sodium nitrate / 40% potassium nitrate salt that is pumped through the parallel test loops by a 9-stage, vertical turbine pump. The three parallel test legs provide locations that can accommodate small component tests such as flow instrumentation devices or valves to large solar collection systems for on-sun testing using molten nitrate salt. The system was designed with 1.4MW of heat removal capability – equivalent to the solar gain of a large aperture trough module.During startup and commissioning of the system, the pressure transducers were identified as having a significant amount of thermally induced drift. This drift came from both diurnal ambient variations as well from operational heating from the process fluid. Exacerbating these difficulties is the requirement of MSTL that the pressure transducers operate over a wide temperature range in the course of a single test operation cycle. Sandia has taken steps to evaluate the pressure variation and to reduce this variation through temperature control. This work has greatly reduced the variability in the pressure transducers, but further improvements are on-going. The presentation will report on the efforts taken to reduce variability and the resulting performance of the transducer systems. In the course of describing the pressure transducer efforts, the system performance will also be presented along with some lessons-learned in the commissioning and startup of this test capability.