The effect of upstream flow disturbances was tested on 4 flow meters from 4 different LNG flow meter manufacturers in VSL’s cryogenic research and calibration facility using liquid nitrogen. The upstream flow disturbances investigated comprised a blocking plate and a double bend, and their effects were contrasted against “ideal circumstances” with no upstream flow disturbance and insulated flow meters. In addition, the effect of meter insulation was investigated. The calibration curves of both ultra-sonic and Coriolis meters exhibit good repeatability and typical behavior for the flow meter type. This gives confidence in the facilities master meter calibration method. The results will be published at a later stage. The results will be compared with the water tests which were already successfully completed by NEL, and which were performed in the same metering setups to enable a systematic comparison of flow meter performance under water and cryogenic conditions. Tests on another 2 flow meters are planned, and when these are completed comparison of water and liquid nitrogen data will be started to fully understand the influence of flow disturbances on measurement uncertainty.
The Cryogenic Research and Calibration facility. Components are: 1) Liquid nitrogen storage tank, 2) cryogenic liquid storage tank, 3) primary Standard for mass flow utilizing the gravimetric method, 4) meters-under-test section, 5) working standards, a set of Coriolis mass flow meters, 6) heat exchangers and pumps, 7) Nitrogen warmer and 8) control room.