0428同步年報-2021-全

Facility Status 101 heat load was reduced by using vacuum-shielded and super-insulation-shielded types. The G10 material is used to provide support inside the pipe. Figure 3 depicts the structure of a keep-full device. This vacuum-protected keep-full device is also vacuum- protected. A buffer contains a single mechanical ball-float valve. The ball-float valve exhausts the GN 2 away at the start of the two-phase flow of nitrogen flowing through the buffer's entrance. The ball blocks the exhaust port within the ball-float valve until the LN 2 fills the buffer. The two-phase flow of fluids occurs as a result of heat ingress, and liquid nitrogen vaporizes to nitrogen gas in the branch line. This condition can cause an accumulation of gaseous nitrogen in the pipeline, especially if there is little or no flow. The gas that has emerged is exhausted via the keep- full device. The branch line is completely mechanically and automatically filled with liquid nitrogen. A sound-suppression device was hence designed to diminish the noise by altering the flow velocity and the audio structure. The structure of this sound-suppression device, shown in Fig. 4 , which uses the porous characteristics to reduce the air vibration to decrease the noise, mainly refers to a common exhaust muffler for motor vehicles. This muffler is classified as a resistance muffler, also known as an acoustic filter. The most basic type of expansion chamber is a thick tube with a large cross-section connected to the airflow channel tube, but the end is a thin tube. Adjusting the length of the cross-section buckle of the expansion chamber (large tube) affects the reflection and interference performance of the sound wave. There was no sound-absorbing material installed. This sound-suppression device is located at the exhaust port of the keep-full device. The condensation or icing occurs because of gaseous nitrogen at a low temperature. We wrapped an electrical heating wire around the surface to bring the exhaust up to room temperature. Figure 5 depicts the LN 2 branch line for TPS 13A . The vacuum-shielded branch pipe is about 6 m long, and the sound-suppression device is about 1 m long. Several tests were carried out before the installation on-site. A cold shock test was performed on the branch lines, which were filled with liquid nitrogen. The goal was to investigate the effects of thermal stress on fittings and welds. Each fitting and weld was tested at 80 K and after being warmed to room temperature. This procedure was repeated three times. The measured rate of helium leakage was less than 1.0 × 10 −9 mbar L s −1 in the evacuation mode with vacuum level 1.0 × 10 −3 mbar. The pipeline was filled with helium at 5 barg for leak testing. The standard rate of leakage of the sniffing mode is less than 1.0 × 10 −5 mbar L s −1 . Figure 6 (see next page) shows the pressure fluctuations of a tank, as well as the upstream and the downstream pressures of the pressure-regulating device. The pressure of the tank fluctuated from 2.6 to 2.7 bar gauge (barg) when the 60-m 3 LN 2 tank was refilled from the LN 2 truck; the pressure rose briefly to 2.9 barg, but the pressure upstream Fig. 4 : Sound-suppressor device. Fig. 5 : LN 2 branch line for TPS 13A . Fig. 3 : Keep-full device (+ buffer + exhaust port).