Abnormal noises are detected in pipeline vibration during the conversion of cold ammonia to hot ammonia in the tank farm

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In the original design for the liquid ammonia tank area, liquid ammonia at -33°C was pressurized to about 1.8 MPA using a pump, and then heated to 20°C via an ammonia heater (using low-pressure steam as the heat source and methanol as the intermediate heat transfer medium; the methanol level was about 1/3 of the total volume of the heat exchanger, with it covering the low-pressure steam tubes), before being sent to the spherical tank for storage. However, in actual production, after liquid ammonia at -33°C is pressurized by a pump, the following abnormal conditions occur: 1. After the pressure pump starts up, the outlet pressure remains at around 2.5 MPa; as the outlet valve of the pump opens, the outlet pressure drops. The outlet temperature of the ammonia heater fluctuates between -2°C and 12°C, and the outlet pressure of the pressure pump also fluctuates along with it, resulting in intermittent vibrations and unusual noises in the subsequent liquid ammonia pipelines. 2. When the flow rate at the pump outlet is low, the temperature at the heater outlet remains stable at around 10°C. There is continuous slight vibration and noise at the bottom of the spherical tank; however, this condition does not last long, as the temperature at the heater outlet begins to fluctuate significantly intermittently, along with abnormal noises and vibrations. 3. When the flow rate at the pump outlet is about half, the ammonia heater emits intermittent humming sounds indicating liquid flow; shortly thereafter, abnormal noises and vibrations occur in the downstream pipes. 4. Once the outlet valve of the pressure pump is fully opened, the temperature at the heater outlet drops to -11°C; at this point, pipe vibration and abnormal noises cease. However, the temperature at the bottom of the spherical tank drops to 0°C within a short time, exceeding the specified control limits, which forces the pump to stop operating. Personal on-site preliminary assessment: It is possible that liquid ammonia vaporizes in the ammonia heater, causing the pressure at the pump outlet to fluctuate accordingly; this leads to air being entrained in the liquid ammonia, which in turn causes abnormal noises and vibrations in the subsequent piping. In the situations mentioned above, it has been impossible to determine the exact cause. Therefore, I kindly ask the teachers in the communities for their guidance, as well as any valuable experience and suggestions they might have. Thank you!