Refrigeration system replacement method

The principle of handover and replacement of refrigeration system replacement is: fully recover ammonia from the refrigeration system, reduce external emissions, and shorten the replacement time 1. Reduce the liquid level of 108-F and 106-F to the minimum (about 5%), but be careful not to cause overpressure in 107-F. Completely close LCV-13, 14 and their front and rear valves and bypass valves. 2. After the liquid level of 109-F, 110-F, 111-F, and 112-F is pulled to the lowest level and TI1-37, 38, and 39>0℃, stop 105-J. In this operation, pay attention to the temperature and pressure changes of 110-F, 111-F, and 112-F, and open the chill valve in time for adjustment to prevent the safety valve from tripping. 3． central control: ⑴Lower PIC-7 and PICA-8 to normal pressure. ⑵Fully open MCV-24, LCV-12. ⑶All about LCV-19. ⑷Fully open FCV-9, FCV-10, FCV-11. ⑸Fully open LCV-15, LCV-16, LCV-18. 4. on site: ⑴Receive the central control instruction to stop 1-3P-1/2 and close the 1-3P-1/2 inlet stop valve. ⑵Receive the central control command to stop 109-JA/B and close the LCV-19 rear valve and bypass valve. ⑶Fully open PCV-1828, 1830, front and rear valves and bypass valves. ⑷Fully open all three refrigeration valves. ⑸Fully open the 129-C and 125-C inlet stop valves. ⑹Fully open 109-J inlet, outlet and return valves. 5. replacement: ⑴For nitrogen replacement, first confirm that the front and rear stop valves of PIC-7 and PICA-8 are fully open. ； Set PIC-7 and PICA-8 at 0.05MPa ； Use N120 connected to the upper drain of NH-14-6″ to perform nitrogen replacement. ⑵ Discharge points 107-F, 109-F: PCV-8 and PCV-7 110-F, 111-F, 112-F: Safety valve bypass 117-C, 118-C, 119-C: Low point discharge diversion 109-J: LCV-19 front shower 6.1-3P rear pipeline first confirm that the ammonia delivery stop valve to diurea is fully closed, connect a temporary hose to the FCV-18 front shower to drain out the ammonia, then disconnect the front flange of the ammonia delivery stop valve, and connect nitrogen from the FCV-18 front shower for replacement. 7. At 117-J, first confirm that the 117-J inlet valve is fully closed, and then connect a temporary hose to the shower guide behind the 117-J outlet valve to drain out the ammonia. 8. The discharge principle is to carry out discharge displacement of the flash tank first, then the heat exchanger, and finally the pump and other points. Choose 2 to 3 points each time you discharge to ensure the replacement gas volume without causing too much impact on the environment. If a low-point diversion is chosen as the discharge outlet, a hose must be connected to lead it to a safe place far away. 9. Water flushing takes into account that it is difficult to completely replace ammonia in the system during nitrogen replacement. After most of the ammonia has been replaced by nitrogen, CW is introduced into the system to flush the water inlet point.: 117-C, 118-C, 119-C shell side drainage points: 1-3P pump body lead shower, LCV-19 front lead shower, 117-C, 118-C, 119-C shell side shower, 117-J outlet lead shower precautions: ⑴Before water enters, the ammonia stop valve for hydrogen removal and recovery and the ammonia stop valve for hydrogen recovery must be fully closed to prevent water from entering the ammonia side of the cold box E201B and freezing the equipment. ⑵Before entering water, LCV-15, 16, 18, 19, MCV-24 and bypass, three cold shock valves must be fully open, and PCV-7, 8 must be moved to the manual fully open position to prevent negative pressure from forming in each flash tank. ⑶The liquid level in each flash tank shall not exceed 50%.

Stop adding ammonia 2-3 hours before stopping. After stopping, press the remaining ammonia in the ammonia cooler to ammonia recovery, and then replace it with nitrogen. It usually takes 2 hours to pass the replacement. Just use an ice machine to vacuum before driving.

We use the method of releasing the pressure first, then flushing nitrogen, and then releasing the pressure when the pressure reaches 2KG. Repeat 3-5 times, the replacement effect is very good.

The replacement of the refrigeration system is not a simple pressure relief replacement, because if there is residual liquid ammonia in the system, after the vacuum is evacuated, there will still be pressure and ammonia after a period of time. The method of replacing it with nitrogen is the same. Therefore, in actual operation, the equipment or pipelines that need to be repaired should be pressurized with ammonia. Use nitrogen to press the ammonia in the pipelines or equipment to the storage tank or ammonia recovery, then isolate it from the system, and then replace it with water. Only after the final analysis and sampling are qualified can equipment maintenance and pipeline fires be started. When driving, it can be replaced by vacuuming, or it can be replaced with nitrogen and then ammonia.

We consume ammonia-cooled liquid ammonia before stopping, and try to push the liquid ammonia back to the small tank of the ice machine. After the gas ammonia pressure drops, we stop the ice machine. For each maintenance, add water at a low point and vent it at a high point until the released water has no ammonia smell and is considered qualified. This replacement is complete and never goes wrong.

Three or four hours in advance, Synthesis stops adding ammonia in advance to use up the ammonia, and then opens the valve for ammonia absorption. After the pressure drops, turn on the ice machine to pump, and then use steam to heat wash and replace it. It continues like this, and it is very safe.

However, I have read some information that the refrigeration system must be evacuated after overhaul, usually to 600-700MMHG, and maintained without leakage for 2-3 hours, and then filled with nitrogen to replace and relieve the pressure. The vacuuming is usually repeated 2-3 times. I don’t know how you usually restore the pressure to normal pressure after your system is evacuated?

We first press out the liquid ammonia as much as possible, and then release the pressure from the system. After the pressure is released, water is passed through the system, and then the low-point flange is removed to drain. Generally, it is OK after two times. However, the drained water needs to be diluted with dilute acid, which is more troublesome to operate. However, this replacement is complete and there is no need to worry about getting angry. We did this during the two ice machine renovations in July and October. The effect is good.

We have never washed it with water, we just use N2 replacement to heat and evaporate the low-point liquid ammonia vapor.