Low-temperature antifreeze measures

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7.1 Anti-freezing and anti-condensation measures for utility media during the commissioning and operation of Series A 7.1.1 Anti-freezing measures for low-pressure saturated steam 1) Use of steam equipment ① Main low-pressure saturated steam pipes, as well as drain pipelines at the ends and at expansion joints. ② Reboilers: Heat regeneration tower reboiler (161E112), HHC stripping column I reboiler (161E118). ③ Special application area: Cleaning steam for methanol filters (161S103/105A/B) ； Maintenance steam for methanol/water/HCN separation tower (161T105) ； Low-pressure saturated steam for heating cold flare gas ； Public utility station within the boundary area ； Steam tracing station within the boundary area and the corresponding condensate drain station. 2) Anti-freezing and anti-condensation measures
① On-site inspections should be intensified to check whether the main pipelines in the pipe racks, the aforementioned equipment, steam tracing pipes, all steam tracing stations, the condensate transfer system, and steam traps are functioning properly. Should a drop in temperature be observed in any tracing pipe or steam trap, prompt measures must be taken to clear any blockages, thereby preventing freezing and cracking of equipment and pipelines. ② For the steam used for maintenance and cleaning of the methanol filters (161S103/105A/B), when it is not in use, the valve at the root of the low-pressure saturated steam main should be closed (a temporary blind flange should be installed on the flange behind the valve, along with a clear label); meanwhile, the low-point drain valve should be opened to drain any condensate and prevent freezing. ③ Within the boundary area, the expansion bends of the low-pressure saturated steam main pipes and the end drain traps must be in proper operation; regular inspections should be carried out to check whether the temperature of these traps is normal, and any drop in temperature should be addressed promptly by clearing blockages. ④ An isolation valve is added at the junction of the low-pressure saturated steam pipeline and the main pipe within the site to directly isolate and prevent freezing of the low-pressure saturated steam in winter. ⑤ Activate the heating steam for the instrument measurement points and strengthen inspections to prevent incorrect interlock actions of the plant due to errors in the instruments at low temperatures during startup and operation in winter. (Specifically, instrument personnel are responsible for freeze and condensation prevention.) ⑥ The root valve of the on-site level gauge is heated using low-pressure saturated steam; regular inspections should be carried out on site to ensure that the heating line remains unobstructed, and any drop in temperature should be addressed promptly by clearing any blockages. ⑦ Anti-freezing and anti-condensation measures in cases of pressure drop or malfunction/interruption in the low-pressure saturated steam network: During commissioning operations, a drop in the pressure of the low-pressure saturated steam network may prevent the normal supply of steam, thereby affecting both the low-pressure steam users within the plant and the tracing systems. Under such circumstances, it is necessary to reduce the load according to process requirements. Enhance on-site inspections by using thermometers to check whether the temperatures of all heat tracing lines and traps at various low-pressure saturated steam heat tracing stations and condensate recovery stations are within normal ranges. If the temperature of each heat tracing tube and trap drops to 5°C, it is necessary to promptly remove the flange in front of the trap and fully open the corresponding steam heat tracing tube manual valve in order to flush out water until a large amount of steam is discharged. This prevents debris from causing blockages or condensate from accumulating and freezing, which could damage the heat tracing pipes. Once the pressure in the steam pipeline system returns to normal, the flanges should be reinstalled promptly. If the low-pressure saturated steam supply to the pipeline network is interrupted, the first action at the site should be to fully open the drain lines along the low-pressure saturated steam supply in the 310 pipe gallery to allow water to flow, while simultaneously closing the steam isolation valve and fully opening the drain lines downstream of that valve. Conduct a thorough inspection of all low-pressure saturated steam users within the plant area, ensuring that the drain valves at the lowest points of each pipeline are opened in a timely manner to remove accumulated water, which is then dried using nitrogen or air. When the low-pressure saturated steam pipeline network is restored, it is necessary first to increase inspections; the low-pressure saturated steam drain valves in the 310 pipe gallery should be kept fully open to allow water to flow through the pipes and prevent water hammer. Once the pipes have been properly warmed up, the opening degree of the drain valves should be adjusted appropriately to allow a small amount of water to flow out for anti-freezing purposes. 7.1.2 Anti-freezing measures for low-pressure superheated steam systems 1) Equipment using low-pressure superheated steam ① Drainage and blowdown pipelines at the ends of the main pipelines in the low-pressure superheated steam pipe racks within the battery limits, as well as at expansion joints. ② Reboiler of methanol/water/HCN separation tower (161E115), low-pressure superheated steam for heating cold flare gas. 2) Anti-freezing and anti-condensation measures ① Before starting up the plant after feeding materials, it is necessary to ensure that all low-pressure superheated steam pipelines are properly warmed up; the drain valves and low-point drains should be opened to remove any condensate from the pipelines, thereby preventing water hammer and freeze-thaw damage to the equipment. ② Strengthen on-site inspections, especially when the ambient temperature is low at night; increase the frequency of inspections accordingly based on the ambient temperature. During these inspections, pay close attention to checking whether the drain and steam traps in all low-pressure superheated steam pipes (including both main and branch pipes) are in good working condition and unobstructed, as well as to ensure that there is no ice formation in the pipes ； Is the discharge from each temporary low-point drainage measure site normal? ； Check whether each drain valve is operating properly, and keep detailed records. ③ During on-site inspections, if freezing or blockage is detected in equipment, pipes, valves, instruments, etc., it is necessary to connect rubber hoses to supply low-pressure saturated steam in order to thaw them promptly and prevent the pipelines from cracking. At the same time, the relevant supervisor should be informed to ensure the safety of the equipment and systems. 7.1.3 Anti-freezing measures for the circulating water system 1) Circulating water users ① Circulating water coolers: Boiler feedwater cooler (161E121), methanol water cooler (161E111), recycled gas cooler (161E123), H2S fraction cooler (161E113), HHC stripping column I condenser (161E117), methanol/water/HCN separation column condenser (161E120), recycled gas compressor oil cooler (161E125), recycled gas compressor after-cooler (161E126), unqualified condensate mixer (161MX001). ② Pumps for cooling the circulating water in the mechanical seal tanks (161P104A/B, 161P105A/B/C, 161P106A/B), cooling water pumps (161P118A/B), condensate pumps (161P001A/B); cooling of the packing in the bearing housing of the recycle gas compressor and cooling of the motor of the recycle gas compressor. 2) Anti-freezing and anti-condensation measures for circulating water pipelines: ① During operation in winter, strengthen regular inspections; when the ambient temperature is low, increase the frequency of inspections and keep proper records, addressing any areas where freezing or condensation occurs promptly. ② For the operational circulating water coolers, it is necessary to ensure that the inlet and outlet manual valves are open, as well as the bypass valve (set to 2-3 turns), in order to prevent freezing and condensation in the circulation system ； When the associated water coolers are shut down, if the circulation water network can still operate normally and stably, the inlet and outlet valves for the circulation water should be fully opened to ensure smooth flow of the circulating water within the equipment and prevent the formation of stagnant water, which could otherwise cause damage to the equipment. If the circulating water network cannot maintain stable operation and it is not possible to effectively isolate the circulating water from the equipment that is not in use, then the inlet and outlet valves should be closed, and temporary blind flanges should be used to effectively isolate the equipment. The bypass valve should be opened fully to allow circulation of water; at the same time, drain valves should be opened at the lowest points of the equipment’s piping as well as above the inlet and outlet valves, in order to remove any water accumulated in the equipment and pipes. Air or nitrogen should be introduced at the higher points to continuously purge the piping system, with the waste water being discharged through the drainage ports on the equipment. 7.1.4 Anti-freezing measures for the potable water system 1) Equipment using potable water: Potable water is primarily used in the eyewash stations within the area. During winter, when these devices are in operation, it is necessary to activate the electric heating elements of the eyewash stations to ensure proper heating, as well as to keep the water supply lines for the eyewash stations unobstructed. If there is an interruption in the supply of service water during commissioning and it remains unavailable for an extended period, promptly close the battery limit valve and install an “8”-shaped blind flange. Then, open the low-point drains on the pipelines of all eyewash stations to drain the water, followed by drying with compressed air. 2) Anti-freezing and anti-condensation measures for domestic water pipelines: During the use of eye wash stations in winter, enhanced inspections should be carried out on site; if any leaks or blockages in the pipes of the eye wash stations are detected, they must be addressed promptly. 7.1.5 Anti-freezing measures for the desalinated water system 1) Equipment using desalinated water: Desalinated water is used in the tail gas scrubber tower (161T108), the maintenance pipelines of HHC stripping tower I (161T109), the H2S fraction scrubber tower (161T110), as well as in the cleaning pipelines and related equipment of the methanol filters (161S103/105A/B). 2) Anti-freezing and anti-condensation measures for desalinated water ① During the operation of the plant in winter, conduct more frequent inspections to ensure that the steam tracing for all desalinated water users is functioning properly, and to guarantee that the desalinated water pipelines remain unobstructed. If the boundary valve for the desalinated water in the winter parking area is closed, a rubber hose is used to divert flow from the main desalinated water pipeline located 310 pipes ahead of the boundary valve into the gutter, with the valve kept slightly open to ensure a small amount of desalinated water flows out to prevent freezing. ② For each desalinated water pipeline within the area, those desalinated water users who have manual valves at the main pipes in the utility tunnel should close the upstream manual valves at the junctions with the main pipelines within the area when they are not in use for extended periods during winter. The low-point drain valves of each desalinated water user should be opened, or any accumulated water in the low-point dead zones should be drained off, and the areas should be purged with nitrogen to prevent freezing and damage to equipment and pipelines. 7.1.6 Anti-freezing measures for the medium-pressure boiler feedwater system 1) Equipment using medium-pressure boiler feedwater: shell side of the BFW cooler (161E121), temperature-adjusting water for the methanol/water/HCN separation column reboiler (161E115), and maintenance water for the methanol scrubber (161T101). 2) Anti-freezing and anti-condensation of medium-pressure boiler feedwater: During the operation of the plant in winter, regular inspections should be carried out to ensure that the heating systems connected to the medium-pressure boiler feedwater systems are functioning properly, thus maintaining unobstructed flow in the boiler feedwater pipelines. Steam tracing was put into service for the medium-pressure boiler feedwater pipeline 161BW1031-50 and 161BW1032-50 leading to 161E121; hot water tracing was also activated on pipeline 161BW1034-50, which runs from the BFW cooler (161E121) to the ammonia pre-wash tower (161T107). The valves at both ends of maintenance pipeline 161BW1012-50, which connects the medium-pressure boiler feedwater to the methanol wash tower (161T101), were closed. The drain valves on the pipeline were opened to drain all accumulated water, and the pipeline was purged with nitrogen until it met the required standards. Heating with low-pressure saturated steam is enabled on pipelines 161BW1030-50 and 161BW1029-50, which carry medium-pressure boiler feed water to the reboiler (161E115). 7.1.7 Anti-freezing measures for the production water system 1) Equipment using production water: Flush water in the utility stations of the pump house and the circulating air compressor house. 2) Anti-freezing and anti-condensation measures for process water: During winter production operations, anti-freezing measures must be taken for the flushing water pipelines at utility stations within the plant boundary to ensure that the temperature inside the buildings remains above 5°C. (If the indoor temperature can be maintained above 0°C, rubber hoses should be promptly connected at the process water interfaces of each utility station; the manual valves should then be kept slightly open to allow a small amount of water to drain into floor drains, thereby preventing freezing and condensation.) 7.1.8 Anti-freezing measures for the hot water tracing system 1) Locations where hot water tracing is used: various hot water tracing users on the process pipelines within the boundary area, as well as the hot water tracing stations. 2) Heating water supply and return pipelines for process pipelines, as well as anti-freezing and anti-condensation measures: ① During winter operation of the plant, activate all heating water supply systems for relevant users to protect the equipment and process pipelines within the facility from freezing damage, and carry out regular inspections. When the ambient temperature is low, increase the frequency of inspections appropriately and keep proper records; if freezing blockages occur, thaw them out promptly. ② During the winter period when heated water is in use, if there are significant leaks among the users of heated water within the designated area, it is necessary to take immediate action. After obtaining permission from the dispatch team, close the inlet and outlet manual valves in that area, and open the auxiliary valves outside those valves to ensure smooth circulation of the heated water outside the area. Additionally, activate the drain valves at the lowest points of each user of heated water within the area to remove any accumulated water. Once the leak is fixed, the system can be put back into use promptly. ③ At each hot water tracing station within the battery limits, regular inspections of all tracing coils must be carried out to ensure the unobstructed operation of the hot water tracing system and prevent freezing. 7.1.9 Anti-freezing measures for the fire protection system: To prevent freezing and condensation in the fire protection systems, regular inspections should be carried out on the fire hydrants in each factory building to ensure that such problems do not occur. The temperature inside these buildings must be maintained above 5°C. The exposed outdoor parts of fire protection equipment can be insulated by using thermal insulation blankets. Any water that accumulates in the valve chambers of fire pumps or beside the fire hydrants should be removed promptly. Note: Strengthen on-site inspections of the aforementioned anti-freezing and anti-congelation components. In case of any congelation, report it immediately and use a rubber hose to introduce low-pressure steam (or hot water) for timely thawing, so as to prevent equipment damage due to freezing. 7.2 Measures to prevent freezing and condensation of valves: 1) In the areas under consideration, no water accumulation shall occur in cast-iron valves, drain valves, and other similar components used in systems such as steam, water, moving equipment, and pre-washing systems, in order to prevent freezing inside the valves at low temperatures, which could lead to their cracking. During winter, all valves must be protected from freezing and condensation through appropriate insulation measures, and regular inspections should be carried out. If necessary, temporary measures can be applied to the low-point drain valves based on the actual conditions on site to prevent freezing and condensation. 2) If freezing occurs in equipment, pipelines, etc., it must be addressed promptly, and anti-freezing measures must also be taken for the relevant valves; no valve should be overlooked. Thorough inspections must be carried out to ensure that the valves do not crack due to freezing. 3) If freezing blockage of the valve is detected on site, the valve body can be slowly heated with hot water or gradually preheated using low-pressure steam. (Note: When operating the valve, turn it on and off slowly; forced opening or closing is strictly prohibited. ) 7.3 Measures to prevent freezing and condensation of instruments 1) Strengthen on-site inspections; for important components such as level gauges, differential pressure gauges, and root valves in various towers and tanks, insulation measures must be implemented and maintained in good condition. 2) During the commissioning phase of Series A, the instrumentation and control personnel are required to be on site to check that the insulation and heating systems of all transmitters (pressure gauges, differential pressure gauges) are functioning properly. 3) It is required that the instrument control personnel strengthen inspections to ensure that the heating systems for the pipeline flow meters in Series A are unobstructed. 4) Contact the instrument and control personnel to strengthen inspections to ensure that the flanged level gauges in Area A are functioning properly, and that the insulation and heating systems are in good condition. 5) Contact the instrument and control personnel to reinforce inspections to ensure proper heating in the A-series online analysis booths (161AI1009, 161AI1013), as well as in the analysis instrument cabinets and outdoor analysis instrument boxes. 6) For the control valves in Series A that are equipped with heating, regular inspections should be carried out to ensure that the heating system is functioning properly. 7.4 Anti-freezing and anti-condensation measures for static equipment: 1) Strengthen inspections during winter, and promptly remove water accumulation, ice, and snow from various equipment as well as along the inspection routes; ice formations hanging at high heights should be broken off to prevent them from falling and causing injury. 2) All equipment that requires insulation must have proper insulation; any damaged insulation should be repaired in time before winter arrives. 3) For equipment using media that are prone to freezing, any heating systems installed must be put into use, and regular inspections should be carried out to ensure smooth operation of these heating systems. 7.5 Anti-freezing and anti-condensation measures for rotating equipment 7.5.1 Anti-freezing and anti-condensation measures for operating pumps 1) When the ambient temperature is near 5°C or lower, it is necessary to increase the frequency of inspections to monitor the temperature inside the pump room, as well as the frequency of checks on pumps that use cooling water or coolant from seal tanks, in order to prevent interruptions in the supply of cooling water or blockages in the pipelines that could lead to freezing. 2) When the ambient temperature is low and the cooling water supply is suddenly interrupted, the operators on duty must increase inspections to ensure that the temperature of the operating pumps remains within acceptable limits, while also maintaining a normal indoor temperature. 3) It is necessary to carefully check whether the insulation and cooling systems of all pumps are in good condition. For mechanical equipment that transports low-temperature media, the protective air (nitrogen) supply should remain active to prevent freezing and damage at the mechanical seals. 7.5.2 Anti-freezing and anti-condensation measures for standby pump sets 1) For standby pumps equipped with a cooling water system, inspections should be increased during winter to ensure smooth circulation of the cooling water system and maintain an appropriate water volume; during periods of low ambient temperatures, the water volume should be increased accordingly. 2) For the standby pumps in the water delivery, condensate, or pre-washing systems, the pump inlet valves must be opened, and the temperature inside the pump room must be kept above 5°C of the ambient temperature. If the on-site conditions are not satisfactory, the pump can also be switched regularly to keep the pipeline temperature above 5°C, thereby preventing freezing and damage to the pipes and pumps. 3) For mobile equipment with insulation (cooling), its insulation (cooling) layer must remain intact and undamaged. 4) Strengthen inspections in accordance with the workshop’s requirements and carry out regular turning of the machine; if it becomes impossible to turn the machine or other problems arise, measures should be taken promptly to address them. 7.5.3 Anti-freezing and anti-condensation measures for decommissioned pumps 1) For pumps that are taken out of service and require cooling water, the inlet and outlet valves for the cooling water must be closed, or the cooling water system must be disconnected from the pump body. All water remaining in the pump body and water jacket should be drained, and the system should then be dried using nitrogen. 2) If the circulating water network is normal, open the inlet and outlet valves of the cooling water to keep the cooling water system unobstructed, and strengthen inspections. 3) Close the inlet and outlet valves of the pump; if there is internal leakage in the valves, blind plates must be used for isolation. 4) When shutting down rotating equipment, open the low-point anti-condensation vents to purge and drain any accumulated liquid and water from within the equipment cavities. If the elevation of the vent point is higher than the lowest point of the pump body, the flange must be removed for drainage depending on the circumstances. 5) Turn the machine once a day; increase the frequency of turning it when the ambient temperature is low. 7.6 Anti-freezing and anti-condensation measures for structures and buildings
7.6.1 Anti-freezing and anti-condensation measures for structures
1) During winter operations, snow on the following operating platforms and inspection pathways must be promptly removed to ensure the safe passage of operators. The areas involved are as follows:
① Pathways at all entrances/exits of the main pump house and the ground outside; all inspection pathways located on the upper levels of the pipe racks above the pump house. ② Inspection walkway in the recycle gas compressor building. ③ Operation platforms for frames 1#, 2#, 3#, and 4#. ④ Snow and ice have accumulated around the 161V109/110 storage tank. ⑤ Snow has accumulated in the inspection passages of various towers, storage tanks, heat exchangers, etc. ⑥ Paths branching off from the road and inspection walkways along the external pipe rack for the Rectisolve unit. 2) Promptly eliminate leaks from stationary and moving equipment as well as various pipelines, to prevent steam, condensate, and water from various users from causing freezing on pipe bridges and at high points. In case of ice formation, remove it promptly or set up safety warning signs to prevent falls and injuries. 7.6.2 Anti-freezing and anti-condensation measures for buildings 1) Thoroughly inspect the glass on the doors and windows of each factory building, and repair any damage or holes promptly. During winter, close the doors and windows; install cotton door curtains at the entrances to the pump rooms and factory buildings, and place thermometers at each entrance. During on-site inspections, closely monitor the temperature changes at these locations. 2) During the winter commissioning and operation of the installation, it is necessary to ensure that the heating system in the plant is operating properly. In particular, attention should be paid to monitoring the temperature of the plumbing systems near the pump room entrances and windows; if the heating system fails, electric heaters can be used temporarily to maintain an adequate indoor temperature. The indoor temperature in pump rooms and circulating gas compressor buildings must be maintained at no less than about 5°C, to prevent freezing damage to the fire-fighting water facilities, circulating water pipelines, pumps, and certain process pipelines located inside due to excessively low temperatures. The doors and windows of the pump room should be closed. To prevent the accumulation of toxic and harmful gases inside the pump room, air circulation must be ensured; the axial flow fans in the pump room should be activated as appropriate depending on changes in the temperature within the building. If the facility is shut down in winter, some axial flow fans must be stopped promptly to prevent the fire-fighting water and circulating water in the pump room from freezing at low temperatures and damaging the equipment. 7.7 Anti-freezing and anti-condensation measures during emergency or planned shutdowns of the unit: During the winter period, when the A series is put into operation for testing or running, in the event of an emergency shutdown due to an unexpected situation (or a planned shutdown), the system must carry out anti-freezing procedures in accordance with the following steps. 7.7.1 Anti-freezing and anti-condensation measures for water systems: Circulating water coolers (161E111/113/123/117/120), cooling water for pump seal tanks (161P104AB, 161P105ABC, 161P106AB), condensate pumps (161P001AB), oil coolers at the 161P105A/B/C oil stations ； Medium-pressure boiler feedwater heat exchanger and reboiler (161E121/E115) ； In the demineralized water system (161T108/110/109/S103/105), the medium-pressure boiler feed water and demineralized water services are shut down during a plant-wide shutdown. Depending on the actual circumstances, the manual valves on the main pipeline and all branch lines leading from the medium-pressure boiler feedwater and demineralized water to the rectisol washing system should be closed. Where necessary, nitrogen purging should be performed at the low points of each pipeline to prevent freezing damage to the pipes and equipment. Ensure that the heating systems for pipelines such as those carrying desalinated water and boiler water are operating properly, provided that the steam system and the hot water piping systems are functioning normally. When the circulating water system is shut down, the supply and return valves of all circulating water users must be closed. The bypass valve should be opened to prevent freezing and condensation. The supply and return drain valves, as well as the drain valves on the tube side of water-cooled equipment, should be opened to drain all water from the equipment and pipelines. If necessary, nitrogen purging should be performed to prevent damage to the pipes and equipment due to freezing. 7.7.2 Anti-freezing and anti-condensation measures for heat exchangers handling moist process media
When the process media flowing through a heat exchanger contains moisture, water from the media condenses in the tube side or shell side of the heat exchanger after shutdown. At low temperatures, this can cause damage to the heat exchanger itself, as well as to valves and drain valves located at the inlet and outlet of the heat exchanger. For such medium heat exchangers (such as 161E114/127), it is necessary to strengthen the drainage at the lowest points of the tube side and shell side in a timely manner. When the heat exchanger is not in use for an extended period, it must be properly isolated. Open the low-point drains or drain any accumulated liquid at the low-point flange joints. Compressed air or nitrogen should be used to purge any dead zones, thereby ensuring that the equipment isn’t damaged by freezing. For the 161E116 floating-head heat exchanger in the pre-washing system, antifreezing can be achieved by feeding methanol into the HHC decanter (161V101) via 161LV1042, thereby filling both the tube and shell sides of 161E116 with methanol having a purity of no less than 70%. 7.7.3 Anti-freezing and anti-condensation measures for various towers, tanks, and discharge pipes: After the low-temperature methanol washing process is stopped, the water content in the towers associated with the main and pre-washing systems is relatively high. If this water is not removed promptly or if the methanol concentration in the system is not increased, pipe blockages and equipment failures can occur if the shutdown lasts for an extended period of time. To prevent freezing of the pipes, valves, instruments, etc. associated with the various towers in the pre-washing system – such as the exhaust gas washing tower (161T108) and the H2S fraction washing tower (161T110) – it is possible to use the method of maintaining a methanol concentration in the pre-washing system at no less than 70% during operation. For the ammonia pre-washing tower (161T107), if the shutdown time is short, check on-site whether the hot water heating coil at the bottom of the tower is operating properly. If the parking time is too long, on-site, the ammonia pre-washing tower (161T107) as well as the process water, wastewater, naphtha, and return pipeline drains in the affected area should be promptly opened to drain the contents, and N2 should be used for continuous purging of the pipelines. 7.7.4 Anti-freezing and anti-condensation measures for steam and condensate systems 1) When there is a steam supply interruption and the outside temperature is low, the amount of condensate increases sharply. To prevent the piping networks, pipes, reboilers (161E112/115/118), condensate drain stations, etc. from being damaged by freezing, the bleed valves before and after the traps should be opened on site in a timely manner, or the flanges should be disconnected to drain the condensate. Drain valves must be installed at all steam piping networks and at the lowest points of each heat tracing system. After shutdown, as long as the residual pressure in the pipes is not high, the condensed water should be drained immediately until it is completely removed, or the pipes can be purged using nitrogen or air. Open the low-point drain valves for each user, as well as the main pipe drain valves at each low-pressure steam tracing distribution station, to drain any water accumulated in the piping and tracing lines; enhanced drainage and inspection should be carried out for these tracing lines. The condensate in the condensate recovery tank (161V001) should be sent away based on the results of condensate analysis by operating pumps 161P001A/B, and measures should be taken promptly to ensure that the drainage systems of tanks 161V001 and pumps 161P001A/B are protected against freezing and condensation. 2) If parking for an extended period, close the zone manual valve. Slightly open the pilot drain valve at the boundary valve, connect a temporary rubber hose to lead the flow to the gutter for anti-freezing purposes. After draining the water accumulated in the equipment and pipelines within the area, depending on the conditions on site, compressed air or low-pressure nitrogen can be used to blow out any remaining water in the steam pipelines, thereby preventing the equipment, pipelines, valves, etc. from cracking due to freezing. 7.7.5 Anti-freezing and anti-condensation measures for moving equipment: When the system is shut down in winter, the biggest challenge for pump and machinery equipment is to prevent freezing and condensation. For the pumps in the pre-washing system as well as the condensate pumps (161P001A/B) and the circulation water pumps (161P118A/B), measures should be taken promptly to drain the liquid from the lowest points. If it is difficult to completely remove the liquid inside the equipment, nitrogen or air can be used for purging, or electric heating can be applied along with inspection and disassembly to empty the area. Some indoor equipment is connected to heating systems in a timely manner or additional heating devices are added to maintain warmth. The operational status of electrical heating equipment is checked from time to time to ensure it is stable and reliable, while regular inspections are also carried out to verify that pumps are functioning properly. 7.7.6 Anti-freezing and anti-condensation measures for key equipment and process pipelines during parking 1) Anti-freezing and anti-condensation measures for the bottom of the ammonia pre-washing tower (161T107): During short-term shutdowns of the plant in winter, to prevent freezing of the liquid in the bottom of the ammonia pre-washing tower (161T107), the system is kept under pressure, and the minimum flow rate of feedwater to the medium-pressure boiler in tower 161T107 is maintained. A temporary rubber hose is used to drain a small amount of liquid continuously from behind the level control valve (161LV1024A) into the drain trench; the control room must monitor the liquid level in the ammonia pre-washing tower closely. If the hot water heating system supplies heat properly, the hot water heating at the bottom of the tower remains in operational condition. In the event of long-term parking, the system releases pressure to drain the water accumulated in tower 161T107, and then nitrogen is introduced to clean out any water that may remain in hard-to-reach areas, thereby preventing freezing and condensation. (Note: During a long shutdown of the unit, once the drainage treatment to prevent freezing is completed, the system must be filled with nitrogen at a slight positive pressure for protection.) 2) Anti-freezing and anti-condensation measures for the exhaust gas scrubber (161T108): When the unit is shut down and the pre-washing system is not in operation for an extended period, the demineralized water isolation valve must be closed; at the end of the demineralized water pipeline in the 310 pipe rack, a rubber hose should be used to drain a small amount of liquid into the gutter in order to prevent freezing and condensation. Within the boundary area, drainage is carried out from various low points such as Tower 161T108 and related desalination pipelines; the water accumulated inside the tower, in the pipelines, and in the exhaust gas washing pumps (161P108A/B) is removed, followed by purging with nitrogen. If the shutdown period is short and the hot water heating system is functioning properly, the hot water heating at the bottom of the tower can be kept in operation. 3) Anti-freezing and anti-condensation measures for the equipment and pipelines associated with the H2S fraction washing tower (161T110): When the unit is shut down, the low-point drains of the equipment, pipelines, and pumps should be opened to remove any methanol-containing water from the tower promptly; nitrogen should be used for purging to prevent the 161T110 tower as well as the related pipelines and valves from being damaged by freezing. 4) Anti-freezing and anti-condensation measures for the methanol/water/HCN separation tower (161T105) and HHC stripping tower I (161T109): If the supply of low-pressure saturated (superheated) steam is stopped, the towers 161T105/161T109 will be unable to operate. If the parking time is too long, the temperature inside the tower will continue to drop, posing a risk of freezing at the bottom of the tower. If steam supply is interrupted for an extended period, the unit must be shut down. In such cases, the low-point drains of the equipment, pipelines, and pumps should be opened to promptly remove the methanol-containing wastewater from the unit, and air purging should be carried out to prevent the equipment from being damaged by freezing. Note: To prevent freezing of the important towers, pipelines, valves, and instruments in the aforementioned pre-washing system, a single cycle of methanol can be initiated in this system, raising the methanol concentration to over 70% in order to protect the equipment and related pipelines from freezing. 7.7.7 Anti-freezing and anti-condensation measures for the plant instruments after shutdown during winter testing 1) Ensure that the heating systems for the plant instruments are in good condition; repair any defects in these heating systems promptly. 2) For equipment and instruments in media other than methanol, the medium can be completely drained; no special treatment is required for the level gauges. If the equipment cannot be cleaned thoroughly, it is necessary to remove the flange of the level gauge to drain the medium, and the diaphragm box of the level gauge flange should be fully protected. For transmitters and flow meters, the pressure guiding tubes or flange connections should be disconnected to ensure that the medium is completely drained. 3) Low-pressure nitrogen should be used to purge the equipment and instruments in non-methanol media to prevent freezing, and steam tracing should be activated promptly. 7.7.8 Anti-freezing and anti-condensation measures for process pipelines in the out-of-bounds area during shutdown 1) Anti-freezing measures for naphtha-related pipelines: After shutdown, it is necessary to ensure that hot water heating is continuously in use for the naphtha pipelines, and regular inspections should be carried out to verify that the heating system is functioning properly. Additionally, nitrogen purging should be initiated on these pipelines without interruption to maintain unobstructed flow and prevent freezing. 2) Anti-freezing and anti-condensation measures for the acidic gas desulfurization recovery pipeline: After the plant is shut down, hot water heating for this pipeline must be kept in use, and regular inspections should be carried out to ensure that the heating system is functioning properly. Low-pressure nitrogen from the sulfur recovery unit should be used to continuously purge the pipeline in the reverse direction of the low-temperature methanol washing process, thereby preventing blockages due to freezing (U-shaped bends with drainage systems should be installed on the acidic gas pipelines in the ductwork at the discharge area). 3) Anti-freezing measures after the shutdown of the wastewater treatment pipeline: Continuous heating with hot water is maintained for this pipeline, and inspections are intensified. Nitrogen is also blown continuously through the wastewater pipeline on-site to ensure it remains unobstructed and free from freezing. 4) Anti-freezing measures for the process water pipeline leading to the gas-water separation unit during shutdown: Keep the hot water heating in operation for this pipeline and enhance inspection efforts ； When the process water to gas-water separation pipeline is out of service ； Contact the dispatch team to coordinate gas, water separation, and the use of an air source for reverse purging, so as to ensure that the pipelines remain unobstructed and free from freezing blockages. 7.7.9 Anti-freezing and anti-condensation measures for fire water 1) When the plant is shut down, it is necessary to keep the fire water system unobstructed, and regular inspections of the fire water facilities on site should be carried out. Ensure a proper supply of fire-fighting water. In particular, the temperature inside each factory building must be kept normal, and it must not drop below zero degrees. 2) If the fire water system stops operating, on-site personnel must promptly open the manual valves at each fire water connection to drain the water and prevent freezing or condensation. They should also maintain close contact with the dispatch team regarding the specific time when the fire water supply will be restored, and close the valves at those connections as soon as the fire water system is back in operation. 7.7.10 Anti-freezing and anti-condensation measures for hot water and heating water 1) In the event of a disruption in the supply of hot water, the upstream and downstream manual valves at the hot water connection point should be closed immediately on site. The upstream and downstream bypass valves should be opened fully, and the drain valves at the bottom of each hot water heating station should be activated to drain any accumulated water, thereby preventing freezing and condensation. If the disruption lasts for an extended period and cannot be resolved promptly, air should be introduced at a high point in the hot water heating station and used to purge each hot water heating pipe until no water remains. 2) In the event of a disruption in the heating water supply, shut off the heating water isolation valves in the pump room and the circulating air compressor building; open fully the bypass valves on the supply and return pipelines. When the indoor temperature in the pump room and the circulating machine building drops below 5°C, the heating system still cannot provide heat, so it is necessary to remove the plug valves at the lowest points of each radiator in order to drain any accumulated water and prevent freezing. Once the heating water supply is restored, the heating system can be put back into use. 7.7.11 Anti-freezing and anti-condensation measures for facilities related to the external pipe gallery managed by the unit: 1) Comply with the requirements of the overall anti-freezing and anti-condensation plan for shutting down the units in the purification workshop; strengthen on-site inspections to ensure that all hot water heating stations located beneath the 310 pipe gallery are in good working condition. The low-point drain requires a small amount of discharge (the rubber hose leads it to the gutter and from there to the accident tank). If the interruption in the hot water heating system lasts too long, the fluid inside the pipeline is drained, and low-pressure nitrogen is used to dry it out in order to prevent freezing and condensation. 2) Prevention of freezing of low-pressure saturated steam and superheated steam along the lines beneath the 310 pipe tray through line drains: Enhanced on-site inspections ensure proper control of the discharge volume from these drains; the drains equipped with traps for low-pressure saturated steam are in good condition and allow smooth flow of water. If the steam pipeline network is interrupted, all drains along the line should be opened promptly to drain the condensed liquid resulting from steam condensation, thereby preventing freezing.