[Q&A Question 065] 2016.06.24

1. Perform flushing and purging in the order of the process flow. During purging, follow unified instructions, maintain close communication with relevant units and positions, and keep accurate records of the purging process. 2. Steam should be used in a concentrated manner to avoid excessive usage or unstable pressure, which could affect the purging effect. 3. It is necessary to adhere to the principle of draining condensate first and then introducing steam, with the introduction of steam being done slowly – starting with a small amount of steam before increasing it – in order to strictly prevent water hammer. 4. When purging the pipeline with steam, it is necessary to do so slowly in the initial stage as a preheating process. It is crucial to avoid increasing the steam flow rapidly after starting the steam supply, as this could cause the pipeline to expand suddenly due to heating. If there is no time for compensation, the pipeline may be lifted, resulting in the loss of pipe supports, deformation of the pipeline, fragmentation and falling off of the insulation layer, tilting of the pipe supports, cracking of welds, and separation of gaskets. 5. During steam purging, contact the instrumentation team to purge the instrument nozzles along with the leads. The safety valve is not involved in the purging process and is removed during purging. 6. When encountering equipment such as heat exchangers, air coolers, towers, and containers, first remove the inlet flange for purging; once it is clean, proceed to pass through the equipment. Be sure to use a shield to protect the flange surface when it is removed. When purging a heat exchanger, if one side is not to be purged, the vent valve must be opened in advance to prevent pressure buildup ； Pass through the air cooler slowly. When the container is filled with water, the upper vent must be opened to prevent overpressure. 7. Those equipped with glass plate level gauges and sampling ports should be purged along with the equipment pipelines. 8. Ensure thorough purging with no dead corners; the leak testing pressure for low-pressure systems shall be ≤ 1.0 MPa. 9. After the purging and pressure testing are completed, the vent valve and drain valve should be opened to prevent a negative pressure from forming inside the tower or vessel (Note: When venting the hydrogen sulfide removal tower and the distillation tower, the top vent valve of the tower should be opened). 10. The hydrogen system is purged with nitrogen. 11. Any small pipeline connections that are not listed shall be purged with temporary steam. 12. Underground pipelines shall not be purged with steam; they must be purged with air instead. 13. The pipeline purging time should be no less than 0.5 hours until the pipeline is clean. The steam purge should have sufficient velocity (not less than the operating flow velocity), generally not less than 20 m/s. 14. When purging through, it is generally done by venting from the removed spool; if that is not possible, the flanges are removed for venting. 15. When steam passes by the pump, it is purged through the inlet and outlet connection valves, preventing steam from entering the pump to protect it. 16. Generally, after the purging of a pipeline is completed, the removed valves and flanges must be reinstalled, and the connection valve for that pipeline must be closed before purging the next section of pipeline can proceed. 17. Before the equipment inlet section is purged, it is not allowed to purge the towers, vessels, and heat exchangers. 18. For longer pipelines, purging should be carried out in sections by removing the flanges; once the preceding section has been thoroughly purged and found to be satisfactory, the flanges are reattached to proceed with purging the subsequent section of the pipeline. 19. During purging, tools can be used to gently tap the dead corners of the pipes and the bottom of the pipelines in order to loosen debris, but care should be taken not to damage the pipelines. 20. Pay attention to ensuring thorough purging; if the pressure of the purging medium is low, the intermittent pressure-holding method should be used, with purging carried out in one pipeline at a time at a flow rate of no less than 20 m/s

　　1. Before conducting the strength test and pressure tightness test on the piping system, it should be purged and cleaned in sections. 2. The method of purging and cleaning should be determined based on the requirements for using the pipeline, the working medium, and the degree of dirt on the inner surface of the pipeline. For liquid or gas pipelines with a nominal diameter of 600 mm or more, manual cleaning is advisable; for liquid pipelines with a nominal diameter of less than 600 mm, water cleaning is suitable; and for gas pipelines with a nominal diameter of less than 600 mm, air purging is appropriate. Steam pipelines should be purged with steam; non-thermal pipelines must not be purged with steam. The purging sequence is generally carried out in the order of main pipes, branch pipes, and drain pipes. 　　3. Before cleaning the pipes, a detailed cleaning plan should be prepared, and the cleaning should be carried out in segments according to the system. 4. Equipment and pipes that cannot be cleaned should be separated from the cleaning system. 　　5. After the pipeline has been successfully purged, no other work that could affect the cleanliness inside the pipeline shall be carried out, except for the specified inspection and restoration tasks; furthermore, the \"Pipeline System Purging Record\" must be filled out

First the main pipe, then the branch pipes; the purging medium does not enter the equipment

Install blind flanges on the branch lines, and take measures to prevent splashing at the liquid discharge ports

Principles for flushing and purging process pipelines: 1. The pipelines to be flushed and purged must have been inspected and approved, meeting the required standards. 2. During the flushing and purging process, easily clogged components on the pipeline such as flow meters, orifice plates, control valves, flame arresters, steam traps, and burners must be removed. The sampling valve, instrument pressure tapping valve, safety valve, level gauge connection valve, and drain valve are closed. 3. When flushing the pipeline with water, if the pipeline diameter is large, an appropriate amount of compressed air can be added to enhance mixing. 4. During flushing and purging, the discharge outlets must not be blocked; they should be kept fully open for discharge. 5. Whenever dealing with equipment or containers, a blind flange must be installed at the inlet. Where a bypass is available, it should be used; if no bypass exists, the area can be flushed in sections. 6. When flushing and purging encounters a vertical pipe, flush from top to bottom; for the main collection pipe, flush from the main pipe toward the collection end. 7. When flushing horizontal pipelines with valves in between, the flange before the valve should first be removed, the valve closed to clean the section ahead, then the flange reinstalled before continuing to flush the subsequent section, in order to prevent debris from accumulating at the bottom of the valve. 8. When flushing, the valve should be turned fully open or fully closed; if anything prevents it from being operated, the valve must be disassembled for inspection. 9. If there is a check valve in the pipeline that is to be flushed in reverse, the check valve can be removed and installed in reverse direction; it can then be put back in place after flushing. In some cases, a short pipe can be used as a substitute. 10. After the flushing and purging of the entire system is completed, all temporary piping and blind flanges shall be removed, and the disconnected sections shall be restored to their original state. 11. The purging and inflation pressure of all equipment shall not exceed the design pressure. Precautions for flushing and purging process pipelines: 1. When using steam for purging, be careful to avoid burns due to the high temperature. 2. During the flushing process, be careful of the surrounding environment when discharging water to avoid injuring anyone. 3. During purging, first use the purge medium to clear the pipelines, then gradually increase the pressure and raise the flow rate. 4. When using steam for purging, first warm the pipes and drain the condensate, then gradually increase the amount of steam used for the purging process. 5. During flushing and purging, the blind flanges at the boundary areas must be removed; coordination must be carried out in advance before removing them. 6. Before starting the purging, the pipelines for the purging medium and the container must be pre-purged to ensure that the purging medium is clean. 7. Contact the instrumentation personnel to pre-sweep the instrument branch lines. Once the main line has been swept and passes inspection, it is not allowed to sweep the instrument branch lines back into the main line, as this would re-contaminate the pipeline. 8. The purge steam should preferably not pass through the pump body; if it must, permission from the equipment crew is required, and reversing the flow direction through the pump is not allowed.

1. Piping used to transport gaseous media in process pipelines is generally purged with air. 2. Air purging should be carried out using the large compressors of the production facility, or by storing air in large containers within the facility for intermittent purging ； The purging pressure must not exceed the design pressure of the vessels and pipelines, and the flow velocity should be no less than 20 m/s. 3. When purging oil-free pipelines, oil-free compressed air should be used. 4. The inspection method for air purging involves using a white cloth or a target plate painted white at the exhaust outlet of the pipeline to be purged; it is considered successful if no rust, dirt, or other contaminants are present on the target plate within 5 minutes. 5. The angle between the purge port and the ground should be between 30 degrees and 45 degrees; the pipe section of the purge port must be welded to the corresponding pipe section in a smooth manner, and the diameter of the purge port must meet the required standards. 6. The length of each purge operation should not exceed 500 meters; when the pipeline length is greater than 500 meters, purging should be carried out in segments. Purging with steam 1. Steam purging is suitable for pipelines that carry power steam or thermal steam; it is not applicable to non-thermal pipelines, as issues such as thermal expansion are not taken into account during their design. 2. Steam purging should be carried out using steam at a high flow rate, with the flow velocity not falling below 30 m/s. 3. Before steam purging, the pipes should be warmed up first, water should be drained promptly, and the thermal displacement of the pipes should be checked. 4. Steam purging should be carried out by: introducing steam — gradually heating the pipe — maintaining a constant temperature for 1 hour — purging — stopping the steam supply and cooling down — then heating the pipe again, maintaining a constant temperature, and performing a second purge. This process should be repeated at least 3 times. 5. Medium and high-pressure steam pipes as well as the steam turbine inlet pipes should be inspected using smoothly flat aluminum target plates; for low-pressure steam, wooden target plates are used. The target plates are placed at the steam outlet, and they are considered qualified if they are free of any dirt.

Start with the main pipeline before dealing with the branch ones; drain water to prevent water hammer before steam purging, and copper tools can be used to tap on the pipes during this process

First the main line, then the branches; first the branch lines, then the main line. If using steam purging, be careful to reduce the water flow rate gradually

Precautions for pipeline purging I. Preparation work for purging 1. Ensure that all temporary blind flanges are available, and that compressed air, air supply sources, and the connection pipelines are properly prepared. 2. Remove the control valves from the pipelines as well as the orifice flow meters, and replace them with appropriate bypass devices. Cover the inlet flanges of all moving and stationary equipment with metal sheets. 7?. C8 p e3. The pipeline purging plan is complete and feasible; the purging schedule has been prepared. 4. The pipelines have been tested for leaks using water or air pressure, and the water has been largely removed; the pipelines have been restored to their original installation state. 5. The compressor is capable of operating continuously or intermittently. 6 Z4 k+ S0 K% A* D8 n. ?% \2 @ 6. Safety equipment as well as all necessary items for purging must be prepared. * x1 j `3 L7 L3 n+ e 7. Relevant departments shall assist in carrying out the pipeline purging process, ensuring that no pipeline, valve, or weld is overlooked. Any issues identified during purging must be recorded by a designated person, and they should be addressed after the airflow or pressure is stopped. 8. Once the steam oven is completed, it should have the capability to increase pressure and be able to supply steam at 0.4 MPa to the equipment, while maintaining a stable supply pressure. 9. All drain valves should be removed, and all steam valves must be closed. 10. All steam gaskets must be replaced with graphite wound gaskets; however, the pre-removal openings can be purged, and upon reinstallation they should be connected in accordance with the standard piping specifications. 8 \5 g3 Z* g' _( 1 z% N1 s! n 2. When using steam for purging, it is important to preheat the pipelines first; it is essential to drain any condensate before introducing steam. The introduction of steam should be gradual, following the principle of starting with a small amount of steam before increasing it. Prevent water hammer from occurring; in the event of water hammer, it is necessary to reduce or stop the steam supply and drain the condensate. When supplying steam for the first time, supervision must be provided at the drainage point to avoid burns from the steam. Steam pipes should be purged with high-flow steam, at a flow rate of not less than 30 m/s. During purging, notify all relevant personnel on site; assign personnel to be responsible for each outlet. Pay attention to safety and maintain constant communication with those operating the inlet valves. 3. The pipeline purging should be carried out in an orderly manner, from higher to lower elevations and from larger to smaller diameters. Air purging is performed intermittently using the utility compressor. The purging pressure must not exceed the design pressure of the vessels and pipelines, and the flow velocity should be no less than 20 m/s. 3 A1 h, {; Y9 D) | 4. Isolate the inlets and outlets of all rotating equipment; stationary equipment should be involved in the purging process depending on the circumstances or due to its structure. 5. During the purging process, the valves on the pipelines must be opened and closed frequently in order to blow out any debris that may be trapped in hard-to-reach areas. If you find that the shutter is stuck, do not force it open or close to avoid damaging it.