Purging: Do You Really Understand It? (Series) – Water Flushing
Thread Content
The last edit to this post was made by The wise are enlightened on 2025-1-8 at 12:11. Water flushing 1) Principles and requirements for flushing a. Water flushing should be carried out at the maximum flow rate possible within the pipe, or at a flow velocity of not less than 1.5 m/s; the direction of flushing should preferably be from higher places to lower places. b. The quality of the water used for flushing must meet the requirements specified for the materials of the pipes and equipment to be flushed. c. Flushing should be carried out in a sequential, segmented manner; the cross-sectional area of the discharge outlet should be no less than 60% of that of the pipe being flushed. It is also necessary to ensure that the discharge pipes remain unobstructed and safe. Only after the upstream flushing outlets have been successfully flushed can the process proceed to flush the subsequent sections of the system. d. The pump’s outlet pipeline can be flushed in accordance with the procedures only after the pump’s inlet pipeline has been successfully flushed. e. When the pipeline is connected to the tower, a blind flange must be installed on the inlet side of the tower during flushing; the connection can be made only after the pipeline has been flushed successfully. f. When flushing gas pipelines with water, ensure that pipe racks, hangers, etc., can safely withstand the load when filled with water. g. Where there are devices such as orifice plates, flow meters, valves, traps, filters, etc., on the pipeline, they must be removed or temporary short-circuiting facilities must be installed; only after the previous section of the pipeline has been cleaned can these devices be reinstalled, after which the cleaning process can proceed for the next section of the pipeline. h. Large-diameter pipes with a diameter of 600 mm or more, as well as containers with inlets, etc., must first be manually cleaned thoroughly. j. After flushing the process pipelines, water should be removed from the system as completely as possible. A large vent at the top should be provided during drainage, so that when the liquid level in the container drops, a vacuum does not form inside the equipment and cause damage to it. k. During winter flushing, care should be taken to prevent freezing; after flushing, the water should be drained completely, and compressed air can be used to dry it out if necessary. Water must not be introduced into equipment and pipeline containers lined with fire-resistant materials or other water-repelling materials.
2) Conditions required for water flushing: a. Before flushing the system’s pipes and equipment, it is necessary to prepare a flushing plan. This plan usually includes seven sections: the basis for preparation, the scope of flushing, the conditions that must be met, the preparatory work before flushing, the flushing methods and requirements, the flushing procedure, and inspection and acceptance. b. The equipment and pipelines have been installed, pressure testing has been successful, and verification according to the PID diagram shows no issues. c. Installation of the temporary flushing piping required by the flushing procedure is complete. d. All instruments in this system have been properly calibrated, and the electrical equipment is operating normally. e. Each pump motor passes individual testing and is connected. f. The flushing water has been delivered to the plant area. g. Arrangements have been made for the personnel responsible for flushing and for installation and maintenance staff; the flushing personnel must be familiar with the flushing procedure.
3) Methods and requirements for water flushing: a. Water flushing is carried out in stages according to the flushing procedure specified in the plan; that is, once each flushing port has passed the inspection, the process is resumed to flush the subsequent systems. b. After the inlet pipelines of each pump have been flushed successfully, start the pumps to flush the outlet pipelines in accordance with the procedures; once those are also flushed successfully, proceed to flush the towers and other equipment. c. During flushing, blind plates must be installed on the inlet side of the heat exchangers and towers; access to the equipment is permitted only after the upstream sections have been flushed successfully. d. After flushing the equipment in each tower, it is necessary to enter the tower to inspect and remove mechanical impurities. e. During the flushing process, various pipelines, valves, and other equipment generally need to be flushed intermittently 3 times to ensure an effective flushing result. f. During the water flushing process, all standby pumps must be switched on and off once each. g. After the water flushing is successful, the flushing records for the pipe sections and equipment should be filled out. 4) Inspection and acceptance criteria for water flushing. According to the national standard “GBJ235-82”, it is considered qualified if the color and transparency of the water at the outlet are consistent with those observed at the inlet, unless otherwise specified in the design.
Purging: Do you really understand it? (Series) https://bbs.hcbbs.com/thread-5677878-1-1.html (Source: Haichuan Chemical Industry Forum [Hua Hai Chuan Liu])