After the construction of the central oxygen supply project is completed, it is inevitable to encounter welding slag or foreign matter left in the pipeline. These debris may affect the production, so that the production cannot be carried out smoothly or the expected purpose can not be achieved. Therefore, after the project is completed, it is necessary to purge the pipeline to make the pipeline clean.

In order to ensure the procedures, quality standards, finished product protection, safety precautions, etc. in the pipeline purging process, CAN GAS hereby formulates the following operating procedures.

Scope of application

Central oxygen supply and central suction equipment

Main tools

Air compressor, wooden hammer

Working conditions

1. The purging work is arranged to be carried out after the pressure test of the piping system is qualified.

2. Before purging, the pipeline between the air compressor or steam and the pipeline of the equipment to be purged should be well connected.

Purging operation

1 Construction procedures

Pre-Purge Inspection - Purge - Inspection - Line Restoration - Handover

2 Purging operations

The purging method of the pipeline system should be determined according to the pollution degree inside the pipeline, the working medium and the use requirements. Pipes with a pipe diameter ≥600mm are recommended to be cleaned manually before flushing with water and purging with compressed air. Pipelines that convey liquids with a pipeline diameter＜600mm should not be flushed with water, as it may leave water in the pipeline. Compressed air should be used instead. Non-thermal pipelines shall not be purged with steam.

Before purging, remove the check valve, flow meter, restrictor orifice, regulating valve and other pipe fittings in the pipeline, and hand it over to a special person for safekeeping.

(1) Air purge

20m/s。Compressed air purging uses the compressor and air storage tank of the production unit as much as possible to perform intermittent purging of the pipeline system. The purging pressure should not exceed the design pressure of the container and pipeline, the purging time should be more than 5 minutes, and the flow rate should not be less than 20m/s.

(2) Steam pipelines should be purged with steam. If the non-steam pipeline can not meet the requirements with air purging, it can also be purged with steam, but its structure is required to withstand the influence of high temperature and thermal expansion factors.

When steam is purging the pipeline, the warm pipe should be slowly raised first, and a large amount of condensed water will be generated at this time. Therefore, the flushing pipes in front of each trap along the steam pipeline should be opened in advance to discharge a large amount of dirty condensed water generated during the warm pipe. , and when white steam emerges from the flushing pipe in front of the trap, close the valve on the flushing pipe. The exhaust port at the end of the purged pipe should be led to a safe place outdoors, and the pipe port should be inclined upward and fixed to withstand the reaction force when the steam is blown out at a high speed. The purging should be carried out in stages. First, the main and main pipes are blown clean, and then each branch pipe is purged separately. It should be swept at constant temperature for 15 minutes at a time and then lowered to ambient temperature. Do this 2 to 3 times until qualified.

(3) After the purging is qualified, the removed pipe fittings should be restored, and the unqualified gaskets should be replaced in time.

Quality Control Points

(1) For pipelines and fittings that are not allowed to be purged, remove them in time before purging and keep them properly, temporarily replace them with short pipes or take other measures to complete the purging, and then re-install them.

(2) Before purging, check whether the pipe support is firm, whether the position of the dredging is reliable, and whether the discharge pipe is fixed so as to withstand strong reaction force.

(3) The order of purging should be carried out in the order of main pipe, branch pipe, and dredging pipe, and the blown dirt is not allowed to enter the equipment or the pipeline that has been purged. For the end of each branch pipe connected from the main pipe, an exhaust port or a drain port is provided. The purging of each branch pipe should be carried out one by one according to the gas (steam) source from near to far.

(4) The purging pressure shall generally not exceed the working pressure, and shall not be lower than 25% of the working pressure, and shall not be lower than 0.6Mpa for large-scale pipe networks. When purging, the flow rate of the purging medium should not be lower than the working flow rate.

(5) In addition to non-ferrous metal pipes, when purging, use a hammer (wooden hammer for stainless steel pipes) to hit the pipes, especially key parts such as welds and dead ends.

(6) Record: keep a record of purging of the piping system

Quality Standard

 1. During the air purging process, when there is no smoke and dust in the exhaust, check the exhaust port with a white cloth or a wooden target plate painted with white paint. For example, the target plate is free of rust, dust, moisture and other dirt within 5 minutes. , is qualified.

 2. In the process of steam purging, other requirements other than moisture in air purging should also be met.

Finished product protection

After the purging is completed, the purging ports should be closed. For steam purged lines, dry immediately with compressed air.

Occupational health and safety requirements

When using steam to purge, be alert to water hammer and burns. The requirements for this are as follows:

(1) There must be a senior technician with practical experience to operate, the heating pipe should be heated slowly, and the condensed water should be drained well.

(2) Wear protective gloves and do not touch the pipeline, especially the pipeline in the steam inlet section.

(3) Do not face the discharge line directly with your face and hands during inspection.

(4) A warning line should be set up at the steam discharge outlet, and special personnel should be kept to guard it.