The brief oxygen valve leaks and relief valve root cracking Troubleshooting
3 sets of new 21000m3 / h according to the Jiuquan Iron and Steel (Group) Co., Ltd. power plant the ASU project requirements, need original 6000m3 / h air separation plant and the new 3 sets 21000m3 / h air separation plant oxygen in the project, the pipe network of the nitrogen and argon, etc. communicate with each other, to facilitate the gas equilibrium within the company and air separation equipment maintenance. Oxygen pipe connection 6000m3 / h air separation plant oxygen compressor piston export (into the oxygen the spherical tank valve before) with 3 sets 21000m3 / h air separation equipment oxygen spherical tank before pipeline connected to the middle of the installation of a period of fire retardant tube and oxygen filters. The connecting pipes carbon steel pipes, pipe diameter Φ273mm × 8mm intermediate contact the valve using 4MPa oxygen shut-off valve of the DN250mm Contact the valve before the pipe is installed ordinary DN100mm cutoff valve as oxygen relief valve, the valve is installed upright, the root of the distance the pipe about 10cm, and the roots do not add to the neck fixed the the valve upper vent up leads about 80cm.
Failure phenomenon
The oxygen pipe connections after normal run of about a year, there have been leaks.
(1) DN250mm oxygen-specific cut-off valve is closed lax. Although the valve is closed, but gas leaks on the downstream side at the flanges.
(2) DN100mm oxygen the relief valves roots cracking. The main reason is due to piston oxygen compressor outlet section The section of the pipeline is located just larger vibration, resulting in long-term vibration valve connecting pipe at the bottom of the main channel junction cracking, a large number of medium-pressure oxygen diffuse security risks.
Production mainline with a large amount of oxygen, and did not install the valve in 3 sets 21000m3 / h air separation plant side source cut off its supply of oxygen gas pipe network, no time to eliminate this safety hazard. Moved temporarily produced a steel clamp of the oxygen pipeline diffuse at a temporary processing, and set up a temporary warning area within a range of around 10m. Pursuing a dream content management system
Treatment measures and process
Oxygen generator overhaul process has been carried out simultaneously with the overhaul of the main line of steel, iron and stainless steel process. Processing maintenance plan according to the company, on September 27, 2006, the above-mentioned security risks specific measures:
As a section of pipe (1) the original DN250mm oxygen dedicated shutoff valve, the valve is open all year round; and fastening both sides of the flange to ensure flange connections do not leak oxygen. The re-installation of a pressure in the pipeline for the 614MPa's DN250mm oxygen specific cut-off valve, this valve as usual operation with shut-off valve (middle contact the valve).
(2) Repair welding relief pipe cracking at and fixed this paragraph pipes and valves; replacement of 6000m3 / h air separation plant carries oxygen pipe three-way valve.
Prepared before construction materials and spare parts, and TIG welding machine down chain equipment to the site, in advance of the the new oxygen liaison valve skim suppress Φ273mm × 8mm carbon steel pipes, 90 ° stainless steel tee valve, 45 ° elbow and 45 ° Y-shaped three-way valve descaling, degreasing, and polished beveling. Pipeline construction site, contact the valve at the pipe cutting at the new oxygen to produce mobile maintenance platform or scaffolding. Early production the new oxygen liaison valve blanking plate. New contact oxygen valve on the intake side flange welded stainless steel with a length of approximately 115m pipeline, the other end of the stainless steel pipe welding a 4MPa, flange DN250mm. Resection original 4MPa, DN250mm oxygen contact the valve the north side of the east bracket beams in advance, and will need to remove the the pipeline the lower part of the steel plate resection, set the necessary support to the platform at the same time, able to ensure the removal of the pipe vertical drop. With 12mm steel plate production the original oxygen liaison valve blanking plate, slightly larger than the outside diameter of the blind plate flange outside diameter, blind board according to the size of the flange screw hole drilling, and tapping. At the same time, causing the accident in order to prevent the gas can not be fully ruled out Once oxygen pipe blower site preparation in advance to ensure timely mandatory on-site for the wind. Advance loosen 6000m3 / h air separation plant oxygen compressor carries oxygen valve inside of the flange, and send the corresponding gap left between the oxygen valve and flange blowing point for networked pipeline. dedecms.com
Construction, according to relief two hours, replacement 1 hour, pipeline removal of six hours, new valves and piping installation of six hours to purge one hour, one hour to suppress the leak and recovery aspirated (pumping blind plate and aspirated) 1 hour procedures for construction organization, a total of 18 hours. Relief, replacement is completed, the construction workers at a distance of the interconnection pipeline three-way valve 6m at the oxygen compressor outlet pipelines and pipeline 6000m3 / h air separation plant to send the oxygen pipeline 6m at bevel cutting. And cut in more than two baffle to prevent oxygen leaking into the pipe the contact valve flange apart. Contact the removal of the original oxygen valve 6000m3 / h air separation plant side flange screws to disengage the flange, blind plate is secured to the valve flange, to ensure blind plate does not fall off. Will remove the pipe vertical drop, to prevent contact valve flange apart oxygen leaked into the pipes, reserved pipeline bevel cut at set bezel, dismantle the the original oxygen liaison valve blanking plate. Short section of stainless steel, and the flange and the new oxygen contact the valve (the valve is fully open state) with the the original oxygen liaison valve flange connection. Determine the flange fastening slowly close the new oxygen liaison valve, and additional blind side of 6000m3 / h air separation plant in the new oxygen liaison valve plate.
After construction, polished original pipeline welded joints, while Φ273mm × 8mm the welding oxygen compressor outlet pipe 45 ° elbow pipe carries oxygen Φ273mm × 8 mm, 45 ° Y-shaped three-way valve. After welding, the maintenance personnel in cooperation with the crane, and will add oxygen the contact valve outlet flange (Fa Lanti before with export pipeline welding) and is connected with the valve. After connecting, the export pipeline other end with 45 ° Y-shaped three-way valve welding, the oxygen compressor outlet pipe 45 ° Y-shaped three-way valve welding. copyright dedecms
Implementation effect
After construction, the recovery aspirated operation, dismantle new oxygen contact valve blanking plate, oxygen spherical tank Blind board to recover various oxygen compressor carries oxygen valve, open the new oxygen liaison valve replacement pipeline residual nitrogen with oxygen. 10 minutes later, the gas composition in the pipeline diffuse laboratory, carries oxygen to pass back to normal. The the oxygen pipeline relief valve the root cracking Processing and retrofitting Contact valves transformation success.
Conclusion
The security risk exclusion, one month before construction to begin preparations for start personnel, materials, equipment and technology programs. Prepared to work fully, in advance of the scene may appear targeted prevention, the actual construction schedule is fully controllable, slightly earlier than originally planned to complete the construction time.
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