New technology of plastic shot peening for cylinder double-head fastening screws

3.2 Improve the water resistivity of water using water. It is recommended that the water resistivity of the water-washing equipment of the substation equipment is not less than 3.3. The salt density of the equipment to be flushed is carefully implemented. The “Guidelines for Charged Water Washing of Electrical Equipment” (SD129-84) on critical salt density It is stipulated that in the equipment area prone to accidents, the critical salt density value is reduced by 1 to 2, that is, the number of charged water flushing is increased, and the concentration of the sewage is reduced.

3.4 Measures for the tight skirt equipment with small umbrella spacing For the tight skirt equipment, the water jet water column should be very slow when it is flushing. When flushing to half, it should be retraced several times to confirm that the lower part is cleaned and then the water column is raised. After washing, do not immediately remove the gun and turn off the water. The water should be rewound again to avoid residual dirt in the umbrella skirt.

3.5 Measures for large-diameter equipment (such as CT, PT, etc.) Flushing large-diameter equipment must use the double-gun tracking method. When flushing to 1/3~1/2 of the equipment, the double-gun rotation angle is the gunman. Rotate an angle in the same direction, and keep the angle between the two guns unchanged. Rinse the lower part at multiple angles again, make sure there is no dead zone and clean it, then raise the water column again, and it should rise slowly and retrace multiple times.

3.6 Adding additional sheds To ensure the safety of charged water rinsing and to prevent equipment from flashing, adding an additional silicone rubber shed to the equipment is an effective measure. The shed can effectively cut off the rain or water. When the sewage is connected, the accident of water flushing is reduced. Generally, 2 pieces can be installed in 110kV equipment and 4 pieces can be installed in 220kV equipment. Large diameter and dense skirt equipment should be installed first.

New technology for plastic shot peening of cylinder double-head fastening screws The upper and lower cylinders of power plant steam turbines are fastened by double-headed screws, and they are all coated with anti-sintering occlusion agent, such as molybdenum disulfide. In the long-term operation of the steam turbine, the anti-seize agent is firmly attached to the surface of the screw. When the steam turbine is uncovered, the old anti-bite agent on the surface of the screw should be removed, and a new bite agent should be applied to make the steam turbine buckle. There are a large number of double-headed screws in the horizontal section, and the diameters of the high, medium and low pressure cylinders are also different. The cleaning work is complicated and the amount is large. For example, there are 550 double-head screws of 8 different diameters in the horizontal section of the 1100MW nuclear steam turbine. Shot blasting is a general mechanical cleaning method, but it is not suitable for double-head screws because this process is detrimental to the base metal. The traditional cleaning method is carried out manually with a wire brush and a cleaning oil agent, which is time consuming and unfavorable for labor protection.

Nippon Electric and Morikawa jointly developed a plastic shot peening device for cleaning the turbine head to tighten the double-headed screws. The unit can be cleaned without the need for the double-headed screws to remain tightened on the lower cylinder. Compared with the traditional manual cleaning, the 550 double-headed screws of the 1100MW nuclear steam turbine are taken as an example: the number of manpower is reduced from 7 to 8 to 1 to 2, from 183 to 275 working hours to 46 working hours, and the staff does not touch the anti-bite agent. The organic solvent will not be inhaled, and the waste under the evaporation of the gas will not fly outwards, and the dry cleaning will be used to clean the site.

The plastic shot peening used by Japanese companies has three kinds of materials, namely, flaky resin melamine formaldehyde resin and acrylic resin, and the shot size is 0. The shot blasting device is placed on the lower cylinder joint surface after uncovering, and the cleaning is a One screw is carried out. The device has a sealed cover and the cleaning work is carried out inside the cover. Shot peening and other utensils are collected and can be used repeatedly without spilling. Broken shot peening and anti-bite agent waste are collected by a vacuum recovery unit. The blasting device has a guide ring that allows the nozzle to rotate around the screw being cleaned and maintain a certain gap between the nozzle and the surface of the screw. The nozzle can also be moved up and down so that the entire surface of the screw can be uniformly sprayed. The circumferential speed of the nozzle of the shot blasting device is 122i/min, and the vertical movement speed of the nozzle is 240mm/min. The spray pressure of the shot peening is 0.19~0.48MPa, which is taken from the compressed air pipeline with a factory pressure of 0.7MPa.

According to the state of the workpiece, according to the experience of the operator, various parameters of the device are set, and the whole operation is fully automated according to the program. The cleaning results are all clear of the anti-bite agent, the thread is clean and clear, and the effect is good.

China Power Information Center Zhao Wangchu feed

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