Plug-in hydraulic pressure test valves (also known as plug valves) are commonly used on main steam and reheat steam pipelines of thermal power plants as hydrostatic tests on boilers, superheaters, main steam lines, reheat and reheat pipelines Isolation device. After the hydrostatic test, the plugging valve may remain on the pipe as a passageway. Blocking valve is one of the commonly used supporting valves for power station boilers. Its main structure is two kinds of blocking plate type and worm gear type. At present, the country has been fully able to support the production of such hydraulic test valves for subcritical, supercritical and ultra-supercritical units below 1 000 MW. The unit below 600MW has basically achieved localization and has been in good use after years of operation. Water pressure test valve structure block plate: hydraulic test valve by the valve body, valve cover, seal ring, four open-loop, test block board, support plate, preload screws and diversion tubes and other components, the specific structure and working conditions related. Pipe test state, the support plate and the blocking plate installed inside the valve, tighten the preload screw so that the blocking plate sealing surface between the initial seal than the pressure, blocking the flow of medium to the outlet side, the media pressure so that the blocking plate and the valve sealing surface Between the seal to produce adequate pressure, regardless of the level of pipeline test medium pressure, can ensure that the seal to meet the support plate side of the pipeline test. To be the end of the test, remove the blocking plate, installation of diversion and bonnet, the valve at this time as a section of pipe. Re-test, still replaced by blocking board. Block board sealing surface material can be stainless steel, carbide or O-ring, the cavity ring can be enhanced by flexible graphite or metal seal ring pressure self-sealing structure. Plug-plate valve is similar to the normal use of a period of pipe, the valve flow resistance can be neglected, the unit thermal efficiency without any impact. Drawback is the demolition of the valve cover, seal ring and other parts of the test, time-consuming effort, easy to damage the seal ring, especially the metal seal ring, the need for spare parts. Worm wheel drive flap type: Worm wheel drive flap hydraulic test valve by the valve body, seat, bonnet, seal ring, four open-loop, valve, rocker and worm drive and other components. When the pipe test, turn the worm wheel drive hand wheel, the valve flap turned to the closed position, and produce a certain pre-pressure, the media filled by the medium pressure to achieve high-pressure seal, to meet the pipeline test. After the test, the valve flap to the lowest position, does not affect the normal flow of working medium. Blocking plate and flap structure have obvious advantages and disadvantages. Flap valve has the advantage of the test without disassembly parts, just turn the hand wheel worm gear, opening and closing saving time and labor, the disadvantage is that there will be some fluid resistance, while the valve body cavity cross-section is approximately square to ensure In the high pressure test the valve body has sufficient rigidity, you must increase the body cavity wall thickness or additional ribs. Flush-type plug-in valve plug-in blockage compared to large flow resistance, resulting in some energy waste, but little effect on unit efficiency.