Is a very important safety valve protection valve, widely used in various pressure vessels and piping systems, when the pressure in the system pressure exceeds the set value, it automatically opens, the surplus in the media released into the atmosphere to go to ensure the safety of pressure vessels and piping systems running, to prevent accidents, and when the pressure back down to work within the system pressure, or slightly lower than the working pressure can automatically shut down. Reliable safety valve work is directly related to equipment and personal security, so attention must be given.

    First, the valve leakage

    Normal operating pressure in the equipment, valves and valve seat sealing surface took place more than allowed levels of leakage, ball valve leakage will not only cause loss of media. In addition, the media will continue to leak to the destruction of the hard seal material, but the common safety valve sealing surface is metal on metal materials, although sought to do is smooth, but with pressure to be the case in the media do to absolutely no leakage is very difficult. Therefore, the working medium is the steam valve, the required pressure value, if invisible in the export side, it can not find a leak to seal property that is qualified.

    Second, the body with surface leakage

    Means between the upper and lower body leakage at the joint surface, causing leakage of the main reasons that the following aspects: First, the bolt tightening force with enough surface or tight side, causing a bad combination of surface sealing surface. Second, the valve seal with the tooth surface does not meet the standards. Third, the body surface flatness with poor or live in a hard pad of impurities caused seal failure.

    Third, the impulse does not move the safety valve safety valve emperor

    This phenomenon is often referred to as the main safety valve refused to move. Resist the main valve in the boiler is running against a very large, a major equipment problems, seriously affect the safe operation of equipment, once the operation of the pressure vessel and the line of medium pressure over rated, the main safety valve does not move, the equipment can easily run over pressure equipment damage and major accidents.

    Fourth, the impulse emperor back seat safety valve safety valve back seat for too long delay

    The main reasons for this failure occurs the following two aspects:

    On the one hand, the main valve piston chamber the size of the leakage of steam, although the impulse valve back seat, but the existence of the pipeline and the piston chamber of the steam pressure is still high, push the piston downward force is still large, As a result the main valve back seat slowly. Way to eliminate this failure, mainly through large throttle opening and increase the throttle opening aperture to be resolved, opening the throttle valve and throttle opening large increase in diameter are made to stay in the pulse tube emission out of steam quickly , thereby reducing the pressure of the piston, so acting on the piston downward thrust decreases rapidly, a brass ball valve in the steam box associated media and the main safety valve upward thrust upward pull of their own under the action of the spring back quickly Block.

    The other reason is that the main valve of the moving parts and fixed parts of excessive friction between the main valve back seat can also cause delays to solve this problem is the main safety valve moving parts and fixed parts with the gap control in the standard range.

    Fifth, low pressure safety valve back seat

    Low pressure relief valve on the boiler back seat to run a lot of economic damage, the back seat pressure is too low to cause a lot of media time-out emissions, resulting in unnecessary energy loss. This failure occurred in the 200MW unit used by the A49H spring pulse valve, the analysis was mainly caused by the following factors:

    The first spring pulse discharge valve on the large amount of steam, this form of the impulse valve in the open, the media continue to discharge, to promote the main safety valve.

    Caused by low pressure back seat of the second factor: the valve core and oriented with the gap set improperly, with the gap is too small, the impulse valve seat after the start, in this part of the kinetic energy of instant throttle high pressure area formed and will valve lift, the delay time for back seat, when the container down to low, the kinetic energy pressure zone pressure decreases, the impulse valve back seat.

    Eliminate this failure is carefully check all parts of the spool and the guide sleeve dimensions, with the gap is too small, reducing the valve sealing surface is straight to the waste gas cap flap valve or increase the diameter and the guide sleeve valve radial clearance between the to increase the flow area of ??the parts, so that the steam flows through the throttle too much when the Bu Zhiyu, leaving the partial pressure increases the kinetic energy of the formation of a high pressure area.

    Caused by low pressure back seat of the moving part to another reason is that friction force, some parts of a jam, the solution is to carefully check all moving parts, strictly in accordance with maintenance standards for maintenance of various components, each component will be adjusted to meet the gap the standard range, eliminating the possibility of Jam.

    Sixth, the frequency of jump safety valve

    Frequency hop refers to the valve seat back and after the slightest increase in pressure, turn the safety valve open, and repeated several occasions, a phenomenon known as the safety valve of the "frequency jump." Mechanical properties required safety valve safety valve action in the whole process of opening up to the required height, does not allow jamming, tremor and frequency of jumps. Frequency of jumps very bad seal on the valve is easy to cause the sealing surface of the leak. Analysis of the main reasons for the pressure is too high and the safety valve on the back seat, back seat pressure is high, the surplus in the media container less emissions, safety valves have back seat, and when the operating personnel to adjust properly, pressure inside the container will quickly rise up, it is also causing safety valve, as this can open the throttle valve opening big way to be eliminated. Large throttle opening after the piston chamber to the main valve steam source to reduce, to promote the downward movement of the piston to the smaller, less likely the main safety valve, thus avoiding the main safety valve consecutive start.

    Seven, the flutter valve

    Safety valve in the discharge occurred during the jitter phenomenon, called the safety valve flutter, flutter phenomenon caused by metal fatigue easily, so that the mechanical properties of the safety valve down, causing serious equipment problems, considerable vibration occurs The main reasons are the following:

    Improper use of the ball valve on the one hand, the choice of the emission capacity of the valve is too large (relative to need in terms of emissions), elimination method is to use the valve should be rated as close as possible the equipment necessary for displacement of emissions.

    On the other hand is due to imports of small diameter pipes, less than the valve diameter of imports, or imports of vascular resistance is too large, the method is to remove the valve installation, the inlet tube diameter is not small dry valve inlet diameter or reduce the resistance of pipeline imports. Discharge pipe resistance is too large; resulting in emissions caused by too much back pressure is a factor of flutter valve, pipe emissions by reducing the resistance to be addressed.

    Boiler safety valve is present from the main, the auxiliary valve package components, and mechanical and thermal control of dual protection, and some less prone to failure, but to fully grasp the valve common cause of the malfunction and the elimination of the malfunction can be handy when dealing with them, for ensuring the safe operation of equipment is of great significance.

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