The reason is that the main safety valve on the other hand, the moving parts and fixed parts of the friction between the too large will cause the main valve seat to slow to address this problem is the main safety valve moving parts and components with a fixed gap standards within the scope of the console.
2.5, the pressure relief valve low back seat
Block, low-pressure safety valve to the economic operation of the boiler against a great back seat is too low pressure will cause a lot of media time-out emissions, resulting in unnecessary energy loss. Such failures occur in the 200MW unit A49H used in pulse-type safety valve spring, the analysis is mainly due to the following factors:
First, the spring pulse of the discharge valve on a large quantity of steam, this form of safety valve in the open impulse, the dielectric constant discharge, and promote the main safety valve action.
On the one hand, pre-impulse pressure safety valve safety valve because the main output of the media and not continue to rise, so the steam inside the pulse tube or along the drum set me to continue the flow of gas in conjunction impulse impulse to maintain the safety valve safety valve action.
On the other hand as a result of such a safety valve type of impulse is the medium flow through the valve core and the orientation of the gap between the sets of the flow of the main safety valve piston chamber, the media out of impulse sealing surface safety valve, in its kinetic energy around the pressure areas, to spool up, they continue to meet the impulse discharge safety valve, steam emissions the greater the kinetic energy of the pressure zone valve core part of the pressure the greater the effect on the spool upward thrust of the greater, the less impulse valve easy back seat, this time to eliminate this failure is related to throttle small, so that the outflow of the medium impulse flow to reduce the safety valve to reduce pressure on the region of kinetic energy of the pressure relief valve so that the impulse back seat.
Block, low back pressure caused by the second factor is: spool and oriented with the gap set improperly, with the small gap in the safety valve Kai Block impulse, the moment in this part of the energy expenditure by a high pressure zone, will spool up, the delay time back seat, when the container down to low, the kinetic energy to reduce pressure on the pressure, impulse valve back seat.
Eliminate this failure is a serious examination of the valve core and parts of sets of size-oriented, with off-hour gap, reducing the valve sealing surface resistance Checkpoint-style steam valve cap or increase the diameter of valve and valve guide radial clearance between the sets of to increase the flow passage area of the site, so that when the steam flow through too much not to reduce expenses, increase of partial pressure of the kinetic energy of the formation of a high pressure zone.
Block, low back pressure caused by another reason is that the friction parts of the campaign, and some parts have a jam The solution is to check all moving parts carefully and strictly in accordance with standard maintenance overhaul of the parts, the parts will be adjusted to meet the gap standards, to remove the possibility of jam.
2.6, the frequency of safety valve jump
Refers to the frequency jump back seat after the safety valve, to be a slightly elevated pressure, safety valve will open, repeated several times there, a phenomenon known as the safety valve of the "frequency jump." Requirements of safety valve safety valve in the mechanical properties during the entire movement to open up to the required height cards do not allow stop there, tremor and frequency jump phenomenon. Jump frequency of safety valve seal is extremely detrimental to easily cause leakage sealing surface. Analysis of the main reasons for back seat with the safety valve of high pressure on the back seat pressure is high, medium container surplus emissions less back seat has a safety valve, when adjusted to run properly, the pressure vessel will soon or up, so also the result of valve movement, as this situation can throttle opening degree of the opening to be eliminated. After the throttle valve opening, leading to the main steam safety valve piston indoor source reduction, and promote the downward movement of power piston smaller, the main safety valve smaller chance of action in order to avoid a row to start the main safety valve.
2.7, a safety valve chatter
Safety valve in the emission arising in the course of the jitter phenomenon, saying it was a safety valve flutter, flutter can easily cause the occurrence of the phenomenon of metal fatigue, so that the mechanical properties of the decline in safety valve, resulting in serious equipment problems, the occurrence of chatter The main reasons for the following areas:
On the one hand, improper use of the valve, the discharge capacity of selected valve too (as opposed to the need in terms of emissions), the elimination method is to choose the valve should be as close as possible to the rated capacity of the necessary equipment emissions. On the other hand is due to imports of small diameter pipe, the valve is less than the import path, or importing too much resistance, the elimination of the method is installed in the valve, so that imports of valves tube diameter not less than the import Path or reduce the resistance to the import pipeline. Discharge pipe resistance is too large, resulting in excessive emissions of the North when the pressure valve is caused by the flutter of the factors that can reduce emissions through the resistance of pipeline to be addressed.
3, Conclusion
Boiler safety valve on the common cause of failure analysis and proposed a specific solution, although the utility boilers are the main safety valve, matching the composition of secondary valve and the use of mechanical and thermal control of dual protection, and some fault not occur, but only a full grasp of the safety valve to eliminate common failure causes and methods to deal with at the time of failure can be handy, to ensure the safe operation of equipment has an important significance. ball valve Trunnion Mounted Ball Valve Floating Ball Valve Top Entry Ball Valve Three way ball valve V Type Ball Valve
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