【 Weak current College 】 control valve common troubleshooting methods (3)

Third, the control valve leakage solutions (6)
1) increase the seal grease method
On unused seal grease for valves, consider increasing the sealing grease to improve stem seal performance.
2) increase the fill method
To improve packing on the valve sealing performance, can increase the fill method. Usually adopts double-layer, multi-layer mixed filler forms, simply increase the number, such as 3 tablets to 5 pieces, the effect is not evident.
3) replace the graphite packing method
Extensive use of PTFE packing, because of its operating temperature-20 to + 200 ° c, when the temperature in the upper and lower, the change is large, the sealing is decreased significantly, aging fast, short life. Flexible graphite filler can overcome these shortcomings and long service life. Hence all the factories will replace PTFE packing with graphite packing, or even new buy-back of the regulator will also be one of the PTFE packing with graphite packing after use. But using graphite packing of backlash, initially have also generated mat, this must be taken into account.
4) change direction, reset the P2 in the stem end method
When △ larger P, P1, is large, seal sealing P2 P1 obviously difficult. Therefore, you can take to change the direction of approach, the P1 in the stem end to P2 in the stem end, this pressure is high, the pressure difference of valve is more effective. Such as bellows valve is usually sealed P2 should be considered.
5) using lens cushion seal method
For the upper and lower lid and seal, seat of the upper and lower body sealing. If the plane seal, at high temperature and high pressure, tightness, causing a release, you can instead use the lens cushion seals can be satisfied with the results.
6) replace the gasket
So far, most of the gasket is the use of asbestos plate, at high temperatures, poor performance, life is short, causing leaks. This is the case, you can instead use the wound gasket, "O"-rings, many plants have already adopted.

IV. control valve vibration solution (8 way)
Increased stiffness method 1)
On the oscillation and the slight vibration, increases the stiffness to eliminate or reduce such as selection of great stiffness of the spring, use piston actuators and other approaches are possible.
2) increased damping method
Increased vibration damping is increasing, such as friction sleeve valve plug may use the "O" ring seals, adopting the have large friction, graphite packing, etc. to eliminate or weaken the slight vibration or have a certain effect.
3) increases with the size, reduce the Guide clearance method
Axis plug-shaped valve general guidance dimension are smaller, all valve clearance is generally larger, 0.4 ~ lmm, which produce machinery vibration is helpful. Therefore, in the event of minor mechanical vibration, size by increasing orientation, reducing the clearance to weaken the vibration.
4) change the throttling element shapes, eliminate resonance method
As a result of the so-called vibration source control occurs at high speed flow, pressure, the throttle mouth is rapidly changing, and change the throttling element shape to change the oscillator frequency, resonance is not strong, relatively easy to solve. Specific method is in vibration within the valve to open degree surface turning 0.5 ~ 1.0mm. As a family in the vicinity of the installation of a self-operated pressure control valve, the resonance effects produced Whistler employees rest, we dropped the core surface vehicles, resonance 0.5mm squealing sounds disappear.
5) replace the throttling element eliminate resonance method
Its methods are: ① replace to change the flow characteristics, logarithmic, linear to log-linear; ② 1.check forms. If the shaft plug shape to "V"-shaped trough valve core, the two-seater valve shaft plug into a socket type; will open window sleeve to make up the holes of the sleeve. As a fertilizer factory a DN25 two-seater valve, the valve stem and valve connection often broken, we confirm that the vibration for resonance, the linear characteristics of the valve into logarithmically spool, the issue is resolved. As an Aviation Institute laboratory used a DN200 sleeve valve, plug produce strong rotation could not come into use, will open the window of the sleeve to make up the holes of the sleeve, the rotation immediately disappear.
6) replacement valve type to eliminate resonance.
Different structure of the control valve, its natural frequency natural, replace the valve type is fundamentally eliminate resonance of the most effective way. A valve in use resonance formidable — strong vibration (severe damage to the valve), strongly rotating (even the stem is vibration and torsion), and strong noise (up to 100 DB) valve, as long as it is replaced by a single structure differences larger valves, and immediately effective, strong resonance miraculously disappeared. If the vinylon factory of new expansion project selection one DN200 sleeve valve, these three phenomena are present, DN300 pipes with the beat, the plug rotation, 100 decibels of noise, resonance opening 20 ~ 70%, consider resonance opening large, use a two-seater valve, resonance, the commissioning of the fine.
7) reduce cavitation vibration method
Due to cavitation bubble burst of natural steam vibration, should reduce cavitation on the way. ① Let bubble burst resulting impact energy does not function in solid surface, especially the valve core, but rather to let the liquid absorption. Sleeve valve has this feature, so you can use axis plug-plug into a socket type. ② to reduce cavitation of all means, such as increasing throttle resistance, increasing the pressure contraction mouth, grading or in-line pressure, etc.
8) avoid vibration source wave hammer method
External vibration source wave hammer vibration caused by valve, apparently control valve normally to be avoided, if the vibration, should take appropriate measuresbr>