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In what range is the opening of regulators generally reasonable? There is a saying that it should not be > 30%, or even as small as possible.
Are there any relevant standards?
A:
For quick response time, the self-operated regulating valve is designed with a quick-opening valve core, and the general stroke is short, so the regulating performance
is relatively rough. As can be seen from JORDAN's flow meter (as shown below), when the set pressure deviation value is less than 5%, the CV value is only 0.21, and the
opening is about 10%. The greater the flow capacity behind, the greater the deviation value, and the worse the regulating accuracy.
Therefore, the opening of self-operated regulating valve is generally between 5% and 30%.
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Is it possible to open or close the low-pressure pneumatic butterfly valve of DN800 in 3 seconds? How to achieve it?
A: Yes, it can be achieved. Some manufacturers can do it in 0.5-2 seconds at the earliest.
For example, the single-acting actuator of air-operated valve is closed by spring force, and the speed is no problem. Open to increase the intake speed and exhaust speed,
specifically, increase the air inlet and outlet of the pipe, air supply amplifier and actuator. The opening speed is affected by the on-site air supply pressure.
If the air supply pressure is too low, the air bag and booster valve < br >
If it is too fast, it needs to be equipped with hydraulic buffer.
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Excuse me, the gate valve globe valve adopts hydrogen medium, at normal temperature and low pressure (150LB/300LB). What should be paid attention to in this kind
of valve?
Answer: Due to the particularity of hydrogen medium (small molecule, easy to permeate and hydrogen embrittlement, explosiveness, etc.), the quality of valve body and bonnet is very high.
Forgings are preferred for valve body and bonnet materials, such as castings for large-diameter valves, but RT secondary film standards must be made;
The design and manufacture of valves should not have sharp chamfers, all chamfers should be smooth and excessive, and the machining accuracy and surface degree of parts are very high;
Valves need to be cleaned strictly;
During the pressure test, the strength test needs gas strength test, not just water strength test;
If it is a hydrogen valve, the requirements will be higher. The material of the valve needs to control the contents of C, S and P, and the crystal phase test is needed.
Valves with hydrogen medium can also be tested with hydrogen according to the SHELL 77/308 specification.
Be sure to pay attention to fire prevention, anti-flying and anti-static < br >
Valve of hydrogen pipeline should adopt ball valve and globe valve. When the working pressure is greater than 0.1 MPa, it is forbidden to use gate valves. The valve should be oil-free and degreased. The sealing surface of the gate valve will be scratched and damaged due to friction during relative movement. Once damaged, there will be "iron powder" falling off from the sealing surface, so fine iron powder is easy to catch fire, which should be the reason why the gate valve is not recommended in oxygen and hydrogen pipelines. However, the existing hydrogenation units in China adopt UOP process, including uniform gate valve and Y-section. The maximum pressure of the gate valve is 2500Lb, and the diameter is 12 inches. The Chevron process adopts orbital ball valve. Theoretically, it is good to degrease and the valve material does not contain combustion-supporting components. The hydrogenated hydrogen valve does not need to be degreased, because the medium is oil+hydrogen. Under high temperature and high pressure, the naphthenic chain is broken into a long chain, and the long chain becomes a short chain. This is the purpose of hydrogenation. Hydrogen is a combustion agent, oxygen is a combustion improver, and only the valve with combustion improver needs to be degreased, and chlorine is also a combustion improver, so the valve with chlorine-related environment should be degreased.
Do you also need to pay attention to the requirements of fugitive micro-leakage for medium hydrogen and stem packing?
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How to realize the normally open and normally closed when the electric actuator loses power?
A: Add spare battery, super capacitor, spring reset and electro-hydraulic for large thrust or torque.
The following picture shows the actuator with spring return < br >
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reduced bore valve and full bore valve mean？
A：reduced bore valve ：Reducing ball valve, which means that the diameter of the ball is smaller than that of the valve, is commonly used.。
full bore valve：Full-bore ball valve for pipeline or viscous medium.
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Does the control valve in SIS need feedback?
A: SHBZ06-1999 Design Guidelines for Emergency Shutdown and Safety Interlocking System in Petrochemical Industry,
6.2.10 The final component should be provided with valve position indication.
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what is the material of high-pressure liquid ammonia valve body?
A: It is recommended to choose 304 stainless steel or 316 stainless steel.
Due to the serious gasification of liquid ammonia after passing through the control valve at the moment when the valve is opened and depressurized, the local temperature will
drop sharply, resulting in the local Ivylinna Lee of the valve. Generally, ordinary carbon steel can withstand the temperature of about -20 degrees, which is unbearable with high
pressure.
Case: When the chemical fertilizer plant was overhauled, the valve of the liquid ammonia pipeline was frozen and could not move, and there was an ice pimple outside, and the valve
body inside was frozen together. During the overhaul, the maintenance personnel knocked on the valve body, and the valve body was ejected due to the operation under pressure,
resulting in the instantaneous leakage of ammonia gas, causing casualties.
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When the electric valve is controlled to open, when will it stop? Is it interlocked by opening the limit switch, or will it automatically stop when the
valve itself is opened?
A: If the switch valve is pressed by the limit switch, if the control valve is pressed by the control panel, it will be determined by the control signal.
From the design and manufacture of electric on-off valve, the first thing is that the limit switch cuts off the power supply of the motor. Secondly, if the limit
switch fails, the protection circuit will detect torque, temperature, over-current, over-voltage, overload, under-current, under-voltage, etc. Just cut off the power
supply of the motor and the protection will stop.
There is also that if it is not debugged well, there is also that the valve is in place, but the actuator is not in place, it will exceed the torque or the motor will overheat,
resulting in closure.
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Hydrogenation multi-stage pressure-reducing angle valves are mostly linear, and they are not resistant to cavitation with on-site reaction. Is the linear flow
characteristic more resistant to cavitation than the spool with equal flow characteristics?
A: The medium of this valve is hot high oil \ cold high oil is used for flow regulation, which is usually the cut-out structure of the valve core, such as FISHER NOTCHFLO DST
and Meso 78400. This valve core is also called axial flow valve core, and the flow characteristics are determined by the valve core, and the outside is a guide cover, not a valve cage.
Because of the large differential pressure, multi-stage pressure reduction is needed, and this structure is relatively easy to make linear, so it is not equal to 100, so it is not
equal to 100.
If the user requests to wait for hundreds, he should tell the user that this structure is not equal to hundreds, and should not say that it is not as linear and durable as hundreds.
There is no direct relationship between flow characteristics (equal hundred, linear) and cavitation resistance.
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What is the full valve stroke time?
A： full open to full close & full close to full open time
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Under what circumstances may the valve medium flow direction and sealing direction be different?
A: For example, only the butterfly valve is installed at the pump outlet. When the valve is closed, in order to prevent the blade from reversing due to internal leakage of
the butterfly valve, it should be pointed to the pump, and the sealing direction should be pointed to the pump first to avoid internal leakage. The real two-way metal sealing
butterfly valve bears the same pressure in the forward direction and the reverse direction, and there are few manufacturers in China that can do it.
Therefore, the pump outlet is generally equipped with a check valve. Generally, large centrifugal pumps can use butterfly valves, and the outlet of the pump is butterfly valves
and hydraulic check valves in turn. Note that this is a hydraulic check valve.
