Issues regarding the use of control valves under conditions of high pressure difference and large diameter.
Thread Content
1. Regarding large pressure differences or large diameters, the underlying issue is essentially that the thrust generated by the actuator is not sufficient. That’s why solutions such as angle-type control valves and balanced spools are used. But I think that increasing the output air pressure of the electrical valve positioner, thereby enlarging the area of the actuator’s diaphragm, could also increase the actuator’s thrust, right? 2. Also, I’ve never worked with angle valves and balance valve spools; I don’t really understand their working principles. How does a corner valve reduce the pressure difference? It seems that the flow path makes a 90-degree turn, and its internal structure is similar to that of a globe valve. There’s also a balance spool; it has balance holes that direct pressure to the downstream side. In that case, can’t the valve be kept closed even when it’s in its fully closed position?
Please give some support; I hope experts can offer their advice.
The flash point of the angle valve has no effect on the internal components of the valve, resulting in minimal damage to it. As for the balanced sleeve valve, you have also explained its principle clearly; it does not leak when in the fully closed position. As for the large diameter and high pressure difference you mentioned, exactly what values those are? Sleeve valves can’t be manufactured just by specifying those parameters, and the cost of these two types of valves is also quite high
Does that mean that angle valves do not reduce the thrust required from the actuator, but rather reduce the damage caused by flashing to the valve core?
1. The original poster should thoroughly understand the basic structure of each valve; there’s no need to complicate things. 2. The physical concepts learned in junior high school are sufficient to explain the interrelationships between the valve diameter, the actuator, and the pressure difference. 3. While the actuator has significant force, the driving motion is not necessarily stable. In other words, the imbalance of the valve should be as small as possible.
The key to making a selection is to take into account the lifespan of the valve internals. The actuator should be chosen based on calculations to determine the appropriate acting force; the actuator manufacturer can handle this calculation. Domestic actuators don’t cost much either
If the pressure in the pipeline is very high, simply increasing the air supply to the locator will not help. First of all, too high an air pressure will shorten the lifespan of the diaphragm. Second, for air-operated actuators, increasing the air supply pressure has no effect. The only option is to increase the spring strength, but the results will not be ideal; moreover, when the pipeline pressure is high, single-seat valves become very unstable. Only valves with a sleeve-type structure can enable stable regulation
Are there any detailed structural diagrams of the balance valve internals? Thank you