在单芯的情况下，如果介质是流动开放型，则阀的稳定性好，但是如果介质是流动封闭型，则阀的稳定性低。双座阀有两个滑阀，下滑阀关闭流量，上滑阀打开流量。因此，当使用小开口工作时，流量关闭滑阀会引起阀振动。这就是双座阀不能用于小开度工作的原因所在。

In the case of a single core, if the medium is a flow open type, the stability of the valve is good, but if the medium is a flow closed type, the stability of the valve is low. The double seat valve has two slide valves, with the sliding valve closing the flow rate and the upper slide valve opening the flow rate. Therefore, when working with a small opening, the flow closing slide valve will cause valve vibration. This is why double seat valves cannot be used for small opening operations.

为什么双密封阀不能当作切断阀使用

Why dual seal valves cannot be used as shut-off valves

双座阀芯的优点是平衡力双密封阀结构，允许压差大，而它突出的缺点是两个密封面不能同时良好接触，造成泄漏大。当人工强行用于切割时，效果显然不好。不建议进行许多改进(例如双密封套筒阀)。

The advantage of a dual seat valve core is the balanced force dual seal valve structure, which allows for a large pressure difference. However, its prominent disadvantage is that the two sealing surfaces cannot make good contact at the same time, resulting in large leakage. When manual force is used for cutting, the effect is obviously not good. It is not recommended to make many improvements (such as double sealed sleeve valves).

什么直行程的自力式压力调节阀防堵性能差，角行程阀防堵性能好

What kind of straight stroke self operated pressure regulating valve has poor anti blocking performance, while angle stroke valve has good anti blocking performance

直行程阀芯垂直节流，介质水平流入和流出。阀腔中的流路不可避免地会旋转，这会使阀的流路变得非常复杂(看起来像是反向的S型)。因此，有许多死区为媒体沉淀提供了空间，并且随着事情的进展，它们会造成堵塞。四分之一转阀的节气门方向是水平的。介质水平流入和流出，因此很容易清除脏介质。同时，流路简单，并且存在用于介质沉降的空间。由于尺寸小，所以角行程阀防堵性能好。

The straight stroke valve core is vertically throttled, and the medium flows in and out horizontally. The flow path in the valve chamber inevitably rotates, which makes the flow path of the valve very complex (looking like a reverse S-shape). Therefore, there are many dead zones that provide space for media sedimentation, and as things progress, they can cause blockages. The throttle direction of the quarter turn valve is horizontal. The medium flows in and out horizontally, making it easy to remove dirty media. Meanwhile, the flow path is simple and there is space for medium settlement. Due to its small size, the angle stroke valve has good anti clogging performance.

为什么直行程自力式压力调节阀阀杆较细

Why is the stem of a straight stroke self operated pressure regulating valve thinner

它涉及简单的机械原理：高滑动摩擦力和低滚动摩擦力。直行程阀的阀杆向上和向下移动，填料被轻微压缩，从而使阀杆变得非常紧密，填料的回流差较大。因此，阀杆设计得非常小，填料使用低摩擦系数的PTFE填料来减少反冲，但是阀杆很薄，容易弯曲，填料成为一个问题。寿命短的解决此问题的方法是使用行程阀杆或1/4回转阀。其阀杆的厚度是直阀阀杆的厚度的2至3倍，并选择了寿命长的石墨填料。阀杆刚度好，填料寿命长，其摩擦力矩反而小、回差小。

It involves simple mechanical principles: high sliding friction and low rolling friction. The stem of the straight stroke valve moves up and down, causing the packing to be slightly compressed, making the stem very tight and resulting in a large backflow difference of the packing. Therefore, the valve stem is designed very small, and PTFE packing with low friction coefficient is used to reduce backlash. However, the valve stem is thin and prone to bending, making the packing a problem. The solution to this problem with a short lifespan is to use a stroke valve stem or a 1/4 turn valve. The thickness of its valve stem is 2 to 3 times that of a straight valve stem, and graphite packing with a long service life is selected. The valve stem has good stiffness and long packing life, but its friction torque is actually small and the backlash is small.