Valve pressure and operating condition selection

The valve is like a switch on the pipeline. The pressure figure marked on it is not something that can be simply glanced at and then dismissed. If you make the wrong choice, the entire system might encounter problems or even be in danger. How to interpret this pressure actually mainly lies in understanding its relationship with temperature.

Here is the most crucial principle: Valves are made of metal, and metal has a temper - it becomes "soft" when exposed to high temperatures, and its strength decreases. The same valve may be able to withstand 20 kilograms of pressure when it's cool, but if you throw it into a scorching environment of several hundred degrees Celsius, it might not even be able to handle 10 kilograms. Therefore, you must never just look at its pressure value at room temperature. You must ask yourself: "At the extremely hot temperature at which it actually operates and is lethal, how much strength will it still have left?"

After understanding this, you will be able to clearly understand the pressure rating of the valves. Valves marked with PN16 have a slightly lower pressure capacity and are suitable for use in our daily life, such as in household water supply and community heating pipes. Those marked with PN40 or Class 300 have a higher pressure capacity and are generally used in factory steam pipes. There are even more powerful ones, marked with PN100 or above, which are specifically used in power plants and large oil refineries. These places are extremely hot and under high pressure, and ordinary valves simply cannot withstand them.

So, here is the most practical method for selecting valves for you. First, figure out the situation of your own pipeline: what is flowing inside? How hot can it get? What is the maximum pressure? Second, take these numbers and go to the valve manufacturer to get a sheet called "Pressure-Temperature Chart". Find the corresponding high temperature on this chart and check if the pressure number listed there is greater than your actual pressure. If it is, then there is no problem!

Apart from pressure and temperature, you also need to check what is flowing through the pipeline. If it's water or air, most valves can be used. But if it's corrosive chemical solution, you need to choose a "corrosion-resistant" one, such as a valve made of stainless steel. Otherwise, it will be corroded and unusable soon. It's like serving soup. Clear water can be served in a plastic bowl, but spicy and sour soup is best served in a ceramic bowl. The principle is the same.

Also, don't forget to check how the valves are connected to the pipes. Some valves have screws on both ends and can be screwed on, this is called threaded connection and is suitable for small pipes. Some large valves have round discs at both ends that need to be fixed with bolts, which is suitable for thick pipes. And there are some that are directly welded onto the pipes, and the latter is the most sturdy and is generally used in the most important and places where water leakage is not allowed.

So, here is the most practical method for selecting valves for you. First, figure out the situation of your own pipeline: what is flowing inside? How hot can it get? What is the maximum pressure? Second, take these numbers and go to the valve manufacturer to get a sheet called "Pressure-Temperature Chart". Find the corresponding high temperature on this chart and check if the pressure number listed there is greater than your actual pressure. If it is, then there is no problem!