1. From the front of the pressure relief valve, you can see the letter "O", which is the abbreviation of the English word "open", which means open. There is also an arrow pointing counterclockwise near the letter "O", that is, counterclockwise rotation means opening the pressure relief valve.

2. From the front of the pressure reducing valve, you can see the letter "S" on the other side. As can be seen from the picture below, it is the abbreviation of the English word "shut", which means close. You will also see a clockwise arrow near the "S". Rotating in the direction of arrow will close the pressure reducing valve.

3. When opening the pressure reducing valve, look at the valve from the front and turn it counterclockwise to open the pressure reducing valve.

4. After opening the valve in this way, when the heating is not hot, you must check the room heating to open the valve and turn it counterclockwise.

Extended data

There are two main types of valve structures: spring type and lever type. Spring type means that the seal between disc and seat depends on the spring force. The type of lever depends on the force of lever and heavy hammer.

With the need of large capacity, another pulse safety valve, also known as pilot safety valve, has appeared, which consists of main safety valve and auxiliary valve. When the medium pressure in the pipeline exceeds the specified pressure value, the auxiliary valve is opened first, and the medium enters the main safety valve along the conduit, and the main safety valve is opened to reduce the increased medium pressure.