1. Define the purpose of the valve in the equipment or device, and determine the working conditions of the valve: applicable medium, working pressure, working temperature, etc.

2. Determine the nominal diameter and connection mode of the pipeline connected with the valve: flange, thread, welding, etc.

3. Determine the way to operate the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electric or electro-hydraulic linkage, etc.

4. According to the medium transported by the pipeline, working pressure and working temperature, determine the materials of the selected valve shell and internals: gray cast iron, malleable cast iron, nodular cast iron, carbon steel, alloy steel, stainless steel, acid-resistant steel, copper alloy, etc.

5. Determine the valve type: gate valve, globe valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap, etc.

6. Determine valve parameters: For automatic valves, first determine the allowable flow resistance, discharge capacity, back pressure, etc. According to different needs, determine the nominal diameter of the pipeline and the diameter of the valve seat hole.

7. Determine the geometric parameters of the selected valve: structural length, flange connection form and size, height size of the valve after opening and closing, size and number of connecting bolt holes, and overall size of the valve.

The installation and maintenance of safety valve should pay attention to the following matters:

All kinds of safety valves should be installed vertically.

There should be no resistance at the outlet of the safety valve to avoid compression.

Before installation, the safety valve should be specially tested and its official sealing should be checked.

Safety valves in use should be checked regularly.