What are technical considerations in choosing a valve?

What technical performance should be paid attention to when selecting valve?

1. Sealing performance

Valve sealing performance refers to the sealing parts of valve’s ability to prevent leakage of medium, it is the most important technical performance index of the valve. There are three sealing parts of the valve: the contact between the opening and closing parts and the sealing surface of the seat; Packing and stem and stuffing box matching; Body to bonnet joint. A leak at the front of the valve is called an internal leak, which is often referred to as a loose closure and will affect the valve’s ability to block the medium. For block valves, internal leakage is not allowed. The latter two leakage is called external leakage, that is, the medium leakage from the valve to the valve. Leakage will cause material loss, pollution of the environment, even serious accidents. For flammable explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.

2. Flow media

After the medium flowing through the valve will produce pressure difference before and after, so that the valve has certain resistance to the flow of the medium, the medium to overcome the resistance of the valve will consume certain energy, so when designing and manufacturing the valve, it is necessary to reduce the valve resistance to the flow of the medium as far as possible, reduce the loss of energy.

3. Opening and closing force and moment

Opening and closing forces and moments are the forces or moments that must be applied to open or close the valve. Close the valve, the need to make the open-close part and send a form a seal between the two sealing surface pressure, but also overcome the friction stem and other parts of the friction force, therefore, in the process of opening and closing, the valve must exert closing force and close moment, so the design and manufacture of valves should strive to reduce the closing force and close moment.

4. Opening and closing speed

The opening and closing speed is expressed by the time required for the valve to complete an opening or closing action. Generally, there is no strict requirement on the opening and closing speed of the valve, but some working conditions have special requirements on the opening and closing speed, such as some requirements for quick opening or closing, in case of accidents, some requirements for slow closing, in case of water hammer, etc., which should be considered when choosing the valve type.

5. Service life

It represents the durability of the valve, is an important performance indicator of the valve, and has great economic significance. Usually in order to ensure that the seal requirements to open and close the number of times, can also be used to express the time.