Performance of sealing

The sealing performance of the valve refers to the ability of the sealing parts of the valve to prevent the leakage of the medium, which 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 valve seat; Packing and stem and packing box matching place; The connection between body and bonnet. The former leakage is called endoleak, which is commonly referred to as lax closing, and will affect the ability of the valve to cut off the medium. For the cut-off valve class, endoleak is not allowed. The latter two leaks are called leakage, that is, the medium leaks from the valve to the outside of the valve. Leakage can cause material loss, pollution of the environment, and serious accidents. For flammable, explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.

Medium of flow

After the medium flows through the valve, there will be a pressure loss (the pressure difference before and after the valve), that is, the valve has a certain resistance to the flow of the medium, and the medium will consume a certain amount of energy to overcome the resistance of the valve. In order to save energy, the resistance of the valve to the flow medium should be reduced as much as possible when designing and manufacturing the valve.

Opening and closing force and opening and closing moment

Opening and closing force and opening and closing moment refer to the force or moment that must be applied to open or close the valve. When closing the valve, it is necessary to form a certain sealing pressure between the sealing surface of the opening and closing parts and the hair seat, and to overcome the friction between the stem and the packing, the stem and nut threads, the stem end support and other friction parts, so a certain closing force and closing torque must be applied. In the process of opening and closing the valve, the required opening and closing force and opening and closing torque are changed. Its maximum value is at the final instant of closing or the initial instant of opening. Valves should be designed and manufactured to reduce their closing force and closing moment.

Opening and closing speed

The opening and closing speed is expressed as the time required for the valve to complete one opening or closing action. Generally, there are no strict requirements for the opening and closing speed of the valve, but some conditions have special requirements for the opening and closing speed. If some require rapid opening or closing to prevent accidents, some require slow closing to prevent water hammer, etc., this should be considered when selecting the valve type.

Motor sensitivity and reliability

This refers to the sensitivity of the valve to changes in medium parameters. For the throttle valve, pressure reducing valve, regulating valve and other valves used to adjust medium parameters and safety valve, trap valve and other valves with specific functions, its functional sensitivity and reliability are very important technical performance indicators.

Service life

It indicates the durability of the valve, is an important performance index of the valve, and has great economic significance. It is usually expressed by the number of opening and closing that can ensure the sealing requirements, and can also be expressed by the use time.