What Are The Main Functions Of The Regulating Valve?

There are nine main functions of the regulating valve: ① regulation; ② cut-off; ③ overcoming pressure difference; ④ anti-blocking; ⑤ corrosion resistance; ⑥ pressure resistance; ⑦ temperature resistance; ⑧ weight; ⑨ appearance. Let’s analyze the main functions of the regulating valve below:

Regulation function

The primary function of the regulating valve is regulation, which is mainly manifested in 5 aspects:

① Flow characteristics – the flow characteristics reflect the relationship between the opening of the regulating valve and the change of flow, in order to adapt to different system characteristics requirements, such as the flow regulation system needs a fast response speed logarithmic characteristics; the temperature regulation system needs a slow response speed and a linear flow characteristic. The flow characteristics reflect the regulation quality of the regulating valve.

② Adjustable range R – the adjustable range reflects the flow range controlled by the regulating valve, expressed by the ratio of R=Qmax/Qmin. The larger the R, the wider the range of the adjustable flow and the better the performance index. Usually the valve has R=30; good valves, such as V-type ball valves, have R=50; multi-function regulating valves have R up to 100200.

③ Small opening performance – some valves are limited by the structure, and the small opening performance is poor, resulting in jumps and oscillations, and R becomes very small (that is, Qmin is very large), such as double-seat valves and rubber-lined butterfly valves. Good valves should have fine-tuning functions for small openings, which can meet the regulation of very small flows, and the work requires a very balanced operation. Such valves include V-type ball valves, eccentric rotary valves, and multi-function regulating valves.

④ Flow coefficient Kv – system (Kv), which indicates the ability of the flow through the valve. The larger the Kv value of the same caliber, the better. Angle travel valves (ball valves, butterfly valves, multi-function regulating valves) are 2 to 3 times that of straight travel valves (single seat, double seat, sleeve valves).

⑤ Regulating valve speed (response time) – meet the system’s speed requirements for valve action.

Cut-off function

The cut-off function is indicated by the leakage index of the valve. Cut-off usually means that the leakage is less than 0.001%, and the highest level is VI (bubble level). It reflects the intrinsic quality of the valve. In the use of the valve, there is a great reflection on the large leakage of domestic valves.

Overcoming pressure difference function: Why are rotary valves used more and more?

It is usually expressed by the allowable pressure difference when the valve is closed. The larger the allowable pressure difference, the better this function. If it is not considered carefully, the valve core will be pushed open by the pressure difference, causing the valve to not close in place and the leakage to exceed the standard. Therefore, to ensure the valve cut-off, it is necessary to overcome the working pressure difference when the valve is closed. Usually, the allowable pressure difference of single-seal valves is small, such as single-seat valves, angle valves, diaphragm valves, and three-way valves; the allowable pressure difference of double-seal valves and transfer valves is large, such as double-seat valves, ball valves, and multi-function valves. From the perspective of leakage and overcoming pressure difference: single seal valve has small leakage but small allowable pressure difference; double seal valve has large leakage and large allowable pressure difference; only rotary valve has small leakage and large allowable pressure difference, which is one of the important reasons why rotary valves will be used more and more.

Anti-blocking function: Which type of valve has good anti-blocking performance?

For the adjustment of unclean media or even clean media, welding slag and other debris in the pipeline may cause valve blockage or jamming, so the valve should have good anti-blocking function to make it normal. The best anti-blocking performance is the rotary valve with the simplest flow path, such as ball valve, butterfly valve, eccentric valve, multi-function regulating valve; valves with complex flow and valves guided by upper and lower bushings are prone to jamming, such as single seat valve, double seat valve, sleeve valve, etc. Rotary valves not only have good anti-blocking function, but also have small leakage and large allowable pressure difference, so their use will become more and more extensive.

Corrosion resistance function

Resist corrosion and erosion of the medium to increase the service life of the valve. The corrosion of the valve is caused by the chemical properties of the medium. It is usually solved by corrosion-resistant materials. Erosion is caused by high-speed flowing media, media containing particles, and media that produce flash evaporation and cavitation. The solution is to use wear-resistant materials and adopt anti-cavitation and anti-erosion measures in the structure. If the high-pressure valve, the regulating valve working with a large pressure difference, and the regulating valve used for medium containing particles, this problem should be considered.

Pressure resistance function

It reflects the strength and safety index of the regulating valve, that is, the medium cannot leak out through the seal and the valve body defects. It is usually tested with 1.5 times PN when leaving the factory. Forging structure is the best for high-pressure media; cast iron valves have the lowest pressure resistance, and cast steel valves are usually selected.

Temperature resistance function

The strength and hardness of the material are functions of the temperature. High temperature will reduce the strength of the valve body material. In order to meet the requirements of the strength index of the valve under different temperature conditions, the temperature resistance of the valve material must be carefully considered and the structure of the regulating valve must be reasonably designed. To ensure that the regulating valve has good strength and safety at working temperature.

In temperature resistance considerations, in addition to temperature, the impact of temperature difference (like pressure difference) should also be considered.

Weight and appearance

Industrial products require a pleasing appearance. People require instrumentation for the appearance quality of regulating valves; lightweight and miniaturized under the premise of meeting the function. The latter can obviously save materials and facilitate transportation and installation. At present, the more ideal appearance of the regulating valve is the electronic multifunctional regulating valve.