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Common problems in the use of Motorized Regulating Valve

September 12,2023

Electric control valves are important executing unit instruments in industrial automation process control. With the increasing level of automation in the industrial field, it is being increasingly applied in various industrial production fields. Compared with traditional pneumatic control valves, Motorized Regulating Valve have obvious advantages: energy-saving (only consuming electrical energy during operation), environmentally friendly (no carbon emissions), fast and convenient installation (without the need for complex pneumatic pipelines and pump workstations).

Below is a brief summary of some common problems with Motorized Regulating Valve.


1. Why is it easy for a double seat valve to oscillate when working with a small opening?

For a single core, when the medium is a flow open type, the valve has good stability; When the medium is flow closed, the stability of the valve is poor. A double seat valve has two valve cores, with the lower valve core in the closed position and the upper valve core in the open position. This way, when working at a small opening, the closed valve core is prone to causing valve vibration, which is why a double seat valve cannot be used for working at a small opening.

2. Why cannot double seal valves be used as shut-off valves?

The advantage of a double seat valve core is its force balance structure, which allows for a large pressure difference. However, its prominent disadvantage is that the two sealing surfaces cannot make good contact at the same time, resulting in large leakage. If it is artificially and forcibly used for cutting off situations, the effect is obviously not good, and even if many improvements have been made to it (such as double sealed sleeve valves), it is still not advisable.

3. Why is the anti blocking performance of angle stroke valves good?

The valve core of a straight stroke valve is vertically throttled, while the medium flows in and out horizontally. The flow channel in the valve chamber inevitably turns and turns, making the flow path of the valve quite complex (shaped like an inverted "S" shape). In this way, there are many dead zones that provide space for the precipitation of the medium, which in the long run can cause blockage. The throttling direction of the angle travel valve is in the horizontal direction, where the medium flows in and out horizontally, easily taking away unclean medium. At the same time, the flow path is simple, and there is little space for medium precipitation, so the angle travel valve has good anti blocking performance.

4. Why is the stem of a straight stroke regulating valve thinner?

It involves a simple mechanical principle: high sliding friction and low rolling friction.
The stem of a straight stroke valve moves up and down, and if the packing is slightly compressed, it will wrap the stem tightly, resulting in a large backlash. For this reason, the valve stem is designed to be very small, and PTFE fillers with small friction coefficients are commonly used as fillers to reduce backlash. However, the problem caused by this is that the valve stem is thin, making it easy to bend, and the packing life is also short. The best way to solve this problem is to use a rotary valve stem, which is an angle stroke regulating valve. Its stem is 2-3 times thicker than the straight stroke stem, and graphite packing with long service life is used. The valve stem has good stiffness and long packing life, but its friction torque is actually small and the return difference is small.

5. Why is the cutoff pressure difference large for angle stroke valves?

The cutting pressure difference of angle stroke valves is relatively large because the combined force generated by the medium on the valve core or valve plate has a very small torque on the rotating shaft, so it can withstand a large pressure difference.

6. Why does the use of rubber lined butterfly valves for desalination have a short service life?

The desalinated water medium contains low concentrations of acids or bases, which have significant corrosiveness to rubber. The corrosion of rubber manifests as expansion, aging, and low strength. Butterfly valves and diaphragm valves with rubber lining have poor performance, which is essentially caused by the lack of corrosion resistance of rubber. The rear rubber lined diaphragm valve has been improved to a fluorine lined diaphragm valve with good corrosion resistance, but the diaphragm of the fluorine lined diaphragm valve cannot withstand folding up and down and is broken, causing mechanical damage and shortening the valve's lifespan. The best solution now is to use water treatment specialized ball valves, which can be used for 5-8 years.

7. Why should hard seals be used as much as possible for shut-off valves?

The cut-off valve requires a lower leakage as much as possible. The leakage of a soft sealing valve is the lowest, and the cut-off effect is of course good, but it is not wear-resistant and has poor reliability. From the dual standards of small leakage and reliable sealing, soft seal cutting is not as good as hard seal cutting. For example, the fully functional ultra light regulating valve is sealed and stacked with wear-resistant alloy protection, with high reliability and a leakage rate of 10-7, which can already meet the requirements of the shut-off valve.

8. Why did sleeve valves not replace single and double seat valves?

The sleeve valve, which was introduced in the 1960s, was widely used both domestically and internationally in the 1970s. In the petrochemical plants introduced in the 1980s, the proportion of sleeve valves was relatively large. At that time, many people believed that sleeve valves could replace single and double seat valves and become the second-generation products. Until now, this is not the case. Single seat valves, double seat valves, and sleeve valves are all used equally. This is because the sleeve valve only improves the throttling form, stability, and maintenance compared to single seat valves, but its weight, anti blockage, and leakage indicators are consistent with single and double seat valves. How can it replace single and double seat valves? So, it can only be used together.

9. Why is selection more important than calculation?

Compared to selection, calculation and selection are much more important and complex. Because calculation is just a simple formula calculation, its essence lies not in the accuracy of the formula, but in the accuracy of the given process parameters. The selection involves a lot of content, and a slight carelessness can lead to improper selection, which not only leads to waste of manpower, material resources, and financial resources, but also results in unsatisfactory usage effects, leading to several usage issues such as reliability, lifespan, and operational quality.

10. Why are there more and more pneumatic valve piston actuators?

For pneumatic valves, piston actuators can fully utilize the pressure of the air source, making the size of the actuator smaller and more thrust than the diaphragm type. The O-ring in the piston is also more reliable than the diaphragm, so its use will be increasing.

11. Why is the stem of a straight stroke regulating valve thinner?

It involves a simple mechanical principle: high sliding friction and low rolling friction. The stem of a straight stroke valve moves up and down, and if the packing is slightly compressed, it will wrap the stem tightly, resulting in a large backlash. For this reason, the valve stem is designed to be very small, and PTFE fillers with small friction coefficients are commonly used as fillers to reduce backlash. However, the problem caused by this is that the valve stem is thin, making it easy to bend, and the packing life is also short. The best way to solve this problem is to use a rotary valve stem, which is an angle stroke regulating valve. Its stem is 2-3 times thicker than the straight stroke stem, and graphite packing with long service life is used. The valve stem has good stiffness and long packing life, but its friction torque is actually small and the return difference is small.

12. Why is the cutoff pressure difference large for angle stroke valves?

The cutting pressure difference of angle stroke valves is relatively large because the combined force generated by the medium on the valve core or valve plate has a very small torque on the rotating shaft, so it can withstand a large pressure difference.

Hongsen Electric Control Valve has won the trust of many customers for its professional and reliable performance. Whether it is a refrigeration equipment manufacturer, engineering contractor, or refrigeration system operator, we adhere to the principle of continuous innovation and high-quality service, and work together with you to create a safe and efficient refrigeration environment.

Choosing the electric control valve of Hongsen Machinery, you have chosen a safe and reliable refrigeration partner. Let's work together to achieve perfect control over refrigeration and provide stable support for your business.

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