1 Piece Ball Valve: Ten Reasons

I often encounter various questions from customers using 1 Piece Ball Valve. Below, we've summarized some of the most common questions, defining them as the "Ten Whys About Valves." We hope this helps:
1. Why should hard-seal valves be used whenever possible?
Shut-off valves require the lowest possible leakage. Soft-seal valves offer the lowest leakage, and while they offer excellent shutoff performance, they suffer from wear resistance and poor reliability. Considering the dual criteria of low leakage and reliable sealing, soft-seal shutoff valves are inferior to hard-seal shutoff valves. For example, a full-function, ultra-lightweight regulating valve, with its seal and wear-resistant alloy protection, offers high reliability and a leakage rate of 10⁻⁷, which already meets the requirements of a shutoff valve.
2. Why can't double-seal valves be used as shutoff valves?
The advantage of a double-seat valve's spool is its force-balanced structure, allowing for large pressure differentials. However, its significant disadvantage is that both sealing surfaces lack simultaneous contact, resulting in high leakage. Artificially and forcibly using it for shutoff applications will clearly yield poor results, even with numerous improvements (such as the double-seal sleeve valve).
3. Why do double-seat valves tend to vibrate when operating at small openings? For a single-seat valve, valve stability is good when the medium is open; it is poor when the medium is closed. A double-seat valve has two valve cores: the lower valve core is closed and the upper valve core is open. Therefore, when operating at small openings, the closed valve core is prone to valve vibration, which is why double-seat valves cannot be used for small openings.
4. Why do linear control valves have poor anti-clogging performance, while angular-turn valves have good anti-clogging performance?
The spool of a linear valve throttles vertically, while the medium flows in and out horizontally. The flow path within the valve cavity inevitably curves and makes the valve flow path quite complex (e.g., an inverted "S" shape). This creates many dead zones, providing space for the medium to settle, which can cause blockage over time. Angle-turn valves throttle horizontally, allowing the medium to flow in and out horizontally, which easily carries away impure media. At the same time, the flow path is simpler, leaving less room for the medium to settle, so angular-turn valves have good anti-clogging performance.
5. Why do linear control valves have thinner stems? Linear-stroke control valves operate on a simple mechanical principle: high sliding friction and low rolling friction. As the stem of a linear-stroke valve moves up and down, the packing is slightly compressed, which tightly wraps around the stem, resulting in a large backlash. To achieve this, the valve stem is designed to be extremely thin, and the packing is often made of PTFE, a material with a low friction coefficient, to reduce backlash. However, this leads to a problem: a thin stem is prone to bending, and the packing life is shortened. The best solution to this problem is to use a rotary valve stem, or an angular-turn control valve. This stem is two to three times thicker than a linear-stroke valve stem, and the long-life graphite packing is used. This provides excellent stem rigidity, long packing life, and, conversely, low friction torque and backlash.
6. Why do angular-turn valves have a larger cutoff pressure differential?
The reason for the larger cutoff pressure differential of angular-turn valves is that the combined force of the medium on the valve core or disc generates very little torque on the rotating shaft, allowing them to withstand larger pressure differentials.
7. Why has the use of sleeve valves in place of single- and double-seat valves not been as successful as hoped? Sleeve valves, introduced in the 1960s, saw widespread use both domestically and internationally in the 1970s. Sleeve valves accounted for a significant portion of petrochemical plants introduced in the 1980s. At that time, many believed they could replace single- and double-seat valves, becoming the second-generation product. This is no longer the case; single-, double-seat, and sleeve valves are all equally used. This is because sleeve valves offer improved throttling, stability, and maintenance compared to single-seat valves. However, their weight, blockage resistance, and leakage performance are comparable to those of single- and double-seat valves. Therefore, they can only be used together.
8. Why do rubber-lined butterfly valves and fluorine-lined diaphragm valves have a short service life when used with desalted water?
Desalted water contains low concentrations of acids and alkalis, which are highly corrosive to rubber. Rubber corrosion manifests itself as swelling, aging, and reduced strength. Rubber-lined butterfly valves and diaphragm valves perform poorly, essentially due to the rubber's lack of corrosion resistance. The rubber-lined diaphragm valve has been upgraded to a fluorine-lined diaphragm valve with better corrosion resistance. However, the diaphragm of a fluorine-lined diaphragm valve cannot withstand folding up and down, causing mechanical damage and shortening the valve's lifespan. The best solution now is a ball valve designed for water treatment, which can last 5 to 8 years.
9. Why are piston actuators increasingly used in pneumatic valves?
For pneumatic valves, piston actuators can fully utilize the air pressure, making the actuator smaller and providing greater thrust than diaphragm actuators. The O-rings in the piston are also more reliable than diaphragms, leading to their increasing use.
10. Why is selection more important than calculation?
Compared to calculation, selection is far more important and complex. Calculation is simply a simple formula; its accuracy is less important than the formula's precision and more crucial than the accuracy of the given process parameters. Selection involves many aspects, and carelessness can lead to inappropriate selection, resulting in not only a waste of manpower, material, and financial resources, but also unsatisfactory performance and numerous operational issues, such as reliability, lifespan, and operational quality. Summary: The above are the top ten whys of valves. The information is summarized based on my many years of experience in producing fluorine-lined ball valves and is for reference only.