Application scenarios of floating ball valves

Thread Content

Among ball valve products, the floating ball valve is probably the most widely used. It has a simple structure and is easy to disassemble and maintain; by simply replacing the sealing material, it can be used in various environments such as high-temperature, low-temperature, or corrosive conditions. Additionally, its price is much lower compared to other ball valves of the same diameter, which is why users often choose this type of ball valve when purchasing such products. Nevertheless, there are many considerations when selecting floating ball valves; an improper selection can also lead to unnecessary losses. Generally, for media with a temperature range of -30 to 150°C, that are non-corrosive or only slightly corrosive, and under conditions of low pressure difference, floating ball valves with stainless steel ball valves and PTFE seat can be used; this is because the friction coefficient between PTFE and the ball is the lowest, while the friction coefficients of PPL and metal seats are much higher than that. If the temperature exceeds 150°C, PPL should be considered; for temperatures above 250–300°C, a metal seal is necessary. High temperatures also pose other problems, namely the heat dissipation issue of the actuator; if not handled properly, this will **reduce the service life of the actuator. The common solution is to increase the height of the connecting bracket between the valve and the actuator – the higher the temperature, the higher the bracket should be. The material specifications for tetrafluoroethylene state that it can withstand temperatures of 200°C. In reality, however, the quality of domestically produced tetrafluoroethylene often fails to meet this standard, which leads to misunderstandings among users when making choices. For example, when the operating temperature is 180°C, using a ball valve with a tetrafluoroethylene seal results in the material softening and deforming due to heat, causing the ball to get stuck inside the valve body. I have encountered such situations many times. Also, in situations with high pressure differences, floating ball valves are not suitable, especially at outlet vents, as high pressure differences can distort the ball, resulting in inflexible operation of the ball valve or even its jamming. Our company once had a batch of pneumatic floating ball valves used at the Golmud Refinery in Qinghai. Since the user provided incomplete parameters during the selection process, it was not known that these valves would be used in applications with high pressure differences; as a result, they failed to function properly time and again after being installed in the pipelines. After on-site observation and analysis, the cause was identified; by replacing it with an eccentric ball valve, the problem was completely resolved. Furthermore, soft-sealed ball valves do not perform well in low-temperature environments such as Golmud, as the soft sealing materials become brittle at low temperatures, which increases friction, reduces sealing efficiency, and shortens their service life. Another factor to consider is the configuration of the actuator. Floating ball valves achieve sealing through the pressure exerted by two valve seats on the ball; if the pressure is too high, it becomes difficult to open the valve, while if it is too low, internal leakage occurs. Throughout the process of opening and closing, ball valves experience considerable friction; compared to other valves with the same diameter, they require a much larger torque to be operated. This imposes higher demands on the actuators used to control them. In other words, when selecting an actuator for a floating ball valve, it is necessary to choose one with slightly higher specifications to ensure proper operation during use. For ball valves with larger diameters (DN150 and above), it is advisable to choose fixed ball valves, eccentric ball valves, or V-ball valves.