The disc valve in the steam pipeline does not close properly

Butterfly valves should not be used for steam pipelines; it is recommended to use gate valves or globe valves instead.

Gate Valve A gate valve is a type of valve in which the closing element (gate) moves vertically along the axis of the passage; it is primarily used in pipelines to shut off the flow of medium, that is, to operate in either fully open or fully closed position. 　　Generally, gate valves cannot be used to regulate flow. Depending on the material of the valve, it can be used in low-temperature and low-pressure conditions as well as in high-temperature and high-pressure conditions. 　　However, gate valves are generally not used in pipelines for transporting media such as slurry. Advantages: ① Low fluid resistance ； ②The torque required to open and close it is low ； ③It can be used in ring piping systems where the medium flows in both directions; in other words, the flow direction of the medium is not restricted ； ④When fully open, the sealing surface is subject to less erosion by the working medium compared to a globe valve ； ⑤Its structural design is relatively simple, and it is easy to manufacture ； ⑥The structural length is relatively short. Disadvantages: ① It has large external dimensions and opening height, requiring a lot of space for installation ； ②During the opening and closing process, there is relative friction between the sealing surfaces, resulting in significant wear; in addition, high temperatures can easily cause scuffing ； ③Generally, gate valves have two sealing surfaces, which adds some difficulties to processing, grinding, and maintenance ； ④The opening and closing time is long. Butterfly valve A butterfly valve is a type of valve that uses a disc-shaped closing element to rotate back and forth by about 90° in order to open, close, or regulate the flow of fluid. Advantages: ① Simple structure, small size, light weight, low material consumption; not suitable for large-diameter valves ； ②Rapid opening and closing, low flow resistance ； ③It can be used in media containing suspended solid particles, and depending on the strength of the sealing surface, it can also be used for powdered and granular media. It can be used for two-way opening, closing, and adjustment in ventilation and dust removal pipelines, and is widely applied to gas pipes and water pipelines in metallurgy, light industry, power, and petrochemical systems. Disadvantages: ① The flow regulation range is limited; when it is set to 30%, the flow rate exceeds 95%. ②Due to the structure of butterfly valves and the limitations of their sealing materials, they are not suitable for use in high-temperature and high-pressure pipeline systems. The normal operating temperature is below 300°C, and the pressure rating is below PN40. ③Its sealing performance is inferior to that of ball valves and globe valves, so it is used in applications where high sealing requirements are not necessary. A ball valve is derived from a plug valve; its operating element is a sphere, and opening and closing are achieved by rotating this sphere 90° around the axis of the valve stem. 　　Ball valves are primarily used on pipelines to shut off, distribute, and change the direction of fluid flow; those designed with a V-shaped opening also possess excellent flow regulation capabilities. Advantages: ① It has the lowest flow resistance (actually 0) ； ②It does not get stuck during operation (without lubricant), allowing it to be reliably used in corrosive media and low-boiling-point liquids ； ③Complete sealing can be achieved over a wide range of pressures and temperatures ； ④Fast opening and closing can be achieved; the opening and closing time for certain structures is as low as 0.05–0.1 seconds, ensuring their suitability for use in automated systems on test benches. When the valve is opened and closed quickly, the operation is shock-free. ⑤The spherical closure element can automatically position itself at the boundary position ； ⑥The working medium is reliably sealed on both sides ； ⑦When in the fully open and fully closed positions, the sealing surfaces of the ball and the valve seat are separated from the medium, so the medium flowing through the valve at high speeds does not cause erosion of these sealing surfaces ； ⑧With its compact design and low weight, it can be considered the most suitable valve structure for low-temperature medium systems ； ⑨The valve body is symmetrical; especially in the case of welded valve bodies, it can withstand stresses from the pipes effectively ； ⑩The closing element can withstand the high pressure difference during closing. ⑾Ball valves with fully welded valve bodies can be buried directly underground, preventing the internal components of the valve from being corroded; their maximum service life can reach 30 years, making them the ideal valves for oil and gas pipelines. Disadvantages: ① Since the main material used for the seat seal ring in ball valves is polytetrafluoroethylene, it is inert to almost all chemicals. It also possesses a number of advantages, including a low friction coefficient, stable performance, resistance to aging, a wide operating temperature range, and excellent sealing properties. However, the physical properties of polytetrafluoroethylene, including its high coefficient of expansion, sensitivity to cold flow, and poor thermal conductivity, require that the design of the valve seat seal take these properties into account. Therefore, when the sealing material hardens, the reliability of the seal is compromised. Moreover, polytetrafluoroethylene has a low temperature resistance and can only be used at temperatures below 180°C. Above this temperature, the sealing material will age. When considering long-term use, it is generally not used at 120°C. ②Its regulating performance is somewhat inferior to that of globe valves, especially pneumatic valves (or electric valves). A globe valve is a type of valve in which the closing element (valve disc) moves along the center line of the valve seat. Based on this manner of movement of the valve disc, the change in the valve seat opening is directly proportional to the stroke of the valve disc. 　　Due to the relatively short opening and closing stroke of the valve stem in this type of valve, as well as its highly reliable shut-off function, and because the change in the valve seat orifice is proportional to the stroke of the valve disc, it is very suitable for regulating flow rate. 　　Therefore, this type of valve is very suitable for use in cutting off or regulating flow, as well as for throttling. Advantages: ① During opening and closing, the frictional force between the valve disc and the sealing surface of the valve body is lower than that of gate valves, thus it is more wear-resistant. ②The opening height is generally only 1/4 of the valve seat passage, so it is much smaller than gate valves ； ③Usually, there is only one sealing surface on the valve body and the valve disc, which makes the manufacturing process simpler and facilitates maintenance. ④Due to its filler, which is generally a mixture of asbestos and graphite, it has a high temperature resistance rating. Gauge valves are generally used for steam valves. Disadvantages: ① Due to the change in the flow direction of the medium as it passes through the valve, the minimum flow resistance of globe valves is also higher than that of most other types of valves ； ②Due to the long travel distance, its opening speed is slower than that of a ball valve. A plug valve is a rotary valve whose closing element is in the form of a plug; it operates by rotating 90° to connect or separate the passage in the plug from the passage in the valve body, thereby enabling opening or closing. The shape of the valve plug can be cylindrical or conical. Its principle is basically similar to that of a ball valve, which was developed from a plug valve. It is primarily used in oil field extraction, as well as in the petrochemical industry. Advantages: 　　Refer to ball valve. Disadvantages: 　　Refer to ball valve. Diaphragm valve – This type of valve features a flexible diaphragm or a composite diaphragm installed within the valve body and cover; the closing element is a compression device that is connected to the diaphragm. The valve seat can be wavy or the wall of a straight flow channel. Advantages: ① The control mechanism is separated from the medium flow path, which not only ensures the purity of the working medium but also prevents the medium in the pipelines from impacting the working components of the control mechanism. No separate sealing is required at the valve stem, unless such a measure is needed as a safety feature when dealing with harmful media ； ②Since the working medium comes into contact only with the diaphragm and the valve body, both of which can be made from a variety of different materials, this valve is capable of effectively controlling a wide range of working media, especially those that are chemically corrosive or contain suspended particles. ③It has a simple structure, consisting of only three components: the valve body, the diaphragm, and the valve cover assembly. This valve is easy to disassemble and repair quickly, and the diaphragm can be replaced on-site in a short time. Disadvantages: ①Due to the limitations imposed by the valve body lining process and diaphragm manufacturing process, it is difficult to produce large valve body linings as well as large diaphragms; therefore, diaphragms are not suitable for use in pipes with larger diameters, and are generally applied to pipelines with a diameter of DN≤200mm. ②Due to the limitations of the diaphragm material, diaphragm valves are suitable for low-pressure and low-temperature applications. Generally not exceeding 180℃ ； ③The adjustment performance is relatively poor, allowing adjustments only within a narrow range (it can be used for flow regulation when the valve is closed to 2/3 of its open position). A safety valve is a device used as an overpressure protection mechanism in pressurized containers, equipment, or pipelines. When the pressure inside a device, container, or pipeline rises above the allowable level, the valve opens automatically, allowing for complete discharge in order to prevent further increase in pressure within that device, container, or pipeline ； When the pressure drops to the specified value, the valve should close automatically and promptly, thereby ensuring the safe operation of the equipment, containers, or pipelines. Steam traps: When transporting media such as steam and compressed air, some condensate water is formed. To ensure the efficient operation and safety of the equipment, it is necessary to remove this unnecessary and harmful material promptly, so as to maintain optimal performance of the equipment. It has the following functions: ① It can quickly remove the condensed water that is generated ； ②Prevent steam leakage ； ③Remove air and other non-condensable gases. A pressure reducing valve is a valve that reduces the inlet pressure to a desired outlet pressure through regulation, and relies on the energy of the medium itself to maintain the outlet pressure stable automatically. Check valve  is also known as a backflow valve, non-return valve, backpressure valve, and one-way valve. These valves open and close automatically due to the force generated by the flow of the medium itself within the pipeline; they are a type of automatic valve. Check valves are used in piping systems; their main functions are to prevent the backflow of fluid, to stop pumps and driving motors from rotating in reverse, and to allow the release of fluid from containers. 　　Check valves can also be used in pipelines that supply auxiliary systems whose pressure may rise above the system pressure. They can mainly be divided into swing-type (rotating around the center of gravity) and lift-type (moving along the axis).

In our workshop, many butterfly valves fail to close properly even after being closed; for them to function correctly, the valve disc must be perpendicular to the pipeline. However, butterfly valves are also rarely used in steam systems, and moreover, there is a specific orientation for installing them.

Due to their poor sealing performance, butterfly valves are generally used in water or air systems, and are rarely used in steam systems

Due to its design, butterfly valves have poorer sealing performance compared to gate and globe valves, and they inherently allow some leakage; therefore they are used less frequently in steam pipelines. It is recommended to replace them immediately

In my opinion, the person on the fourth floor has already explained everything in great detail; I suggest the original poster study and use that as a reference.

Since the space available for butterfly valves is limited, they are used in this case. As it deals with large steam pipelines with diameters of over 800, gate valves are difficult to operate and also more expensive. Thank you

It’s normal for butterfly valves not to close tightly; that’s just how they perform. To seal it tightly, the valve needs to be replaced.

The steam pipeline with DN800 is indeed a bit too large. Under such circumstances, only butterfly valves can be used. To seal it tightly, the only option is to replace the valve. I have encountered this in my own design work as well: flanged butterfly valves take up more space than clamp-type ones.

It’s rare to see butterfly valves used on steam pipelines; our factory usually opts for gate valves. Butterfly valves have the problem of poor sealing, which ultimately leads to the need to replace them

Now, butterfly valves can also achieve bubble-level zero leakage in terms of sealing performance. Given the operating temperature of steam piping systems, soft-sealed butterfly valves cannot be used; instead, metal hard-sealed butterfly valves should be employed.

Our power plant’s turbines have also used 0.5-second fast-close butterfly valves, PN4.0, but they were imported from Italy； Jiangnan Shipbuilding is also good. Last edited by eastone on 2009-2-9 10:55.]

It is recommended to replace the butterfly valve with a gate valve or globe valve, as butterfly valves are not only directional but also prone to deformation due to force applied at their edges, resulting in inadequate sealing. Moreover, when replacing them, the flanges have to be cut off because the butterfly disc cannot return to its closed position, which is time-consuming and labor-intensive. So replace it while it can still be turned off

Which design firm designed this? They actually used butterfly valves for the steam lines! Anyone with basic knowledge of piping systems knows that although butterfly valves are small in size and easy to operate, their biggest drawback is their poor sealing performance. How can they be used in pipelines carrying high-temperature and high-pressure media such as steam? It’s only a matter of time before leaks occur. The solution is to use a gate valve; if the requirements for regulating steam consumption are not too strict, there is no need to use a globe valve. Although replacing the valve is costly and time-consuming, it is the best solution to ensure the proper operation of the pipeline in the future. This post was last edited by Xiaoxuxu on 2009-2-9 15:43]

In the systems I have worked with, butterfly valves are also used on some of the pipes. Pipes that use butterfly valves are usually larger in diameter, typically over 500 mm; I believe this is the main reason for choosing butterfly valves. Leaky butterfly valves are often the result of imperfect valve tuning during the first time it is put into operation; it is recommended to mark the mechanical position of the valve beforehand before carrying out the tuning. This can largely prevent the door from not closing properly or from closing too far.

Nowadays, butterfly valves are widely used in many steam pipelines, with eccentric butterfly valves being the most common type. If a valve does not close properly, it could be due to issues with its quality or problems during installation. Good eccentric butterfly valves do not experience such problems.

Butterfly valves generally have a specified installation direction – whether the fluid flows from left to right or in the opposite direction. It’s worth trying the other direction. I once had a client who kept saying that as soon as the butterfly valve was installed, it wouldn’t stay closed and there was internal leakage; the installation direction was correct according to the markings on the valve body. It was only later that we found out they were using it in a vacuum system, so the direction needed to be reversed, and it has been working fine ever since

In theory, butterfly valves can be closed tightly, but in practice, those made in China generally do not provide good sealing. If the space permits, it is best to replace it with a gate valve.

Why would steam pipes use disc valves? We use globe valves everywhere; even in electric versions, there are globe valves at both the inlet and outlet