Classification of steam traps

For a steam trap to function as a vapor barrier and water drain, it must be able to “identify” steam from condensed water. “The identification of steam and condensate water is based on three principles: density difference, temperature difference, and phase change. Thus, three types of steam traps were manufactured based on three principles, classified as mechanical, thermostatic, and thermodynamic types. I. Mechanical steam traps: Also known as float-type traps, these utilize the density difference between condensate water and steam; changes in the level of condensate water cause the float to rise or fall, which in turn drives the valve disc to open or close, thereby preventing steam from passing through while allowing water to be drained. Mechanical steam traps have a low degree of subcooling, are not affected by changes in operating pressure and temperature, allow for immediate drainage, prevent water from remaining in heating equipment, thereby enabling the equipment to achieve optimal heat exchange efficiency. Their maximum back pressure rating is 85%, and they offer excellent performance; hence they are the ideal steam traps for heating equipment used in manufacturing processes. Mechanical steam traps come in various types, including free-floating ball type, free semi-floating ball type, lever-ball type, inverted bucket type, and bell-type float type. 1. Free-floating ball steam trap: This type of steam trap has a simple structure; it contains only one finely ground stainless steel hollow ball, which serves both as the float and as the valve element. There are no vulnerable parts, so its service life is very long. The “Yinqiu” brand free-floating ball steam traps are equipped with an automatic air release mechanism, making them highly sensitive and capable of delivering high-quality performance. In a free-floating ball type steam trap, the valve seat is always below the liquid level, creating a water seal that prevents steam leakage and results in good energy-saving effects. The free-floating ball type steam trap drains water continuously, unaffected by temperature and operating pressure fluctuations. It can drain saturated-temperature condensate, preventing water from remaining in the heating equipment and thus enabling it to achieve optimal heat exchange efficiency; with a backpressure ratio of over 85%, it is one of the most ideal steam traps for heating equipment used in production processes. 2. Free semi-floating ball type steam trap: The free semi-floating ball type steam trap has only one semi-floating ball bucket as its moving component; this bucket is open at the bottom. It serves both as the opening and closing element as well as the sealing element. It can resist water hammer, has no vulnerable parts, does not suffer from failures, is durable, and prevents steam leakage. With a backpressure ratio of over 85%, it is capable of removing condensate at saturation temperature; the minimum subcooling degree is 0°C, and no water remains in the heating equipment, thereby enabling the heating equipment to achieve optimal heat exchange efficiency. 3. Lever float type steam trap: The basic characteristics of the lever float type steam trap are the same as those of the free float type; its internal structure features a float connected to a lever that drives the valve core, enabling the valve to open and close as the level of condensed water changes. The lever float-type steam trap utilizes dual valve seats to increase the condensate discharge volume, enabling a large discharge capacity to be achieved in a compact size. The lever float-type steam trap can handle a maximum drainage rate of 65 tons per hour, making it the ideal steam trap for large heating systems. 3. Inverted bucket type steam trap (bell float type): The inverted bucket type steam trap uses an inverted bucket as the level-sensitive element; the opening of this bucket faces downward, and it is connected to a lever that drives the valve core to open and close the valve. The inverted bucket type steam trap can discharge air, is not sensitive to water hammer, has a low subcooling degree, a maximum back pressure ratio of 85%, and enables intermittent drainage. II. Thermo-static type steam traps: These types of steam traps utilize the temperature difference between steam and condensed water to cause deformation or expansion of a temperature-sensitive element, which in turn drives the valve core to open and close the valve. Thermostatic steam traps have a relatively large degree of subcooling, typically ranging from 15 to 40 degrees. They can make use of part of the sensible heat contained in the condensed water; high-temperature condensed water always remains before the valve, preventing any steam leakage and resulting in significant energy savings. Thermostatic steam traps come in diaphragm type, bellows type, and bimetallic strip type. 1. Diaphragm steam trap: The main operating element of a diaphragm steam trap is a metal diaphragm; this diaphragm is filled with a liquid whose vaporization temperature is lower than the saturation temperature of water. There are two options for the opening temperature: 15°C and 30°C below the saturation temperature. The diaphragm-type steam trap has an extremely sensitive response, is not susceptible to freezing, is compact in size, can withstand high temperatures, and can be installed in any position. It features a back pressure ratio of over 70%, is capable of removing non-condensable gases, has a robust diaphragm that ensures a long service life, is easy to maintain, and has a wide range of applications. 2. Bellows-type steam trap: The valve element of a bellows-type steam trap is a stainless steel bellows filled with a liquid whose vaporization temperature is lower than the saturation temperature of water. The valve’s opening and closing are controlled in response to changes in steam temperature; it is equipped with adjustment bolts that allow the operating temperature to be adjusted as needed. Generally, the degree of subcooling ranges from 15°C to 40°C below the saturation temperature. It can handle back pressures of over 70%, is not susceptible to freezing, has a small size, can be installed in any location, is capable of removing non-condensable gases, and boasts a long service life. 3. Bimetallic sheet steam trap: The main component of a bimetallic sheet steam trap is the bimetallic sheet sensor, which deforms when heated as the steam temperature changes, thereby driving the valve core to open and close the valve. Bimetallic sheet-type steam traps are equipped with adjustment bolts that allow the operating temperature to be adjusted as needed. Generally, the degree of subcooling can be set between 15°C and 10°C below the saturation temperature. With a backpressure ratio of over 70%, they are capable of expelling non-condensable gases; they are not susceptible to freezing, have a small size, can withstand water hammer, and tolerate high pressures. They can be installed in any location. Bimetallic strips are prone to fatigue and require frequent adjustment. III. Thermodynamic type steam traps: These types of steam traps operate on the principle of phase change; by taking advantage of the differences in flow velocity and volume as steam and condensed water pass through, they create a pressure difference between the upper and lower parts of the valve element, which in turn drives the valve element to open or close. Since the operating power of thermodynamic steam traps comes from steam, there is significant steam waste. It has a simple structure, is resistant to water hammer, with a maximum back pressure of 50%; it generates noise, the valve disc operates frequently, and its service life is short. Thermodynamic steam traps include the thermodynamic type (disk type), pulse type, and orifice plate type. 1. Thermodynamic steam trap: A movable valve disc is contained within a thermodynamic steam trap, serving both as a sensing element and as the actuating component. Based on the thermodynamic principles related to the differences in flow velocity and volume as steam and condensate pass through, a pressure difference is created above and below the valve disc, which drives the valve disc to open or close the valve. **The standards specify that the acceptable leakage rate for qualified products is 3%-5%, the subcooling degree should be 8°C-15°C, there should be intermittent drainage, the maximum back pressure ratio is 50%, noise is present, the valve discs operate frequently, and their service life is short. 2. Disk-type steam-insulated trap: The working principle of the disk-type steam-insulated trap is the same as that of the thermodynamic trap; it features an additional outer shell surrounding the vapor chamber of the thermodynamic trap. The inner chamber of the shell is connected to the steam pipeline, and the steam within the pipeline itself is used to insulate the main steam chamber of the check valve. This prevents the temperature in the main steam chamber from dropping, maintains the steam pressure, and keeps the drain valve tightly closed. When condensate is generated in the pipeline, the shell of the steam trap cools down, and the steam trap begins to discharge water ； On a superheated steam pipeline, if no condensate is generated, the steam trap will not open, ensuring high operational efficiency. The valve body is made of alloy steel, while the valve core is made of cemented carbide. This valve can withstand a maximum temperature of 550°C; it is durable and has a long service life, making it an ideal steam trap for high-pressure, high-temperature, and superheated steam applications. 3. Pulsating steam trap: A pulsating steam trap has two orifice plates, and it adjusts its opening and closing based on changes in steam pressure. Even when the valve is completely closed, the inlet and outlet remain connected through the first and second small orifices, resulting in an incomplete closure state; as a result, steam continues to leak out, leading to high air leakage. This steam trap has a high operating frequency, suffers severe wear, and has a short lifespan. 4. Orifice plate type steam trap: The orifice plate type steam trap uses orifice plates with different pore sizes, selected based on the required drainage volume, in order to control the amount of steam drained. It has a simple structure; an inappropriate selection can lead to inadequate drainage or excessive steam leakage. It is not suitable for steam-using equipment in batch production or those with large fluctuations in condensate volume.

Classification and working principle of steam traps: Steam traps serve to prevent steam from entering while allowing water to be drained in steam heating systems. Choosing the appropriate steam trap can help steam heating equipment achieve its highest efficiency. To achieve the most optimal results, it is necessary to have a comprehensive understanding of the operating performance and characteristics of various types of steam traps. There are many types of steam traps, each with different properties. When selecting a steam trap, it is first necessary to ensure that its properties meet the requirements for optimal operation of steam heating equipment; only after that should other objective factors be considered. This approach ensures that the steam trap chosen is the right one and effective. A steam trap must be able to “identify” steam and condensate in order to function as a vapor barrier and drain. “The detection of steam and condensate is based on three principles: density difference, temperature difference, and phase change. The mechanical type, also known as the float type, takes advantage of the density difference between condensed water and steam; changes in the level of the condensed water cause the float to rise or fall, which in turn moves the valve disc open or closed in order to prevent steam from passing through while allowing water to be drained. Mechanical steam traps have a low degree of subcooling; they are not affected by changes in operating pressure and temperature. Water is discharged as soon as it appears, preventing water from remaining in the heating equipment, which allows the heating equipment to achieve optimal heat exchange efficiency. With a maximum back pressure ratio of 80% and high operating efficiency, it is the ideal steam trap for heating equipment in manufacturing processes. Mechanical steam traps can be further divided into types such as free-floating ball type, free semi-floating ball type, lever-ball type, and inverted bucket type. 1. Free-floating ball steam trap: The structure of the free-floating ball steam trap is simple; it contains only one moving component – a finely ground stainless steel hollow ball that serves both as a float and as the valve element. There are no vulnerable parts, so its service life is very long. The “YQ” series of steam traps are equipped with a Y-series automatic air discharge device, which is highly sensitive and capable of automatically discharging air, ensuring high performance in operation. When the equipment starts operating, the air in the pipes is expelled through the Y-series automatic air exhaust device. Low-temperature condensate water enters the drain valve; as the level of this condensate rises, the float rises as well, causing the valve to open and the condensate to be discharged rapidly. Steam then enters the equipment quickly, resulting in a rapid increase in its temperature. The temperature-sensitive fluid in the Y-series automatic air exhaust device expands, which causes the device to shut off. The steam trap begins to function properly; the float rises and falls with the level of condensed water, thereby preventing steam from passing through while allowing water to be drained. In a free-floating ball type steam trap, the valve seat is always below the liquid level, creating a water seal that prevents steam leakage and results in good energy-saving effects. The minimum operating pressure is 0.01 Mpa; within the range from 0.01 Mpa up to the maximum operating pressure, continuous drainage is possible without being affected by temperature or fluctuations in operating pressure. It can discharge saturated-temperature condensate water, with a minimum subcooling of 0°C; no water remains in the heating equipment, which enables it to achieve optimal heat exchange efficiency. With a backpressure ratio of over 85%, it is one of the most ideal steam traps for heating equipment in manufacturing processes. 2. Automatic free-floating ball steam trap: The automatic free-floating ball steam trap has only one semi-floating ball chamber as the moving component; this chamber is open at the bottom, and it serves both as the opening/closing element and as the sealing element. The entire sphere can be sealed, offering a long service life; it is resistant to water hammer, has no vulnerable components, operates without failures, is durable, and prevents steam leakage. With a backpressure ratio of over 80%, it is capable of discharging condensed water at saturation temperature; the minimum subcooling degree is 0°C, and no water remains in the heating equipment, thereby enabling the heating equipment to achieve optimal heat exchange efficiency. When the device is first started, the air and low-temperature condensate in the pipeline enter the drain valve through the discharge tube. The bimetallic disc inside the valve pushes the ball apart, opening the valve and allowing the air and low-temperature condensate to be discharged rapidly. When steam enters the ball tank, the tank generates an upward buoyant force; at the same time, the temperature inside the valve rises, causing the bimetallic strip in the discharge element to contract. As a result, the ball tank drifts toward the valve opening, and the valve closes. When the steam in the drum turns into condensed water, the drum loses its buoyancy and sinks; the valve opens, allowing the condensed water to be discharged rapidly. When steam enters the drum again, the valve closes, resulting in intermittent and continuous operation. 3. Bell-type float steam trap: The basic characteristics of the bell-type float steam trap are the same as those of the free-floating ball type; its internal structure features a float connected to a lever that operates the valve core, allowing the valve to open and close as the level of condensed water changes. The lever float type steam trap utilizes dual valve seats to increase the condensate discharge volume, resulting in a compact design with high discharge capacity; its maximum steam discharge rate can reach 100 tons per hour, making it the ideal steam trap for large heating systems. 4. Bell-type float (upside-down bucket) steam trap: The interior of a bell-type float (upside-down bucket) steam trap consists of an upside-down bucket that serves as the level sensor; the opening of this bucket faces downward, and it is connected to a lever that drives the valve core to open and close the valve. The inverted bucket type steam trap can discharge air, is not sensitive to water hammer, and has good anti-fouling properties. It has a low supercooling degree, with a steam leakage rate of less than 3% and a maximum back pressure ratio of 75%; it features numerous connecting parts, and its sensitivity is inferior to that of a free-floating ball type steam trap. Since the inverted bucket type steam trap closes due to the upward buoyancy of steam, it is not suitable for use when the operating pressure difference is less than 0.1 MPa. When the device is first started, air and low-temperature condensate in the pipeline enter the trap. The inverted bucket drops due to its own weight, and the lever connected to it drives the valve core to open, allowing the air and low-temperature condensate to be discharged rapidly. When steam enters the inverted bucket, the steam in the bucket generates an upward buoyant force, causing the bucket to rise; this in turn moves the connecting lever and closes the valve. The inverted bucket has a small hole in it; as some of the steam escapes through this hole, the remaining steam turns into condensed water. As a result, the inverted bucket loses its buoyancy and sinks due to its own weight. The lever connected to the inverted bucket then causes the valve core to open, allowing for continuous drainage in a cyclic manner. 5. Thermodynamic steam trap: The thermodynamic steam trap features two separate valve chambers, which are connected to each other by two stainless steel tubes. It is a combination of a float-type and an inverted bucket-type steam trap. Its structure is advanced and rational; it is able to promptly discharge the condensate formed when superheated steam disappears under conditions of overheating, high pressure, and low load, effectively preventing the leakage of superheated steam and ensuring high performance. The maximum allowable temperature is 600°C; the valve body is made of all stainless steel, while the valve seat is made of cemented carbide steel, ensuring a long service life. It is a specialized steam trap for superheated steam, and it holds two **patents, filling a gap in domestic technology. When the condensate enters the lower valve chamber, the float ball of the auxiliary valve rises as the liquid level increases, and the float ball seals off the steam inlet hole. The condensate rises to the main valve chamber through the inlet conduit; the hanging bucket drops due to its own weight, which in turn causes the valve core to open the main valve and allow the condensate to be discharged. When the condensate level in the secondary valve chamber drops, the float descends along with the level, and the secondary valve opens. Steam enters the inverted bucket inside the upper main valve chamber through the steam inlet pipe; the inverted bucket generates an upward buoyant force, which drives the valve core to close the main valve. When the condensate level in the secondary valve chamber rises again, the next cycle begins, with intermittent drainage.

Serial Number Type Item Mechanical Type Thermo-static Type Thermo-dynamic Type 1 Working Principle Utilizes the density difference between steam and condensate water Utilizes the temperature difference between steam and condensate water Utilizes the phase change of steam and condensate water 2 Drainage Temperature (Subcooling) Saturated (~0°C) Subcooled water (10–30°C) Subcooled water (6–80°C) 3 Steam Leakage Rate 2–3% 1% 2–3% 4 Allowable Back Pressure 0.8P1 0.5P1 0.5P1–0.25P1 5 Size Large Smaller Minimum 6 Installation Direction Horizontal Horizontal, Vertical Horizontal, Vertical 7 Performance Reliable, short operation interval Relatively reliable, longer operation interval Relatively reliable, longer operation interval 8 Service Life Long Shorter Shortest 9 Types Float type (linkage float type, free float type) Bucket type (floating bucket type, inverted bucket type) Bimetallic type, diaphragm type, bellows type Orifice plate type, pulse type, nozzle type 10 Price (DN≤50) 600–1500 yuan 300–500 yuan 200–500 yuan

Thermosiphon valves can be divided into inverted bucket type thermosiphon valves, lever float type thermosiphon valves, free float type thermosiphon valves, disc bimetallic type thermosiphon valves, and disk type thermosiphon valves.