What are the characteristics of inverted bucket steam traps and diaphragm steam traps? How to choose the model?

The diaphragm-type steam trap is of the thermostatic type; it operates by utilizing the temperature difference between steam and condensed water to activate its temperature-sensitive element, thereby controlling the opening and closing of the valve. So in the diaphragm type, some of the heat from the condensate water is reused. Inverted bucket steam traps are mechanical in nature; they represent the earliest generation of mechanical steam traps. Nowadays, free-floating ball type traps are used instead. If the equipment does not allow water to accumulate, then hydrostatic methods cannot be used. The free-floating ball type is quite versatile. I’ve also learned all of this from books; I don’t have any practical experience, so this is just for reference.

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This post was last edited by Qingse Nianhua on 2019-4-30 at 15:49. Working principle of inverted barrel steam traps: The structure of the DT580 series inverted barrel steam traps consists of an inverted float inside the valve body, which is connected to a lever; the upward and downward movement of the float causes the lever attached to it to move, thereby controlling the valve element fixed to the lever to move closer to or away from the valve seat nozzle, and thus controlling the opening degree and operation of the steam trap. The inverted buoy is a cylindrical stainless steel barrel that is sealed at the top and open at the bottom. When the steam system is started, condensate enters the trap through the drum and forms a water seal outside the drum. The weight of the bucket causes the valve core to open, allowing the condensed water to be discharged through the valve nozzle located at the top. The vent hole on the bucket is used to remove the air that accumulates at the top of the steam trap. When steam enters the inverted tank of the steam trap from below, it accumulates at the top of the inverted tank, thereby generating buoyancy on the tank. When the buoyant force is greater than the weight of the barrel, the inverted barrel rises due to the buoyant force of the steam, which in turn causes the linkage to rise as well, reducing the opening degree of the steam trap until it is closed. When the steam inside the tank condenses due to the heat absorbed by the condensation water surrounding it, a very small amount of steam escapes through the vent hole at the top of the tank and reaches the top of the valve body outside the tank. As a result, the weight of the barrel is greater than the buoyant force; the weight of the hanging barrel pulls the valve core, opening the steam trap. The cycle starts over. As can be seen above, the operating principle of the inverted bucket steam trap is that it primarily senses the difference in density between steam and condensate, using a float to operate the opening and closing of the trap. The Watt inverted barrel steam trap utilizes the lever principle without fixed fulcrums; this mechanism does not wear out or get stuck. The presence of a lever makes the operation of the inverted barrel more responsive, and it also allows the steam trap to open under higher pressure differences. At the same time, its effective utilization can balance the unbalanced forces generated by larger valve seats, thereby increasing the flow capacity of the steam trap. The Watt inverted barrel steam trap discharges condensate at the saturation temperature, ensuring very timely drainage; it is therefore one of the best choices for steam traps in various types of heat exchangers.

This post was last edited by Wat Energy Saving on 2019-4-29 at 16:30. Characteristics and application ranges of membrane-type bellows traps and bimetallic traps. By Zhong Yuyu from the Technical Department of Hangzhou Wat Energy Saving Engineering Co., Ltd. The operating principle of pressure-balanced bellows thermostatic steam traps is that the liquid filling inside the bronze or stainless steel bellows in these traps is alcohol or ether, which serves as the heat transfer medium. The thermal expansion and evaporation of the heat medium within the diaphragm of the steam trap drive the opening and closing of its associated steam trap valve element for regulation. At room temperature, the diaphragm of the steam trap contracts, causing the trap to open fully. Upon startup, cold condensate and air are freely discharged through the trap. When condensate water approaching the saturation temperature reaches the steam trap, the thermal expansion and evaporation of the heat medium inside the bellows of the steam trap cause the valve element to gradually close the steam trap. The steam trap opens a second time only when the temperature of the condensed water inside it drops to the set opening temperature. The Watt BW11 bellows-type steam trap features a small size and light weight, but the bellows themselves have many shortcomings in terms of manufacturing and design. Compared to bimetallic types, it can open automatically, unaffected by pressure changes. Due to their fragility, bellows have poor resistance to water hammer. When used with superheated steam, it is prone to cracking. Bellows are prone to abnormal expansion, making it difficult to ensure coaxial alignment between the valve and the seat, which leads to steam leakage. It is difficult to ensure the airtightness of the bellows; therefore, the amount of liquid sealed inside often decreases. The operating principle of bimetallic steam traps is that two metal plates bonded together and having significant differences in thermal expansion bend when heated, thereby driving the connected valve element to open or close for regulation. At normal temperature, the steam trap is fully open; the valve core and seat remain in their maximum open position, allowing for the rapid and continuous discharge of large amounts of low-temperature condensate and air when the steam system is started up. It can speed up the device startup time. Once the discharge of low-temperature condensate is completed, the temperature of the condensate begins to rise. Bending begins with the bimetallic plate having a low coefficient of expansion, and the bending force reaches its maximum before the condensate reaches its saturation temperature, at which point the drain valve closes. Until the temperature drops due to the heat released by the condensate water, the bimetallic plate cools down again, the bending force decreases, and the drainage is opened once more. The closing force of the bimetallic element can be adjusted from outside the steam trap. This structure is simple to adjust during operation, allowing the temperature of the condensed water discharged to be brought close to or below the saturation temperature, and it can also be adjusted to a continuous discharge mode. Compared to bellows-diaphragm type steam traps, the Watt SM bimetallic steam trap has the following features and advantages: it is highly durable and has a long service life. Resistant to impact and water hammer; can be used with superheated steam and saturated steam; adjustable, allowing for efficient utilization of heat. It can be adjusted to a continuous discharge mode in different situations, which can increase the drainage rate. The greatest advantage of bimetallic steam traps is their high strength, as well as their ability to open and close smoothly in response to changes in the temperature of the condensate water. When steam equipment is used to heat liquid substances at atmospheric pressure without needing to reach a boiling temperature of 100°C, the sensible heat contained in the condensate water can be fully utilized. Additionally, from an energy-saving perspective, it is very important to make full use of sensible heat; this allows the condensate to remain in the equipment for a considerable amount of time. During this period, after the sensible heat is effectively utilized, it is then discharged, reducing the temperature of the condensate water. The so-called temperature-regulating steam trap is not classified based on its operating principle, but is named according to the purpose for which it is used. When heating or drying objects, steam is often used as a heat source, while indirect heating is widely applied in various devices such as heat exchangers. Heat exchangers primarily utilize the latent heat of steam; therefore, efforts are being made to improve the operational efficiency and thermal efficiency of these steam-based devices that use indirect heating. Starting from these two points, once the latent heat of steam is utilized to cause condensation into condensed water, the sensible heat contained in that condensed water needs to be removed as quickly as possible; therefore, steam traps are used. It must then have the ability to quickly remove condensed water. There are also many applications where it is necessary to heat the medium to temperatures below 100°C; for example, in the insulation of heavy oil, bimetallic thermostatic valves prove to be very useful. When making use of the sensible heat of more condensate water, the steam trap functions to control the temperature of the medium being heated, thus acting as a temperature control valve.

How to choose a steam trap: We believe that there is no universal trap suitable for all applications; rather, the steam trap must be selected based on the specific requirements of each application. The normal operating pressure and temperature, discharge volume, energy-saving efficiency, service life, and cost of a steam trap are all factors to be considered comprehensively when selecting one. In terms of working principle, the Watt DT inverted bucket steam trap can be used in almost every application, but this is not always the case in practice. Bimetallic steam traps are commonly installed on steam mains with limited installation space, while inverted bucket traps are unsuitable for applications that require subcooled drainage to absorb the sensible heat in the condensate. The simplicity of steam trap technology leads customers to often attempt to meet all requirements with a single type of trap, such as using only inverted drum traps. However, the varying application requirements and device performances mean that a single steam trap cannot meet all applications, as this would otherwise affect the efficiency of the entire system. Therefore, to ensure the proper selection of steam traps, the following factors should be considered: application area, maximum load, system pressure, type of equipment, minimum load, material used, safety factor, back pressure, connection method, steam temperature, whether temperature control is available, whether condensate is recycled, pressure difference, the elevation rise after the trap, and whether an exhaust device is installed. For instant heat exchange units, mechanical steam traps should be chosen; for applications with large fluctuations in steam load, lever float-type steam traps are preferred. For instant heat exchange units and volumetric heat exchangers with relatively stable steam loads, inverted bucket steam traps are more suitable. For insulated heat exchangers, inverted drum steam traps and bimetallic steam traps are the preferred choices. For intermittent heating, lever float steam traps are preferred; for continuous flat-plate heaters, inverted drum steam traps are the first choice. Inverted drum steam traps are also used in vulcanizing machines. For steam pipes, cylinder heads, steam-water separators, and steam traps at the ends of pipes, inverted drum steam traps and disc steam traps are the preferred options. Different types of steam traps can meet specific industrial and application requirements. Stainless steel steam traps designed specifically for clean steam systems can be used in industries such as food and pharmaceuticals. Certain types of steam traps can meet the requirements of specific applications, such as the Watt BW11S trace heating line steam trap. Regarding the material of the check valve, the valve body material must be specified for different application systems; there are various options such as cast iron/ductile iron/carbon steel/alloy steel/stainless steel (including 316L). The connection method for steam traps should be selected based on system pressure and customer preferences. The following connection methods are available for selection – threaded connections: BSP/NPT; sleeve welding, butt welding, flanges, pipe fittings, and sanitary clips for cleanroom systems. Will the ambient temperature drop below zero? Freezing can cause some damage to steam traps, especially those made of brass or cast iron. We know that there are certain types of steam traps, such as thermostatic traps, which not only prevent steam waste but also reduce the discharge temperature of condensate, thereby facilitating the recovery of sensible heat from the process condensate. This type of steam trap is mainly used in some non-critical equipment, such as heat tracing pipes and overhe sized heating coils. Sensible heat can be absorbed or used to heat another process. Alternatively, a cooling tube can be installed in front of the steam trap to ensure an accurate condensate discharge temperature. Any device should be designed with water hammer avoidance in mind. In the event that it occurs, some types of steam traps have better water hammer resistance than other types of steam traps. Generally, steam traps are prone to being affected by entrained particles or pipe impurities. Therefore, the advantages of the DT580 inverted bucket steam trap with its built-in filter are quite evident. Since the discharge orifice of a steam trap is relatively small and prone to being blocked by impurities or pipe slag, it is recommended that a filter be installed upstream of any type of steam trap.

The selection of a steam trap depends mainly on the operating pressure, temperature, and flow rate; as long as it can meet the required safe flow rate under specific pressure and temperature conditions. As for the difference between the diaphragm box type and the inverted bucket type, in terms of Miyawaki’s products, the diaphragm box type belongs to the thermostatic category; it operates based on the temperature difference between steam and condensed water, and its operation is continuous. ＜Advantages＞ 1. Operation is triggered by the temperature of the condensate water, with no issues caused by steam or air. It can also be used directly as an exhaust valve. 2. It discharges condensate below the saturation temperature, prevents steam leakage during operation, and requires no temperature adjustment during installation. 3. There are fewer cases of steam loss due to heat release. 4. Compact box design, low cost, and easy to maintain. ＜Notes＞ 1. Due to the characteristics of the diaphragm box, it cannot be used above 235°C. The upside-down bucket type belongs to the mechanical category; it relies primarily on the difference in specific gravity between steam and condensed water, and its operating principle is indirect. ＜Advantages＞ 1. Strong resistance to impurities: the filter screen is located at the lower part of the valve body, while the valve disc mechanism is at the very top, making it less susceptible to the influence of impurities in the pipeline. 2. By using an open-type float, it is less likely to be damaged by the sudden impact forces resulting from water hammer effects compared to a spherical float. 3. The interior of the body features a U-shaped passage design, and the valve disc is arranged at the upper part of the valve body to form a dual steam-water separation mechanism, ensuring no steam leakage when condensate is discharged. 4. No need to install a thermostatic drain valve (there is a drainage design above the bucket). 5. Easy to maintain and manage (modular internal components are installed on the valve cover). ＜Precautions＞ 1. A certain amount of condensate water must remain inside the valve body; if this amount decreases significantly, the re-evaporation of the condensate water due to high temperatures will prevent the inverted bucket from rising, resulting in steam leakage. 2. The heat release from the ontology results in steam loss.