Technical requirements for the selection, use, and maintenance of steam traps
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Technical Requirements for the Selection, Use, and Maintenance of Steam Traps Chapter 1: Related Concepts Article 1: Definition of Steam Traps A steam trap, also known as a steam and water separator, is an automatic valve that can automatically remove condensate water, air, and other non-condensable gases from steam pipes and equipment, while preventing steam leakage. It is an energy-saving device that helps maintain the desired temperature and heat levels in various heating systems. Article 2 Relevant Concepts 1. Pressure (1) Maximum allowable pressure: The highest pressure that the body of a steam trap can withstand over an extended period at a given temperature. (2) Operating pressure: The pressure at the inlet of the steam trap under operating conditions. (3) Back pressure: The pressure at the outlet of the steam trap under operating conditions. (4) Pressure difference: The difference between the operating pressure and the operating backpressure. (5) Back pressure ratio: The percentage of the operating back pressure or the maximum operating back pressure to the valve’s operating pressure, when the steam trap can function properly at that operating pressure and continuously discharge condensate. Average backpressure percentage = Operating backpressure/Operating pressure x 100%. Maximum backpressure percentage = Maximum operating backpressure/Operating pressure x 100%. 2. Temperature: (1) Maximum allowable temperature: The highest temperature that the steam trap body can withstand consistently at a given pressure. (2) Operating temperature: The temperature at the inlet of the steam trap under operating conditions. (3) Supercooling: The absolute value of the difference between the temperature of the condensate water and the saturated temperature at the corresponding pressure. 3. Steam (1) Saturated steam: Saturated water in a sealed container; if heat is applied from the outside, it will continue to evaporate and decrease in quantity, eventually disappearing entirely to turn the container into steam. At this point, the steam is wet saturated steam. If heating continues, the misty water vapor in it also evaporates completely, resulting in steam that contains no water at all, which is known as dry saturated steam. Wet saturated steam and dry saturated steam are collectively referred to as saturated steam. (2) Superheated steam: Dry saturated steam is reheated, and its temperature rises to become superheated steam. (3) Superheat: The difference between the temperature of superheated steam and the saturation temperature corresponding to that steam pressure. (4) Steam leakage rate: At a certain operating pressure with the operating back pressure at atmospheric pressure, it is the percentage of the valve’s actual capacity to discharge heat-condensed water, which is within the range of 3% to 20% of its maximum capacity to discharge such water; it is calculated as the ratio of the weight of steam that leaks through the valve to the weight of heat-condensed water actually discharged during the same period of time. 4. The capacity of a steam trap refers to its ability to discharge hot condensed water. It is generally calculated based on the maximum emission rate of Kg/h per hour. 5. Safety factor refers to the safety margin provided to ensure the proper operation of the steam trap, even when there is a discrepancy between the actual amount of condensate produced by the steam-using equipment and the capacity specified for the trap. (See Table 2, “Recommended Safety Factor Table for Steam Traps”) Chapter 2: Classification of Steam Traps and Applicable Operating Conditions Article 3: Steam traps are classified into three types: mechanical traps, thermodynamic traps, and thermoelectric traps. Article 4: The types, working principles, performance characteristics, and applicable operating conditions of different types of steam traps are shown in Table 1, \"Classification and Characteristics of Steam Traps\". Table 1: Classification and Characteristics of Steam Trap Types. Trap Type, Trap Design, Operating Principle, Performance Features, Applicable Applications, Remarks: Mechanical types such as inverted bucket type and float type – operate by taking advantage of the density difference between steam and condensed water; the amount of condensed water is sufficient to activate the trap, eliminating the need to wait for the temperature of the condensed water to drop. These traps respond quickly, offer high accuracy and reliability, and typically have a service life of over 18,000 hours. It has a high drainage capacity and high back pressure, with the back pressure ratio reaching over 80%; it can start operating at a operating pressure of 0.01 MPa. The downside is its large size. Heating equipment and heat exchange equipment suitable for main units, as well as for environments with high temperatures, high pressures, and large flow rates. The recovery device for the closed-loop condensate circuit is considered the best choice. Thermostatic bimetallic disc, bellows, and diaphragm types open and close by utilizing the temperature difference between steam and condensed water. They do not rely directly on the movement of condensed water; instead, temperature serves as the driving factor. As a result, their response is slow, their operation cycle is long, they consume more energy, but they have a strong drainage capacity. The service life is generally within 8,000 hours. Small size, low displacement, low back pressure, with a back pressure ratio of 30–40%. Suitable for insulated heating pipelines and areas where condensate is not recovered. If this product is chosen for the condensate recovery system, a recovery pump and a recovery tank must be added; whereas choosing a mechanical type eliminates the need for such equipment, reducing investment costs. Thermodynamic types such as disc, pulse, labyrinth, and orifice types operate by taking advantage of the differences in the thermodynamic properties of steam and condensate water to open and close. They are compact in size and have a low flow rate; their reliability is lower than that of mechanical traps. The back pressure of the steam is limited to less than 50% of the inlet pressure, and their service life is generally within 8,000 hours. Due to the frequent operation of this type of steam trap, it consumes a lot of energy and is not energy-efficient; as such, it was classified as a product to be phased out in the 11th round of evaluations for energy-saving products, and its use is not recommended. Chapter 3: Technical Requirements for the Selection of Steam Traps Article 5: Selection criteria for steam traps 1. Select the appropriate type of trap based on the equipment being used (such as the equipment itself, steam pipelines, heating systems, etc.). 2. Meet the maximum operating pressure and temperature of the equipment being used. 3. Meet the operating pressure difference range of the equipment to be used. 4. Meet the displacement required for the equipment to be used. 5. The valve body and internal component materials meet the requirements of the equipment’s operating processes. 6. Complies with the connection dimensions, methods, and standards for the equipment to be used. Article 6 Principles for selecting steam traps 1. If it is required that the equipment heat up as quickly as possible, that the heating temperature be strictly controlled, and that no condensed water accumulate within the heating equipment, then a mechanical trap capable of discharging saturated water should be selected. 2. Thermal static steam traps should be selected when the heating equipment has a large heating surface area, rapid heating is not required, the heating temperature does not need to be tightly controlled, and it is acceptable for a certain amount of condensed water to accumulate. 3. Consider a safety factor when selecting, based on the drainage capacity of the equipment being used. 4. Determine the drainage volume of the steam trap based on the pressure difference. Article 7: Technical parameters to be considered in the selection of drain valves 1. Condensate load and load characteristics of the steam-using equipment. Steam-using equipment is divided into continuous production discharge equipment and intermittent production discharge equipment. In operation, continuous production units experience minor load fluctuations, resulting in relatively stable amounts of condensed water emitted ； Intermittent production units are started many times a day, and each time they are started, large amounts of air and condensed water need to be removed. When selecting, the load characteristics of the steam-using equipment must be taken into account. 2. Steam conditions: namely, the maximum operating pressure, maximum operating temperature, range of operating pressure differences, and whether the steam is saturated or superheated under actual operating conditions. 3. Capacity of the steam trap: The actual capacity of the steam trap must be ≥ the amount of condensate generated × safety factor. 4. Selection of the safety factor: For the reasons listed below, it is necessary to take into account a safety factor when selecting a steam trap. The selection of the safety factor can be referred to in Table 2, \"Recommended Safety Factor Table for Steam Traps\", as well as the selection guidelines provided by the trap manufacturers. (1) The capacity of a steam trap refers to the amount of condensate that can be discharged continuously, whereas almost all steam traps discharge in intermittent bursts during actual operation. (2) The capacity of steam-using equipment refers to the amount of condensate generated when the equipment is operating normally; however, at the beginning of operation, the amount of condensate produced is much higher than during normal operation. (3) Some heating equipment operates in intermittent mode, resulting in a large amount of condensate water at the beginning of each startup. (4) The condensate from the equipment pipelines must be pumped back to the return pipeline using head pressure. (5) The failure of individual steam traps to prevent leakage causes the back pressure at the rear end of those traps to increase, resulting in a reduced drainage capacity of the steam traps. Table 2: Recommended Safety Factor Table for Steam Trapss No. Usage Condition of Heating System Safety Factor 1 Traps at the bottom of steam distribution cylinders: Condensate can be quickly removed under various pressures 32 Traps on the main steam pipelines: Traps should be installed every 30–50 meters, as well as in front of control valves, at pipeline bends, and at the ends of the main pipelines 33 Traps on branch pipelines: Traps should be installed in front of various control valves where the length of the branch pipeline is 5 meters or more 34 Traps on steam-water separators: Traps should be installed at the bottom of the steam-water separator 85 Traps on heat tracing pipes: With a typical diameter of DN15, traps should be installed every 50 meters or less 26 Single-coil heating (liquid): Rapid heating required 3 No rapid heating required 27 Multi-coil parallel heating (liquid) 28 For flash tanks: The tank diameter must ensure that the velocity of the secondary steam is U≤5 m/s; an air vent valve should also be installed at the top of the tank 89 For jacketed reactors: An air vent valve must be installed above the jacketed reactor 310 For shell-and-tube heat exchangers: 2 When pressure remains constant 3 When pressure is adjustable: ≤0.1 MPa, 20.1–0.2 MPa, 2 >0.2 MPa 311 For single-effect and multi-effect evaporators: If condensate production is >20 t/h, 3 If condensate production is <20 t/h, 212 For fan coils and air heaters: Constant pressure, 2 Variable pressure: 0–0.1 MPa, 2 Variable pressure: 0.1–0.2 MPa, 2 Variable pressure: >0.2 MPa, 313 For rotary drying cylinders: Surface linear velocity U≤30 m/s, 5 Surface linear velocity U≤80 m/s, 8 Surface linear velocity U≤100 m/s, 10 5. Backpressure conditions: Whether the outlet of the steam trap leads to the atmosphere or is connected to the condensate recovery pipeline is an important factor in selecting the appropriate trap. The allowable backpressure ratios for different types of steam traps are shown in Table 3. Table 3: Backpressure ratios of different types of steam traps. The maximum backpressure ratio for various types of traps is as follows: for mechanical types, it should be no less than 80%; for thermostatic types, it should be no less than 30%; for thermodynamic types, it should be no less than 50%, with pulse-type traps requiring a value of no less than 25%. 6. Valve body material: The pressure and temperature of the steam in use are important factors in determining the material used for the valve body of a steam trap. The principles for selecting the valve body material are listed in Table 4, “Table of Valve Body Material Selections”. Table 4: Selection Table for Valve Body Materials. Working pressure in MPa, working temperature in °C, valve body material
(4) When the curved expansion elbow is installed horizontally or upward, its front end should be set as the drainage point； When installed downward, place the lowest part of the elbow as the drainage point. 6. Method of connecting a drain pipe to a steam transmission pipeline (as shown in Figure 3): Install a tee fitting of the same diameter on the steam transmission pipe to serve as a \"water storage chamber\"; connect a drain pipe to the lower part of this fitting, and then install a steam trap. If the main steam pipe tends to produce a large amount of condensate, it is best to install a steam-water separator first, connect a drain pipe below it, and then install a steam trap (as shown in Figure 3d). To prevent impurities that flow into the water storage chamber along with the condensate from entering the steam trap, the drain pipe can be connected at a height of 25~50 mm above the bottom of the condensate storage fitting, while the discharge pipe and discharge valve are installed at the bottom of that fitting. Figure 3 7: Drainage of condensate from buried steam pipes. Generally, a drain valve is installed at the lowest point of the steam pipe. When it is not possible to install the steam trap at the lowest point due to constraints such as the installation location, a return fitting should first be installed at the lowest point to lift the water to the surface, after which the steam trap can be installed. Article 10: Installation of steam traps on steam-using equipment 1. The drainage point should be located at the very bottom of the steam vessel, and the steam trap should be installed at a position even lower than that of the drainage point, and it should be assembled together with a bypass pipe (as shown in Figure 4). Figure 4 2: The bypass pipe should be installed horizontally; if horizontal installation is not possible, it is best to install it in an upward or downward direction. When it is not possible to install a bypass pipe due to constraints, a steam trap with a bypass can be installed (as shown in Figure 5). Figure 5 3: Steam traps should be installed in locations that are easy to maintain, as close as possible to the steam-using equipment, in order to reduce steam resistance. It is advisable to have a supercooled pipe without insulation of at least 1 meter in length in front of a thermostatic steam trap. 4. When the process conditions do not permit the installation of a steam trap at the lowest point of the steam-using equipment, a return water connection should be installed at that lowest point to lift the condensate before installing the steam trap, thereby avoiding steam blockage. 5. Steam traps cannot be installed in series, but two or more steam traps with appropriate capacity can be installed in parallel, or one can be used while the other serves as a backup (as shown in Figure 6). Figure 6: 6. If the condensate downstream of the steam trap is to be recovered, pipes at different pressure levels should be recovered separately. A check valve must be installed on the drain pipe of the steam trap before it enters the recovery main, and it should be connected to the main from above the recovery main in order to reduce back pressure and prevent backflow. 7. Examples of the installation of steam-using equipment and pipeline steam traps (as shown in Figure 7). Figure 7. 8. In cases involving several small devices in the same unit or heating pipelines, it is common to collect the condensate water and install steam traps in a central location to discharge this water (as shown in Figure 8). Figure 8-9: In situations where steam-using equipment is used together, steam traps must in principle be installed either individually or in parallel; it is not permissible to connect the various devices in series and use a single steam trap of large capacity to remove the condensate (as shown in Figure 9). Figure 9 Article 11: Issues to be noted in the installation, use, and maintenance of steam traps 1. Before installing the steam trap, clean the pipes by blowing them with steam or compressed air; after cleaning, clean all filters before installing the steam trap. 2. When draining water from equipment such as steam main pipes or large heat exchangers, a shut-off valve should be installed in front of the drain valve; this ensures that the system can continue to operate without interruption when the drain valve needs to be repaired. When there is a bypass in front of the steam trap, a shut-off valve needs to be installed on the drainage line of the steam trap. Cut-off valves should especially be installed when the pressure in the main drainage pipe is high. 3. Bypassing is not recommended, as it can impair the function of the steam trap when in use. If continuous operation is necessary, two steam traps can be connected in parallel, one in use and one as a backup. 4. If only one union is used, it should be applied on the discharge side of the steam trap. If two are used, horizontal and vertical series connections should be avoided. The best installation method is the right-angled type. 5. For steam traps of the same diameter and type, the inlet and outlet connections should be of equal length, which simplifies maintenance work. Steam traps with connectors of the same length and single-end unions can be stored in a warehouse. When the steam trap needs repair, simply disconnect the union, remove the valve, install a replacement steam trap, and tighten the union. Then the drain valve was repaired, fitted with connectors and a single-end union, and returned to the warehouse. 6. If there are relevant regulations or poor working conditions, a filter can be installed in front of the steam trap to ensure its proper operation. Some steam traps come with built-in filters. If the filter is equipped with a drain valve, the steam supply valve should be closed first before opening that valve. The condensed water inside the drain valve is flushed back to clean the filter screen. Open the steam valve slowly again. 7. Installing a waste pipe can effectively collect scale and sand, thereby reducing erosion on the elbows. The waste pipe should be cleaned regularly. 8. Siphon installations require a water seal, and a check valve must be installed inside or in front of the steam trap (except for differential pressure controllers). The size of the siphon pipe should be one size smaller than the nominal diameter of the steam trap, but it must not be smaller than DN15. 9. In cases where condensed water needs to be lifted and discharged, do not choose a size that is too large for the vertical lifting pipe; it should be one size smaller than what is normal for such situations. 10. If there is no shut-off valve on the outlet pipeline, it is necessary to consider installing a check valve. Installing a check valve in the discharge pipeline can prevent backflow and isolate the steam trap when the test valve is opened ； Installing check valves on the inlet pipelines can prevent the destruction of the water seal in cases of sudden pressure drops, or when the position of the inverted drum-type trap is above the water collection point. 11. In situations where the pressure at the inlet of the main steam trap may drop below the outlet pressure, especially when cold air is present, it is necessary to install a safety drain trap. One such situation is that when using a pressure-regulating heating coil, it is necessary to discharge condensate water into the rising return water pipe. When the discharge capacity of the main drain valve is insufficient and the condensate level rises to a safe discharge level, the safety drain valve comes into operation, allowing the condensate to be discharged before it can enter the heat exchanger. Float-type steam traps serve as safety steam traps with excellent safety discharge performance, as they can handle large amounts of air and are simple to operate. The size (capacity) of the safety steam trap should be the same as that of the main steam trap. Article 12: Anti-freezing protection – A properly selected and installed steam trap will prevent freezing issues as long as steam is flowing through it. But if the steam supply is cut off, the steam will condense into water inside the heat exchanger or accompanying pipes, creating a vacuum. This will prevent condensed water from escaping freely from the system before freezing occurs. Therefore, a vacuum breaker must be installed between the discharge device and the steam trap. If gravity drainage is not used from the steam trap to the return pipe, the steam trap and the drainage pipeline should be drained manually or through a drainage pipe equipped with anti-freezing measures for automatic drainage. Also, when multiple steam traps are installed together in a steam trap station, insulating the steam traps can prevent freezing. Anti-freezing measures include: 1. Do not choose a model of drain valve that is too large. 2. Keep the drain line of the steam trap as short as possible. 3. Incline the drain line of the steam trap downward to accelerate gravity-driven drainage. 4. Insulate the drain line of the steam trap and the condensate return line. 5. When the condensate return pipeline is exposed to atmospheric conditions, it is advisable to install heat tracing pipes. 6. If the return pipe is raised, the vertical discharge pipe should be adjacent to the discharge pipe at the upper part of the return header, and both the discharge pipe and the drain valve discharge pipe should be insulated together. Article 13: Testing methods for steam traps 1. Valve testing method The valve testing method is the most effective one. That is, a shut-off valve is installed on the return pipe to isolate the steam trap from the return pipe (as shown in Figure 10). Figure 10: Things to note after the check valve is opened: (1) Condensate discharge – Both inverted bucket and disc type steam traps discharge condensate intermittently. The float-type operates with continuous discharge, while the thermostatic type may discharge continuously or intermittently depending on the load. When the load on an inverted barrel-type steam trap is extremely low, condensate will still be discharged continuously due to the droplet effect. This way of working is normal under these conditions. (2) Flash steam — Do not mistake flash steam for steam leaking through a steam trap. The heat contained in condensed water under pressure is much higher than that in condensed water at normal pressure; when this condensed water is discharged, this excess heat causes part of it to evaporate again. Therefore, it is important to be aware of flash vapor during use. If steam is continuously emitted and appears as “blue” steam, it is leaking steam. If steam emerges intermittently \"floating\" out (each time the steam trap discharges condensate), forming a white mist, it is flash steam. (3) Continuous steam emission – a fault; see Article 15 for troubleshooting of steam traps. (4) No emission – it may be a fault; see Article 15 for troubleshooting of steam traps. 2. Stethoscope testing method: By using a stethoscope or a steel rod, with one end placed on the steam trap cover and the other end against the ear, it is possible to hear the differences between intermittent and continuous emissions from different steam traps. This proper operating condition is different from the sound of increased flow velocity when the check valve is in the direct flow position. Since other sounds can also travel along the tube, using the stethoscope testing method requires a person with some experience to carry it out. 3. Thermometer detection method: The accuracy of the thermometer detection method depends on the design of the return pipeline and the size of the orifice in the steam trap. Furthermore, when discharging into the common return pipe, it is possible that the temperature at the outlet of the hydrostatic valve under test may rise due to direct connection with other steam traps; this requires someone with appropriate experience to handle it. Article 14: Troubleshooting of steam traps – No drainage. If a steam trap fails to discharge condensate, then: A. The pressure may be too high. (1) The original design pressure difference was incorrect. (2) Pressure has increased due to the lack of a smaller valve nozzle. (3) The pressure relief valve is malfunctioning. (4) The boiler pressure gauge reading is low. (5) After normal wear, the valve nozzle expands. (6) The high vacuum in the return pipeline increased the pressure difference, exceeding the operating pressure difference of the steam trap. B. No condensate or steam enters the trap. (1) The filter in front of the steam trap is clogged. (2) There are other valves closed or blocked on the pipeline before the steam trap. (3) Blockage in the pipeline or elbow. C. Mechanical wear or defects. It needs to be repaired or replaced. D. The drain valve body is clogged with debris. A filter should be installed or the dirt should be removed. E. For inverted barrel-type steam traps, when the vent hole of the float barrel is blocked by debris, the following measures should be taken: (1) Install a filter. (2) Slightly enlarge the exhaust hole. (3) Place a wire in the exhaust hole. F. For float-type steam traps, if the air vent does not function properly, air resistance will occur. G. For thermostatic steam traps, the diaphragm element may be damaged due to water hammer, causing the trap to close completely. H. For disc-type steam traps, the trap may be installed in reverse. 2. Thermal valve – non-drainage: A. Undoubtedly, the water flow moves toward the steam trap. (1) The steam trap is installed on the bypass valve that is leaking. (2) The siphon discharge pipe in the drying drum is broken or damaged. (3) A vacuum has formed in the water heater coil, preventing drainage. Install a vacuum breaker between the heat exchanger and the steam trap. 3. Steam loss: If fresh steam is discharged from the steam trap, it may be caused by the following reasons: A. The valve does not close properly. (1) Scale has blocked the valve hole. (2) Component wear.
B. The inverted barrel-type steam trap is not working. (1) If the steam trap releases fresh steam, close the inlet valve for a few minutes first, then open it slowly. If the steam trap can function at this time, it indicates that the steam trap is in good condition. (2) The non-functioning of inverted barrel-type steam traps is usually caused by sudden or frequent changes in steam pressure. In this case, a check valve can be installed. If possible, the drain valve should be installed below the water collection point. C. For float-type or thermostatic hydrophobic valves, it may be that the float, connecting chain, or thermostatic element is damaged, preventing them from closing. 4. Continuous discharge: If an inverted barrel-type or disc-type steam trap discharges continuously, or if a float-type or thermodynamic steam trap discharges with it fully open, the following factors should be checked: A. The steam trap is too small. (1) Replace it with a larger steam trap, or install another steam trap in parallel. (2) In applications with a low pressure difference, a high pressure difference steam trap may be installed; in such cases, a steam trap with an appropriate valve orifice size should be selected. B. Abnormal water supply conditions, such as bubbling inside the boiler, causing a large amount of water to enter the steam pipes. A water-soda separator should be installed to change the water supply conditions. 5. Slow heating: The water-repellent valve is functioning properly, but the process heating unit fails to heat effectively. A. One or more cells are short-circuited. The solution is to install a steam trap on each pipeline. B. Although it seems effective to handle condensed water, in reality the size of the steam trap selected is too small. Try a larger drain valve. C. The air handling capacity of the drain valve may be insufficient, or air may not reach the drain valve. In either case, an exhaust valve needs to be installed. 6. Strange problems: If the valve functions properly when discharged under atmospheric pressure, but problems arise when it is connected to the return pipeline, check the following points: A. Back pressure reduces the discharge volume of the steam trap. (1) The return pipe is too small—the steam trap gets hot. (2) Other steam traps may leak steam, causing an increase in the pressure in the return pipe – steam trap overheating. (3) The air vent on the condensate tank is blocked — the steam trap is hot or cold. (4) Clogged return pipeline—steam trap overheating. (5) Return pipeline ultra-vacuum — steam trap cooling. Requirements for Quality Inspection and Acceptance of Steam Traps Article 15: The quality inspection and acceptance of steam traps shall comply with the relevant requirements specified in GB/T9093-1999 \"Technical Conditions for Steam Traps\", GB/T12251-1989 \"Test Methods for Steam Traps\", and \"Automatic Steam Traps – Product Testing and Operating Characteristic Testing\". Article 16: The procurement of steam traps requires factory inspection and type testing in accordance with relevant regulations. Article 17: Contents of factory inspection 1. Factory inspection shall be carried out one by one. 2. Factory inspection includes shell testing and operation testing. Article 18: Contents of type testing for steam traps 1. Shell testing 2. Operation testing 3. Test at minimum operating pressure 4. Test at maximum operating pressure 5. Test at maximum back pressure 6. Air discharge capacity test 7. Test at maximum and minimum subcooling 8. Steam leakage rate test 9. Hot condensate discharge volume test. Article 19: Service life requirements for steam traps Steam traps used in continuous production and discharge systems (equipment or systems) are required to have a service life of 3 years ； Steam traps for intermittent production emission devices (equipment or systems) are required to have a service life of 2 operating cycles. Article 20 Test items for steam trap inspection (1) Shell test Standards: GB/T12251-1989 \"Test methods for steam traps\"; ISO6948-1988 \"Automatic steam traps – Product testing and performance testing\" Test medium: Water, kerosene, or other liquids with a viscosity not greater than that of water; the temperature of the medium should be at room temperature. One of the following media may be selected: water (with buffers allowed), kerosene, or other suitable liquids with a viscosity not greater than that of water; steam, air, or any other suitable gas Test pressure: 1.5 times the nominal pressure. For PN＜5MPa and DN≤50mm: 1.5 times the maximum allowable pressure at 20℃ for liquids ； Or gas: 0.6 MPa (gauge pressure). For other specifications, liquid: 1.5 times the maximum allowable pressure at 20°C. Test method and requirements: Apply the test pressure to the assembled steam trap with its inlet and outlet ends sealed. First, seal the inlet and outlet ends of the assembled steam trap, and then apply internal pressure. It should not be painted before testing, nor should it be covered with other materials that may provide sealing and hinder leakage. Anti-chemical corrosion treatment and internal lining are allowed. The testing equipment shall not subject the steam trap to any external forces that could affect the test results. Test duration, Nominal diameter DN/mm, Test duration in seconds, Nominal diameter DN/mm, Minimum test duration in seconds: ≤50: >15; DN≤50: 15; 65–100: >60; 65≤DN≤200: 60; 250≤DN: 180. Result evaluation: Within the specified time, there shall be no leaks in the housing, nor any residual deformation of the internal components. If leakage through the pressure-bearing walls is observed, the test is considered failed. (II) Performance tests of steam traps 1. Operation test (1) Testing method: First, steam is introduced into the steam trap, followed by the introduction of hot condensate water at a certain load rate. At least three complete cycles are required for this test to be considered complete. For mechanical steam traps whose sealing pair is below the sealed float and are equipped with a water seal function, they can be tested using air and water. (2) Performance requirements: When only steam is present inside the drain valve, it should be closed. When condensate is introduced, the steam trap should be opened (the time required to open varies depending on the type of steam trap). The steam trap should be closed again after the condensate has been drained. For disc-type steam traps, when the inlet is in a fully vapor state, the flutter frequency of the valve disc is no more than 3 times per minute. 2. Minimum operating pressure test (1) Test method: When conducting the operation test in accordance with the method specified in the operation test, gradually reduce the test pressure until the steam trap can no longer open or close properly. (2) Performance requirements: The minimum test pressure at which normal operation can be maintained is the minimum operating pressure. The minimum operating pressure should not be greater than the value specified in the design. 3. Maximum operating pressure test (1) Test method: While conducting the operation test in accordance with the method specified in the operation test, gradually increase the test pressure until it reaches the maximum operating pressure designated in the design. (2) Performance requirements: Throughout the entire testing process, the drain valve must be able to open and close properly. 4. Maximum operating backpressure test (1) Test method: When conducting the operation test at the maximum operating pressure using the method specified in the operation test, gradually increase the pressure at the outlet of the steam trap until it can no longer open and close properly. (2) Performance requirements: The highest outlet pressure at which the drain valve can still open and close properly is the maximum operating back pressure. The percentage of the maximum operating back pressure to the maximum operating pressure (i.e., the maximum back pressure ratio) shall meet the following requirements: a. For mechanical types, it shall be no less than 80% ； b. For thermodynamic types, it should be no less than 50%, with pulse types requiring no less than 25% ； c. The thermostatic type should be no less than 30%. 5. Air discharge capacity test (1) Test method: Pass air with a pressure not exceeding 0.3 MPa into the steam trap, and then observe its air discharge capacity. (2) Performance requirements: The drain valve shall be capable of releasing air. It is permissible for the drain valve to close briefly within 5 minutes, but the closing time shall not exceed 1 minute. The steam trap must not experience air blockage when removing air and other non-condensable gases. 6. Tests for maximum and minimum supercooling (1) Test method: Steam is introduced into the check valve to close it, and then saturated temperature water and condensate water are introduced. If the drain valve does not open immediately, wait for it to cool down gradually until it opens automatically (the temperature of the inlet condensate at the time of opening is the valve-opening temperature). Then, the temperature of the condensate water is gradually increased until the steam trap closes automatically (the temperature of the inlet condensate water at the time of closure is the closing temperature). (2) Performance requirement: The absolute value of the difference between the valve-opening temperature and the saturation temperature at the corresponding pressure is the valve-opening subcooling. The maximum value of the supercooling upon valve opening is the maximum supercooling. The maximum supercooling shall not exceed the value specified in the design. The absolute value of the difference between the valve-shutting temperature and the saturation temperature at the corresponding pressure is the valve-shutting subcooling. The maximum value of the supercooling upon valve opening is the minimum supercooling. The minimum supercooling shall not exceed the value specified in the design. 7. Steam leakage test (1) Test conditions a. The test pressure PS and load rate RL shall be in accordance with the specifications in Table 10–56. Test pressure PS and load rate RL for the steam leakage test: Nominal pressure PN/MPa, PS/MPa, RL (%): 1.6, 0.8; 5±2; 4.0, 1.2; 6±2; 6.4, 2.0; 7±2; >6.4, >2.0; 8±2. b. For each test, the load test shall last no less than 5 minutes, and the no-load test shall last no less than 10 minutes. c. Each steam trap shall be tested at least three times, and the average of the test results shall be taken. The deviation of the value measured in each test from the average shall not exceed 10%. d. During the test, the pressure fluctuation of the hydrophobic valve under test shall not exceed ±1.5%, and the temperature fluctuation shall not exceed ±3°C. 8. Hot condensate discharge test (1) Test conditions a. The measurement of the hot condensate discharge for each trap should be carried out at 5 representative points within the operating pressure range, under a given subcooling degree. b. Each pressure point shall be tested at least three times, and the average value of the test results shall be taken; the deviation of each individual measurement from this average value shall not exceed 10%. c. During formal data reading, the pressure fluctuation before the tested steam trap shall not exceed ±1.5%, and the temperature fluctuation shall not exceed ±3°C. (2) Calculation of heat-condensed water discharge The calculation of heat-condensed water discharge is carried out using the measurement method selected during testing, according to Equation (1) or Equation (2) below: QH = πD² / 4 × 3600 / t Equation 1 Where QH is the discharge volume of heat-condensed water (kg/h) ； D—Inner diameter of high-pressure tank (m) ； V—Specific volume of water in the high-pressure tank (m3/kg) ； t—test duration (s) ； Z1—Water level at the start of the high-pressure tank (m) ； Z2—Water level at the end of the high-pressure tank (m). QH = (g2 – g1) × 3600 / t Equation 2 Where g1 is the mass of the measuring tank at the start of water addition (kg) ； g2—Mass at which water addition to the metering tank is terminated (kg). (3) Performance requirement: The discharge volume of the thermally condensed water at a given subcooling degree should not be less than the value specified in the design.
May I ask: Where does LZ’s information come from, in which standard?
Thank you, LZ; this will now solve the problem of direct drainage from the hydroseparator inside the unit!