A steam trap is an automatic valve that releases condensate and non-condensable gases, but must block the passage for the working steam.<\/p>\n\n\n\n
In a steam system, some of the steam inevitably gives off heat and condenses. If the water is not removed, it accumulates in the steam line, heater, or heat exchanger, impairing heat transfer, accelerating corrosion, and creating conditions for water hammer. <\/p>\n\n\n\n
The purpose of a condensate drain is not limited to a simple drain. A functioning device maintains the required temperature regime of the equipment, reduces steam losses and helps return hot condensate to the boiler room. So, it is a small element with a disproportionately large impact on the stability of the entire system.<\/p>\n\n\n\n
At the inlet, the device receives a mixture of condensate, air and steam. Inside, a sensitive element reacts to one of the physical characteristics of the medium: density difference, temperature or rapid pressure changes. When condensate appears, the valve opens; when steam reaches the seat, the mechanism closes the channel. It is the method of recognizing the medium that determines the type and scope of application of the device.<\/p>\n\n\n\n
For the movement of condensate, a positive pressure difference between the pressure upstream of the device and the back pressure downstream is required. The smaller this difference, the lower the actual throughput. Therefore, the manufacturer's table is read according to the operating conditions.<\/p>\n\n\n\n
There is no one-size-fits-all solution for all steam systems. Steam piping, temperature-controlled heat exchangers, and high-temperature trace lines all have different start-up modes, loads, and air removal requirements. Therefore, it is worth comparing the response characteristics.<\/p>\n\n\n\n
The float reacts to the liquid level: when condensate fills the housing, it rises and opens the valve through the lever. When the level decreases, the spool returns to the seat. The discharge occurs almost continuously, so this option works well on heaters and heat exchangers with variable load. The built-in thermostatic air vent facilitates start-up when the system is filled with cold air.<\/p>\n\n\n\n
Here, the flow drives a disk that lies above the seat. The cold condensate lifts the thermodynamic disk and flows into the outlet channel. The appearance of steam and secondary boiling change the pressure in the chamber, which causes the disk to be pressed against the seat. <\/p>\n\n\n\n
The design is compact, resistant to vibrations and water hammer, and can operate with high pressure and superheated steam. At the same time, its operation is cyclical, and excessive back pressure can disrupt operation.<\/p>\n\n\n\n
The thermostatic mechanism responds to temperature. As long as the medium is cooler than the steam at the current pressure, the valve is open and allows air and cooled condensate to pass through. When the temperature approaches the saturation temperature, the capsule, fluid element, or bimetallic plate moves the valve and closes the passage. This delay is useful for tracing, but is undesirable where the accumulation of condensate immediately reduces the thermal power.<\/p>\n\n\n\n
Threading makes the assembly compact and convenient for small diameters, but the requirements for sealing and the condition of threaded connections increase. The flange takes up more space and requires proper tightening of the fasteners, but it facilitates the dismantling of heavier equipment and is often used on industrial lines of larger DN. The final choice is determined by the pipeline standard, nominal pressure, steam temperature, permissible sealing material and maintenance regulations.<\/p>\n\n\n\n
The device is mounted at points where condensate flows by gravity: <\/p>\n\n\n\n
It should be located close to the drainage point, in the position specified in the passport. A shut-off valve and filter are usually installed in front of it, and if necessary, a check valve and control unit.<\/p>\n\n\n\n
One device should not be used for several consumers without calculation: different pressures can block the outlet from equipment with lower pressure. Correct wiring is no less important than the model of the device itself.<\/p>\n\n\n\n
The selection of a condensate drain begins with determining its task. Equipment for draining a steam line, process unit, air heater or tracing system operates under different conditions, so there is no universal solution here. For example, for heat exchange equipment, rapid drainage of significant volumes of condensate is important, while in tracing systems the load is usually lower, but it is necessary to maintain a stable pipeline temperature.<\/p>\n\n\n\n
After that, the operating and starting pressure, temperature, maximum condensate flow rate and available pressure drop are determined. Also, where the condensate will be discharged is taken into account: <\/p>\n\n\n\n
The backpressure, and therefore the actual performance of the equipment, depends on this scheme.<\/p>\n\n\n\n
No less important are the requirements for air removal, permissible condensate subcooling and operating mode. Under constant load, the steam trap must operate stably for a long time, and under cyclic load, it must respond quickly to system starts and stops. Comprehensive consideration of these parameters helps to select a model that will effectively remove condensate without steam loss and reducing equipment performance.<\/p>\n\n\n\n
The working and maximum allowable pressure, temperature, pressure in the return line and their actual difference are required. The body material (cast iron, carbon or stainless steel, less often brass) is chosen based on compatibility with the medium and passport limits. It is not possible to automatically equate the flange class to the permitted parameters in any mode: the allowable pressure depends on the temperature.<\/p>\n\n\n\n
The maximum condensate flow rate is calculated, not the average, especially during a cold start. The manufacturer's recommended safety factor is applied to the calculated load, and the required model is found from the throughput graph at the actual pressure drop. A device that is too large will not correct the incorrect scheme, but may operate unstable and cost more.<\/p>\n\n\n\n
Most often, they choose only by pipe diameter, ignore backpressure, confuse normal and starting load, mount the housing in the wrong orientation, or do not provide a filter and access for service. Another mistake is to try to "treat" water hammer by replacing one device, although the cause is often undischarged condensate, an unsuccessful slope, or a too small return line.<\/p>\n\n\n\n