Working principle and applications of steam traps

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A steam trap is a valve used in steam pipelines and equipment to automatically discharge condensate, air, and other non-condensable gases, while preventing the leakage of steam. Types of steam traps: Based on the different working principles of steam traps, they can be classified into the following three types: Mechanical type: Operates based on changes in the level of condensed water inside the trap. Floating ball type: The float is a closed, hollow sphere with its opening facing upward. Floating bucket type: The float is a bucket-shaped element with its opening facing upward. Floating bucket type with opening facing downward: The float is a bucket-shaped element with its opening facing downward. Thermostatic type: Operates based on changes in liquid temperature. Bimetallic strip type: The sensing element is a bimetallic strip. Steam pressure type: The sensing element is a bellows or cartridge filled with a volatile liquid. Thermodynamic type: Operates based on changes in the thermodynamic properties of the liquid. Disk type: At the same pressure, the different flow rates of liquid and gas result in varying dynamic and static pressures, which drive the disk valve element to move. Pulsating type: Condensate water at different temperatures passes through throttling orifice plates arranged in series; the resulting differences in pressure between these orifice plates drive the valve element to move. Working principle of the steam trap: The steam trap is installed between the steam heating equipment and the condensate return header. While driving, the bucket is at the bottom with the valve fully open. After entering the steam trap, the condensate flows to the bottom of the tank, filling the valve body and submerging it entirely; thereafter, the condensate is discharged to the return water header through the fully open valve. Steam also enters the steam trap from the bottom of the tank, occupying the upper part of the tank and creating buoyancy. The barrel rises slowly, moving the lever toward the valve seat until the valve is completely closed. Air and carbon dioxide gas gather at the top of the drain valve through the exhaust holes in the barrel. The steam discharged from the exhaust vents condenses due to the heat dissipation by the steam trap. When the incoming condensed water begins to fill the tank, the tank starts to exert a pulling force on the lever. As the condensation level continues to rise, the force generated increases until it is sufficient to overcome the pressure difference and open the valve. As the valve begins to open, the pressure difference acting on the valve disc decreases. The barrel body will drop rapidly, causing the valve to open fully. The non-condensable gases accumulated at the top of the steam trap are discharged first, followed by the condensate. As the water flows out of the tank, it carries the dirt with it and out of the drain valve. As the condensate is discharged, steam begins to flow back into the drain valve, and a new cycle starts.