The structural form and working principle of the drain valve

The steam trap plays a role in blocking steam and discharging water in the steam heating system. Choosing the appropriate steam trap can enable the steam heating equipment to achieve the highest efficiency. To achieve the desired effect, it is necessary to have a comprehensive understanding of the working performance and characteristics of various types of steam traps.
There are many types of steam traps, each with different performances. When selecting a steam trap, one should first choose its specific performance to meet the optimal operation of the steam heating equipment, and then consider other objective conditions. Only in this way can you select the required steam trap correctly and effectively.
The steam trap must be able to "identify" steam and condensate water to achieve the purpose of blocking steam and discharging water. "Identifying" steam and condensate water is based on three principles: density difference, temperature difference, and phase change. Thus, three types of steam traps of different types are manufactured based on these three principles, classified as mechanical type, thermal static type, and thermal dynamic type.
1. Mechanical type steam trap
The mechanical type is also called the float type. It uses the density difference between condensate water and steam, through the change in the liquid level of condensate water, to make the float rise and fall, driving the valve disc to open or close, achieving the purpose of blocking steam and discharging water. The mechanical type steam trap has a small overcooling degree and is not affected by changes in working pressure and temperature. It discharges water as soon as there is water in the heating equipment, and there is no water remaining in the heating equipment, enabling the heating equipment to achieve the best heat exchange efficiency. The maximum back pressure rate is 80%, with high working quality, and is an ideal steam trap for production process heating equipment.
The mechanical type steam trap has free float type, free semi-floating type, lever float type, and inverted bucket type.
2. Thermal static type steam trap
This type of steam trap uses the temperature difference between steam and condensate water to cause the deformation or expansion of the sensing element, which drives the valve core to open or close the valve. The overcooling degree of the thermal static type steam trap is relatively large, generally ranging from 15 degrees to 40 degrees. It can utilize part of the sensible heat in the condensate water, with the valve always containing hot condensate water at the front, without steam leakage, and has significant energy-saving effects. It is an ideal steam trap for steam pipelines, heating pipelines, small heating equipment, heating equipment with low temperature requirements, and other small heating equipment.
Thermal static type steam traps include diaphragm type, bellows type, bimetallic strip type, etc.
3. Thermal dynamic type steam trap
This type of steam trap is based on the phase change principle. It uses the different thermodynamic principles of flow velocity and volume change when steam and condensate water pass through to cause different pressure differences in the valve plate, driving the valve plate to open or close the valve. Because the working power of the thermal dynamic type steam trap comes from steam, the steam waste is relatively large.
The structure is simple, resistant to water impact, the maximum back pressure is 50%, there is noise, the valve plate works frequently, and the service life is short.
Thermal dynamic type steam traps include thermal dynamic type (disc type), pulse type, orifice plate type, etc.