Hydrostatic drain valve-1

Release time:

2024-04-01

Thermal static trap is also called constant temperature trap. It is different from the mechanical type drain valve, that is, the mechanical type drain valve depends on the position of the liquid level in the valve body to open and close the drain valve, while the basic principle of the thermal static type drain valve is that the temperature determines the opening and closing of the drain valve. In other words, it uses the principle of temperature difference between steam (high temperature) and condensate (low temperature), and uses bimetal or bellows as temperature sensing elements. It can change its shape with the change of temperature (expansion or contraction of bellows, bending of bimetal), and use the displacement of this temperature sensing body to open and close the drain valve. If there is steam in the bellows (high temperature), it will expand, thus closing the drain valve; and when the condensate (low temperature) flows in, it will shrink and open the valve to drain the condensate. According to the use of different temperature sensing elements, their forms can be roughly divided into bellows type, bimetal type, film box type and temperature control type.

Bellows drain valve

The operating element of the bellows type drain valve, i.e. the temperature sensing element, is the bellows. The shape of the bellows is just like a small lantern. It is a sealed metal container with a freely expandable wall thickness of 0.1-0.2mm. The water or volatile liquid with lower boiling point than water is enclosed inside. The shape of the bellows also changes significantly with the change of temperature (displacement), that is, when the temperature is high, the closed liquid evaporates into steam, which expands the bellows by the pressure of steam; when the temperature is low, the steam condenses and reduces into liquid, so the bellows contracts again. The bellows is fixed on the upper end of the drain valve body, and the lower end is connected with the valve disc.

The operation principle of the trap is: when the steam is started, it is in normal temperature state, the closed liquid inside the bellows is not vaporized, and the bellows shrinks in the open valve state. Therefore, the air flowing into the trap and a large amount of low-temperature condensed water are discharged from the outlet through the valve seat hole, and the temperature of the condensed water also rises rapidly; with the change of temperature, the bellows senses the temperature, and its internal extension makes the valve disc close to the valve seat. Therefore, when the water or high-temperature condensed water of approximate saturation temperature flows into the drain valve, the bellows will expand further and turn off the valve.

The temperature of condensed water in the drain valve drops to the set opening temperature one day, and the bellows shrinks proportionally according to the change of temperature, so as to open the valve. This action is repeated to realize the action of opening and closing valve, so as to eliminate the water of audit.