Hydrostatic drain valve-2

Release time:

2024-04-02

Bellows drain valve

The bellows steam trap has the advantages of small volume and light weight, but the bellows itself has many shortcomings in manufacturing and structure, such as: because the bellows are relatively fragile, the water hammer resistance is poor, if used on superheated steam, it is easy to crack; it is difficult to ensure the airtightness of the bellows, so the sealed liquid is often reduced; the bellows is easy to generate abnormal expansion, so it is difficult to ensure the valve flap and The valve seat is coaxial, easy to leak steam; compared with bimetal type, it has poor dynamic response to pressure change.

Based on the above reasons, at present, alcohol or ether is used as the filling liquid and sealed into the bronze bellows. It can only be used on the indoor steam heating radiator (heat exchanger) with the pressure below 0.1MPa (1kgf / cm), and it is used as a special drain valve, that is, it is mainly used as a "heat dissipation and water drainage valve".

Advantages of bellows type drain valve: the drainage temperature can be adjusted between 70 ~ 100 ℃, which is convenient for use; it can prevent the discharge of high-temperature condensate and maintain the heat energy of steam pipeline; continuous drainage, no noise; small steam pressure, no impact on the use of fluctuations; simple structure, small volume, easy to install and at will; increase the condensate displacement by increasing the diameter of bellows; good air exhaust performance, no noise Fear of freezing; zero leakage, back pressure rate of 75%.

Bimetallic drain valve

Bimetallic sheet is composed of two metal sheets with different expansion coefficients. When the bimetal sheet is heated, the metal with high expansion coefficient has larger expansion than the metal with low expansion coefficient, and the bimetal sheet bends. The main valve is driven close to or away from the valve seat by the bending force generated when the bimetal is heated. When the temperature of the drain valve is low, the bimetal plate is in a loose state, and the main valve leaves the valve seat. When the steam enters the equipment, the air and low-temperature condensate can be discharged through the drain valve. When the process begins to heat up, the temperature of the condensate gradually rises, and the bimetallic sheet begins to deform. The metal plates with low expansion coefficient contact with each other and arch up, then pull the main valve to move towards the valve seat direction, and close the valve.

The performance curve of bimetallic sheet is close to that of saturated steam as much as possible. The bending deformation of bimetallic sheet is directly proportional to its length and almost linear to its temperature. It should be noted that the performance curve of bimetallic steam trap cannot be close to the performance curve of saturated steam as that of pressure balanced steam trap, so the change of pressure will affect the temperature difference between saturated steam and discharged condensate. Another point to be noted is: the condensate discharge of bimetallic steam trap.