The selection of
Needle Valve should meet the use requirements. First of all, we must understand the specifications and models of Needle Valve. When using and identifying, we should pay special attention to whether the sealing surface material, valve body material and nominal pressure meet the requirements, as well as sealing, adhesion and other issues. Needle Valve are generally used for steam. The valve body material is carbon steel and the valve seat material is stainless steel.
The nominal pressure of the Needle Valve requires a reference temperature of 120℃, while the
Universal Valve body is 200℃. When the medium of the Universal Valve exceeds 200℃, the maximum allowable working pressure is lower than the nominal pressure. Therefore, for boilers with saturated steam pressure exceeding 1.47MPa and superheaters, Needle Valve should be selected according to the working temperature.
The number of Needle Valve. For boilers with a rated evaporation capacity of >0.5t/h, at least two Needle Valve shall be installed. For boilers with an evaporation capacity of ≤0.5t/h, at least one Needle Valve shall be installed. Needle Valve must be installed at the outlet (or inlet) of the separable economizer and the outlet of the steam superheater.
The Needle Valve should be installed vertically to the ground and installed at the highest position of the drum and header as much as possible. The outlet pipe and valve for taking steam shall not be installed between the Needle Valve and the drum or between the Needle Valve and the header.
Verification of the opening pressure of the Needle Valve. The opening pressure of the Needle Valve should be adjusted and verified according to the value specified in the table. For boilers using only one valve, the opening pressure of the Needle Valve is adjusted according to the lower value in Table 1.2-2; for boilers with superheaters, the Needle Valve on the superheater is adjusted according to the lower pressure.
For boilers with separable economizers, the opening pressure of the Needle Valve on the economizer is 1.1 times the working pressure of the installation location. For boilers with economizers and superheaters, the opening order of the Needle Valve is: first the superheater Needle Valve, then the drum, and finally the economizer, in order to follow the principle of ensuring good safety performance of components with high working temperatures.
