Author: Site Editor Publish Time: 2018-10-06 Origin: Site
The needle valve is evolved from the globe valve, sometimes called the needle valve globe valve. The specific difference is that the disc of the needle valve is a sharp cone, which is inserted into the valve seat like a needle.
The needle valve is a kind of valve that can be precisely adjusted. For example, the cutting distance for flame cutting. The knob for adjusting the flame temperature is a needle valve. The instrument needle valve is an important part of the instrument measuring pipeline system. The function of the globe type and the ball type is to open or cut the pipeline passage.The diameter of the general needle valve is smaller than that of the general valve, and the general diameter is less than DN25mm.
The difference between globe valve and needle valve:
The needle valve has good sealing performance and long service life. Even if the sealing surface is damaged, it only needs to replace the vulnerable parts and can continue to be used. Install the needle valve so that the flow direction of the medium matches the direction of the arrow on the valve body.
The globe valve is a forced-sealed valve, so when the valve is closed, pressure must be applied to the valve flap to force the sealing surface to leak. When the medium enters the valve from below the valve flap, the resistance to be overcome by the operating force is the friction between the stem and the packing and the thrust generated by the pressure of the medium. The force of closing the valve is greater than the force of opening the valve, so the valve stem The diameter of the stem should be large, otherwise the valve stem can be bent. There are three types according to the connection method: flange connection, thread connection, and welding connection.
The globe valve is a widely used valve in the pipeline. It is popular because of the small friction between the sealing surfaces during the opening and closing process, which is relatively durable, the opening height is small, the manufacturing is easy, and the maintenance is convenient. It is suitable for high pressure in medium and low pressure.
The closing principle of the globe valve relies on the pressure of the valve bar, so that the sealing surface of the valve disc and the sealing surface of the valve seat are closely fitted to prevent the medium from flowing. The globe valve allows only one-way flow of the medium and is directional when installed. The structure of the globe valve is longer than the gate valve, and the fluid resistance is large. When the machine is operated for a long time, the sealing reliability is not strong.
Needle valve is easy to install and disassemble, and the connection is tight. It is the function of opening or cutting the pipeline in the meter measuring pipeline system. The needle valve is a valve that can be accurately adjusted, and has good sealing performance. It is generally suitable for small flow, high temperature and high pressure gas or liquid medium, and is also suitable for use with a pressure gauge.
The needle valve is an important part of the instrument measuring pipeline system. It mainly has a globe valve type and a ball valve type. Its function is to open or cut the pipeline passage. The needle valve has the advantages of convenient installation and disassembly, fast connection, favorable fireproof, high explosion-proof and pressure resistance, good sealing performance, etc. So it is also widely used in power station, oil refining and chemical plant.