Large Diameter Gate Valve Carbon Steel Gate Valve

Large diameter gate valve Carbon Steel Gate Valve

I. use

The large caliber gate valve is suitable for class 150-2500, small caliber pipeline with working temperature of - 29-425 ℃ (carbon steel) or - 29-500 ℃ (stainless steel) to cut off or connect the medium in the pipeline. Different materials are selected, which can be respectively applied to water, steam, oil, nitric acid, acetic acid, oxidizing medium, urea and other media. It is widely used in oil pipeline.

II. Key points of installation

1. The installation position, height, inlet and outlet direction must meet the design requirements, and the connection shall be firm and tight.

2. The handle of all kinds of manual valves installed on the insulation pipeline shall not be downward.

3. Visual inspection must be carried out before the installation of the valve, and the nameplate of the valve shall comply with the provisions of the current national standard "general valve mark" GB 12220. For the valve with working pressure greater than 1.0 MPa and cut-off function on the main pipe, strength and tightness performance test shall be carried out before installation, and the valve can only be used after it is qualified. During the strength test, the test pressure shall be 1.5 times of the nominal pressure, and the duration shall not be less than 5min. The valve shell and packing shall be qualified if there is no leakage. During the tightness test, the test pressure is 1.1 times of the nominal pressure; the duration of the test pressure shall meet the requirements of GB 50243 standard, and it is qualified if there is no leakage on the sealing surface of the ram.

III. working principle

According to the configuration of sealing surface, wedge gate valve can be divided into wedge gate valve and parallel gate valve. Wedge gate valve can also be divided into: single gate pole type, double gate plate type and elastic gate type; parallel gate valve can be divided into single gate plate type and double gate plate type. According to the screw position of the valve rod, it can be divided into two types: open stem gate valve and concealed stem gate valve.

1. When the large caliber gate valve is closed

The sealing surface can only be sealed by the medium pressure, that is, the sealing surface of the ram is pressed to the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is self sealing. Most gate valves adopt forced sealing, that is, when the valve is closed, the gate shall be forced against the valve seat by external force to ensure the sealing of the sealing surface The gate valve of the gate valve moves in a straight line with the stem, which is called rising stem gate valve (also called rising stem gate valve). Generally, there is trapezoid thread on the lifting rod. Through the nut at the top of the valve and the guide groove on the valve body, the rotating motion is changed into linear motion, that is, the operating torque is changed into the operating thrust.

2. When the large caliber gate valve is opened

When the lifting height of the ram is equal to 1:1 of the valve diameter, the flow passage is completely unblocked, but this position cannot be monitored during operation. In actual use, the vertex of the valve rod is taken as the mark, that is, the position that can not be opened is taken as its full open position. In order to consider the phenomenon of locking due to the change of temperature, the valve is usually opened to the vertex position, and then turned back 1 / 2-1 circle as the position of fully open valve. Therefore, the full open position of the valve is determined by the position of the RAM (i.e. stroke).