Valve is a large number of petrochemical installations in a wide range of important pressure piping components, it has a cut-off, regulation, conduction, to prevent back flow, pressure stabilization, diversion or overflow, pressure relief, etc.; valves are also the most complex components in the pipeline, it is generally assembled from a number of parts and components, the structure of the complexity of the technology content is high.
Valves are widely used in various petrochemical and chemical plants. The cost of pipeline materials accounts for about 15% to 20% of the total project investment, and the investment cost of valves and piping accounted for about 50% of the total cost of more than 50% of the various types of valves, of which the proportion of different types of valves, refinery installations, for example, various types of valves in the device accounted for the total number of valves in the proportion of respectively: 80% of the gate valve, globe valves, 8%, check valve 6%, these three types of valves in the petrochemical production unit is the most widely used valves, other valves accounted for 6%, the valve investment accounted for 5% to 8% of the device. Taking 2.5 million tons/year normal decompression device and 1.4 million tons/year catalytic cracking device as an example, the valve specifications account for the proportion of the total number of valves as follows: DN ≥ 400 3%, DN150~350 12%, DN50~100 25%, DN ≤ 40 60%.
The following are several common valves used in the petroleum field:
Gate valve, also called gate valve, is a widely used valve. It is a widely used valve. Its closing principle is that the sealing surface of the gate and the valve seat sealing surface is highly polished, flat and consistent, fit each other, can prevent the medium from flowing through, and rely on the top of the mold, the spring or the mold shape of the gate, to enhance the sealing effect. It is mainly in the pipeline to cut off the role.
Its advantages are: small fluid resistance, opening and closing energy, can be used in the case of two-way flow of media, no directionality, full open sealing surface is not easy to erosion, the structure of a short length, not only suitable for small valves, but also suitable for large valves.
Gate valve according to the stem threads are divided into two categories, one is the open stem, the second is the dark stem. According to the gate structure, it is also divided into two categories, one in parallel and the other in mode.
Globe valve, also known as the cut-off valve, is the most widely used type of valve, it is popular, is due to the opening and closing process between the sealing surface of the friction is small, more durable, opening height is not large, easy to manufacture, easy maintenance, not only for low pressure, but also for high pressure.
Its closing principle is to rely on the pressure of the valve lever, so that the valve sealing surface and the valve seat sealing surface close to prevent the flow of media.
Globe valve only allows the medium to flow in one direction, the installation of directional. Its structural length is greater than the gate valve, while the fluid resistance, long-term operation, sealing reliability is not strong.
Globe valves are divided into three categories: straight-through, right-angle, and straight-through inclined globe valves.
Check valve is relying on the force of the fluid itself to open and close the valve automatically, its role is to prevent the medium back flow. It has many names, such as check valve, check valve, single flow gate. According to the structure can be divided into two categories.
(1) Lifting: the valve moves along the vertical centerline of the valve body. This type of check valve has two kinds: one is horizontal, installed in the horizontal pipeline, the valve body shape is similar to the globe valve, the other is vertical, installed in the vertical pipeline,.
(2) Rotary: valve rotates around the pin outside the seat, this type of valve has a single valve, double valve and multi-valve points, but the principle is the same.
Pump suction pipe suction bottom valve is a deformation of the check valve, its structure and the above two types of stop valve is the same, only its lower end is open, so that water can enter.
Butterfly valve is also called butterfly valve, as the name suggests, its key component is like a butterfly facing the wind, free swing.
Butterfly valve flap is a disk, rotating around an axis within the valve seat, the size of the angle of rotation, is the valve’s degree of opening and closing.
Butterfly valves are characterized by lightness, saving material than other valves, simple structure, rapid opening and closing, cutting and throttling can be used, low fluid resistance, and labor-saving operation. Butterfly valve can be made into a large caliber. Where butterfly valves can be used, it is better not to use gate valves, because butterfly valves are more economical than gate valves and have better adjustability, butterfly valves are used in hot water pipelines widely.
The working principle of ball valve is to rotate the valve love to make the valve open or closed. Ball valve switch light, small size, can be made into a large caliber, reliable sealing, simple structure, easy maintenance, sealing surface and the ball surface is often in the closed state, not easy to be medium erosion, in various industries have been widely used.
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