1. Gate valve (model: Z41H)
Generally speaking, gate valves are widely used in petrochemical and electric power industries, mainly in the main pipeline. They can be used at high temperature, medium high temperature, medium large diameter. The medium used for gate valves is generally oil, steam and water, and the higher temperature is 425 ℃. The gate valve has no directionality in installation. It can be installed horizontally or vertically. The gate valve is characterized by good sealing performance.
If the medium of the gate valve is acid, then we cannot use carbon steel, but use stainless steel (P), and the higher use temperature is 200 ℃. If the medium is still oil or steam, but its temperature exceeds 425 ℃, then we should choose alloy steel (I) with temperature ≤ 550 ℃. Or stainless steel (P), temperature ≤ 600 ℃. When the diameter of the gate valve is large (generally greater than 1000mm), we should add spur gear or bevel gear transmission as recommended by the customer, so that it is convenient to open. The main disadvantage of the gate valve is that the opening height is large, and the maintenance of the sealing surface is difficult.
2. Stop valve (model: J41H)
It is mainly used on the auxiliary pipeline, and the diameter should not exceed 200mm. The operating conditions of the stop valve are similar to those of the gate valve, but the installation of the stop valve is directional (low inlet, high outlet). Generally, it is widely used in steam pipelines. The disadvantage of the stop valve is that the fluid resistance is large.
3. Butterfly valve (model: D71X, D373H)
The butterfly valve is generally divided into center line butterfly valve and eccentric butterfly valve, and the materials are cast iron, carbon steel and stainless steel. Cast iron butterfly valve is generally applied to the system pipeline with corrosive medium and pressure of about 10kg at room temperature, and the sealing ring is generally rubber. It is widely used in construction and industrial fields, especially in water supply and drainage systems. With the extensive application in the industrial field, higher requirements have been put forward for its corrosion resistance and high temperature resistance. In recent decades, eccentric butterfly valves and hard sealing butterfly valves have been increasingly recognized. The butterfly valve can close and regulate the flow on the pipeline. It is simple in structure, light in weight and easy to open and close.
In the use of butterfly valve types, we should pay attention to two points: 1, anti-corrosion; 2. High temperature resistance.
Considering that some medium in the pipeline is acidic (or alkaline) and has certain temperature requirements (greater than 80 ℃), the general rubber seal ring can no longer be used, but the F seal ring (≤ 150 ℃) should be used. At the same time, the butterfly plate should also be replaced (with stainless steel plate, etc.). If corrosivity and temperature have higher requirements, hard sealing butterfly valve shall be used. For example: D373H-16C (P)
In terms of transmission form, generally larger than 200mm diameter, worm gear transmission shall be adopted.
4. Ball valve (model: QA41F)
It is widely used in petroleum, chemical industry, long-distance pipeline and other fields. The fluid resistance of the ball valve is small. The valve seat of the ball valve is divided into floating valve seat and fixed valve seat. Floating valve seat is generally used for medium and small caliber (below DN200), and valve seat selection of ball valve is very important. Generally, it is selected according to its temperature. Polytetrafluoroethylene (F) is used when the temperature is less than 150 ℃, and para polystyrene can be used when the temperature is less than 250 ℃ For PPL, the metal seal must be selected before going up. In addition, whether there are hard particles in the medium of the ball valve is also important for valve seat selection. It should be noted that the ball valve has two ball valves, three-way ball valves and four-way ball valves, which is one of the differences between it and other valves.
5. Check valve (model: H44H)
The check valve is also called one-way valve. It is less used in pipelines. The characteristics of the check valve are: when the pressure in the pipeline changes abnormally, the check valve can play a pressure relief role, and the check valve is always normally closed under normal working conditions.
6. Safety valve (model: A41H)
The safety valve is only used on the pipeline as a protective device to prevent excessive overpressure. It should be noted during procurement that the starting pressure of the safety valve should be requested from the customer.
In addition to manual operation, electric valves are used to control many key pipeline parts, mainly for remote control. It is necessary to correctly select the model of electric actuator. Electric actuators are generally divided into ordinary type, outdoor type and outdoor type. When purchasing electric valves, special attention should be paid to their working conditions, such as temperature, environmental media, etc. In general oil depots (such as airports and docks), such as light oil, flammable and explosive (gasoline, aviation kerosene, etc.), explosion-proof electric actuators should be selected, and explosion-proof signs should be provided. D Ⅱ BT4 uses explosion-proof electric valves (downhole) for coal mines. Its working voltage should be 660V instead of 380V. In addition, the electric valve can be switched manually. At the same time, if there are requirements for opening time of some electric valves, double speed operation shall be adopted to meet the requirements. Also, we need to have a general understanding of the electric head brand. The domestic ones include "Yangxiu" and "Tianjin Ertong", while the foreign ones include "Rotoc" in Britain, "Rimitroc" in America, and "Siemens" in Germany. Reasonable quotation shall be made by selecting different electric actuators.
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