Angle control valve flow path is simple, small resistance, under normal circumstances apply to the positive use (installation). However, it is recommended that the angle control valve be used reversely at high pressure drop to improve the unbalanced force and reduce the damage to the valve core. At the same time, it is also beneficial to the flow of the medium and avoids the coking and clogging of the control valve. Angle valve in the reverse use, in particular, should be avoided for a long time a small opening to open the case, to prevent strong oscillations caused damage to the spool. Especially in the trial production stage of chemical plant, due to the low load at trial production, the design process conditions can not meet the requirements very quickly. The reverse angle valve should be avoided as long as possible, and should be avoided Angle control valve is damaged. Key words: angle control valve; reverse use (installation); small opening; easy to damage In the production process automatic adjustment system, the control valve is an important and indispensable part, called the production process automation "Hands and feet" is one of the terminal control elements of an automatic control system. It is composed of two parts of the implementing agencies and the valve. From the hydraulic point of view, the control valve is a local resistance can vary the throttle element, the control valve is in accordance with the input signal by changing the stroke to change the drag coefficient, so as to achieve the purpose of regulating the flow. 1, the structure and use of angle control valve 1.1 Angle control valve structure Angle control valve in addition to the angular body, the other structures are similar to the single-seat valve, its characteristics determine its simple flow path, small resistance , Especially for high pressure drop, high viscosity, containing suspended solids and particulate matter fluid regulation. It can prevent coking, sticking and clogging phenomenon, but also easy to clean and self-purification. 1.2 Angle control valve is used in reverse, reverse In general, the angle control valve are used to install forward, that is, the bottom out. Only in the case of high pressure and high viscosity, easy to coke, containing suspended particulate matter case, it is recommended reverse installation, the material side into the bottom. The purpose of the reverse angle control valve is to improve unbalance force and reduce the wear on the valve core, but also conducive to high viscosity, coking and suspended particulate matter containing the flow, to avoid coking and plugging. 2, reverse the use of angle control valve Analysis Jilin Chemical Industry Co., Ltd. imported from Germany, acetaldehyde device, pv-23404 angle valve in the high pressure drop process conditions, it is recommended reverse use. In the water linkage test, the angular control valve produces a strong oscillation, and issued a harsh noise, after 4h test spool rupture. At that time, foreign experts believe that the quality of the spool is not due to manufacturing. The author thinks it is not a quality problem, but due to unreasonable use. The following analysis of the reasons for the fracture. We know that, at the moment, butterfly valves and diaphragm valves are completely symmetrical in structure, and all other control valves are asymmetrical. When the regulating valve changes the flow direction, the value changes due to the change of the flow path. The normal flow of all types of control valves are to open the spool in the direction (forward use), the manufacturer also provides the ability to flow when the normal flow) value and flow characteristics. When the control valve is used in the reverse direction, the flow capacity of the control valve will increase when the fluid flows in the direction of closing the valve spool. Water linkage test, the simulation process conditions can not be quickly reached the normal state, the control valve in a long time at a small opening state use, due to the role of unbalanced force, there will be serious instability. Therefore, the control valve will produce a strong shock and make a harsh noise, resulting in the valve core quickly broken. In the normal process conditions, the opening of the control valve is moderate, even if the small opening is also short, so the control valve can be used normally and safely. 3, Conclusion Under normal circumstances, the angle control valve are not recommended for reverse use, only in the high pressure, high viscosity, easy coking and suspended particles containing media is recommended reverse use. Reverse use, should avoid long-term small opening operation, especially in the test should pay more attention.