Electrical three-way regulating valves come in two types: convergence and divergence. They are composed of an electric actuator and a three-way valve for convergence or divergence adjustment. Powered by electricity, they accept a unified standard signal of 0-10mA DC or 4-20mA DC to drive the valve opening to correspond with the operating signal. The function of the convergence valve is to divide a single fluid into two. Divergence-convergence valves can only be selected together, but when DN ≤ 80, convergence valves can be used for divergence applications. They can replace two single or double seat regulating valves, saving investment and occupying less space. Three-way regulating valves are commonly used for regulating two media in heat exchangers and for simple mixing adjustments.
Safety valves are mainly widely used in: steam boilers, truck or rail tankers, oil wells, high-pressure by-passes of steam power equipment, pressure pipelines, pressure vessels, etc. Installation precautions: (1) New safety valves should be accompanied by a product certification, and a re-inspection should be conducted before installation, with a lead seal and a safety valve calibration certificate issued. (2) Safety valves should be installed vertically and placed at the gas phase interface of the vessel or pipeline. (3) The outlet of the safety valve should have no resistance to avoid back pressure; if an exhaust pipe is installed, its inner diameter should be greater than the outlet diameter of the safety valve. The exhaust outlet of the safety valve should be frost-proof. For containers containing or toxic substances, the exhaust pipe should lead directly to an outdoor safe location or have proper treatment facilities, and no valves should be installed on the exhaust pipe. (4) No valves should be installed between pressure equipment and safety valves. For containers containing, storing, or toxic or adhesive media, a stop valve may be installed for ease of replacement and cleaning, but its structure and diameter should not hinder the normal operation of the safety valve. During normal operation, the stop valve must be fully open and sealed with lead. (5) For pressure vessels containing or toxic media, a safety device and recovery system must be provided for the medium discharged by the safety valve. The installation of lever safety valves must maintain a vertical position, and spring safety valves should also be installed vertically to prevent interference with their operation. During installation, attention should also be paid to matching, the coaxiality of parts, and ensuring that all bolts are evenly loaded. The cross-sectional area of the short connecting pipe between the safety valve and the boiler pressure vessel should not be less than the flow cross-sectional area of the safety valve. The entire safety valve should be mounted on a single connection pipe, and the cross-sectional area of the connection pipe should be no less than 1.25 times the total flow cross-sectional area of the safety valve.
When the valve seat adjustment ring is raised, the degree of pressure accumulation increases, which reduces the stage of proportional valve opening and allows for a quicker transition to a sudden rapid opening. Therefore, raising the valve seat adjustment ring can help lower the discharge pressure. It should be noted that the adjustment ring should not be raised too close to the valve disc. Otherwise, in low-temperature valves, leakage at the sealing surface could cause the valve to open suddenly and prematurely. However, since the medium pressure is not enough to keep the valve disc open at this point, the valve disc closes immediately, resulting in frequent valve jumps. The valve seat adjustment ring is mainly used to reduce the proportional opening stage of the valve and regulate the discharge pressure, while also affecting the return seat pressure. The upper adjustment ring is used to change the angle of deflection of the flowing medium after reflection below the valve disc, thereby adjusting the magnitude of the fluid force to regulate the return seat pressure. Raising the upper adjustment ring reduces the deflection angle and the fluid force, increasing the return seat pressure. Conversely, lowering the upper adjustment ring decreases the return seat pressure. Of course, while changing the return seat pressure, the upper adjustment ring also affects the discharge pressure, with raising it increasing the discharge pressure and lowering it decreasing it, but the impact is not as significant as on the return seat pressure.
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