【Haichuan Chemical Valve Knowledge】What is the difference between flow and pressure regulating valves and fixed cone valves?

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Flow and pressure regulation: In water conduit tunnels, water diversion projects, and dam drainage systems, flow and pressure regulation valves and fixed conical valves are two common types of outlet control devices. Although both can be used for pressure difference dissipation and flow regulation, there are fundamental differences in their structural principles, control characteristics, and applicable operating conditions. I. Differences in structure and working principle: Throttle and pressure control valves typically use sleeve or piston-type structures. The water flows through the valve seat into the porous sleeve; by moving axially, the flow area is altered, and multi-stage throttling takes place inside the sleeve. It is characterized by an S-shaped or zigzag flow path, requiring the fluid to change direction within the valve chamber. A fixed conical valve has a conical tip directly attached to the end of the valve body, with the valve seat and the cone forming an annular throttling gap. The flow enters axially and is ejected outward along the surface of the cone, with the flow channel remaining essentially straight. The closing element is usually a cone fixed to the valve stem, which changes the annular area by moving back and forth; however, the shape of the cone remains constant and does not change as the opening degree varies. II. Differences in hydraulic control characteristics: Flow and pressure regulating valves exhibit typical linear or equal percentage control characteristics, maintaining good control accuracy even at low opening degrees. They are suitable for applications that require maintaining a constant pressure downstream or precise flow control, such as water plant inflow regulation or pressure zoning control. Its relationship between outlet pressure and flow rate is relatively stable, and it is not easily affected by fluctuations in the backpressure in the downstream pipeline. Fixed cone valves exhibit nearly quick-opening characteristics, with flow increasing rapidly at low opening degrees and then leveling off in the later stages. Its exit flow is a conical water film entrained by air across the entire cross-section, with energy dissipation primarily occurring through diffusion in the air. It is more suitable for discharge or release applications, such as reservoir flood discharge and ecological release, and is less appropriate for closed-loop control systems that require precise maintenance of downstream pressure. III. Differences in application conditions: Flow and pressure regulating valves are suitable for use at the end of pipelines or within valve chambers where there is a large pressure difference, high flow rates, and continuous regulation is required. It can withstand large pressure differences, and the cavitation area is confined within the sleeve, resulting in minimal damage to the valve body. Due to its compact structure, it occupies less space and can be installed underground or indoors. Fixed conical valves are usually installed outdoors at the outlet of channels or downstream of dams; they must have space for free discharge and cannot be directly connected to downstream pipelines. It effectively dissipates the energy of the discharged water flow, generates almost no vibrations or noise, and its surface is not prone to the accumulation of debris, making it suitable for water bodies with high sediment content. However, it occupies significantly more space, and the mist emitted from the outlet can have an impact on nearby electrical equipment. IV. Difference between maintenance and cost: The internal sleeves, sealing rings, and valve seats of flow and pressure regulating valves require high precision; they are usually made of stainless steel and undergo hardening treatment, which results in high manufacturing costs. If the water quality contains a high amount of sand, the small holes in the sleeve tend to wear out over time, requiring the entire throttling assembly to be replaced. The structure of a fixed conical valve is relatively simple, with few sealing surfaces; the main wear-prone components are the sealing ring at the front end of the cone and the guiding mechanism, resulting in low replacement costs. However, its overall volume is large, requiring long straight pipe sections and heavy foundations, resulting in high civil engineering costs. The choice of valve type depends on the project’s requirements regarding control precision, installation method, and energy dissipation in the environment: flow and pressure regulating valves are suitable for precise adjustments in pipeline systems, while fixed cone valves offer greater reliability and cost-effectiveness in applications involving free discharge. What is the difference between a valve and a fixed conical valve?