Relationship between valve flow rate and pressure
Thread Content
There is currently one DN65 control valve with the following specifications: 1. The pressure before the valve is 1.65 MPa, while the pressure after the valve is 0.4–0.5 MPa. 2. The flow rate range is 0–2 t/h, with a typical flow rate of 0.65 t/h. I would like to ask: when the pipeline flow rate is at its maximum value of 2 t/h, can the pressure after the valve be kept at 0.5 MPa or below? Does the valve need to be reduced in diameter?
The control valve should not have a necking effect; with such comprehensive data available, just let the manufacturer choose the appropriate model for you. The opening degree should be above 50% to avoid excessive shock
It is possible to use a reducing valve, by reducing the diameter of the valve seat
1. The relationship between pressure drop and flow rate for a valve is determined by the Cv value specified during its design. 2. When the friend who posted the question provided the above information, only the mass flow rate was given; the density of the fluid was missing, which makes it difficult to obtain accurate results. 3. The flow channel may be slightly larger or smaller; the opening degree of the valve element can generally meet the requirements for a certain specific value. However, from the perspective of control valves, it is important to maintain a linear characteristic within the desired flow range in order to ensure smooth control
1. Even at the maximum flow rate of 2 T/h, the flow velocity is low when the DN65 valve is fully open; it is even lower at normal flow rates. 2. Since there are no Cv data available from valve manufacturers, an estimation is made using the resistance coefficient of gate valves for pipe resistance: at a flow rate of 2.0 m3/h, with a local pipe diameter of 20 mm and an opening degree of 12.5%, the pressure drop is 15 m. This means that if a DN65 valve is used, it will not be possible to achieve a pressure drop unless the valve is nearly closed. 3. Therefore, in this water conveyance pipeline, a fitting (or valve) with high resistance loss needs to be installed to serve the purpose of reducing pressure, after which a control valve is used to adjust the flow rate.