Throttle valve necking
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Dear colleagues and seniors: Is there any standard for the reduction size of control valves on pipelines? Fine chemical industry. 1. For the pipelines in the process design, versatility is taken into account; the minimum diameter is DN25. Since the actual flow rate is very low, the inner diameter of the control valves calculated to be required is often only 5 mm, 8 mm, 10 mm, etc. Is this in compliance with the regulatory requirements? 2. Is it better to reduce the pipe diameter before and after the control valve, or within the control valve itself? (The cost difference for DN25 and smaller sizes doesn’t seem very significant). Thank you!
In the fine chemical industry, whether the reduction in diameter of control valves meets standards depends primarily on the specific application requirements and the properties of the fluid. Regarding your question: 1. Selection of the inner diameter of the control valve: During process design, even if the minimum pipe size is DN25, if the actual flow rate is very low, it may indeed be necessary to use a control valve with a smaller inner diameter (such as 5mm, 8mm, 10mm, etc.). This is usually allowed, as long as the fluid flow and control requirements can be met, and the selection of the control valve is based on engineering calculations regarding flow rate, pressure loss, and fluid properties. When designing, it is necessary to refer to the specific specifications of the control valve products and the manufacturer’s recommendations. 2. Selection of the diameter reduction method: Regarding whether to reduce the diameter of the pipes before and after the control valve or within the control valve itself, in general, reducing the diameter inside the control valve (that is, using a control valve with a smaller inner diameter) is often the better choice, as this helps to reduce the required installation space and may also lower some of the installation costs. Especially for small sizes of DN25 and below, it is usually simpler and more economical to use control valves with a smaller inner diameter directly. However, the specific choice still needs to be determined based on the actual pipeline layout and operating conditions. In summary, the selection of control valves and the method of reducing their diameter require comprehensive consideration of flow rate, pressure, fluid properties, as well as the overall design requirements of the system. It is recommended to have in-depth discussions with the control valve supplier or professional engineers to ensure that the requirements of the process are met while maintaining the economic efficiency and safety of the system. .
You’re welcome. If you have any other questions or need further assistance, feel free to ask. Wish you success in your work! .
Fine chemicals involve very small tubes; ask the designer
Generally, the diameter of a control valve is smaller than that of the pipes connecting the inlet and outlet, as the valve itself is designed for regulation, thereby controlling the pressure and flow rate of the fluid. The manufacturer selects the appropriate model through different calculations. It is also normal to obtain values indicating a smaller valve opening; this is mainly due to the flow velocity being higher than that in the pipeline. In China, foreign standards are also adopted, with corresponding standards for control valves; however, the calculation of valves still relies mainly on the valve manufacturers (who are highly specialized in aspects such as valve body design). I work with control valves for oil and gas pipelines. If convenient, we can have a technical discussion. My WeChat ID is 924549064
There are control valves with a DN25 size that have a very low CV value. You need to calculate the required CV value for the control valve, and then purchase one with a nominal diameter of 25. In my workshop, many of the DN25 control valves have a value below 0.1.
The reduced diameter inside the control valve, combined with the characteristics of the valve spool, especially its performance at low flow rates.