Old K says every week – talking about things in the petrochemical design industry. Post 49: How to increase the pressure drop of control valves in the control valve specification table

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This post was last edited by henglinkou on 2021-5-24 09:19. Old K’s weekly series – Talks about matters in the petrochemical design industry, Post 49: How to increase the pressure drop of control valves in the control valve specification sheet. In engineering design, the process engineering team needs to submit a control valve specification sheet to the automation engineering team; one of the most important parameters in this sheet is the pressure drop before and after the control valve. Many designers are not sure how to determine this value. The pressure drop across a control valve can be considered in two scenarios: 1. When the starting pressure and ending pressure in the pipeline where the control valve is located are known, the pressure drop across the control valve is calculated as follows: Control valve pressure drop = (Starting pressure – Ending pressure) – Pressure generated by the height difference – Pressure loss due to pipeline resistance – Pressure loss due to resistances of devices between the starting and ending points. The pressure generated by the height difference is positive when the ending point is at a higher level than the starting point, and negative otherwise. 2. The pipeline in which the control valve is located is either the pipeline after the pump or the pipeline after the compressor. In such cases, when calculating the pump head and the outlet pressure of the compressor, it is necessary to assume a certain pressure drop across the control valve first in order to determine these values. If the pressure drop assumed is too low, energy is saved, but the regulation effect will be poor; conversely, if the pressure drop assumed is too high, energy is wasted, but the regulation effect will be good. It is generally required that the ratio of the pressure drop across the control valve to the total resistance drop of the piping system be around 0.3; the total resistance drop of the piping system includes the frictional loss in the pipes, the resistance losses due to equipment located at the start and end of the pipeline, the pressure drop resulting from height differences, and the pressure drop across the control valve. Tip: You can enter “Lao K’s Weekly Thoughts – Talks about things in the petrochemical design industry” into the website’s search engine to view previous posts