Does process design need to take into account the valve opening degree?
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This post was last edited by jmdc on 2017-10-14 at 15:55. Why does process design need to take into account the valve opening degree? In the initial process design, when determining parameters such as flow rate, pipe diameter, and flow velocity, it should be designed based on or assuming that all valves are in the fully open state, right? If, during normal operation, a set of equipment has valves that are not always fully open or do not come close to being fully open, can it be considered that the design of this equipment is unreasonable, or that such usage is unreasonable? (Because the valves themselves cause losses such as pressure drop; the more valves there are, the smaller the opening degree, and the greater the losses.)
In general, during design, even when the designed flow rate is reached, the valve isn’t meant to be fully open. If it is fully open, then the valve’s regulating function is lost; in that case, it’s cheaper to just use a pipe directly. My personal understanding. Waiting for an expert to give an explanation.
The maximum flow rate is determined by the pipeline; valves have little impact
The selection of valves should be determined based on the process requirements. They can be divided into two types: those with switching function and those with regulating function. Valves with a switching function generally have a diameter equal to that of the pipeline; for valves with a regulating function, the appropriate size should be chosen based on parameters such as flow rate range and pressure drop – it is not necessary for their diameter to match that of the pipeline; it can be smaller, or it can also be the same.
It depends on whether you choose a globe valve or a control valve
During design. The material quantity under normal operation is determined based on material balance, from which the maximum and minimum quantities are identified. An appropriate pipe diameter is then selected based on the maximum quantity. The control valve is sized by considering the maximum, normal, and minimum flow rates as well as other parameters; at the maximum flow rate, the valve opening generally does not exceed 80%. Therefore, during normal production, the valve is not opened fully or close to full opening. Moreover, when calculating the valve, the allowable pressure difference specified in the design requirements is already met.
The process engineering team usually specifies the minimum, normal, and maximum flow rates, and the instruments are selected based on these values. The opening degree of the valve is not considered by the process engineering team.
Based on the process parameters, there are maximum and minimum design values; generally, when the value is at its maximum, the valve opening is around 55-65%, which facilitates adjustment
Based on the process parameters, there are maximum and minimum design values; generally, when the value is at its maximum, the valve opening is around 55-65%, which facilitates adjustment