Selection of flow restriction orifice plates
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Our company plans to replace one of the control valves in the steam system. Since the Cv value of the new valve is almost twice that of the old one, we are concerned that the discharge capacity of the safety valve downstream may not be sufficient. There are two proposed solutions: 1. Install an additional safety valve downstream； 2. Add a set of flow-limiting orifice plates to limit the maximum flow rate after the new valve is put into use. My question 1: Will adding a flow restriction orifice plate pose an obstacle to the proper operation of the control valve? Question 2: I consulted the design manual; to calculate the orifice diameter, the pressure after flow restriction is required. How can this value be determined? Question 3: If it is feasible to add orifice plates, are there any requirements regarding their location?
This post was last edited by CHANGBAISHI on 2022-4-7 07:35 to explore whether it can be solved from another perspective. Firstly, the original safety valve was designed based on the optimal amount of discharge that the equipment could produce, and this discharge volume has no inherent connection with flow restriction mechanisms. So there is no need to consider adding facilities such as flow restrictors. If there is an increase in parameters such as the discharge volume and pressure of the equipment, then the discharge capacity of the safety valve needs to be taken into consideration. Furthermore, it is necessary to consider whether an increase in the CV value of this valve meets the process requirements, and whether it will have an impact on any changes needed in the process for the equipment. It is recommended to send a simple diagram to clarify the actual position of this control valve in relation to the safety valve, which will facilitate discussion. For reference.
For applications with specific requirements regarding flow rate, the valves should be configured according to the parameters specified in the original design. For reference.
I have the standard documents; I just don’t know how to give them to you. How about adding me as a friend?
The purpose of adding a flow-limiting orifice plate is to keep Qmax, which occurs when the valve is fully open under extreme conditions, below the maximum discharge capacity of the safety valve. My concern is whether the pressure drop resulting from the flow-limiting orifice plate will affect the valve’s regulation characteristics.
If a flow-limiting orifice plate is to be used, how about installing it in front of the pressure control valve? It does not affect the pressure behind the valve, while limiting the maximum amount of steam that can flow in.