Why are flow rate data required when purchasing self-acting control valves from a valve factory?
Thread Content
This post was last edited by Catalyzing a Grain on 2018-7-14 at 17:42. I have already provided the valve factory with the diameters of the nitrogen and compressed air pipelines, as well as the pressure before and after the valves. However, they insist that I provide the maximum flow rate, normal flow rate, and minimum flow rate, but I don’t know these specific values. When I asked the designers, they said that they have never been asked about flow rates when purchasing self-acting control valves; it is sufficient to provide only the pipe diameters and the pressures before and after the valves. The design tells me that the minimum value is 0, which is when it is turned off ； So, may I ask everyone how exactly this data volume should be filled in? Can the normal data volume be the same as the maximum data volume? Can the minimum flow rate be 0? Help, beginners don’t understand it!
The design team says that for normal traffic, 75% of the maximum traffic volume should be used – is that acceptable?
Look for design materials~~If that doesn’t work, then find the places where gas is used downstream; together, those will suffice~~
Your team doesn’t know how to do proper design; without any traffic data, how can you calculate the CV value or conduct any verification? Such a design should just be abandoned.
I don’t understand design; it’s nonsense. Cv must be present
The design for these columns related to flow rate should be provided by the process engineering team; asking the instrumentation team is pointless, as they either lack the necessary expertise or are irresponsible.
It’s obvious at a glance that the process design is poor-quality; the maximum, minimum, and normal values are determined through process balance diagrams and require calculations. Those who claim the minimum value to be 0 clearly have no understanding of process design at all
Hello, generally, the parameters required for purchasing a control valve include: the valve diameter, the pressure before and after the valve, the type of medium, the temperature of the medium, and the operating conditions. With these parameters, a quote can be provided. However, if purchasing, a Cv value still needs to be provided, as it relates to pre-production calibration. Please learn about the characteristics of self-acting flow control valves: 1. The flow rate can be set according to design or actual requirements, and it can automatically eliminate fluctuations in system pressure differences to maintain a constant flow rate. 2. The flow display values are all the randomly calibrated flows on the test bench (m³/h). 3. Thoroughly resolve the issue of high pressure difference at the proximal end and low pressure difference at the distal end. 4. Overcome uneven temperature distribution in the system and improve the quality of heating (or cooling). 5. Reduces the design workload, as there is no need to handle pipes. 6. Decreases the amount of water circulating in the system, thereby reducing system resistance. 7. Eliminates the need for flow reallocation when switching heat sources in multi-source heating networks. 8. Reduce the difficulty of network tuning by simplifying complex tuning tasks into straightforward traffic allocation.
Indeed, it’s useless to simply look for information related to instrumentation; the flow rate is determined through process calculations. Additionally, calculating the CV value of control valves requires knowing the flow rate
I asked the design team for the maximum/normal/minimum flow rate data, and they said that the minimum value is 0 when it’s turned off； The normal flow rate is supposed to be the amount used in our workshop – we just write that amount down. They don’t know it, but our new workshop still hasn’t been built yet ； For the maximum flow rate, let me mention one value – do you think it’s reasonable? Anyway, I don’t understand it and think the scale is too large: for the nitrogen pipeline, it’s DN50 before the valve at 0.2 MPa, and DN100 after the valve at 3 KPa. The design team said that the maximum flow rate calculated is 800 m3/h, and they recommended using 75% of that maximum value as the normal flow rate.
Self-acting control valves also belong to the category of control valves. Can you choose another control valve without specifying the flow rate? Therefore, when selecting a self-acting control valve, it is also necessary to specify the flow rate; otherwise, if the flow capacity is insufficient, the valve will not function properly