Calculation of the pressure-reducing and flow-limiting orifice plate in the nitrogen sealing pipeline of storage tanks
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I’ve also read some discussions on forums regarding this topic and looked up some information, but I’m still not quite sure how to choose the appropriate calculation method. I hope friends with experience in this area can give me some advice; it would be great if they could provide a calculation sheet as well. Thank you in advance.
A nitrogen-sealed self-acting control valve can be used directly; there is no need to install an orifice plate.
To prevent damage to the tank caused by a malfunctioning control valve, the pressure is first reduced to some extent using an orifice plate.
I seem to have orifice plate calculation software, but my rank is too low to upload it
The flow restriction orifice plate calculation software that was just uploaded is available here: http://bbs.hcbbs.com/thread-390064-1-1.html
I’m not sure whether you want to calculate the flow rate for a flow control orifice plate or that of a nitrogen seal
There’s no need, right! 1. A control valve can be installed to adjust the flow rate or pressure, with the selection based on the actual conditions on site. 2. A safety valve is installed on the storage tank; if the automatic control valve fails and nitrogen continues to flow into the tank, causing overpressure inside it, the safety valve will activate to protect the tank. Recommendation: The safety valve of the storage tank should be retested and adjusted at least once a year to ensure safe and proper operation.
Know the flow rate to calculate the flow-limiting orifice plate
Actually, there are more cost-effective methods: 1. Calculate the maximum flow rate of liquid exiting a storage tank; the diameter of the orifice is then determined based on this flow rate of nitrogen used for nitrogen sealing. 2. A breathing valve should be installed on the storage tank, along with a pressure alarm as well.
The Petrochemical Design Manual, Volume 4, provides the calculation methods; iterative calculations are required using the flow coefficient charts. First, determine the pressure difference across the plate under the operating conditions to assess whether flow is at a critical level. Then, assume a flow coefficient (usually 0.6 is chosen initially), calculate the pore size using the relevant formula, and check the flow coefficient against the chart corresponding to that pore size. If the flow coefficient differs significantly from the initial value, reset the values and recalculate. For the flow coefficient chart, no regression equation has been seen yet; manual iteration is the only option.
Thank you! I was using the same software, but I didn’t know where the formula came from; it was only after reading what was posted above that I found out.
I’m not very clear about these things!