Seeking advice on selecting the upper limit for differential pressure in orifice plates
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In standard throttle device design documents, there are usually several settings for the upper limit of differential pressure. For example, with 4 ranges such as 10, 16, 25, 40, 60, how is the upper limit of the differential pressure determined? 1. How to make a choice considering pressure loss? According to the data, taking pressure loss into account, there are two values: the upper limit for the differential pressure across the orifice plate = (2–2.5)*pressure loss, and the upper limit for the differential pressure across the nozzle = (3–3.5)*pressure loss. I’m not sure if this is correct 2. How to make a choice without considering pressure loss?
Four different differential pressure values correspond to four different flow rate values. Minimum, Normal, Maximum, Full pipe. The traffic volume also gets larger from one to the next. Usually, the largest corresponding relationship is chosen
The upper limits for differential pressure are set at 10 kPa, 16 kPa, 25 kPa, 40 kPa, and 60 kPa, which helps to reduce the number of different models available for differential pressure transmitters. When the operating pressure of the medium is low, a smaller pressure loss is acceptable; 10 kPa or 16 kPa can be selected ； When the operating pressure of the medium is at moderate levels, a low pressure loss is acceptable; 16 kPa or 25 kPa can be selected ； When the operating pressure of the medium is high, a small pressure loss is allowed; 40 kPa or 60 kPa can be selected.
How are the medium operating pressure ranges of low, medium, and high defined? Could you explain it in more detail?
The flow rate is proportional to the square root of the pressure difference; moreover, the level of this pressure difference across the orifice plate is closely related to the operating pressure of the fluid. If the flow rate is high, choose a larger range; if the flow rate is low, choose a smaller range. If you can’t do the calculations and are not sure what range is most appropriate, then leave it to the person who sells the orifice plates to carry out the calculations and make the selection. Worrying about trivial things only leads to mistakes and wastes time and energy; it’s better to use that energy to go home, hug your wife, and play games. That’s what’s right to do. :lol.
"The upper limit for differential pressure on orifice plates = (2-2.5)*pressure loss; the upper limit for differential pressure on nozzles = (3-3.5)*pressure loss. Who said that? Tell me who said it – go take off your shoes, go get some shit in the toilet first, and then come and suck my mouth. :Lol, the differential pressure range should be 1.1 to 1.4 times greater than the differential pressure value corresponding to the maximum flow rate – that’s the ideal range. Just like when you marry a wife, she needs to be a match for you, right? If you were to marry a dinosaur elephant that’s several times older than you, wouldn’t you need to use a ladder to get up to her in order to have sex? :lol
This can only be used as a reference; everyone hopes for a larger pressure difference, as this ensures more accurate measurements.
This is stipulated in the automatic control design manual.
This post was last edited by 1111111 on 2018-9-20 09:48. Is that so? ! Ugh, that chapter in the manual was written by that jerk! Pull him out, those shoes covered in shit – slap him in the mouth. . Let’s think about it: the peak flow rate generally does not exceed 1.5 times the rated flow rate. As for the pressure difference, the peak pressure difference is 2.25 times the rated pressure difference. The manual further increases this peak pressure difference – that is, the pressure loss – by a factor of 2 to 2.5, resulting in a value that is 4.5 to 5.6 times the rated pressure difference. This means that when the equipment is operating at the rated flow rate, the current output of the pressure gauge will be less than 7.5 mA, which is less than 22% of the full scale. When the device operates at 1/2 of its rated flow rate, the current output of the differential pressure gauge will be less than 4.9 mA, which is less than 6% of the full scale. The differential pressure gauge is not working properly at all! The span of the differential pressure gauge signal is significantly too small! This violates the basic principles of using pressure instruments, and it will cause serious problems in signal acquisition, likely resulting in insufficient accuracy in signal collection. .
The term \"pressure loss\" we’re talking about might not refer to the same thing; I understand that the pressure difference must be higher than the pressure loss. As for exactly how many times higher, I don’t have the means to determine it. Since it’s written in the book, there must be a reason for it. When I calculate the throttling device, sometimes a higher multiplier works well as well.
Oh. . . . . . It seems we need to first figure out which parameter is meant by \"pressure loss\" as mentioned in the manual, and what its value is. The pressure loss, as I understand it, refers to the peak value, ultimate value, or maximum value of the pressure difference across the throttle element under the relevant conditions. .