Design of Orifice Plate

Replies

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  Ramani Aswath

  Flowrate Calculation for an Orifice Flowmeter
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  CE Designer

  bioramani

  Flowrate Calculation for an Orifice Flowmeter
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  Thanks, I got some good info there. But what i really need is to design an orifice that will allow me to drop from 800 to 100 psi. Having some trouble with that 😕
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  CE Designer

  If anyone can provide some assistance here is some more info:
  The medium is oil
  The density is 920 kg/m3
  viscosity = 0.1 pa s
  pipe I.D. = 1.939
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  Ramani Aswath

  CE Designer

  If anyone can provide some assistance here is some more info:The medium is oil, The density is 920 kg/m3, viscosity=0.1pa s, pipe I.D.=1.939

  Why not use a valve? That is a rather large pressure drop. Unless the flow rate is known it is not possible to work out a design. Then again, it will do the job only at that flow.
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  Lalit77

  Ya you can also use FRL unit.With the combination of filter,regulator and lubricator you can regulate various pressures also.
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  CE Designer

  bioramani

  Why not use a valve? That is a rather large pressure drop. Unless the flow rate is known it is not possible to work out a design. Then again, it will do the job only at that flow.

  Well we want to use an orifice plate with flange taps so we can measure flow rate. Most formulas and calculators ask you for the orifice bore, pressure drop and flow rate upfront. Im asked to design the bore for a given pressure drop. All I know is that the bore has to satisfy the beta ratio.
  This is something completely out of my expertise. I took the challenge anyway. Flow is like 6 gpm max but i will change.
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  Ramani Aswath

  Even then we have a problem. There appears to be a design requirement to reduce the pressure from 800 to 100 psi and simultaneously measure the flow. If the orifice pressure drop is that high the flow measurement will be quite inaccurate. Can you consider a small bore plate upstream to do the pressure drop and a down stream orifice for measurement? I do not care much for that idea. It just might work though.
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  CE Designer

  bioramani

  Even then we have a problem. There appears to be a design requirement to reduce the pressure from 800 to 100 psi and simultaneously measure the flow. If the orifice pressure drop is that high the flow measurement will be quite inaccurate. Can you consider a small bore plate upstream to do the pressure drop and a down stream orifice for measurement? I do not care much for that idea. It just might work though.

  Thats a possibility, thanks. What would you recommend, 800 to 400 instead. If so how will i go about designing an orifice bore for that.
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  Ramani Aswath

  It might be better to use a longish small bore pipe up stream to drop the pressure, though this occupies some length. I still do not understand if there are two independent design requirements. One, to reduce line pressure from 800 to 100 psi and another to measure a flow of 0 t0 6 gpm. Unfortunately the pressure drop is itself a function of the pipe size or an orifice size. Is the flow being controlled elsewhere and only a reading required? If so, there would be a pressure drop at the control point.
  You can use this for calculating the pipe size: #-Link-Snipped-#
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  CE Designer

  I too am unsure. From what I understand the orifice meter has two stages. The orifice plate creates a pressure drop and this pressure differential is used to determine the flow rate by the orifice instrument. I am not sure why i was asked to design this orifice to create a pressure drop from 800 to 100 psi. Why does it have to be this. There must be a way of determining the pressure drop that an orifice will provide given the bore of the orifice.
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  Ramani Aswath

  The link I gave does that calculation. My concern is something else. Generally flow meters are used to cause minimum interference with the fluid flow.
  In this case the pressure drop is enormous and will involve a heavy loss of power. The lost pressure drop will appear as heat in the oil. I am unable to understand how 800 PSI came up in the first place.
  For small flows a capillary flow meter does quite well. It is also very simple and cheap.
  At the next level is the orifice meter. This does cause some pressure drop. However, it occupies less space and at the lowest level it is just a plate with a hole in it and a pressure gauge. A venturi meter is more efficient with hardly any pressure loss. However, it is more expensive and occupies more space.
  Let us see if we can do a quick calculation on the parameters given.