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Can I Install Regulators in Series to Maintain a Constant Flow Rate for a Constant Load Application.

I am planning to install a combination of pressure regulators in series to maintain a constant flow rate for a constant load application. P1 --> (Regulator 1) ---> Pint -----(Regulator 2)----> P2. 

P1 is fluctuating between 3 psig and 7 psig. Even if we don't have Regulator 1 installed, Regulator 2 will maintain P2. The load is a Kiln, with a constant gas requirement of 6440 SCFH. 

As the regulator flow rate works on delta P, so what I am trying to do is maintain a constant delta P across Regulator 2 even if the P1 fluctuates. 

Set P2 = 2.5 psig 

Set P1 = 3 psig 

I hope to see a constant flow rate to the load, even if the pressure P1 fluctuates. 

Need input on that pleas.  

Jawad Waheed

• 20 Nov 2017 11:03 AM
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9 Replies

• Jeff_Welch

  

  • 20 Nov 2017 2:57 PM

  Hello Jawad,
  
  Based upon the information you provided, I would point you towards the 133H regulator; however, I would need more information to make a final determination (material, size, accuracy requirements). The 133H has a balanced port, and is therefore not affected by inlet pressure swings. This regulator also has a quick speed of response, which is something a kiln sometimes requires.
  
  I'll give you an inside sales senior engineer contact so they can assist you with any follow up inquiries or with ordering.
  Nareshkumar.Sampath@Emerson.com

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• Jawad Waheed

  

  • 21 Nov 2017 6:47 AM

  In reply to Jeff_Welch:

  Hello Jeff,
  
  Thank you for your reply. We already had Fisher 299H in possession, so were planning to install this for this application. I am going through the 133H and will comment on it later. I would like to discuss this issue in the light of fundamental fluid dynamics principles. The target is to maintain a constant gas flow rate at 2.5 psig for a constant load application. Essentially if the outlet pressure remains the same, irrespective of the regulator i choose, the flow rate must be the same. But it increases due to the increase in inlet pressure. So what we are trying to do is put another regulator behind the first regulator, to maintain a steady pressure supply to the final regulator and finally maintaining a constant flow rate of gas to the load.

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• Scott Sandy

  

  • 21 Nov 2017 3:46 PM

  In reply to Jawad Waheed:

  Hello Jawad,
  I do believe that the 133 h will be a better option for your installation. But regardless of the regulator that you decide to use your setpoint for intermediate pressure is to low . You should look to increase it at least 2 Psig over your desired outlet pressure.

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• Jawad Waheed

  

  • 22 Nov 2017 9:49 AM

  In reply to Scott Sandy:

  Hello Sandy,
  Actually the problem is that, the minimum inlet pressure we encounter is 3 psig, so we will size our regulator system in such a way that even on 3 psig supply pressure we can get a flow rate of 6440 SCFH at 2.5 psig. What we dont want is, that when the supply pressure (main pressure) increases from 3 psig to 5 or 7 psig, the flow rate remains constant and the outlet pressure remains constant at 2.5 psig.

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• Scott Sandy

  

  • 22 Nov 2017 11:54 AM

  In reply to Jawad Waheed:

  The 133 series will maintain a constant outlet pressure regardless of fluctuations in inlet pressure. I have used them in distribution systems where inlet pressures drop 8 Psig .

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• Jawad Waheed

  

  • 22 Nov 2017 12:38 PM

  In reply to Scott Sandy:

  Good to hear that.. but what about the flow rate? will that remain the same as well irrespective of the inlet pressure?

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• Jawad Waheed

  

  • 22 Nov 2017 12:41 PM

  In reply to Scott Sandy:

  by the way we were planning to install 299H

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• Scott Sandy

  

  • 22 Nov 2017 5:52 PM

  In reply to Jawad Waheed:

  The flow rate should stay the same as long as your inlet pressure stays above the set point.
  I personally don’t see the need for adding another regulator. Any questions feel free to call me 8623335429. Scott

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• Jawad Waheed

  

  • 23 Nov 2017 1:15 AM

  In reply to Scott Sandy:

  Thank you Scott, at what time you are available, as I am GMT +5, I would certainly like to call

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