Terms in the software
Gespeichert von semiramis badri am 21. Dezember 2021 - 10:18
Forums:
Hi there!
I am new to Conval. I want to design PSV/PRV with it. Could anyone help me understanding the below terms and what are the right ranges of values for them within Pressure Relief Valve design module.
1- What is flow reserve for and what should its value be?
2- In which range should be the maximum set pressure?
3- how could I choose the right valve from the "select valve" section when no match with my required DN?
I would be grateful if someone could help me understanding these contents.
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Terms in the software: PSV/PRV sizing
Dear Mrs. Badri,
Thank you for your enquiry. The questions you are asking have less to do with CONVAL® itself than with the general procedure for designing PSV/PRV.
General information about the fields can always be found in the online help in CONVAL® itself.
In other words, the "flow reserve" is the percentage by which the flow possible with the selected valve exceeds the required flow.
It should never be less than 0%, but how high it may be depends on its application, but usually not more than 50%.
If it is greater than 50%, CONVAL® will advise you to look for a smaller valve.
The "flow reserve" can possibly be limited with a "lift stopper".
You can switch off the filter, allowing to see / select any valve in the database.
But when selecting a no suitable valve, CONVAL® indicates the not matching parameters resulting out of your selection, e.g.:
Basically, however, your process requirements define the parameters for the calculation. CONVAL® is the tool that determines solutions with the given condition according to the rules of the applied standard.
Kind regards
CONVAL® Support Team
Orifice
Thank you Mr Vogt.
There is another question for me for an orifice design section; when I receive the warning message "The theoretical mass flow is used for calculation , the calculated throttle for the orifice may not be sufficient" what shall I do in this case to tackle this problem and not increasing dramatically my orifice diameter?
Orifice
Dear Mrs. Badri,
The information "The theoretical mass flow is used for calculation, the calculated throttle for the orifice may not be sufficient" is displayed if you use the option safety-related applications and calculate the throttle orifice d for a given flow rate.
As an alternative to the standard calculation method, two further options methods are available in CONVAL.
Use this option if you want to ensure that the calculated flow is never exceeded.
Use this option if you want to ensure that the calculated throttle orifice always allows the required flow rate.
Kind regards
CONVAL® Support Team
Calculation of the superimposed back pressure
Dear Dirk,
Many thanks for your comprehensive explanation. Today I noticed my appreciation message was not sent to you! strange!
There is another question for me regarding designing the pressure relief valves. In the "Medium" section of the software, there is "Pressure" part and there are Pb and Pae, but how could one calculate the superimposed back pressure? Could you help me out please.
Thank you in advance!
Best regards,
Semiramis
Calculation of the superimposed back pressure
Hallo Semiramis,
We gladly accept your thanks.
The superimposed backpressure (pu) is defined by the API 520 as the static pressure that exists at the outlet of a pressure relief device at the time the device is required to operate. It is the result of pressure in the discharge system coming from other sources and may be constant or variable.
The superimposed back pressure is a value which must be entered manually by the user in CONVAL. (The default setting is 0 bar(g) / blow off into atmosphere). The "calculation" / determination of the superimposed backpressure must therefore be done by the user based on design / process data of the blow-off line.
Kind regards,
Benedict Nowak
Thank you Benedict!
Thank you Benedict!