4 replies to this topic

[Musab Ammad]

Respected members,

 

I am a junior engineer and it was assigned to me that i calculate breathing capacities for PVRV's and emergency valves for 40 tanks(most of tanks were filled with fluids whom physical data and properties are not known or provided from client) and to verify vendor provided data to ensure that vendor quoted valve sizes & capacites are acceptable or not. I calculated breathing capacites as per API 2000 but i couldn't find any method to in API regarding valve sizing.

I continously follow this forum and learn alot always, in some of the threads it is mentioned that technical paper 410 is to be used for calculation of valve size etc etc. I still am unable to get the philosphy that how to utilize pressure drop function for valve sizing due to my lack of knowledge.

so after manually calculating the breathing capacities i thought to do these calculation in excel with my limited knowledge. During surfing internet i found a formula (stated below in red) but couldn't find any reference about this formula

 

kd =[ {(0.269906*(Outlet pressure/Inlet pressure)}^2-{0.751687*(outlet pressure / inlet pressure)+1.18178)}*0.95]

*outlet pressure/inlet pressure OR p2/p1 OR pressure ratio

 

It stated that dividing the total breathing capacity (i.e. inbreathing/outbreathing/Emergency) by kd to get therotical flow and i calculated back the area required to flow by the equation provided in API 2000 to calculate therotical flow.

My excel sheet is attached for your review, i utilized the same formula of kd and calculated valve size by calculating theoratical flow.

Being a process design engineer i have learned that never trust a told value, always calculate your own value so that you can prove how you do it, i am confused about presenting this sheet because this formula is not justified because i don't have any reference for this formula.

I thought it will be nice to have your opinion and suggestion about this problem of mine.

 

This excel sheet might seem bit odd due to my limited knowledge of excel and being inexperienced in making calculation sheets. And it would be very kind of you to spare your precious time to provide your comments about my problem and making this sheet more user-friendly.

 

 

Regards,

 

Ammad Khan

 

 

 

 

 

 

Attached Files

•  Venting Calc Compelete API 2000-Rev 0.xlsm   51.77KB   163 downloads

[fallah]

Ammad Khan,

 

API 2000 has nothing to do with PVRV and EV sizing but is used to calculate the required in-breathing/out-breathing capacities and emergency relief load. Then prepare the valves data sheets based on such info and by sending to reputable vendors leave the sizing/selection to be done by them... 

[Musab Ammad]

Thank you fallah for your prompt response.

 

I concur with your statement that API 2000 has no reference for PVRV and EV sizing. But if the provided valve size and stated capacity from vendor is to be verifed then how should some one wet the provided data by vendor. I know that vendor take responsibility of safe operation based upon provided parameter in datasheet, however, for my own learning I want to calculate a tentative size which might be same or 1 size differ with vendor provided size.

 

I would like to have your opinion about Clause # 6.3.2.2 of API 2000 , which covers equation 20, 21 & 22 to calculated first theoratical flow and then dividing actual flow by theortical flow to calculated discharge coefficient. Can we reverse the procedure if we somehow managed to calculate discharge coefficient and then calculated theoratical flow proceeding toward valve size ( Amin =is the minimum flow area of the device) ??

[fallah]

Hi,

 

You can do the calculation as per the method you mentioed and would reflect the calculated size, but just as preliminary size, in the valve data sheet asking vendor to review and evaluate. Anyway, the proper size would be specified/finalized by venor...

[Musab Ammad]

Yes, i see eye to eye that this calculated size is perliminary or tentative. It certainly to be reviewed and evaluated by vendor and the size specified by vendor is to be finalized.

 

Thank you very much for your time.