4 replies to this topic

[hayder]

hi all
iam designing sperical LPG tank i have psv and pcv goes to flare system i need to know how to calculate max. and min. upstream press and max. and min . downstream pressure
also i have no knowledge about how to calculate the flowrate goes to psv and pcv the line size is 3 inch.....set pressure of the tank is 18.2 kg/cm2 and tank cap. is 523 m3 please i need your help and iam waiting for reply with my bestregards

[Art Montemayor]

Hayder:

You have not supplied any information on your personal profile, so I don’t know if you are a student or not. Are you?

The reason I ask is because no one in a real life engineering project is made responsible for designing a spherical LPG storage tank without the required experience and professional expertise. This is a rather small spherical tank (diameter = 10 m) that, from practical experience, will not be competitive with a the normal, standard cylindrical bullet tanks used conventionally in LPG storage.

Your statement: “i need to know how to calculate max. and min. upstream press and max. and min . downstream pressure” makes no process sense. “upstream and “downstream” of what? If you mean upstream and downstream of the LPG storage, then it really makes no sense. That is not calculated; it is a given piece of data.

You state: “have no knowledge about how to calculate the flowrate goes to psv and pcv the line size is 3 inch”. This makes even less sense. How is it that you can’t calculate the PSV capacity and yet you have established a line size of 3 inches? Anyone responsible for designing a spherical LPG storage tank had better be an expert on how to protect such a tank with an appropriately designed PSV and complete identification of the base worse case scenario that the PSV is designed to address.

Please explain your situation and query before our members put any serious time into reading your original post. Is this a real design case or an academic assignment?

[hayder]

Dear friend iam sorry may be i couldnt explain My query well ..iam process engineer. I have to check the design of psv and pcv. ON THE LPG TANK WHICH GOES TO FLARE and to fill the datasheet of its .and because iam new with this design just i have the below data...design press of tank 18.2 kg/cm2 and the size of pcv 3 inch . In the datasheet i need to Calculate and fill in the blank the max. and min. Upstream press and the same in downstream . I hope its clear now and if its not can i put my email..........with respect to u all

[Art Montemayor]

Dear Hayder:

You are still failing to explain your query and to furnish the necessary basic data. This has nothing whatsoever to do with the English language – or any other language. It has to do with putting your thoughts and knowledge on paper. For example:

You now state that you “have to check the design of psv and pcv”. Does this mean that you are NOT DESIGNING the spherical storage tank as you first stated? Does this mean that the 10 meter diameter LPG spherical tank is an EXISTING TANK? If so, does that also mean that you have been assigned to fill in a data sheet for both the PSV and PCV that are to be found on this tank?

Or are you supposed to fill in the data sheet for the spherical tank? In any event, why don’t you respond to my request and furnish us with a P&ID of the existing installation? Furnish us with copies of the tank, PSV, and PCV data sheets so that we can see what is missing and what you are referring to.

Give us information on the Hazop that surely has taken place with regards to this tank and the installation. Who designed the installation and who did the calculations for the equipment sizing – especially the PSV and PCV.

Who has done the calculations for the worst case scenario for both the PSV and the PCV? Please furnish those calculations and the justification for the worst case relief scenario. We can help sort and identify what is important and what important information is missing as well as what important process engineering information is required to fill in the data sheet. But we need clear, concise, and accurate basic data.

Your email address is not necessary to generate what is required to arrive at an engineering solution. What is required is clear, concise, and accurate basic data.

[kkala]

Quite agreeing to the above posts, I can suppose that the task has been given to you without adequate explanations. You can ask for them, e.g. from your supervisor or other relevant person in your organization. This may be needed even for some of the clarifications requested in this thread.
When first employed, I was given a few tasks principally aiming at familiarization, requiring searching mainly in existing documentation (plus little actual data). Is your case similar?
Nevertheless familiarization with LPG handling facility can be the first step (may have been already realized). Then understanding of the purpose of PSVs / PCVs on the LPG sphere. http://www.cheresour...fire-protection '> http://www.cheresour...fire-protection can be helpful on this (bypass points not clear to you), also showing that the task may more complex than what first look indicates. Then searching for engineering practices of your organization to guide you how to work, as well as for relevant data sheets (as built). Then you have to specify flowrates through PSVs or PCVs (based on several events / contingencies) and estimate corresponding ΔPs to flare header, in order to find pressures downstream PSVs / PCVs.
Task can be simpler in case you find e.g. the flow rate of PSV somewhere in the documentation and supervisor accepts it as valid, along with the related conditions (pressure, temperature).
It is noted that pipes connected to PSV are currently sized here for rated PSV flow rate, even at fire case. Advise on this matter is welcomed (I find it OK, but other views can be met).
I believe that somebody from your organisation should closely supervise your work, implemented for the first time. And also answer your queries (Forum can contribute to the latter). This is the practice of Engineering Companies I have worked at.