ANSI Flange 300# Failing at Design Pressure 3

[Mechanical_Gau]

Hello Friends,

We are designing Propane Mounded Storage Tank for Water Capacity of 119,000 Liters. Here are the following details with the SS.

Working Pressure - 12 kg/cm^2 (171 psi)
Design Pressure - 21.356 kg/cm^2 (304 psi)
Corrosion Allowance - 1.5 mm (Is it fair to have 1.5 mm (0.059") or should we go for 3 mm (0.11")as it is ?)
Temperature - (-)42 deg C (-41.11 deg F) to (+) 55 deg C (131 deg F)
Density of Propane - 0.441 kg/m3 (0.02753lb/ft3)
for more details pls see the attachment

My query is, how come the nozzle is failing for 300# and passing for 150# ? Nozzle is failing at MAWP. MAWP is 22.33 kg/cm2 (317psi)

Your kind response will be highly appreciated.

Regards

​

 

[Mechanical_Gau]

According to Indian Standards it is imperative to select 300# Flange for Propane and LPG service. Kindly help me over.

 

[SnTMan]

Not clear to me what's going on there, but, nozzle flange rating should have no effect on reinforcing.

If failing on reinforcement perhaps static head is the cause? You are going to need to carefully check your inputs & outputs, IMO.

Cannot offer any opinion about the CA, what is industry practice for the class of work?

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[MJCronin]

Some Questions:

1) What is the "SS" ??

2) My experience has been that nearly all propane tanks in the USA are designed to a MAWP of 250 psig. Why are you designing to a much higher pressure ? (Because the client said so is not an acceptable response)

3) A corrosion allowance of 1.0 - 1.5 mm is a common choice for propane service. (Check the vendors of these tanks on the internet) IMHO 3 mm is excessive

MJCronin
Sr. Process Engineer

 

[TomBarsh]

The dialog clearly shows the "Flange Rating: 50.732 kgf/cm^2" in blue text at the bottom of your screenprint. Therefore the flange is passing, contradicting your post's title.

But as others have indicated, the flange rating is only one aspect of getting the nozzle with flange to pass the design requirements. It's likely that there is insufficient reinforcement as per UG-37, etc, to support the design pressure. You'll have to review the calculations for this and for any other insufficiencies.

 

[LittleInch]

Might be nothing, but your dia basis for your nozzle states ID? Should be OD?

But if nothing changes but it works when you put in class 150, then I don't know. Maybe weight of the flange and blind exceeds some stress value on the nozzle pipe itself? a 20" class 300 WN flange and blind is quite a lot of weight.

So try a thicker nozzle and see if it goes away.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[marty007]

I don't use that software, so I'm not familiar with its quirks.

One thought, do you have the software designing nozzle reinforcement for the vessel MAWP? If so, could the 150# flange be limiting the MAWP of the vessel such that the opening reinforcement passes? But when you put in a 300# flange the vessel MAWP increases and the nozzle now fails?

As I said, just a guess.

 

[cbPVme]

I would suggest that you actually go through the calculation report and see where the failure is occurring. PVElite gives you a step by step set of calculations. You should be able to trek through and see where the failure is occuring. Do this for the 150# and 300# and compare the differences.

 

[Mechanical_Gau]

Hello Friends,

Thank you very much for all your replies. The problem got solved. I have increased the thickness considerably with approval and things are now fine. Thank you once again.

@MJCronin SS --> Screen Shot
BTW MJCronin, why in America do you take particularly 250 psi ? is there any reason for that?..Regards

 

[SnTMan]

Mechanical_Gau, you gonna tell us what was going on with the 150# flange?

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Mechanical_Gau]

@SnTMan .. The problem was it was passing on 150# flange but not for 300#

 

[TomBarsh]

"The problem was it was passing on 150# flange but not for 300# "

Assuming that the nozzle and opening were designed for the same pressure in both cases (which isn't necessarily so, with software options) then the issue is likely that due to the longer hub length of the Class 300 flange the projection of the nozzle neck was decreased sufficiently (assuming that the projection to the face of the flange was identical in both cases) so that the reinforcing area A2 in the nozzle neck was reduced such that the total reinforcing area was insufficient. This would result from ASME Code UG-40(e) stating that material within the flange hub cannot be utilized as reinforcing area.

 

[MJCronin]

Gau .....

You never bothered to answer my question, but yet you demand more information from me ....

You state that your application is for "mounded storage" and that your vessel MAWP is 317 psig.

The vapor pressure for propane at 100F is approximately 172 psig. Your mounded design will never reach 100F

Again, in my opinion, a MAWP of 317 PSIG is too conservative ...

In the US, the NFPA organization makes a distinction between propane storage acting as vehicle engine fuel containers (subject to shock and overpressurization) and those acting for space heating and the like. Pressure vessels for engine service shall be designed to 312 psig, others to 250 psig

http://www.nfpa.org/Assets/files/AboutTheCodes/58/58_A2016_LPG-AAA_FDagenda_Part2.pdf

Additionally, the 250 psig standardization for propane pressure vessels means that ASME vessel shops can fabricate a whole range of products on spec, and compete in the marketplace for both propane and anhydrous ammonia vessels.

https://hansontank.com/ammoniatanks.html

MJCronin
Sr. Process Engineer

 

[SnTMan]

@SnTMan .. The problem was it was passing on 150# flange but not for 300#

Yeah, I knew you had said that. I thought, perhaps, you might have discovered why.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Mechanical_Gau]

Hello friends and MJCronin,

I am sorry for the delay.

I really appreciate your answer for the same it has however increased my knowledge. The reason that it was failing because it was not sustaining on that thickness. hence 300# flange was failing and 150# was passing. That is all i can say.

BTW, i am not demanding to answer i was just curious to know why US has specifically design consideration for 250 psig. Peace