Double Walled Pressuer Vessel Certification 2

[abuanaselmasry]

Dear All;

I have successfully designed a Jet-A SS double walled pressure vessel and hydrotested. The internal vessel is the main vessel. The outside vessel is for leak detection as well as will work as a standby vessel in case of the failure of the internal vessel till the maintenance or replacement of the internal vessel. Hence, I have designed both internal and external vessels for the same conditions. I have not applied the internal pressure of the outside vessel as external pressure for the internal vessel. As per my understanding, they will not operate independently as expressed in UG-99 (e)(1). There is no inlet and outlet nozzles for the external vessel, liquid will fill-up only from the leakage of the internal vessel, if happens. In addition, UG-19 (a) says:
"Each element including the common elements, shall be designed for at least the most sever condition of coincident pressure and temperature expected in normal operation."
I have stated the operation scenario in the MDR. But, Is there any special requirements to be marked in nameplate in order to avoid full pressurizing the outside vessel where as the inside vessel is atmospheric? Could a caution similar to the one required for Heat Exchanger be sufficient? If common element marking is required, then the entire inside vessel is a common element. Could you please advise what to do, the vessel is waiting only for nameplate attachment and ASME Stamp application.
Best Regards,
M.Salaheldin

Regards,
M.Salaheldin
Static Equipment Mechanical Design Engineer

 

[fegenbush]

I would complete the data report similar to that of a heat exchanger as you have mentioned. I would also seek the advice of your Authorized Inspector to confirm that they agree with your approach.

 

[GenB]

In my opinion. You need 3 lines: 2 stampings for the first vessel on internal press and temp, external press, and temp. And one for the outer vessel internal press.and temp.

 

[abuanaselmasry]

Thanks for your replies.

I have filled the MDR for Multi-walled vessels. I have used Items 6~11 for the outside vessel & Items from 14~18 for the outside vessel. MDR for me is filled satisfactory, however, only nameplate marking I'm still doubtful. The 3 lines suggested by @GenB is not sufficient as per my understanding. It means the outside vessel can be pressurized independently from the inside vessel which is not considered as well as not applicable in the operation. Commonly if we have differential pressure for the common element, it has to be marked in the nameplate, but, for the current case the entire internal vessel is a common element!! I'm really confused

Regards,
M.Salaheldin
Static Equipment Mechanical Design Engineer

 

[gr2vessels]

I sense some problems with the design;- this is a typical self bunded fuel storage tank, not a pressure vessel. It is most likely designed for combustible liquid (as opposed to the flammable liquid). The external shell is suppose to be vented and a flame arrester fitted to this vent. There are several standards available in the world for the design of this equipment, with stringent requirements of safety. The design to a pressure vessel code does not provide the safety required for handling flammable or combustible liquids. Be on the safe side and review your design for compliance with codes like UL 142, but also British, Australian codes, etc.
Cheers,
gr2vessels

 

[abuanaselmasry]

Thanks gr2vessels for your reply. The process design and safety of the vessel operation is decided by a very famous European company. We already offered them UL 58 during offer stage, but they have insisted to design it for ASME Code. ASME VIII Div.1 is very stringent code. Requirements of UL 142 and UL 58 are less than ASME VIII Div.1. Both internal and external vessels are provided with Vent nozzles equipped with Pressure safety valves, but since it is in our client scope, I'm not sure if has flame arrestors, however, I agree with you in this point. The outside vessel is mainly of Leak Detection and equipped with Leak Detector. The vessels, mechanical wise, are well designed and fabricated with top quality and stringent inspection since it is for Saudi Aramco (3 inspectors rather than our inspector are included). RT results are acceptable....... My confusion is mainly for the certification and marking requirements to avoid any mis-use and/or operational accidents at site, specially it will be installed in offshore platform.

Regards,
M.Salaheldin
Static Equipment Mechanical Design Engineer

 

[gr2vessels]

It doesn't matter if the vessel was designed to a pressure vessel code, as long as it is safe from the operation point of view.
1. All the inlet outlet nozzles must be in the top of vessel, fitted with anti-siphon valve, to prevent accidental siphoning of the fuel on the ground. There must be a form of overfilling protection, typically you use a standard mechanical float valve designed for fuel tanks. You can use level controllers, linked to the filling control panel.
2. You must protect the tank during filling with a relief valve fitted with a flame arrester. Also, you need an oversized emergency relief valve, with no flame arrester, for fire case.
3. You need to vent the interstitial space of the double skin, in case of breach of the inner shell. I would also put a small 1" drain valve just in case...
4. Again, safety is your main concern, any design which cannot prevent the fuel spill is wrong!
Cheers,
gr2vessels

 

[GenB]

gr2vessels. According to your answers, is it fair to say that this is a combination ASME-UL construction? which is common for insurance compliance specially.

 

[abuanaselmasry]

Just of a good news. The vessel is ASME Stamped and MDR is signed. The vessel is protected from fire by N2 blanket.
Thanks to all.

Regards,
M.Salaheldin
Static Equipment Mechanical Design Engineer