38" ID Flange for Subsea Application (external pressure)
38" ID Flange for Subsea Application (external pressure)
(OP)
I'm trying to choose a flange for a subsea vessel but I'm having some problems to make the best choise.
a) In subsea equipments I always go for a API 6A/17D flange, but it goes up to 30" size, so 38 inches is way to big for API flanges. And API don't address what to do for bigger flanges.
b) I thought about ASME flange with ring type joint, but ring gasket according to ASME 16.47 is suitable up to NPS 36 (35 ID).
c) I couldn't find any note at ASME code regarding external pressures. I'm talking about REAL EXTERNAL PRESSURE (1500 psi), not just vacuum pressure.
d) ASME class 900 is 100 psi lower than my need of 2300psi internal pressure. And no bigger pressure class is available. Extrapolation on ASME tables is not allowed either.
I have 1500psi external pressure (3000 feet water depth)and 2300psi internal pressure.
Thanks in advance,
Mathias
a) In subsea equipments I always go for a API 6A/17D flange, but it goes up to 30" size, so 38 inches is way to big for API flanges. And API don't address what to do for bigger flanges.
b) I thought about ASME flange with ring type joint, but ring gasket according to ASME 16.47 is suitable up to NPS 36 (35 ID).
c) I couldn't find any note at ASME code regarding external pressures. I'm talking about REAL EXTERNAL PRESSURE (1500 psi), not just vacuum pressure.
d) ASME class 900 is 100 psi lower than my need of 2300psi internal pressure. And no bigger pressure class is available. Extrapolation on ASME tables is not allowed either.
I have 1500psi external pressure (3000 feet water depth)and 2300psi internal pressure.
Thanks in advance,
Mathias





RE: 38" ID Flange for Subsea Application (external pressure)
http://www.ltsusa.com/L005%20COMPACT%20FLANGE.htm
Cheers,
gr2vessels
RE: 38" ID Flange for Subsea Application (external pressure)
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: 38" ID Flange for Subsea Application (external pressure)
when the vessel is pressurizet at 2300psi internal pressure, that is a design point;- when is de-pressurized at the bottom of the ocean, the external pressure will be 1500psi, the second design point (minus the atm pressure). The 800 differential pressure is a no-no, because it will explode at 2300 psi or implode at 1500 psi. The question however is the use of suitable interconnecting flange, when the B16.5 and B16.47 limits are exceeded. The Norsok type of compact flanges have been specifically developed for this particular application, along with several other interconnecting jointing solutions for deep sea piping/pressurized equipment.
Cheers,
gr2vessels
RE: 38" ID Flange for Subsea Application (external pressure)
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: 38" ID Flange for Subsea Application (external pressure)
If the minimum shell thickness was selected to resist only 800 psi, the vessel will explode when internal pressure will be 2300 psi and normal atmospheric external pressure. Or will be crushed under external 1500 psi and atmospheric internal pressure, at the bottom of the sea.
Again, all this is my assumption only, it was never said the vessel will always be safeguarded against full internal pressure or full external pressure. It was my deduction when mathias28 said that "ASME class 900 is 100 psi lower than my need of 2300psi internal pressure. And no bigger pressure class is available. Extrapolation on ASME tables is not allowed either." Perhaps his last sentence is a bit ambiguous, that both pressures might not exist simultaneously or the other way around? Sh..ugar, now I am going around...
Cheers again,
gr2vesels
RE: 38" ID Flange for Subsea Application (external pressure)
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: 38" ID Flange for Subsea Application (external pressure)
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: 38" ID Flange for Subsea Application (external pressure)
When i said that class 900 is 100 psi lower than what I have, is that, according to ASME, selcting my material and my temperature, the allowable pressure was 2200psi.
About the differential pressure: I always have to design my vessel disregarding the "compensations" that may occurs.
Let me explain:We need to test it before install, so as the tests are made at the factory it will be atmospheric outside. And when installed it's all empty and sealed so it will keep atmospheric pressure inside until I open the valves for the wellhead. That's why we must consider both situations separatedly.
Regards,
Mathias
RE: 38" ID Flange for Subsea Application (external pressure)
You suggest me to go for compact flanges. I didn't mention before to not address the answers to that solutions, but I've heard about this with another company, Vector flanges http://vectorint.edge.be/index.cfm?PageID=18601
This flanges as I could see is based on FEA analisys and the geometry must be developed by myself and then Qualified. on API flanges, for example, the standard provides us all the dimensioning and it's all proven, so no qualification is required.
Do you know something more about this LTS Energy you sent me the link?? and about this issues I said about compact flanges?
Mathias
RE: 38" ID Flange for Subsea Application (external pressure)
Also, I'm sure there is a misunderstanding, you cannot develop the compact flange profile, that is part of the standard and is supplied to you by the fabricator (like Vector for eg.) to your specification (NB, rating, material if you want) with full guarantees. That's what you are paying for, so you don't need to design the flange.
For the nice finish, nobody is using anymore the ASME / API flanges for sub-sea applications.
Cheers,
gr2vessels
RE: 38" ID Flange for Subsea Application (external pressure)
I completely agree with you about ASME flanges.
For the aplication I need, 1000 meters water depth (up to 2500 meters for other), Vector flanges said that their flange are not suitable for high external pressure and offered a flange with a HX sealring (NORSOK shows only IX sealring). See what they say about external pressure:
"The IX sealring has external pressure capacity however we would recommend the use of HX sealrings for subsea use."
http://www.group-vector.com/index.cfm?PageID=18633
This makes me think that I can't use Compact Flanges as shown at the L005, since Vector do not trust on that for high external pressure.
I'm able to follow a standard and design a flange myself, FEA analyse and qualify, but the HX sealring is not mentioned at the NORSOK standard.
Do you think I have to buy from Vector this not standard special flange or delevop a new connection based of our on experience on hub-and-clamp flanges?? (we've already design a 28" clamped flange using a mettalic seal)
Cheers,
Mathias
RE: 38" ID Flange for Subsea Application (external pressure)
I would gladly take over from you the selection of the most appropriate flange for your application;- my fees are standard consulting fees and I can provide the support of my business for your project. The other option for you is to put together a specification for what you need, start searching on the internet (type in the google 'sub-sea compact flanges') and select 10-20 suppliers you consider able to provide a suitable product. The Norsok website can provide you a very credible standard for the selection of suitable supplier. Send your specification to the selected suppliers and start reviewing carefully their submission. Select the best one (technically and commercially) and call him in for further negotiations and technical clarifications. You could also contact a number of sub-sea operators, they gladly will advise who was their best selection/supplier of flanged or clamped connections and what was the outcome of their similar construction. It's really not that complicated.
Cheers,
gr2vessels
RE: 38" ID Flange for Subsea Application (external pressure)
I'l do that for sure. I've already started some conversations with Vector as I told you, but now I see that I can go deeper on my researsh and ask other companies and operators as well.
Thank you very much for your time and help. :)
Cheers,
Mathias28