Buried Flange and Valve Flange leak protection

[Daddywigs]

Hi,
I think you will find this one fun to think about…. Sorry it is so long to read, but I do think you will find it worth the read.

I'm helping a client with with a 50 yr old 250 mile stretch of pipeline in service with gasoline and diesel with a number of buried flanges and buried flanged mainline gate valves. The buried flanges used to be used for insulating cathodic protection purposes; however, this is no longer needed.

We have some concern of the integrity of the gaskets for both the flanges and the flanged valves. We are looking at differing technologies to mitigate any potential leaks from these components.

Of course, we can purge different parts of the line with traditional methods (stopples, freeze plugs, smart pigs), and either cut-out and/or replace these components; however, this action would require the line to be taken down and out or service for days at a time - and potentially many times.

We are in the middle of looking at options to repair or mitigate these components - and preferably without taking the line down and out of service, or at least not taking the line down for more than a day at a time.

We have found a manufacturer that can fabricate a large diameter pressure vessel sleeve that can fit over the flanges and welded in place without taking the line down. Because we want to keep the mainline valves operational and can’t cover them, we have not found any thing like this for the valves.

Some folks have suggesed glas fiber wraps and carbon fiber wraps around these components.It seems possible that we could uncover, blast, clean, and wrap the entire flanged connection with layers and layers of fiberglass or carbon fiber and epoxy resin and bury.

Does anyone have experience using these products in a similar application?


Does anyone have any other ideas or options out there we could look into?

 

[BigInch]

Are the flanges leaking now?

Hot tap either side of the valve with two stopples and install a smaller diameter bypass valve, remove the flanged pieces and replace them with weld end valves. Pull the stopples and be done with it.

Why fart around with glue and fiberglass that will probably blow in 5 years or less and why do you think you need to shut the line down to do a hot tap bypass? I find it hard to believe your welded pressure vessels will be cheaper, won't require lowering the pressure any more than a hot tap would, will require more excavation, can be adequately tested now or readily inspected in the future, will have positive effect on line stresses, give you any degree of assurance that the flange inside is maintaining integrity... etc. etc. Are you really going to field weld a "split-seam pressure vessel", seal weld (fillet weld, I'm having a hard time seeing that detail)? to the existing pipe, hydrotest it, (can you radiograph it?) and seal weld around the existing pipe? I don't think the learning curve is going to be great on that one. Make a test mockup in the pipe yard and see how it goes first.

**********************
"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/

 

[Daddywigs]

Thanks.
No these are not leaking now. And the risks are fairly low that they will leak in the future; however, the risk is there and this is why our client committed to doing something for risk mitigation.

We have considered hot tap and by-pass; however, just like stopples, by the time you factor in all the people involved, 3 digs per site, etc etc, we are on the order off $200K per site. If on the other hand, since these are not leaking, if we could just offer a bit more protection/assurance that they will not leak in the future with a glass or carbon fiber wrap, for something like $15K per site, we are way way ahead.

We are planning on manufacturing a mock of the pumpkin sleeve, just to make sure we can "kick the tires" and feel good about it's implimentation.

 

[BigInch]

Do you have statistical leak detection on the lines now?

If you want to do it on the cheap, I'd just dig a post hole for a HC detector with a cell phone transmitter to report status once a day. For a flange that hasn't leaked yet (after 50 years) its hard to get too concerned enough to dig it up and coat it, but I'll just bet that as soon as you did, that'll probably be enough to get them thinking about leaking right there.



**********************
"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/

 

[BigInch]

I mean, when in doubt, "If it ain't broke, don't fix it", right?

**********************
"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/

 

[Daddywigs]

BinInch,

Your thoughts are very similar to mine. I have not seen a system with a post hole HC detector and cell phone. This crossed our minds. Are you aware of someone who has done this? Proven? if so.... I'm all over it!

Ya, I know, it is hard to justify fixing it if it ain't broke.... but there is a commitment to do something, not just wait for the next one. Apparently there have been enough leaks to be concerned that it will happen again. There are about 30 of these buried, so anyone of them could potentially leak someday.

 

[BigInch]

I do believe in committment to safe and secure operations, but, just like too many block valves can start to increase the potential for leaks, sometimes being proactive can have adverse effects.

Anyway, that aside, not personally, but talk to these guys before you discount that potential solution.

http://www.slicksleuth.com/pdf/IOSC2008paper.pdf

Put in a tiny little % for me, if its a go.

**********************
"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/

 

[BigInch]

You do know that leak detection systems based on statistical analysis are capable of detecting very small leaks, right. The longer time history you have, the capability to detect smaller leaks is enhanced. It is not out of the question to be able to be determine a reasonable probability of a leak of a few gallons over a few months or so, depending on the exact attributes of the system.

**********************
"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/

 

[dcasto]

we used Plidco flange seals regualy. If you are concerned about leaks, replace the underground with aboveground. I hate weld in valves because of damage to seal faces and if the valve breaks, big issue.

no leak detection system I've seen can see a drop a second from a flange. a .5% leak may be found in a few hours at best. Modesett was good, but not that good.