Hydrostatic test for a Steel Tunnel Liner

[21121956]

Hello everybody:

According to ASCE, “Manuals and Reports on Engineering Practice N° 79”, hydrostatic testing is not a mandatory requirement for penstocks; but, for one or another reason, almost always the hydro test is performed.

Here I go with my queries: that aforesaid remark applies as well to steel tunnel liners? Can the hydrostatic test be substituted by non-destructive examinations (radiographic, ultrasonic or magnetic-particle)? Or simply, for plain cylinder pipe steel linings the hydro test is not required at all?

Only as a manner of reminder, a steel tunnel liner is required to prevent the migration of tunnel leakage and over its external surface is injected low shrink backfill concrete to fill the annular space between the steel lining and the excavated rock surface.
Any comments will be welcome. Thanks


El que no puede andar, se sienta.

 

[cvg]

you could conduct a leak test on a lined tunnel, but seems like it would be difficult at best to determine where the leak was occuring.

http://www.fhwa.dot.gov/reports/centralarterytunnel/index.htm

 

[21121956]

Hello everybody:

I beg your pardon cvg if I do not follow your answer but, the hydrostatic test is intended to be performed to check for leakage through the welding beads of the steel pipe that will be manufactured from steel plates.

By the way, reading the Sec. 5.2 Test Procedures of AWWA C200 - 97, it says: "NOTE: By agreement between the purchaser and the manufacturer, other non destructive test methods may be used in lieu of the hydrostatic test". This proposal is for test in penstocks.

El que no puede andar, se sienta.

 

[miningman]

Interesting question. Penstocks and associated tunnels can develop high hydrostatic internal pressures... obviously a function of the elevation differences between the ends. From the owners perspective, he wants to be very comfortable that leakage is VERY close to zero as`any loss from the tunnel / penstock is that much less water to the turbines and power generated. However this is only the minor consideration. Altho high internal pressures can be expected, typically these structures are not that far from surface. This means that the possibility of hydrojacking has`to be considered. This is REALLY bad news when it occurs and a lot of up front expenditure can be justified to prevent even the possibility of this occurring.

 

[cvg]

you didn't say this was a penstock. C200 is for water utility pipe, not hydropower applications. Since penstocks have high pressure fluctuations, dynamic pressures, vibrations caused by resonance and issues with fatigue, not to mention the fact that to repair a penstock is extremely costly - why wouldn't you do a hydro test?

 

[rconner]

Actually, ASCE MOP actually contains a section that addresses "Steel Tunnel Liners" to some extent. Likewise, AWWA M11 also mentions the application of "Penstocks" (along with many other sorts of water lines), and M11 cross-references to ASCE MOP No. 79 as well as "Steel Plate Fabricators Engineering Data", Volume 4 Buried Steel Penstocks (1992) in areas.
Some Engineers probably use some guidance from all these references as they see fit. That being said, I think the OP probably doesn't find exactly what is needed or wanted with regard to practical acceptance (testing etc.) specifically of tunnels in these references, and I agree w/ apparent inference of cvg (that Big job he linked to might could have benefited from something more effective to end up with better results?)

 

[21121956]

Hello everybody:
Thank you for your feedback. In a general manner, the layout of the project is as follows: at the end of the power tunnel of 2.660 m, the last 150 m will be lined with a plain pipe of structural steel plates.

Downstream, connected to this steel tunnel liner will be installed a butterfly valve (for safety of the penstock) and then, coupled to the valve, it will be welded the upper part of the penstock (properly said) of 550 m in lenght.

The hydrostatic test for the penstock is out of discussion. But the original question is regarding with the need for a hydrostatic test for the steel tunnel liner. Is it mandatory or not to do so? or, is it accepted to perform other substitute checks, tests or controls in order to give a Final Acceptance of this structure?

Once again, thanks to all.

El que no puede andar, se sienta.

 

[miningman]

I dont think you are ever going to get a definitive answer to your query. It highly depends on from what perspective one is viewing the question. If one is responsible for generation of the project specs, and dont fully understand the practical limitations of filling the annulus between the rock and the exterior of the steel pipe, and you are a "cut and paste" kinda guy, and you find a reference to such hydrostatic testing, of course you are going to incorporate a requirement for such testing.

If you are the end user, or the general contractor , I would expect to focus on the quality of the grouting work that is done after the low shrink concrete has been placed. If this grouting is done properly, then the end user, contractor or engineer should not care if the steel pipe leaks like a seive , because the grouting will have sealed all the available leakage paths and water leakage is therefor zero.

 

[cvg]

if you are designing to a code or standard, than determine what code that is and it should be clear what type of testing is required. If not than it is up to you and the owner to determine what testing is necessary. again, going back to my original post, segmental tunnel liners, installed one plate at a time into a tunnel are difficult at best to perform a hydrostatic test. and with proper grouting, should not be required.