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Re: Tank settlement

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I doubt if you will find flexible pipe in 30" pipe size for your application. As I wrote in my earlier email, you may have to plan on getting rid of the bulk of settlement during hydrotest.

I have used the flexible pipe solution with 8" pipe on a 200' dia tank. Due to various considerations and constraints the tank was supported on a 5' thick concrete mat. The schedule would not allow for extended hydrotest. Thus, a plan was required to make the tank work without hurting the pipes and the tank. The estimated settlement for the mat supported tank was 20". The flexible hose was custom designed. The first pipe support was adjustable in the sense that the height could be lowered as the tank was settling. The owner is supposed to have a program to monitor settlement and adjust the pipe support height as necessary. After the settlement is stabilized, the adjustable pipe support will be replaced with a hard one. Pipe stress analysis was performed, taking in to account tank settlement to assure that the pipe will not be adversely stressed and the resulting nozzle loads were checked against API 650 allowables (Appendix P).

If the pipe carries a chemical or a petroleum product, you need to be concerned with the compatibility of the material used in the flexible "pipes" with the liquid carried by the pipe. Please call the tech support in the following companies and discuss your requirements.


--- On Fri, 9/26/08, Bhavin Shah <> wrote:
From: Bhavin Shah <>
Subject: Re: Tank settlement
To: seaint(--nospam--at)
Date: Friday, September 26, 2008, 4:28 PM

Thanks for the reply.

Can you give any reference for the flexible pipe coupling for 200mm of
the differential settlement ?


On 9/24/08, Paul Blomberg <paul.blomberg(--nospam--at)> wrote:
> 150 mm (6") is a lot of settlement. Talk to the Geotechnical
Engineer on
> methods to lower the settlement. Alternatives include piles and different
> soil stabilization techniques. You might also be able to place overburden
> on the site to allow the soil column to consolidate, then remove the
> overburden and place the tank. This technique might take a long time to
> effective in clayey soils.
> Again, the Geotechnical Engineer is the person to talk with.
> I have used a flex connection on the tank pipes when settlement was
> over the long haul. That pipe coupling accommodated the differential
> movement (200mm) without overstressing the pipe. I don't know if they
> available for a 30" diameter pipe.
> Paul.
> Phoenix, AZ. USA
> On Wed, Sep 24, 2008 at 10:18 AM, Bhavin Shah
> wrote:
> > This is regarding tank (15.0m diameter & 15.0m height) supported
> > ring wall (inside of the ring wall has been filled up with the
> > compacted sand.) resting on clayey soil.
> >
> > For design of the foundation total settlement at the tank has been
> > considered as 150mm (immediate settlement =15mm + consolidation
> > settlement = 135mm) as per the soil report. However, as informed by
> > Piping engineer, for pipes (30" dia.)connected to the tank,
> > permissible differential settlement is only 50mm because of the
> > congested plant and as per the flexibility analysis.
> >
> > Kindly advice what measures may be taken so that tank foundation can
> > be designed for 150mm of the settlement.
> >
> > Thanks
> > Bhavin
> >

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