Pipeline Inspection

Hello dhinesht,

You haven't described what the pipe material is nor the type of pipeline. We need to know this.

I suspect that you have a gravity sewer line, perhaps with manhole access at intervals along the line? Also, if a sewer line was it laid at a constant gradient using a pipeline laying laser and checked with a surveyor's instrument of some kind (like a level, transit or theodolite)? Hopefully this pipeline was installed along straight alignments between manholes, and not along a curved horizontal alignment.

If so, you can perform what is called a "lamp test" conducted with a high intensity flashlight or man-portable "lamp". Any vertical deflection and horizontal alignment deviation will be quite apparent when shining the light down the barrel. Make certain that you a very high strength light, preferably over 1 Million Candle Power. Really, it all depends on the length of the pipeline segment....it may be difficult to perform this test when the length of the segment is in excess of 300 Feet. You'll need a person on each end of the pipeline segment if it's a sewer line that you have there. Any sewer inspection guide will tell you how to perform it....Google Search it or find a applicable test booklet from any of the major sewer pipe manufacturers. You can contact the technical engineering representative from one of those companies, say like Certainteed Corp. or John's Manville who product PVC pipe, etc.

If you're not a Contractor, then contact one of your local Contracting firms in your area who have experience installing pipelines of all types. They should be able to assist you.

Ummmm, I'm a little confused why the pipe that you described would be Elliptical in shape when loaded and circular under load? As far as I know, it's usually the other way around! If you can, please comment in this regard.

Good luck!

The proper way to correct this is to correct the instalation situation so the pipe does not deflect.

Your description leads me to guess that you are using flexoble pipe material. If the pipe is deflecting due to external loads (like vehicles driving over shallow burried pipe) or internal load effects (in some way that I cannot imagine), then there will be a fatigue process happening that will lead to pipe failure over time.

You need to isolate the pipe from whatever is causing the deflection.

If this is not possible, then you need to base the pump calculations on the (limiting) available cross section rather than the notional "free state" conditions.

If the amount of deflection is under 5% the effect should be minimal. For gravity sewers 5% is allowed. I have trouble understanding why it might be a concern for a pumps system with outh knowing the fluid, flow or velocity, and pipe size and material. If you really feel a need to analyze in depth, you need to know the Reynolds number, pipe roughness ratio, hydraulic radius, and other fluid mechanics factors that I have forgotten from my college class 35 years ago. I'm not sure it is worth that level of analysis, but with more details I (or some one else) could come up with more detailed info.