Testing Method For Existing DIP 1

[lawayosh]

Is there a method for testing in-the-ground DIP that would provide information about the condition of the pipe and/or lining? This would be for an existing water system to several large buildings. The DIP runs under and adjacent to roadways, sidewalks, other utilities and the always reliable unforeseen conditions.

Any info would be appreciated as it would be a huge help to upcoming large projects if we can determine the condition of the existing DIP.

Yosh

 

[cvg]

you can dig it up and cut coupons out of the pipe. These can be examined to determine the condition of the pipe. You can hydrotest to determine if there is any leakage.

 

[s0eebuch]

If you're chasing down leaks, you can look at the smartball by pure technologies.

Expensive but it does work.

http://www.puretechnologiesltd.com/pdf/brochures/1609_Smartball.pdf

If you can empty and isolate the line, then you might be able to run a CCTV camera through it. We do this for gravity sewer lines all the time.

 

[rconner]

Of course it follows that any time there are system modifications or tie-ins is also a good opportunity to examine the condition of the pipe.

Examinations of any existing pipeline when exposed can of course include visual observations of the surface, pecking any suspect areas with something like a welding (flux etc.) “peck hammer”, or even ultrasonic thickness measurements (that use a special small sonar-like instrument coupl(ant)ed intimately to the outside surface of the pipe, and subsequently the speed of sound in the specific metal to deduce the thickness from travel time of reflections etc.) Any kind of saw-cut etc. through the pipe metal will of course also reveal a fresh metal-edge that is indicative of the soundness of that cross-section. Also, when any kind of connections or “cut-ins” of valves etc. or sizeable “taps” are made in the pipeline e.g. for service connections, miscellaneous pipe pieces or “coupons” from these operations are sometimes retained by Owners and Engineers for detailed examination, of course that is possible inside and outside with such samples.
While it is a somewhat more disruptive procedure, as has been mentioned small investigatory coupons can even be cored or cut from an existing pipeline with or without pressure on the line, and a dependable tapping sleeve, saddle, or repair clamp etc. can thereafter be assembled for a pressure-tight closure over the hole. Safety is of course paramount when digging etc. around working pipelines.

While I guess rust or isolated tubercles might be observed in some aggressive waters in internal inspections, it may be unusual with this somewhat unique lining system to see perforation from the inside-out or even significant internal corrosion depth penetration of cement-mortar lined iron pipes in most normal potable water services, even at small damaged or metal sliver/thin areas of such linings.

In the case of ultrasonic readings appropriate procedures for outside surface coupling must be followed, and the instrument in these cases must be appropriately calibrated for the specific metal involved to obtain accurate readings. Obviously also, even an accurate ultrasonic thickness measurement is at best a snapshot of the thickness at the time, and unless prior accurate measurements were taken at the location or ongoing measurements are taken one would not really know if the thickness was somehow pre-existing at that location, or instead indicative of some sort of meaningful deterioration over time. Ductile iron pipe from the factory has been available and might be installed at any particular location with a great many different classes and wall thicknesses per size, and even modern individual pipes are subject to some allowable thickness variations according to standard, from end-to-end as well as circumferentially.

Likewise, I am aware that many enterprising folks/entrepreneurs are working on many other sorts of in some cases much more complicated technologies, it appears hoping to “cash-in” on real needs (and maybe even now some hype?) over condition assessment and asset management regarding the huge amount of existing piping out there. I believe there will likely be some real value to some of these technologies in some circumstances. Speaking however of any kind of indirect instrumentation readings including ultrasonic, care should be taken in the analysis of and decisions made from the results obtained. Seemingly alarming indirect observations or readings obtained should probably be verified by some direct hands on the pipe/physical observations as previously discussed, the cause for any problems analyzed as best possible, and the remaining strengths/reliability of the system for present/future service conditions analyzed (e.g. strength-of-materials and otherwise) before decisions to replace are made. In other words, “trust but verify” may be good philosophy in this as well as many other matters.

 

[lawayosh]

Thanks to all for responding. Sorry for the delay in getting back to you. I was off last week due to post-surgery (foot) recovery.

The DIP in question is the potable water and fire protection systems for many large buildings, some of it possibly dating back to the 1950's. With some of the DIP getting up in years, our mechanical engineering and design folks would like to be able to determine the condition and the possible necessity of repair or replacement.

It seems that for buried pipe the best way would be to pothole, take some physical specimens and examine them. I'll pass the info on, thanks again.

Yosh

 

[cvg]

I would do more than just take specimens of the pipe as it is only a piece of a larger pie. You should do a full inspection and records review.

Surface conditions over the pipe - is surface water kept out of the trench, are there any depressions;

past O&M records - any record of leaks or repairs?, any records at all? Are as-builts available and have they been kept up to date?;

Conditions of the trench backfill including type of material, in-place density;

type of joints and restraint;

presence or absence of any corrosion protection, mitigation or monitoring systems which might include polywrap, joint bonding, test stations, active or passive cathodic protection system;

condition/operability of the valves should also be evaluated.

 

[lawayosh]

Exposing any more than by potholing will be very disruptive and expensive as just about all of the water distribution system is adjacent to structures or (mostly) under paved vehicle and pedestrian thoroughfares.

There should be records of any leakage incidents. Finding as-builts is another matter due to the possibility of some sections having been in the ground for 50 years or more and whether the contractors were held to the requirement for as-builts at the end of the job on every contract.

Was just informed that the system probably consists of DIP and Cast Iron Pipe, 8, 10 and 12 inch diameters with working pressure of 80 PSI. They do not know how much pipe is cement mortar lined.

Will ask if there are any corrosion protection or monitoring systems in place.

 

[rconner]

In the “1950’s” there was of course a heavy municipal and other use of gray cast iron piping in that era for water service, and a less widespread use of the very new ductile iron at least in normal water applications.
As positive identification (I.D.) of material could be deemed important, it may therefore not hurt to look a little closer at least at those older pipes. In the case of ductile iron piping, there are usually cast or stamped marks near or inside the bells of pipe and/or outer bodies of fittings “DUCTILE”, “DI”, “DUCT”, (along with manufacturer and year identification etc.) to differentiate those items from earlier castings, and some early pipes may have also had similar identifications also dual painted quite visibly on the barrels.
Any barrel iron/sample/location can however also be I.D.’d by grinding and polishing a small area, simply etching same with an etchant like nital etc., and then looking at the surface with a microscope etc. to see quite characteristic distinguishing microstructures (see e.g. page 3-1 at

http://www.acipco.com/adip/products/Sect3.pdf

or

http://www.metassoc.com/pdf/MAI_Minutes-12_04.pdf

etc.) In the case of gray cast iron the darker graphite is in the form of flakes, with a dendritic etc. appearance, whereas the graphite is predominantly nodular in the case of ductile iron as shown.
There was thus at least some concurrent supply of gray cast and ductile iron pipe up until a near universal use of ductile iron pipe in the mid-late 1970’s (when it was no longer manufactured by major USA companies in favor of ductile iron pipe only).

 

[dicksewerrat]

You might even have some poured and caulked lead joints in the system. This ould be the oldest portion.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[sam74]

Couldn't you perform a fire hydrant flow test using hydrants at either end or where available, then if you know the pipe diameter and material place it in epanet and see what C value you have to adjust the pipe to in order to reproduce the test results. Or leave the C value as "new pipe" and adjust diameters to reproduce test results. Then you could say it is (assumption)an existing 8 inch line performing like a 4 inch line. Wouldn't that give you an initial estimate of deterioration