Testing of underground ductile iron pipe
Testing of underground ductile iron pipe
(OP)
a project is calling for 30" ductile iron class 52 pipe with push joints to be installed under a roadway with both ends left open for pressure testing after the roadway is back filled. The drawings call for quick flanges (sometimes referred to as EZ flanges or break flanges) to be installed on the ends of the pipe along with steel blind flanges to enable the pressure testing of the piping.
My question is if this quick flange and blind flange combination is a proper method of capping the ends of the pipe? The test pressure of 200 psi would produce very large forces on the ends of pipe of around 135,000 lbf.
My question is if this quick flange and blind flange combination is a proper method of capping the ends of the pipe? The test pressure of 200 psi would produce very large forces on the ends of pipe of around 135,000 lbf.





RE: Testing of underground ductile iron pipe
I suggest that you talk with the vendors of the piping and the "push-on" devices about testing of thier systems. I am sure that they have encountered this problem before.
As I recall, the "push-on" devices rely on developing tensile forces onto a lip moulded into the pipe wall, or into a device that relies on friction and compresses the outside pipe diameter.
Please tell us more about your final resoultion, what brand of piping and connector you use and the propper way to test in this situation...
Best Regards
-MJC
RE: Testing of underground ductile iron pipe
http://www.ebaa.com/index.php?page=1100
RE: Testing of underground ductile iron pipe
I agree with cvg's post, you need to restrain almost the entire length of pipe under the roadway. It may be possible to brace the pipe ends during testing so that the middle does not push apart. Normally 2-3 pipe lengths would need restraints, not just the pipe ends.
RE: Testing of underground ductile iron pipe
However, restrained joint pipes in general are NOT really necessary, at least just for hydrostatic testing, of many even quite large diameter and high pressure unrestrained piping sections. In a case in point I am aware of a project several years ago, that I suspect involved in toto a half million feet or so of 1200mm ductile iron piping. Except for rather small footages, all piping was just standard unrestrained joint pipe. It is my understanding every stick of that pipe was successfully subjected to a 30-32 bar (435-465 psi) field hydrostatic test. By and large, this was accomplished by quite substantial and temporary external buttressing behind end closures for each test section, up to the task. I believe the bulkhead thrust on 1200 mm DIP at 30 bars pressure is about 834 kips. In the particular case I happened to see on that job, the Contractor employed a system of interlocking precast concrete blocks he simply made a form for and poured (with lifting loops cast in). Imagine a very large sort of lego block construction, large enough by gravity and friction to effectively sustain the load (by the way, this firm happened to be Egyptian). I think locations of future valve vault construction may have sometimes been chosen to put down and take up such temporary buttresses. This was incidentally a quite “sustainable” construction, as they simply loaded up the blocks and trucked them from testing location to location (who knows, they may still be using same!) Virtually the same thing can be accomplished with a transverse big steel I-beam or two(many Contractors have such leftover beams on their yards), and a good many railroad ties stacked vertically against a soil wall/cross-trench behind same (I have seen up to 48” unrestrained lines tested up to 175 psi in this manner.) Can throw in a big hydraulic cylinder to keep things “tight”, even if blocking slightly undersized. When the testing is over, load everything up and maybe no one is out really anything, other than labor to construct, compared to the cost of restrained joint pipes?
As to closures used, while there are a great many sorts of closures available for ductile iron piping I guess I have nothing against the field adaptable flanges, but of course in and of themselves they basically just provide a platform to fix a blind flange to a pipe plain end. In this and all Engineering work, Newton’s third law must nevertheless be respected by Engineers, particularly when large forces are involved (maybe the next joint buried down the line a few feet may be pulled out, and should be inspected?) I believe some of these devices bite into the outside metal of the plain end for restraint, that could be a concern if the permanent connection to the line might eventually result in another rubber gasket trying to seal down on the same axial area (I guess I’ve never heard of a leak from such, but maybe something to think about?)
RE: Testing of underground ductile iron pipe
RE: Testing of underground ductile iron pipe
Using mechanical joint fittings with retainer glands is another option but more costly. My concern would be that if the ends of the pipe are not braced the joints may still seperate.
RE: Testing of underground ductile iron pipe
RE: Testing of underground ductile iron pipe
RE: Testing of underground ductile iron pipe
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Testing of underground ductile iron pipe