The metal known as copper readily oxidizes when exposed to moist ambient air forming an egg-shell-thin yet highly protective green patina on its surface. The best example of this over time is the Statue of Liberty, located in the New York Harbor for nearly 200 years. Her &#;-inch thin original skin has not diminished over her significant time in the harsh marine conditions, mainly due to the naturally occurring patina.
You can find more information on our web, so please take a look.
The simple fact is - oxidation is not rust. Rust is a destructive form of metal disintegration over time. Oxidation happens and then remains stagnant and protective of the substrate to which it is attached unless ambient conditions become more corrosive than oxidation can resist.
While the green patina of copper offers a highly desired visual appeal, the same oxidation process upon the surface of a Ductile iron pipe results in varied shades-of-cinnamon splotchy appearance upon its entire surface. This annealing oxide layer on DI pipe and fittings, much like the patina on copper, is so thin it&#;s barely measurable yet serves to prevent deeper pitting or degradation of the metal in standard ambient conditions.
The problem is, unlike copper, it's not attractive to the eye, and therefore, all Ductile iron pipes are coated with an NSF-61 certified asphaltic-based paint known as sealcoat. Water-based sealcoats are common today and are much friendlier to the environments of the foundry and the external world.
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Ductile Iron fittings (connecting to existing DI pipe)
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(Mechanical)
(OP)
Goto Solid to know more.
3 May 10 10:56All,How do ya'll show connects to existing ductile iron (say, class 350, push-on joints) with new ductile iron (class 350, push-on joints)?In other words, do you show a sleeved coupling ( http://www.ejprescott.com/products/Clamps/DuctileIronPipeCouplings.pdf ) from the plain end of the existing pipe to a plain end of new pipe? Or can the contractor install a fitting (tee or bend) directly to the existing ductile iron?Any experienced insight would be most appreciated!
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(Civil/Environmental)
3 May 10 11:40If you are sure it is Ductile, the outside diameters are pretty much standardized and you can feel free to use a fitting or valve in order to make a connection. A lot of time we encounter gray cast and then it's easier to use a "Dresser" style clamp with a wide range of gaskets allowing for a wide range of OD's. Another reason for a clamp is if severe surface corrosion is encountered.
Steve
(Civil/Environmental)
3 May 10 14:37You can also use what is called a flange adapter or uni-Flange if you need to connect to a flanged fitting. If you are connecting to an MJ , you can use megalugs.
For pipe to pipe connections, a dresser coupling like Stevewag suggests or a MJ couplier can be used.
(Civil/Environmental)
3 May 10 17:17If the end of the existing pipe has been saw cut, you will be left with a sharp edge which may cause a problem by damaging the gasket of a push-on fitting. The edge should be beveled slightly. Or use a mechanical joint fitting.
(Civil/Environmental)
3 May 10 20:14I think you are thinking correctly, that it may be best generally to make the connection of new piping extending from an existing ductile iron pipe plain end with some sort of double-hubbed item (such as a mechanical joint sleeve, valve, fitting etc.) This method had the feature/advantage that the new piping can be thereafter be installed bells ahead, that is the recommended means of laying this pipe.
(Mechanical)
(OP)
4 May 10 08:27Great, thanks to all for the replies.
Stevewag, I have as-builts to go by, which may or may not be accurate. An alternative would be test holes - but the client doesn't always want to pay for them. They keep telling me they have As-Builts, so why the need for test holes? ha!
Maury, good point although my hope is this is something a reputable contractor would know how to handle. I have the US Pipe Ductile Iron Pipe booklets which detail how to field cut and assemble the various joints - I would hope the contractor has these also!
rconner, I hadn't considered bell direction. Thanks for that. It seems the additional cost of a coupling is worth it, considering the benefits and potential issues which can be avoided by their use.
My question stems from two sources: One - a coworker doing the peer (QA/QC) review on my design was asking why I didn't use a coupling for a particular connection. His comments couplings were the only fitting to be used for DI to DI connections. Two - the various contractors I've been dealing with as of late do not seem very knowledgable in the use of the couplings I've spec'ed ( the EJPrescott and Smith-Blair, both very similar to the Dresser couplings but NSF and AWWA approved). Their comments were causing me to wonder how they were connecting DI to DI and what fittings they were using.
Thanks again for the responses.
(Civil/Environmental)
4 May 10 09:54s0eebuch,I would not use a coupling on an ductile to ductile connection. I would use one when I had no other alternative such as connecting ductile (or C 900) to an over or undersized pipe, or when making a repair from a main break. Instead I specify that a solid sleeve be used if not using another type of MJ fitting to connect to an existing main. The solid sleeve is normaly between 8 and 12" long versus the 6 inches normally availible with a coupling. This give much more pipe gap availible to get a group of fittings into place. This fitting should be in the online EJP catalog, I have the paper (page B-4) one in my office.When I do need to use a coupling, instead of the "dresser" syle coupling I use one like the Romac Macro http://www.romac.com/images/BROCHURES/ROMAC-MACRO-4-page-brochure.pdf As sold by EJ Prescott rather than the Romac 501 from the catalog cut sheet. These couplings (and the Viking-Johnson equivelent) do not have to be disasembled to slide onto the pipe, have a torque spec for the bolts, only two bolts no to tighten, the gaskets can be (and need to be) field modifided to fit a wide range of pipe outside diameters without having a variety of gaskets and endrings on hand.I never liked tightening the dresser style couplings to the point that the bolts are starting to bow. Also I have been around main breaks where the bolts rusted away after a few decades causing a leak.I would question a pipe laying crew putting MJ fittings in the ground (and conecting to existing mains) if there was no torque wrench on site since most (there may be an exception) MJ glands now manufactured have instructions that require specific tourquing. Also they should have an outside diameter or pi tape on hand to measure and verify the outside diameter of any pipe.The book I prefer to have on hand is the Clow (McWane) "Pipe Economy" it has great detail on pipe installation and availible fittings that the McWane corporation produces with all of its subcompanies.I am both the engineer and owner on my projects, so I have a vested interest that the work goes well. If not, I do hear it from my coworkers.Good Luck!Jefferson
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