Deflection in PVC pipe 2

[ADIAMOND]

I'm working on design for layout a 16" PVC waterline:

In general, what are my options for snaking through a road, achieving deflection less than that from using an 11 1/4 bend?

Does a deflection coupling involve one joint or two? (I'm trying to figure out the max deflection allowed given that my jurisdiction allows 1 1/2 degrees per joint)

 

[civilperson]

Try using half and quarter lengths of pipe, giving many more joints per length for flexibility in alignment.

 

[ADIAMOND]

What about a deflection coupling - does it involve one joint or two?

 

[civilperson]

A union, bell/bell coupling, has two joints as does each length of pipe with one at each end shared with the neighboring length of pipe. Total number of joints is equal to number of lengths of pipe and individual connectors. I am not familiar with "deflection coupling" terminology, but I assume one additional joint would apply.

 

[rconner]

If you are talking about unrestrained joints, you may want to check with who in the "jurisdiction" established the maximum deflection criteria (to find out exactly what their concern is). If the concern e.g. is lateral thrust/blow-out in unrestrained joints, while you can argue numbers of joints there is quite a percentage difference (in fact ~100%)in lateral thrust if a coupling at that location is deflected a total of 3 degrees or 1-1/2 degrees. At some point and magnitude of pressure, (particularly lightweight and slick) pipes might blow out.

 

[civilperson]

PVC pipe is usually solvent welded so joint blow out is not a concern. Push joints with O-rings can require restraint.

 

[cvg]

typically joint deflection is for a bell and spigot connection and at most 1.5 degrees would be allowed at each joint. I have not seen "unions" used for 16" pipe. Flex couplings are available but would be very expensive.

 

[rconner]

While not professing to be much of an expert on the subject, I would think (based on the record) it is highly unlikely that in the year 2008 someone would be designing a 16" pvc waterline to be joined in the field by "solvent cement". In fact, AWWA C905, AWWA Standard for Polyvinyl Chloride (PVC) Pressure Pipe and Fabricated Fittings, 14 In. Through 48 In. (350 mm Through 1,200 mm), for Water Transmission and Distribution" appears to now have the requirement, "4.2.4.1 Elastomeric gaskets. One gasket shall be furnished with each bell end of every pipe, fitting, and coupling. Elastomeric gaskets shall meet the requirements of ASTM F477 for high-head (50 ft of head or higher) applications." (Some manufacturers, however, might want to fabricate with shop control/conditions e.g. cheap, and even large, fittings however by segmental solvent cement or fusing etc., and I think this is currently allowed by this same standard)

 

[bimr]

Someone whot thinks that large diameter PVC pipe is usually solvent welded in the field, should spend an afternoon trying to do so.

Restrained Joints are usually used for this application; PVC Pipe Uni-Flang/Ford, EBAA Iron Inc.1. Mega-lug series.

 

[LCruiser]

In my experience, I don't think restrained joints are needed for pulled joints = depending on the backfill situation. Pulling (angling) is controlled by extension of one side of the joint, for example 1". Arctan 1"/16" = 3.5° Extension will be a manufacturer's limitation.

Are you "snaking" through a street that is required to remain open? You might want to just do bends - you *will* have to restrain them though.

 

[stanier]

Why not post form the PVC lengths into the radius you need? In fact if you leave the PVC in the sun for a while the outer surface will expand and the pipe will go banana shape. Install it and backfill. The creep properties of the PVC will ensure the pipe wall stress will relax over time.

Solvent cementing ABS pipe up to DN800 is done successfully in Australia. So DN400 PVC is considered a "snack".

Another suggestion is that you use PE or ABS for the section of the street where you need the radius. Flange connections can be used to join the PE to the PVC. PE can be laid in one length and pull around the radius you need. No need for costly excavation and concrete in thrust blocks as required for DICL or MSCL.

 

[cvg]

unfortunately, in the United States, at least in the regions I have worked, ABS is only (sometimes) allowed for sewers and HDPE is generally not allowed for permanent use in public right of way at all. 16" PVC must meet AWWA C905 specs which does require gasketed or mechanical joints, not cement. For private industry, ABS, PE or other pipe materials can be used at will.

 

[stanier]

The ABS in the USA is not the same as that in Australia, ASIA, Middle East or Europe. Eurapipe or GF pipe is not the same grade that had the failures of yesteryear.

The difference as I understand is that the Tyco produced ABS in Australia is from a master batch of resin that has the butadiene coplymerised with the styrene acrylonitrile whereas other manufacturers may have blended the polymers post production. This latter process results in the butadiene not being grafted to the SAN polymer molecules.

http://www.tycowater.com/plastic_pipeline_systems

If you cannot use ABS then the PVC is what you stuck with I guess.

 

[civilperson]

Lots of misinformation, applicable only to local jurisdiction. Please state the locale to which your rule applies.

 

[rconner]

With all due respect trying to envision the powerful solvent environment that might be involved in gluing every joint of big plastic pipe together in some conditions on sites kind of makes my liver quiver just thinking about it... I guess for some unimaginable reason unless someonewanted to do it on purpose (see e.g. first group under "Adhesives" at

http://www.serenitylane.org/druginfo/inhalant_abuse.html)!

 

[stanier]

ABS to AS3518 is NOT "glued" together. The process is a chemical weld whereby ABS is dissolved in MEK. The solution is applied to a cleaned end of pipe and socket. The socket has a taper. The pipe is inserted into the socket and a force held. The taper creates an interference fit. When cured the MEK (methyl ethyl ketone) has evaporated via the ABS molecular structure.

If the welded joint is sectioned there is no apparent join line. Testing by CSIRO and the manufacturer has demonstrated the welded joint is stringer than the parent material.

This jointing techniques is routinely used on major sewage & water treatment plants, mineral processes, power station, chemical plants, district cooling systems, building services and desalination plants up to DN800 and Class15 (15 bar) rating.

Now rconner is a known advocate of ductile iron. I find the constant negatives given in respect of other technologies to be unprofessional. Ductile iron has a place in industry and I use it frequently but there are other technologies in use around the world.

 

[rconner]

The first meaning of the word "glue" in my unabridged Webster's dictionary is, "To join with glue or a viscous substance; to cause to hold fast..." Now I guess if your ABS glue is not "viscous", or it does not accomplish these objectives, I should indeed apologize. It does however appear to be a quite powerful solvent, as I believe I referred to in my post, but maybe the workers and the environment are gratified to hear (per your post) that it "has evaporated via the ABS molecular structure." If I have said anything else that is not technically correct, please let me know, as I am indeedcan "advocate" for the truth.
Now, I do not believe it is in the spirit of these lists to herein attempt (to in ad hominem or attack the messenger fashion) to define exactly who each individual is that responds to threads. While that can be in some cases a much easier debate or political tactic than addressing the technical issues, I would prefer to keep discussions or differences of opinion on these lists in technical terms. As to "professional", at least I do not continually promote by name brand products (such as Tyco abs pipes?) from the country of the poster's origin, as I have seen some do on these lists.

 

[cvg]

actually, I can find nothing in rconner posts on this thread to show that he is promoting DIP or that he is maligning pvc pipe. Only point of dispute is that cemented joints are not standard operating procedure in the US and some attempt at humor regarding the noxious properties of the glue. Frankly, this is a forum for technical discussion and all need to be aware that there are opposing viewpoints. There is absolutely no reason to take anything personally.