PVC, CPVC, PVCI, MPVC? 1

[mattski72]

I am replacing a (15%)bleach fill line to a bulk storage tank. A run of the piping will be outside exposed to the elements while most of it will be covered. I know PVC is a good choice, but can I mix PVCI with PVC. I know that CPVC has better resistive properties to caustic fluids but do I really need it in a fill line to a vented tank? Is there a good reference out there with a good explanation of what the different add-ons ("C", "M", "I", etc.) to PVC are for?

 

[kenvlach]

C = chlorinated. An extra Cl atom replaces an H on the vinyl monomer. This gives CPVC higher temperature resistance and somewhat better chemical resistance than PVC.
Some CPVC info

http://www.ppfahome.org/cpvc/index.html

Type I PVC is a bit denser and stronger than Type II PVC.
Physical properties of the 2 types are compared in a table, along with ABS, PE, PB & PP, at

http://www.cheresources.com/plpipezz.shtml

I'm not sure what "M" means (modified?, maybe a Type analogous to copper tubing, which comes in K, L & M), but it seems to be a thin wall version of PVC pipe:
"The lower safety factor and thinner wall of MPVC pipes means that a given pressure class of pipe will operate at higher wall stress than a PVC pipe of the same class under identical operating conditions."

http://www.vinidex.com.au/VINIDEX/L...N-4H.0.2001Fatiguedesignforthermoplastics.pdf

 

[kenvlach]

Lots of plastic pipe technical data available at Plastics Pipe Institute

http://www.plasticpipe.org/general/general_publications.php

E.g., TR-4/2005 B
PPI Listing of
Hydrostatic Design Basis (HDB),
Strength Design Basis (SDB),
Pressure Design Basis (PDB) and
Minimum Required Strength
(MRS) Ratings for Thermoplastic
Piping Materials or Pipe

Re your application:
1) Be sure to paint exterior piping for protection from UV in sunlight;,see
PVC Pipe - UV effects?
thread194-139218

2) I recall reading that caustic attacks solvent-welded (aka. glued or cemented) joints in PVC & CPVC pipe. Fusion-welded PP was recommended as alternative.
[at

http://www.finishing.com/Letters/index.html,

but can't find the thread].

 

[nigel228]

Hi Mattski72,

PVC-M is modified PVC. The modifiers are typically Chlorinated PE's. The modifiers increase the ductility of the material and therefore the impact characteristics of the pipe. This pipe is used mainly in Australia, UK, NZ and South Africa.
PVC-M I believe has the same chem resistance properties as PVC-U.
For your application (sodium hypochlorite?)I would have thought either PVC-C or U would be acceptable.
George Fischer in the US should be able to supply info on chem resistance without a problem.
As a rule of thumb I wouldn't mix PVC-C and U lines, solvent cements, etc.

 

[BSQUAREDBUCKEYE]

Here in Ohio where the outside temperature can go from 50 or 60F or hotter with sun load on the pipe to the 20s or 30s does not make plain thermoplastics a good choice. Cold temperature embrittlement is always a concern. Along with impact resistance and thermal expansion. And then there is the instbility of NaOCl with sun load. Indoors PVC would be fine, but outside we'd spec a dual laminate PVC with FRP overwrap. Although it is more expensive, you have greater spans, shorter expansion loops and better impact resitance.