Can I use PVC for plumbing in the reactor, wash tank, and drying tank? - Diesel Forum

tpendergraft · 01-03-2006, 12:52 PM

Can I use PVC for plumbing in the reactor, wash tank, and drying tank? I would like to use PVC if it won't react with the biodiesel, it should holdup OK to the relatively low pressures and heat involved in the process. What experience have you guys had with it?

girlmark · 01-03-2006, 02:25 PM

unfortunately it tends to leak in this application. ALso, PVC valves have handles that are more difficult to turn than brass valves- and the handles sometimes break off after you've gotten some biodiesel on them (like from grabbing them with our oily gloves or something like that).

Mark

tpendergraft · 01-03-2006, 07:24 PM

girl_mark: First let me say I bought your book and I love it. I have already made a couple of batches with its insights, keep up the good work! And now to the questions:

Is it the heat, pressure, or the chemicals that cause the leaks in PVC? The reason I ask is that I would like to be able to "hard pipe" some of the systems for a neater appearance at a cheaper cost. Could high temp PVC (the kind used for household hot water applications) be better?

Another question for you too... I am currently using Nylabraid PVC hose, brass ball valves, black iron fittings, and galvanized 3/4" hose barbs for each end of the many hoses. What is your opinion on the use of some galvanized components? Am I setting myself up for an injector disaster or will the filtration take care of any zinc that may "flake off"?

girlmark · 01-05-2006, 05:39 AM

thanks for the compliments!

The zinc issue with biodiesel is different than the zinc issue with petroleum diesel (where galvanizing can flake off).

In biodiesel's case, it causes some changes to happen that can shorten the shelf life of the biodiesel. However, brass will do that too and we usually use brass valves. I'd just go ahead and use it if black iron gas pipe isn't available. You can also strip the zinc galvanizing off the galv. pipe by using muriatic acid.

I'm not sure what fails specifically about the PVC plumbing, I agree with hard-piping everything- hoses are the main cause of spills that I"ve seen!

someone knowledgeable once insisted that the PVC piping leak problem was partially due to improper surface prep , that's entirely possible. Biodiesel dissolves all kinds of things though so it might be the solvent-weld chemicals that can't handle it.

Mark

bork · 01-05-2006, 08:37 AM

PVC cannot handle heat .(also in the plumbing world , inspectors told us not to coat steel hangers underground as it would eventually soften pvc pipe it was supporting.) CPVC can handle heat, but not sure if can handle any oils . I guess the best thing to do is soak different pieces of all materials & observe.

Spencnaz · 01-05-2006, 11:26 AM

Is the zinc issue with biodiesel because it will form zinc oxides from the galvanizing?

I do know that biodiesel is an oxygenated fuel and will oxidize and decompose rapidly (hence its biodegradeability).

girlmark · 01-05-2006, 06:36 PM

no, it's because it acts chemically as a catalyst to start the biodiesel oxidising and polymerising (ie the zinc doesn't go into the fuel, but the fuel itself changes and becomes less stable).

The degradation of the resulting fuel takes time, so the problem is really just that it's shelf life is reduced. No one who's brewing small batches for an F -250 has homebrew sitting around for years or anything. It's a concern for commercial producers who have to worry about someone filling a farm storage tank full of biodiesel and then not using it all winter and THEN having a problem the following year.

Mark

DZLJIM · 01-06-2006, 06:25 AM

I see no reason why PVC could not handle any heat a hot water heater (appleseed processor) could generate. They are used together in a zillion homes everyday...

bork · 01-06-2006, 07:13 AM

[ QUOTE ]
I see no reason why PVC could not handle any heat a hot water heater (appleseed processor) could generate. They are used together in a zillion homes everyday...

[/ QUOTE ]

Pvc is NOT used on water heaters in homes. I have fixed many who have tried.

girlmark · 01-06-2006, 07:26 AM

it's not the heat, it's the chemicals... biodiesel destroys many kinds of plastic and the PVC solvent welds seem to be susceptible. NOw I know that there are many different kinds of solvent-weld glue, and so forth, but enough people have had problems that it seems to be a thing to avoid. PVC hose barbs and other threaded parts seem fine- it's just hte glued joints that have problems.

IN my own experience I had problems with the valve handles breaking off also as they seem to be made of non-biodiesel-resistant material, and touching them with oily gloves got enough biodiesel on them to make them brittle. Or maybe it was because my processor was outdoors at the time, and the sun's UV got to them. But it happened over and over again so I now avoid those even though they're nice and cheap.

Mark

DZLJIM · 01-06-2006, 10:28 PM

No, but all the hot water goes somewhere when it's used: Through the DRAIN pipes, which are PVC...
[img]/ubbthreads/images/graemlins/wink.gif[/img]
I'd go steel black pipe, personally. I picked up a pipe threading set on ebay for like $20, so no big deal making whatever length pipe is needed.
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01stroker · 01-06-2006, 11:43 PM

[ QUOTE ]
[ QUOTE ]
Pvc is NOT used on water heaters in homes. I have fixed many who have tried.

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CPVC(which is a type of PVC but made for the heat) is used in this part of the country on almost all water heaters. But as Mark said, it must be the glue and bio don't get along.

tpendergraft · 01-06-2006, 11:58 PM

I am going to try to plum up my wash/drying tank and pumping system with PVC SCH 40 as well as my filter system. If it works out I will try to plum the reactor where the harsher temps and chemicals reside. PVC is just too cheap IMO to not at least try it on the wash/dry and filter systems. I'll let you guys know what I find out. Thanks for all of the advice!

bork · 01-07-2006, 08:46 AM

Heat softens pvc , Drain dont have pressure & will withstand a little, but I have seen problems under kitchen sinks, The proccesser might work with pvc if not too much heat & no pressure. Also instead of pvc cement, you could try using epoxy for glue joints. I would still use cleaner first, as it is to remove wax from molding proccess, on pvc pipe/fittings.