| Author |
Message |
Nick Morris (Nick3751)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 20, 2005 - 3:26 pm: | |
Alright I've done some number crunching and I think I've got this worked out. Gary used an 1.5 exhaust pipe on his I think I'll go with a 2 inch since I've got a three cylinder cummings with a 15KW genny. If I put that 2 inch pipe inside a four inch pipe that will give me the same amount of space around the pipe Gary has. Then if I either weld my vent pipe into the side of the 4 inch or put some sort of fitting there the rising methane will help pull more air into the chamber that will be open at the bottom(all be it marginally). Also with a 1.5 inch vent running into a 4 inch line I might even get a little acceloration there.
Now the ignition point of methane is around 1000F so I don't think ignition is going to be a problem. With the outer pipe open at the bottom it should allow enough air to back into the tank that I won't need another vent (I'll put one in and plug it just in case though). Since Methane is about half the weight of air it should flow right out the top and not stink up my surroundings.
Also the genny exhaust should be warm enough that is the pipe does get a crack in it the exhaust gas shouldn't flow down the vent to the tank to much if any and instead go on up the vent pipe out the roof.
With this idea I should be able to run one pipe from the bay floor to the roof inside the bathroom wall with the exhaust pipe inside it and the vent pipe plumbed into it. |
David Hartley (Drdave)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 20, 2005 - 6:17 pm: | |
Submarine Snorkle |
Mike Jackson (Mike4104tx)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 20, 2005 - 6:54 pm: | |
That's an interesting idea Nick. I thought you were crazy at first, but I looked up the properties of methane and it looks like it will.
I suppose the main benefit of this is that you only have to make one hole rather than two? What is the worse case scenario that could happen? What else in that bay could be lit off if that pipe leaks? |
busboy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 20, 2005 - 8:02 pm: | |
The exhaust pipe is going to rust or crack eventually. With a simple two-layer pipe the outer pipe will simply get hot. With methane in the pipe the exhaust coming out the crack might set the methane on fire. Dunno for sure but fire and fuel even close seems like asking for trouble. |
Nick Morris (Nick3751)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 20, 2005 - 8:34 pm: | |
The only thing that will be in that bay is my sewer hoses, the hydro hot and house bats along with about 200 gal of fresh water if I'm full.
As for the rusting if it does it will be a while down the road cracking maybe but like I said the temperature isn't there for combustion. I suppose in some extream case maybe the genny could back fire(not likely with a diesel)and send a hot enough fire around about five 90 bends and up the stack and light the methane in which case from what I understand (and have seen on mythbusters) the worst that could happen is a fire comes out the top of the stack. The mixture of methane to air has to be very precise to get combustion hence I think that combustion would be very localized, i.e. wouldn't extend into the tank, and with both ends of a 4 inch pipe open I don't think enough pressure would build to cause the outer pipe to fail. Could be wrong but it makes sence on paper. |
David Hartley (Drdave)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 20, 2005 - 9:21 pm: | |
How about the exhaust fans pulling air through the drain traps or toilet causing exhaust fumes to be pulled back into the tanks and vents then inside the coach. It does happen !
Or **It does happen !
Negative pressure inside the coach for whatever reason can cause odor and fume problems.
Like I said before "Submarine Snorkle"
( like a staggered pipe for the exhaust extending well above the air vent pipe with a diverter. ) |
Nick Morris (Nick3751)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 20, 2005 - 9:39 pm: | |
It could happen if the traps were dry. But if the traps are dry that would mean that noone had used the bus in a while or there was a leak. In any case I don't feel it to be a very large risk.
I had been thinkin about running the exhaust up higher and that would be a good reason to do so say 8 inches or so would cover it don't you think. I wouldn't have to worry about getting water in the vent line since it runs all the way down so a flapper or bent exhaust would cover water in the tail pipe. If it was bent over say 6 inches up and 4 inches back that should allow for enough dilution of the gasses in the air to eliminate any CO trouble don't you think Dr. Dave? |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 20, 2005 - 9:57 pm: | |
Need more negative thoughts?
1. Sewage is one helluva corrosive, what will it do to the exhaust pipe?
2. The sewage tank vent is not a one-way vent, it takes air -in- also,
especially during the emptying of the tank. The intake will be more
often, if you've combined the sink/shower/toilet vent pipe(s) with
the sewage tank vent pipe. Will sooting be a problem to the sewage
system?
3. Will vibration of the exhaust pipe stress/damage the sewage
vent pipe(s)? |
niles steckbauer (Niles500)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 20, 2005 - 10:18 pm: | |
Certainly not a negative comment, I merely ask who determined that Methane gas was such a hazard - Do you know how long the waste (and content/volume of said waste) would have to decompose to methanize? - I do hope your emptying your tanks AFTER EACH USE - Negative pressure can cause gas/odor infiltration in ANY improperly engineered/installed ventilation system, and there appears to be no reason to infer that the original posters design would be any more troublesome than any other design - HTH - Niles |
Nick Morris (Nick3751)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 20, 2005 - 10:36 pm: | |
Hadn't thought about the corosive properties. SS pipe in the vent would pretty well fix that I think. Ten feet or so would be that costly. As for the sooting I think the bent exhaust will stop most if not all exhaust from getting into the vent and there for soot won't be a problem. Vibration....don't know I'm hoping to be able to attach the exhaust at the top and bottom and with an inch all the way around the exhaust it should be plenty of room for any vibration and hopefully there won't be that much that far down the pipe. If I get an inch deflection I've got much bigger trouble.
Keep it comming guys. This is why I love this board lots of folks, experince and time to test ideas before they go into practice!!!!!!!!!!! |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 20, 2005 - 11:21 pm: | |
A section of flexible exhaust pipe at the base should suffice,
for vibration issues.
The corrosive effects would be to the seams in the stainless steel,
more than to the surface itself.
I hate the idea of poking holes in the roof, so I'd much prefer
to take the route you're headed. But I also hate doing the
same job twice. I suppose if you design it to be easily repaired,
it would be a neat way to go? The thought of possibly losing
both the operation of the genset, and the toilet/washing facilities
at the same time while repairs are being made, would bother me
more than the extra hole in the roof..
(I'm a KISS enthusiast) |
t gojenola
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, November 21, 2005 - 4:53 am: | |
On its face this is an interesting concept. Concerns about corrosion of the inner (exhaust) pipe could be eliminated by use of a seamless and non-corrosive material such as stainless steel. Concerns over vibration could be eliminated as well by use of flexible fittings. As for the concerns about methane combustion - I doubt this to be a problem. With the outer pipe open at the top and bottom ends the heat present in the inner pipe would cause an up-draft sufficient to prevent any accumulation of methane.
My only concern has to do with the lateral piping required for either the generator exhaust or vent piping from the holding tank(s) to reach the vertical exhaust pipe. On my own 4106 the generator and holding tanks are about 16 or more feet apart. In this case I think its more practical to have another hole in the roof.
my 2 pfenigs
tg |
Jim Stacy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, November 21, 2005 - 9:36 pm: | |
I ran my genset exhaust (1 1/2") up through 4" class B pipe. This is double walled pipe used for home furnaces through a frame wall. This gives three walls of metal to keep the heat from the structure. You can put your face against the outer pipe under load where it goes through the closet.
The holding tank vent is plastic ending inside the roof vent for the frig. One roof hole and no problems in nearly 10 years.
FWIW
Jim Stacy |