Intersting conversation with Dormont gas line tech rep...

I just got off the phone with a technical support engineer at Dormont. They are the people who make all those flexible blue gas hoses that everyone uses for connecting their LP appliances.
 
Anyway, he was VERY surprised when I told him that many people use their hoses for mobile kitchen and food truck applications! He went on to say that they DON'T RECOMMEND their products in mobile rigs. I told him I've never even seen a different brand !  :)
 
Any thoughts on this? I explained that we all secure our equipment, etc. His concern is the vibration of the hose itself, and the long-term effect on the joint where the hose meets the connector. I think he is way too worried...

We don't use flexible blue hoses. We use a black hose for all our LP gas  stuff, both on the cart and in the RV. Some were custom made by LP gas dealers and others were bought premade.

Do you mean the typical hoses on an RV? My appliances use too much BTUs unless I'm mistaken:
 
6 burner range/oven - 250,000 total BTUs
40lb deep fryer - 105,000 BTUs
single deck convection oven - 90,000 BTUs
 
Because of the flow rates needed, I think I will need 3/4" I.D. hose, and full-flow type cutoff valves. If I'm wrong, I'd love to have suggestions from all of you! I haven't hooked anything up yet, so I've still got time to buy the right stuff...
Thanx, Dave

that is the reason for the hose..... its like a flexible coupler, lol, as far as i know its supposed to be there...... they have the corrugated metal lines that do the same thing, but the connections are the same, i think your gas guy needs to lay off the morning coffee.....
 
only problem i can see with using any style of hose would be if it rubs against an edge from the vibrations, that may cause a problem, but we all know not to let that happen right ??, lol
 
regardless, a drop of thread lock (the blue, not the red) red is permanent, on the last few threads will secure it until someone puts a wrench to it.....
 
you could get fancy and wire lock it also, Lock wiring* is the securing together of two or more parts with a wire which shall be installed in such a manner that any tendency for a part to loosen will be counteracted by an additional tightening of the wire.

I recently purchased a 3/4" yellow flex dormant hose online and it has a red tag stating "Not for use in a mobile application"!  I'm wondering if it's a liability issue or if they did have problems?  Note that some variations come with a cable to be attached to a wall.

i just checked a couple of my boating sites, and 3 different marine distributors...
you dont want to use the flexible metal lines..... they can fatique over time and crack for no apparent reason....something to do with the sonic vibrations....
 
but, on the other hand..... there are countless rubber lines certified for marine use, the look to me to be the exact same thing as the yellow/blue lines from local gas companies.....and if your creating more shock and vibration in your truck/trailer then a boat out on the open water then you might want to change proffesions, lol
 
a quick look and i found 20" pigtails, marine certified, for 25 bucks
 
i always had it in my head that a food truck was akin to a big boat....this is just one more example of why

here is an excerpt from a pro in the marine industry talking to the "skoolie" forums
 
There is another alternative as well. I'm in the marine industry and am involved in outfitting a lot of custom cruising boats. Due to the harsh marine environment and the constant movement of boats the most common propane lines aboard are hoses which are specifically made for the application with swaged ends. Your choice of which system to use for installation of a propane system will be influenced quite a lot by cost of materials and the layout of your bus and how many propane appliances you're supplying. 

In my bus I supply three appliances; the stove/oven, the water heater and a Dickenson Marine stainless vented (direct-air) wall mounted fireplace (heater). Like BruinGilda and many others I am using portable propane bottles mounted in a compartment under the bus to facilitate refilling without having to move the bus to the propane station. I have a manifold just downline of the regulator under the bus to which each of the individual hoses connects. Then there is a single continuous run of hose from the manifold to each appliance. Where the hose enters the bus through the floor there is a purpose built bulkhead fitting (the hose slides through and then a plastic nut is tightened which compresses multiple fingers against a rubber grommet to make a tight seal) to protect the hose and in this case keep critters, spray, fumes, etc outside. The hose then connects directly to the appliance. 

What I like about this system is that I have only one connection inside the bus for each appliance (and specifically right at the appliance) and it's a factory-made swaged fitting of high quality. The connections for the multiple runs are all made under the bus near the propane compartment at the manifold; they should be vapor-tight and sealed well but if they do leak it won't be inside the bus. Shut off valves can be installed at the manifold to facilitate shutting off an individual appliance. 

Several approaches to installing propane systems are viable; this isn't meant to suggest that this method is "the best". I only offer it as an alternative since many folks are not aware it exits. Outlets like West Marine and others carry the hoses. The system is used almost exclusively in yachts today and is designed to withstand the rigors of world cruising sailboats operating in tropical (read harsh) climates.

skoolies are converted school buses for traveling/living

so basically what its saying is...
if you have 4 appliances, then you would install 4 shut-offs outside/under the vehicle and have a continues rated rubber line running to each appliance.....
 
remember, this is boating standards, something no ones food trucks/trailers should ever come close to as far as vibration/harshness of environment is concerned, but it is the ultimate in safety, and it calls for rubber lines !!

Fascinating...I'm still concerned about BTU's and proper flow rates. I have what amounts to a 'manifold' behind the equipment, with 3 connections for the 3 appliances.
I'm guessing I could go from the 3/4" black pipe 'manifold' to shutoff valves, then the rubber hose to the 3 pieces of equipment? This would also eliminate a bunch of elbows and fittings...
Back Alley, where did you see these pigtails? I also need to get the connector that goes from the bottle to the regulator.
Speaking of bottles, is it true that anything smaller than the 100lb. bottles won't flow more that 90,000 BTU's? Obviously that would be a problem in my situation if everything is turned on...

well, the rubber line can be had up to 3/4", and larger im sure, but i have seen the 3/4" sizes.... not sure about fitting sizes, not sure if they are all the same or not......
but yes, i would shut off valve each at the manifold, then you have a way to secure gas all in one spot and running lines to everything would be a snap!
http://www.go2marine.com/category.do?no=14769
http://www.fireboy-xintex.com/propane_detectors.html
should be able to find anything you need between these two...... and these are made with harsh environments in mind, so they may be a little more, but will last much longer over all...
a 20lb tank will do 80,000 until about half full, it just wont have enough vapor pressure after that to keep up with demand (remember, you are burning the vapors that come off the liquid) and that would have to be on a hot day, anything under 70* and your going to start freezing the bottle......
 
here is a good explanation of it ......
The specific latent heat of vaporization is the amount of heat required to convert unit mass of a liquid into the vapor without a change in temperature.  This definition sounds complicated to folks who don’t deal with it a lot.  It can be applied for propane pretty easily.

In other words, when propane vapor leaves the tank, it is taking the energy required to vaporize it to the place where the propane is burned in your appliance.  This energy needs to be replenished to cause more of the liquid propane to vaporize in the tank.  The propane needs energy from the air or ground outside of the tank to flow into the tank to change its state from liquid to a vapor.  

It may be confusing – thinking that heat energy can flow from a 10 degree ambient temperature environment into your propane tank. Where there is more heat energy, it will always flow to where there is less heat energy.  By taking the vapor from the tank to burn it, the amount of heat energy in the tank is reduced to a point where the heat energy in the tank is lower than the heat energy available in the 10 degree environment around the tank.  So heat energy flows from environment into the tank. I bet if you check the temperature of the tank while you are using it, it will be lower than the temperature of the environment around the tank. The question to answer is: will the heat energy flow into your tank fast enough to replenish the heat energy taken away by moving the vapor (and its energy) to your appliance?

Pure propane takes 184 BTU’s/lb to change from liquid to a gas or vapor.  

The higher the temperature you have around the tank, the more energy that is available to flow into the propane in the tank for the change from liquid to vapor.

The better the heat is transferred from whatever surrounds the tank into the tank, the more energy that is available to cause vaporization.  Cold air does not transfer heat energy well (doesn’t have much heat energy).  If you can’t get this heat of vaporization (energy) into the tank fast enough to cause the vaporization, the performance of the appliance suffers.  

The beauty of this kind of fuel is that it has such a low heat of vaporization. Also, at relatively low pressures it becomes a liquid so you can transport a lot of it in a little tank.

Why does more volume of propane work better?  Heat energy at ambient temperature of 10 degrees flows into a 40 lb tank at a constant rate from the environment around the tank. Demand on the tank from the appliance remains the same.  Add a second tank of the same shape and size and you are doubling the amount of heat energy flowing into your reserve of propane with the demand remaining the same … and so on.  More heat flows into 2 tanks than one – your demand remains the same. 

With all due respect, increasing the amount of propane or number of tanks is only one way of making your system work. It is sort of like adding a larger pressure tank to your water system to handle peak water demands.  You still need to use the same amount of energy to fill that pressure tank. 

What is important is how fast the heat energy in the propane tank can be replenished (so it can make the vapor from the liquid) as it is taken away to your appliance.  

 I would insulate the tubing going through the cold environment to the appliance to prevent losing the precious energy gained from environment around the tank.

so in a nut shell on usage needs.... if on a hot day you are freezing your tank, you need to add another tank, because your not running at efficiency, your system is struggling to keep up with demand 

heres a thought i have........
if your system is able to handle say 200,000 btu's total, and you have 4 pieces of equipment that need a total of 220,000 btu's which takes the hit? the one with the largest demand, all 4 equally on an even % basis, or the one with smallest demand ???
 
more research is needed.....

We will be running the iron pipe on our skoolie conversion (yep, I'm familiar with BruinGilda) for the various appliances. The pipe will have "T's" with individual shutoffs on each line. Yes I'm paranoid about LP gas... there are just some things you do and others you don't do.
 
I have the NFPA1192 Standard on Recreational Vehicles (1999 Edition but still applicable for our use... it doesn't change much). I have notes written into it in several places. Among my notes in the LP section I have a notation that "Gastite"hoses are okay (this is a brand of hose) for mobile use. The pipe sizing charts are listed under thousands of BTU per hour. I have the pipe charts saved in an open office spreadsheet (along with other info related to a bus conversion) but haven't gotten it formatted completely and posted on my bus' website. Go talk to the LP dealer in your area. They should be able to help you with sizing etc. We have found that custom dealer made hoses are better than store bought and tended to be cheaper.
 
ON EDIT: Got the document loaded on my website. It's an Excel spreadsheet and the info on the pipe sizes are on the first page. Hope it helps you...
http://aluminumasylum.webs.com/apps/documents/   Download "System Sizing Charts"

"ON EDIT: Got the document loaded on my website. It's an Excel spreadsheet and the info on the pipe sizes are on the first page. Hope it helps you...
http://aluminumasylum.webs.com/apps/documents/   Download "System Sizing Charts"
 
I checked it out, and I saw all the appliance statistics, but not anything on pipes - am i not looking in the right place?
Thanx, Dave

Pipes and tubing is on the very first page of the document. There should be a total of 4 pages. Look down at the tabs on the bottom left hand side. You will see a tab that says "LP Gas Pipe and Tubing Size" click on that. The other pages are simply for a bus conversion. Although you may find the Wire Size Chart applicable.

BackAlleyBurger:
 
I know this is a huge request, but would you be willing to post pictures.  I am in the process of installing propane in my totally electric trailer and would love to see your lines.  All of them, from the rooter to the tooter. 
 
Gilj

lol, my rooter and tooter dont have any lines yet..... im still working on the outside in preparation for the actual build out.... 

Oh, I must have misread.  I assumed you already had your propane lines run and was operational.  Sorry for the mixup.

LOL I'm such a dumbass....thanx for the info!
So I'm gonna use the existing 3/4" black pipe from the regulator to the shutoff valves, and have some3/4" I.D. low-pressure rubber hoses made to go from the valves to the equipment... should not have a BTU problem based on that chart of yours.
Thanx a bunch!!

BackAlleyBurger

  I am using portable propane bottles mounted in a compartment under the bus to facilitate refilling without having to move the bus to the propane station. I have a manifold just downline of the regulator under the bus to which each of the individual hoses connects.

 
So do I understand this correctly......you have to be under your unit in order to change your tanks? You can't just get a propane truck to come and deliver to an outside connection, like they do for home tanks? Where do you live, in what state? I'd never crawl under my trailer in order to remove my tanks to take them for a refill, especially in our (Illinois) winters. It gets cold enough here (5 to 15 below) that I hate taking them off the front of my trailer and throwing them in my jeep for the 1/4 mile drive for a fill up. Brrrrrrr.
Jack

Like BackAlleyBurger, our LP tanks are mounted under our bus and we will drop them off their "shelf" and slide them under the sidewalls of the bus to refill. Skoolies sit high. Our BlueBird sits high enough that I can slide a BBQ tank under the side wall with out tipping it at all. I have a permanent mount LP tank (40 lb) that is on the Class C. We have filled it once. It's much easier to take our BBQ tanks to the refill station than to move the whole RV. We built a homemade "extend-a-stay" for that reason. While in TX, we discovered that the LP trucks would drive thru the campgrounds and refill tanks, both on and off the RV. I have been reading many posts on the RV forums that they are discontinuing that practice due to "insurance" or "local ordinance" reasons.