CNG Supply Line - Tank to Stove 20'

[estarzinger]

Originally Posted by Moxie 38

The issue here is that the hose is attached to a movable, ie. "gimballed" appliance.

Yes, it is standard for appliances with lots of vibration or movement (like dryers and washers) to use a couple foot section of metal jacketed braided hose at the end to take the vibration and chafe. Honestly I would do that even if you were running rubber hose - because with a gimbaled stove there is a chafe potential that could wreck a rubber hose but not a metal braided one.

Again, there are all sorts of specs you could choose but something like http://www.mcmaster.com/#about-braided-hose/=zv3r2z or the "Braided Hose Pump Connectors" here :McMaster-Carr would easily do the job.

You could of course make the entire run of that sort of stuff - but most people would consider that overkill

The superyachts I have project managed have used solid stainless pipe for the long runs with stainless braided to connect to the appliances. That of course can be difficult to retrofit depending on the (lack of) straightness of the hose run. But it is 100% safe and will last forever.

[colemj]

OK, so I don't understand the need for a conductive hose here - this is usually reserved for things like high-flow/high-velocity applications that can build up a static charge over long runs. Your application isn't like this.

If you want electrical bonding between tank and stove, couldn't you just run a wire between them?

Mark

[Moxie 38]

Thank you, Mark. It's a good question, I guess. I assumed from my dialogue with the hose mfr that this is what is needed for CNG on a boat or any type of vehicle. I suppose that a wire securely fastened to the stove and, say the regulator with perhaps a reliable type of clamp would work equally well.

Then I can look for a reinforced hose with swaged fittings both ends perhaps such as the link referred to me by sailorchic34 earlier. I will definitely follow up on this. Thx!

[Mikado]

Give your local Parker store a call. They can build you a hose, fully tested, for any application for a very reasonable price.

Here is a store in CT. I think they have a couple more.

Good luck.

Connecticut's Leading Parker Fluid Connector Distributor

[Stu Jackson]

Originally Posted by sailorchic34

CNG is stored at 3000-3600 psig. If the gas pressure regulator failed open (which can happen though rare) the hose needs to be able to contain the pressure of the propane or the CNG second stage regulator. CSST tubing will not do that.

For those reasons, I don't think CSST tubing would be safe on a boat. But that's just me. The hose in my link on the other hand was tested to 750 psig without bursting.

I agree. My CNG regulator has a second separate fitting for overboard discharge in case of a regulator failure.

[guyrj33]

Try Corp Brothers for CNG hose by the foot.
SYNFLEX CNG HOSE 3/8 DIA at Corpbrothers.com

[antoha]

My (propane) hose is also made of two pieces (and everyone in the yard who looked said it's reasonable): first, a continuous section from tank to fitting under the stove; then a piece from there to stove itself. Stove is gimbaled, and the first section used to be copper (I replaced it as it began showing green in places, and I figured after 40 years I might as well). The second section was always flexible.


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[Moxie 38]

Thank you for your followup reply. Unfortunately, metal tubing (cu, ss, etc.) though easy to terminate with typical mpt / fpt fittings cannot be effectively routed below deck with multiple turns from my stern locker to the galley without pre-bending sections and adding additional couplings.

Additionally, every coupling added to transition from metal tubing at each end to a flexible polymer tubing for termination at both ends produces an additional joint to be watched for potential leaks.

The answer at this time appears to be a CNG compatible flexible hose system - internally conductive or not (who makes up all these rules??) that is abrasion resistant for the motion-related quotient of a boat and able to be terminated with reliable continuity from one end to the other. Why so much scrutiny for the safer CNG than propane??

What has me stymied is the fact that hose for propane transmission is so much simpler and, apparently not questioned, though potentially much more dangerous in a vessel on the water if it were to leak.

[Don Distante]

I have a 1985 cape dory that I keep in Noank CT. It has CNG which works fine for me. Suggest you contact Corp Brothers in Providence RI. It's where I exchange my tanks and they are very knowledgeable and helpful. Maybe they can make up the hose you want or steer you in right direction. Good luck


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[sailorchic34]

Originally Posted by Moxie 38

Thank you for your followup reply. Unfortunately, metal tubing (cu, ss, etc.) though easy to terminate with typical mpt / fpt fittings cannot be effectively routed below deck with multiple turns from my stern locker to the galley without pre-bending sections and adding additional couplings.

Additionally, every coupling added to transition from metal tubing at each end to a flexible polymer tubing for termination at both ends produces an additional joint to be watched for potential leaks.

The answer at this time appears to be a CNG compatible flexible hose system - internally conductive or not (who makes up all these rules??) that is abrasion resistant for the motion-related quotient of a boat and able to be terminated with reliable continuity from one end to the other. Why so much scrutiny for the safer CNG than propane??

What has me stymied is the fact that hose for propane transmission is so much simpler and, apparently not questioned, though potentially much more dangerous in a vessel on the water if it were to leak.

I checked NFPA 52 which ABYC references for hose with CNG systems. Really a good basic hose similar to propane would be fine. Generally copper fittings and copper tubing do not meet NFPA 52. So you will want SS or aluminum fittings.

So hose is not really that big an issue.

CNG is safer the propane inside the boat. But it has a few issues, mainly dealing with the 3300 psig storage pressure and a very complex three stage regulator. It is far more complex due to the pressures of storage. Where as propane at 150 psig storage pressure is rather simple to deal with with a simple single stage regulator. But yes a propane leak inside the boat would be far more problematic then NG.

[guyrj33]

I was told the CNG hose will shrink during a fire and close of the flow of gas. I recall reading in ABYC that all runs from tank to stove or other device must be continuous.

[Perstarebob]

Just how hard is it to find CNG when cruising ? I recently read an article in a fire fighting mag that said as leaks from propane gather in the low areas of a boat waiting for an ignition source , CNG gathers in high areas such as ceilings and are waiting also for an ignition source , CNG also causes problems when breathed as it displaces oxygen .

[guyrj33]

Cng is harder to find than propane, you have to exchange cylinders. Some have made adaptors to allow filling at automotive CNG filling stations.
I don't think it would be likely that CNG would collect in high space in a boat, we do so much to ventilate our boats that I think it's unlikely. Also you need a higher concentration of CNG than propane to support explosion.
CNG is definitely safer than propane, but also more expensive and harder to find. Tanks are also bigger, similar to a SCUBA tank.

[Cheechako]

Originally Posted by antoha

My (propane) hose is also made of two pieces (and everyone in the yard who looked said it's reasonable): first, a continuous section from tank to fitting under the stove; then a piece from there to stove itself. Stove is gimbaled, and the first section used to be copper (I replaced it as it began showing green in places, and I figured after 40 years I might as well). The second section was always flexible.


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Yes, Every boat I've had has had a gimbaled stove and a flex tube from the long tube that terminates behind the stove. This is the same in a cooking stove inside my house also... you cant pull the stove out if it doesn't have a flex hose at the stove.

I think people are over touting the idea that CNG is safer than Propane. They both explode. Plenty of news and video showing NG houses/businesses exploding in the last year. One could even argue that the bilge is spark free and safer than gas floating in the cabin! But either way, it's a bomb!
Convert the damn thing to Propane, use soft copper tubing and "bob's yer uncle"

[guyrj33]

Supply Hoses

To carry the gas from the regulator to the stove or heater, use LPG supply hose of the correct length. Note that while these hoses are only carrying 0.5 psi, they have a 350 psi working pressure rating, so they are dramatically stronger than they have to be. Each supply hose should run continuously from inside the propane tank enclosure to the appliance: this is not a case where you can chain a bunch of fittings together because you ended up a little short on hose. Use a Vapor-Tight Straight-Thru fitting where the hose exits your propane locker. Supply hoses connect to the propane appliance using a 3/8" female flare swivel and connect to the solenoid with a 3/8" male NPT adapter.
Above quote from
Safe Propane Installations | West Marine