CNG tank fill or exchange... PNW... Anacortes, Port Townsend???

[smokey73]

Methane probably doesn’t have the chemical that gives Natural Gas in the US it’s distinctive odor. Not in NG in Europe.

May be the case but that alone wouldn't keep someone from using except you wouldn't be able to tell when you had a leak. Still a good point though. I'll have to inquire with the industrial gas suppliers if there is a "odorant" added to the methane they provide. They can provide everything from "industrial grade" compressed (2000 psig) Methane at 97% pure to "ultra pure" used for experiments and other special applications. Here is the BTU value table for some fuels. It looks like the pure Methane is equivalent to the mid range of the Natural Gas spectrum. I assume that the NG range is due to "concentration" of the flammable portion of the NG (which is typically Methane)
Gas Gross Heating Value (BTU/cuFt)
Butane - C4H10 3225
Methane - CH4 1011
Natural Gas (typical) 950 - 1150
Propane - C3H8 2572

Just thinking out loud and trying to understand the possible complications of using compressed Methane in place of CNG. Any thoughts would be appreciated.

 

[Terry Cox]

Still waiting for a reply as to where I can get my CNG tanked filled in the PNW. Anyone, anyone?

 

[LeslieTroyer]

I think they are all gone now that Sure Marine doesn’t fill them (they supplied a dozen or so places around the Sound). If anyone would know it’s Sure Marine - give them a call.

 

[bay dancer]

Got some info from a friend in the gas business in UK. Methane is often substituted for compressed natural gas when it is for training exercises by people in the gas delivery business. Ie, when ordinary people are not involved and the lack of the added smell intended to warn of a leak is not a concern. Seems that in ordinary use, as with a galley stove, we would probably not notice any performance difference, since methane is typically 80% or so of the composition of natural gas.
Progress, for sure, but there is a big but. Where to get a fill? Major issue is the cylinder and its valve, are they of a satisfactory standard to satisfy the company doing the filling. One suggestion has been to get them tested by a dive shop, which does this for diving tanks routinely and to comparable pressure levels. Would this level of approval be acceptable to a US gas supplier? In the absence of a full gas supply company (which seems likely) would a local welding company be OK with selling on methane from its tanks?
Anybody know about this stuff? If not then that means trying to find dive companies and welding operators and see what they say. Would however be nice to have some input in advance of asking dumb questions ... Anybody have any experience with a CNG leak on a boat? Are there gas detectors for CNG as with the devices that pick up propane?
Far too many questions.

 

[smokey73]

Good questions and I appreciate the input from your "bloke" in the UK. I am the original poster and I am not suggesting that we try to get the tanks "refilled" by anyone, hence no need to get the tanks re-certified or tested by a dive shop. That is because the methane tanks I am referring to would be supplied by and purchased from an industrial gas supplier in DOT container already, certified and pressurized and filled with Methane (filled to 2000 psig with Methane at 93% purity). They are not cheap (about $100) per tank. There may be a credit for a tank return but that is down the pike if we determine we can go that way. Yes, they are expensive but at the cost of conversion being in the vicinity of $3K total, I could buy 30 tanks and that would last 20+ years for me. I don't live on the boat and don't really cook that much.

As far as I know there is no detector for CNG like there is for propane. Of more concern is the lack of a odorant in the Methane. I will inquire if an odorant can be added at the gas supplier facility to solve that problem? The other thing is the valve on the top of the tank and if it is compatible with the regulator for the CNG system. You are right about so many questions. Lets keep researching this.

 

[Terry Cox]

give them a call.

Called them awhile ago and no help. Still looking.

 

[MDBack]

We purchased this tank fill adapter from Ebay: https://www.ebay.com/itm/Sail-Boat-...185908?hash=item2acfa2e634:g:r0UAAOSwzaJX3UrH
We filled our tanks in Minnesota at a car CNG filling station for $1.70 each. Took about 4 seconds. The tanks get warm, but cool and the pressure drops about 200-300 psi. This is our new favorite gadget. It saves us all the hassle with finding someone else to do it. Now just find a filling station and do it yourself. Good Luck!

 

[smokey73]

We purchased this tank fill adapter from Ebay: https://www.ebay.com/itm/Sail-Boat-...185908?hash=item2acfa2e634:g:r0UAAOSwzaJX3UrH
We filled our tanks in Minnesota at a car CNG filling station for $1.70 each. Took about 4 seconds. The tanks get warm, but cool and the pressure drops about 200-300 psi. This is our new favorite gadget. It saves us all the hassle with finding someone else to do it. Now just find a filling station and do it yourself. Good Luck!

Is there an attendant there at the car station and if so does he/she give you a hard time or a "what the heck are you doing" question or look? Does he/she ask to see if the tank has been tested within the last 5 years or any kind of certification? Just asking since these are all reasonable questions they might ask and they might even not allow you to fill. Right now I'm having difficulty at even finding a gas CNG station for starters. Thanks for thee link though. Since you have one of these, do you see any markings on the fittings showing they are rated for the service (cng or gas) and the pressures involved. I have made one of these with "pressure and service rated" parts but don't have the dual gauges, I think I may add the second gauge.

 

[MDBack]

The station we found was completely unattended. The only issue we had was that we needed to fill 2 tanks. After the first "fill" only costing $1.70, I got an alert on my phone of a possible hack to my credit card that locked the card for 10 minutes and we had to use a different card for the second tank. Our tanks are still within the 5 year cert. You can also get that done at welding gas suppliers usually. I watched the YouTube videos about 100 times to get in the mode of what I was about to do. It happens very fast. I think the fittings are all rated for 4000 psi. The filling station was a 3600 psi station and we put 3000 psi into the tanks which subsequently dropped to about 2700 psi. I did think a lot about what I would say if an attendant had issue with what I was doing. I think honesty is the best policy and if they were amenable I could possibly explain the situation and educate. If not, then they are perfectly within their rights to refuse service and that's okay too (but could be tough if you drove a long distance to get there). Maybe a google search and satellite view of the premises before hand... And we all need to help each other in this effort, the more info the better. Maybe we should start a "CNG sticky thread" of good self-serve filling locations???

 

[MDBack]

One more bit of info in case anyone is still wondering. CNG is Methane. Mostly. If you are able to buy pure Compressed Methane then that's great and no problems at all. If you can get a fill of CNG or Compressed Natural Gas you're good too. CNG is just what comes out of the ground when drilling for oil and it is about 93-96% Methane and the rest is ethane, propane, butane, and all the other "anes" in the series. Think of CNG as "Dirty Methane" while "Pure Methane" has just been cleaned up for higher grade uses. Either one burns just fine in CNG stoves and ovens on boats. Also, CNG is lighter than air so leaks will rise to the cabin top and out well before becoming a fire hazard. That's why it's considered safer than propane.
Hope this helps.

 

[smokey73]

MDBack - thanks for the info. I've found a source for 98% pure methane from an industrial gas supplier. Its a little pricey, but still much less than converting to propane and I still like the idea of the CNG being lighter than air. I also have an fill adapter but I like the idea of the two pressure gauges. For the 98% pure methane from the gas supplier I'll have to find out if it has the "odor" added since its odorless if the additive is not in it. It would be nice to be able to detect a leak with the nose though.

I have two tanks with about 200 psig left in one tank and the other tank at about 2000 psig. That should last me for quite a while as I'm not out "cruising" for long periods of time. Just checking for a future need. I'm not having any luck in finding a CNG station near me in Beaufort SC. I can get it near Atlanta (about 4 hrs) or possibly Columbia SC (about 2 1/2 hrs) if push comes to shove but I don't know if I'll get a hard time there until I try and its a long drive just for a try. Thanks for the info and any info from cng/methane gas experts out there is greatly appreciated.

 

[bay dancer]

Thank you MDBack! Adaptor looks much the same as the thing I used to fill O2 aviation tanks. Yeah. Nearest car place is about two hours each way, which is not so bad.

 

[MikeHoncho]

Nooo.... its not quite dead yet! Its not as easy to blow up your boat as one would think. Here is a video from Yachting monthly.

They finally had to resort to bottled CNG.

All any flammable gas takes is the mixture in a flammable range and a hot enough ignition source. Obviously these guys are missing one or more of these elements. Probably getting the atmosphere to the flammable range due to improperly calibrated and/or improperly placed equipment is the issue. The FR of LPG is 2-9.5%

 

[MikeHoncho]

All you Chemist's out there. Since CNG is primarily Methane (maybe all methane except impurities?) why can't you order a Methane tank (size 80) from a welding gas supply store and use that? Is there some reason this won't work? I have found several commercial gas suppliers that can and will sell Commercial Grade Methane in about the $100 for a filled cylinder. I know that is pricey compared to Propane and the energy density of the Methane is less than LPG. This is not a discussion of whether to convert or not. As little CNG as I use each year I could buy a lot of tanks for the price of the LPG conversion (LPG locker, new hoses, safety valves, new stove, etc). As a followup, the question might be if the valve on the top of the tank is left hand thread and the same size as on a CNG tank. I'll have to research that.

Just an out of the box thought - any perspectives (other than change to LPG) are welcome. The conversion has been beaten to death!

Not a chemist.......natural gas predominantly consists of methane. Methyl Mercaptan is added for scent to distribution lines after NG leaves large pipelines. Mercapton is what is added to propane also for scent.
I don't believe mercapton is added to methane welding gas due to its impurity making it undetectable when leaking .
I have no idea about the valves.
Keep in mind that although it rises, you still need to enable it to vent from the "container" to be safe. Keeping your boat closed up will enable cng to be comparably as flammable as lpg .

 

[Scot Yount]

We purchased this tank fill adapter from Ebay: https://www.ebay.com/itm/Sail-Boat-...185908?hash=item2acfa2e634:g:r0UAAOSwzaJX3UrH
We filled our tanks in Minnesota at a car CNG filling station for $1.70 each. Took about 4 seconds. The tanks get warm, but cool and the pressure drops about 200-300 psi. This is our new favorite gadget. It saves us all the hassle with finding someone else to do it. Now just find a filling station and do it yourself. Good Luck!

I live 20 minutes from Boston’s airport. Most big airports run their busses on CNG. I have not used it (cuz my chandlery has tanks for exchange) but it is unattended and easy to use. I assume it is the same in many cities.

 

[Ron20324]

I live 20 minutes from Boston’s airport. Most big airports run their busses on CNG. I have not used it (cuz my chandlery has tanks for exchange) but it is unattended and easy to use. I assume it is the same in many cities.

Yeah, BWI.

 

[MikeHoncho]

I live 20 minutes from Boston’s airport. Most big airports run their busses on CNG. I have not used it (cuz my chandlery has tanks for exchange) but it is unattended and easy to use. I assume it is the same in many cities.

Most county bus systems in the PNW run on CNG. Now we are seeing alot of utility contractor and utility company fleets running on LNG. Alot bigger bang for your buck on LNG.

 

[Scot Yount]

Most county bus systems in the PNW run on CNG. Now we are seeing alot of utility contractor and utility company fleets running on LNG. Alot bigger bang for your buck on LNG.

So people should be able to find it.

 

[MikeHoncho]

So people should be able to find it.

Its out there. It just isn't publicly available. Transfering flammable gas at pressures of 3000psi has its challenges and people aren't as excited about CNGs performance as those who drive a bus and couldn't care less.

 

[Scot Yount]

Its out there. It just isn't publicly available. Transfering flammable gas at pressures of 3000psi has its challenges and people aren't as excited about CNGs performance as those who drive a bus and couldn't care less.

Totally. As I said earlier in this thread....I am going to go to alcohol when my chandlery quits the CNG biz....
I am just sad that those stoves are disappearing