When do i fill my cng tank?

[PAC3142]

I know, when it's empty. But when do I start planning for it?

Our new old boat has CNG for the cooking gas, and the scuba sized tank is at 1500 psi right now. For 3000 psi max fill, ideal gas law suggests that it is half empty. When do I start to plan to refill it? Can it still work at 500 psi? At 100 psi can I still make coffee? I can track our usage, but is there a lower limit, other than 0 psi, where it stops working properly.

I know I'll have to buy/make an adapter, but I'm trying to figure out where that should be in my priorities.

Thanks,
Paul

 

[wufibugs]

Not to hijack this threat, but I've been curious about the rate of use of CNG in normal cooking. I have a pressure cooker aboard that I use quite a bit and it speeds cooking quite a bit. I know this is a nebulous question, but if folks who regularly use CNG for cooking could give me an idea of what they cook and how often they have to fill, it'd help me decide if I should find a good place to store the spare tank on board or just leave it at home and swap out when the other gets low.

 

[Don S/V ILLusion]

I find it hard to imagine no CNG sources located around Annapolis.

The tank is useable down to virtually 0 psi gauge pressure.

We regularly use CNG for cooking, more so in the winter which is prime sailing season here. My experience indicates we go 'through' a full tank in 2 years. Obviously, that duration can change drastically depending on usage rate.

 

[wufibugs]

That's helpful, Don. We have year-round sailing or at least entertaining at the dock so even if I half your duration, there appears to be no need to add the considerable weight of a second tank aboard my 31' boat.

 

[PAC3142]

Don,
Two years per tank is useful. It means I've probably got another year.

As far as I can tell, there are no more sources for cooking CNG near Annapolis. All the places I've seen listed have stopped carrying it.

Paul

 

[Stu Jackson]

I get six months out of a tank (this is over the past 17 years we've owned the boat). I use our boat once a week or once every two weeks minimum. I take three day-two night cruises or longer. We cook onboard and rarely eat out. Coffee & pancakes or eggs for breakfast, lunch is usually sandwiches, spaghetti one night, pan fried steaks for dinner the other. We are fortunate that we have a tank refill place close by our marina. They have recently been required to re-certify all their tanks, so their resupply levels are down, and I have been going by twice a week to see if they have any, I did get one last week. We have a second tank on board. The regulator's pressure gauge shows what's left, it's linear. Since cars and buses uses CNG, some folks have made refill adapters and take their tanks to automobile refueling stations. I put a sticker on each tank, says when it was installed (connected to the stove) and whether it's a full or empty backup to remind me to get the second one refilled. Depending on anyone else's use is foolish without knowing how often and how long they use it. Use the gauge.

 

[TomY]

The regular CNG bottles are called 20 hour tanks. That means a 4,000btu burner(typical small/medium), will burn for 20 hours on one bottle(or tank). Our gauge shows just above 2000lbs when full. I would call 1500 3/4 full. Once down to 1 or 200 pounds, it won't last much longer but you could brew coffee several times.

We use about 2 tanks a season here in Maine. We're(two) onboard 30 or more days and nights per season. When we had 2 kids onboard, we could go through a bottle in a week doing a lot of cooking.

I like CNG but the worst part is the cost for us. We paid our highest rate in 15 years this past season to exchange our bottles: $85.00 per tank in Maine!

 

[wufibugs]

Thanks, Stu and Kris. The reason I ask is that we've been using the BBQ most of the time but in this coming El Nino winter I anticipate the stove will get a lot more action. These tanks are like heavy torpedoes so if I was going to keep a spare on board I would have to design and make a robust rack and tie downs for it, somewhere close to the boat's centerline if possible.

 

[woodster]

The regular CNG bottles are called 20 hour tanks. That means a 4,000btu burner(typical small/medium), will burn for 20 hours on one bottle(or tank). Our gauge shows just above 2000lbs when full. I would call 1500 3/4 full. Once down to 1 or 200 pounds, it won't last much longer but you could brew coffee several times.

We use about 2 tanks a season here in Maine. We're(two) onboard 30 or more days and nights per season. When we had 2 kids onboard, we could go through a bottle in a week doing a lot of cooking.

I like CNG but the worst part is the cost for us. We paid our highest rate in 15 years this past season to exchange our bottles: $85.00 per tank in Maine!

what do they mean by $2.39 gge

 

[PAC3142]

Thanks everyone. We almost succeed in getting on the boat every 2 weeks during the season for an overnight stay, and mostly bbq in the evening. So the stove is used for morning coffee and maybe a rice dish in the evening. Based on all the comments I expect it to last all next season, but I'm going to track usage.

Paul

 

[Benny17441]

I have been following threads on CNG just out of curiosity to see how long boater's ingenuity can keep it alive as a fuel for cooking and heating aboard a boat. There is one thing that does trouble me and that is the use of home made adapters to refill portable tanks at vehicle filling stations. As Stu mentioned Marinas and portable tank filling stations require the periodic certification of tanks but I doubt that individuals going to vehicle filling stations are going to recertify their tanks. I feel that using non certified adapters and tanks is just a recipe for disaster. Not sure about the legality of the use of the adapters but would think it is a kind of tampering and when it comes to tampering with residential and commercial CNG lines and delivery systems there can be stiff fines and consequences.