CNG vent

[jebenz]

I have '87 Hunter Legend 37 that has been recently surveyed for insurance purposes. One of the survey reccomendations was that I vent the CNG locker. The CNG tank is placed in an interior locker behind the galley in the stern cabin. There has never been a vent in this installation and I assume the installation was done by the factory. Question, has any one vented this type of CNG installation, and if so can it be done by drilling holes in the top of the locker thus venting into the cabin (CNG is lighter than air so there should be no worry about it getting to the bilge) or must it be vented to the outside which would require a hole in the hull?
thanks,
JEB

 

[Rick D]

maybe Do Nothing

I am not aware of any such requirement. If it's just a recommendation, I'd ignore it unless that surveyor provides some objective documentation.

 

[Alan]

Absurd!!! venting a CNG locker is pointless. As you already note, CNG is a lighter than air gas and as such is self venting.

 

[Benny]

CNG is lighter than air but is still a good recommendation to have a vent. CNG is flamable and in large concentrations it can be explosive. The fact that it is lighter than air does not make a difference if it cannot escape into the atmosphere where it can disipate. The venting is not required to be to the outside but just to prevent high concentrations in what perhaps could be a location which may lack air circulation. Haven't you ever heard of an apartment building or a restaurant being flattened by a natural gas leak, it is the same concern.

 

[Marco Garcia]

Mine has a vent on the CNG system. It is not a vent of the locker but of the CNG lines ( maybe a High pressure relief ). The thru hull is on the port side by the manual bilge pump discharge..In the picture, Out of the regulator, one line goes to the thru hull, the other to the stove.

 

[Guest]

Hi Jeb, this topic has been covered before. A CNG locker does not have to be vented, unlike propane, gasoline, etc. If it were my boat I would challenge the surveyor to produce the technical document that stipulates such a requirement. I suspect, as before, they will have to amend the report.

Terry Cox

 

[jebenz]

Thanks for everyone's advice, I guess to be on the safe side I'll drill several holes in the top of the locker to allow venting. Incidently the surveyor cited ABYC reccomendations I have checked the web and it seem that you have to pay to get a copy of those regs.
jeb