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Disclaimer:   I am not a spokesperson for the US Coast Guard or ABYC. For an official interpretation of regulations or standards you must contact the US Coast Guard or other organization referenced..   More.....
The entire Electrical Pages, Capacity and Flotation Course,  Gasoline Fuel Systems: Engines and Related  Systems, and supporting spreadsheets, of this website may be purchased and downloaded. They are in ebook PDF format and the spreadsheets are in excel. Payment is through PAYPAL   Go to the store here Available for consulting, or speaking engagements, on boat building standards or boating safety topics.   Located in the Pacific Northwest.  Please contact me for resume' and rates. Contact Me Here

LPG (Propane) and CNG

Standards for installation of LPG-Propane and CNG systems for Cooking, Heating, and Propulsion

LPG - Liquid Petroleum Gas: http://en.wikipedia.org/wiki/Liquefied_petroleum_gas

CNG - Compressed Natural Gas:  http://en.wikipedia.org/wiki/Compressed_natural_gas

The US Coast Guard does not have a standard for LPG or CNG systems on recreational boats.  However, if the boat is used to carry six or less passengers for hire the boat must meet at least the ABYC standard.  If the boat is a passenger vessel under 100 gross tons and carrying more than six passengers then there are standards in the USCG regulations for those boats.

For six pack boats see http://www.uscg.mil/pvs/docs/UPV_GUIDEBOOK_under100GT_CGD11_2014.pdf

For larger passenger carrying vessels https://www.gpo.gov/fdsys/pkg/CFR-2008-title46-vol1/xml/CFR-2008-title46-vol1-sec25-45-2.xml

The American Boat and Yacht Council (ABYC) has standards specifically for LPG (propane) and CNG systems.

The ABYC standard is A-1, Marine Liquefied Petroleum Systems or A-22 Marine Compressed Natural Gas (CNG) Systems.  Contact ABYC for a copy. http://www.abycinc.org/  There is a fee.

There are some other standards that may apply.
A-26 LPG and CNG Fueled Appliances .
A-30 Cooking Appliances With Integral LPG Cylinders

613 Third Street, Suite 10
Annapolis, MD 21403
Phone: (410) 990-4460
Fax: (410) 990-4466

Are there other standards for Propane and CNG?

Canadian Office of Boating Safety has regulations that apply in Section 7 - Fuel Systems. of TP1332
http://www.tc.gc.ca/eng/marinesafety/tp-tp1332-menu-521.htm

UK And EU.  The Recreational Craft Directive has two sections on LPG in A.5.5 and A.5.6.
RCD Download site (Requires a fee) https://cemarking.net/recreational-craft-directive/

There is also an ISO (International Standards Organization) Standard for Small Craft on which the RCD is based:  ISO 14895:2000 and ISO DIS 14895 for Liquid Fueled Appliances
https://www.iso.org/search.html?q=14895

LPG, and to some extent CNG, have become popular because they have a much higher BTU content than traditional fuels such as alcohol and kerosene. LPG is readily available almost everywhere and is easily stored in portable containers.  So they make good fuels for cooking and heating.  However, because of their highly volatile nature they must be handled carefully and fuel systems must be installed correctly to avoid leaks.  LPG explosions can be catastrophic.

Additionally, the storage bottles are steel and susceptible to corrosion so the compartment also must be water resistant so that the bottles stay dry.  Fortunately some bottles are now being manufactured of fiberglass (GRP)  which does not corrode.

The most important thing to remember is that experience has shown that most leaks occur at fittings.  Thus, the fewer fittings the less the risk of a leak. Also LPG is heavier than air so tanks, fittings and appliances need to be in well ventilated areas and vented at the bottom of the compartment rather than at the top, with the venting allowing the vapor to flow overboard.  Some compartment may need forced air ventilation to draw the LPG out and over board.  However, CNG is lighter than air so the opposite is true. Compartments with CNG tanks, fittings and appliances should be vented at the top so the vapor can escape naturally.

Even the storage of small LPG bottles for torches, lanterns and portable cooking appliances,  can be problematic since they are steel and can rust and leak.  There have been instances of these small bottles leaking and causing minor explosions.  They need to be stored in a compartment that ventilates overboard but is otherwise water resistant so that they are not exposed to water.

References:

Safe Boat Propane installations: http://www.pcmarinesurveys.com/Safe%20Boat%20propane%20Installation.htm
Cooking and Heating Appliances On Passenger Vessels Code Of Federal Regulations eCFR Title 46 Chap I Subchap K  Part 121 Subpart B https://www.ecfr.gov/current/title-46/part-121/subpart-b
Boat Safety Scheme (UK) LPG Systems on Boats http://www.boatsafetyscheme.org/boat-examination/non-private-boats/part-7-lpg-installations/
Boat LPG Systems (UK) http://www.boatsurveyor.net/boat-surveyor-lpg-installations/
Maintaining Your Propane System: Cruising World. http://www.cruisingworld.com/how/maintaining-your-propane-system
Propane 101 (this is more about using it than installing it, but is good info) http://theboatgalley.com/propane-101/

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