LPG (Propane) and CNG
Standards for installation of LPG-Propane and CNG systems for Cooking, Heating, and Propulsion
LPG - Liquid Petroleum Gas: See Wikipedia LPG
CNG - Compressed Natural Gas: See Wikipedia 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 larger passenger carrying vessels See the Code of Federal Regulations Title 46 Shipping Sec 25.45
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. 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
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Are there other standards for Propane and CNG?
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)
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.
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