There’s nothing more satisfying than capping a long day on the water with a good meal, be it burgers and dogs on the grill or a culinary extravaganza whipped up by the galley wizard.  Most marine stoves and grills use LPG (liquefied petroleum gas).  It’s efficient, relatively cheap, and widely availability - it’s also highly explosive (particularly with regards to boat installations) which makes regular inspections and tests of the system so critical.

            LPG (a combination of propane and butane gas) turns into a liquid when pressurized, but converts back into a gas once the pressure is removed, a trait that allows easy storage in its concentrated, liquid form.  A negative characteristic, however, is that LPG vapor is heavier than air, which means it tends to “flow” like water, seeking the lowest possible point. 

            With shore installations there tends to be more air flow to aid in dispersing leaking gas, however a boat’s hull is essentially a watertight envelope, meaning explosive gases can be trapped in bilges or other low areas, where they can rapidly accumulate to explosive concentrations.  LPG suppliers are required by law to add an odorant in order to make leaks more noticeable, however just because you can’t smell gas doesn’t mean it isn’t there (the gas can remain after the odorant has dissipated). 

            The goal of any LPG system inspection is to prevent gas leaks (and being ushered into eternity via a fiery explosion of biblical proportions).  In this article we’ll cover basic LPG system installations and inspections, however you should always seek professional advice from a certified installer if unsure about any aspect of inspecting or maintaining your LPG system

Fuel cylinders and storage

            All LPG cylinders must meet DOT (Department of Transportation) or ASME (American Society of Mechanical Engineers) requirements – you can verify your tanks are acceptable by looking for a stamp from one of these organizations near the valve.  Tanks can be mounted on deck or in a dedicated storage locker, however they must be properly secured for sea and in an upright position (tanks should never be mounted in a horizontal position due to the possibility of liquid LPG entering the regulator and flowing into the system).  The above applies to all tanks, regardless their status (full, empty, unconnected reserve cylinders, etc)

            Cylinders mounted on deck have to be located in a well ventilated area (where leaking gas will flow directly overboard), be readily accessible, and protected against weather and/or mechanical damage.  The aft portion of the vessel is typically better in this regard, as tanks will be less exposed to saltwater spray and its corrosive effects. 

            As per the American Boat And Yacht Council (ABYC), dedicated LPG storage lockers must be vapor tight to the vessel’s interior, located above the waterline, and be constructed of (or lined with ) corrosion resistant materials.  Check that your locker has a gasketed cover that latches tightly, opens only from the top, and can be quickly opened without tools (so you can easily access the tank shut off valve during an emergency).

            Location-wise, LPG lockers are required to open directly to the outside atmosphere, however they can be located inside a cockpit locker if mounted high enough that the LPG locker lid can’t be opened without opening the cockpit locker first.  All LPG lockers must also have a dedicated ½” (at a minimum) drain at its bottom that vents directly overboard. 

            When inspecting your locker, make sure all non-LPG system items are removed (that’s where the “dedicated” locker thing comes from) – items such as shackles, tools, etc, can easily damage system components.  Once you’ve removed everything that shouldn’t be in there, check the locker bottom, sides, and seams for damage (corrosion, cracks, holes, etc) that could allow gas leaks into the vessel’s interior.

            Ensure the locker vent hose slopes downwards, is free of blockages, loops, and kinks.  The discharge outlet must be located below the locker and exit the hull above static waterline at least 20 inches away from any other openings (air intakes, sink or bilge pump discharge hoses, engine exhausts, etc) that could allow gas to re-enter the hull. 

Shut-off valves

            Every LPG system is required to have a readily accessible manual or electrically operated (e.g., solenoid) shut-off valve installed in either the low or high-pressure line at the cylinder.  Check that the valve or solenoid remote control is located in the vicinity of the appliance it serves and mounted so you can operate it without reaching over the top of any open flames (such as stove burners). 

Fuel lines

            Copper is used throughout the world in LPG installations, however flexible high-pressure hose is probably safer for marine use.  Visually inspect lines for cracks, brittleness, kinks, and chafing, ensuring each are protected by grommets at all bulkhead, partition, or deck penetrations.  If you have copper lines, in addition to the above verify that all fittings are long nut flare fittings – short nut fittings (such as those used in refrigeration systems) are less reliable and prone to failure due to vibration.

            For flexible hose, check the outer jacket for markings that indicate compliance with Underwriters Laboratory UL21 LP Gas Hose.  You also need to verify that all end fittings are permanent types such as a swaged sleeve or sleeve and threaded insert – no hose clamp fittings allowed.

            Finally, each appliance (galley stove, cockpit grill, etc) has to have its own dedicated supply line originating from inside the propane locker or tank enclosure at the solenoid valve.  Verify this supply line is a continuous run, with no breaks, connections, or “T”s (in order to reduce the possibility of leaks).

Pressure regulators and gauges

            Every LPG system has to have a pressure regulator designed for use with LPG.  For deck mounted cylinders, verify the regulator’s relief valve outlet discharges outside the boat at least 20 inches from any opening (just like the locker discharge).       

            LPG systems are required to have a pressure gauge as well, installed on the cylinder side of the pressure regulator. This gauge allows you to quickly and easily check for leaks. To test the system, turn on the stove or grill, then close all the burner valves, leaving the solenoid switch on.  Note the pressure gauge reading, then close the tank valve – the gauge reading should remain constant for at least three minutes.  If the pressure drops, then you have a leak (or leaks) and must inspect the entire system.

            Use leak detection fluid or a detergent solution to locate leaks.  You’ll typically find them at fittings and connections, although they can occur any where in the system due to chafe or physical damage to supply lines or other system components.  Don’t use solutions containing ammonia (it attacks brass fittings) and unless you want top billing at the Darwin Awards website, never use a flame to check for leaks. 

The thrill of the grill

            Because grills are located above decks, boaters tend to treat them with a more cavalier attitude when it comes to safety – bad idea. According to the Insurance Information Institute, barbecues result in more than two thousand fires, over 300 grill related injuries, and at least three deaths annually.  Here’s some tips on how to avoid becoming a barbeque statistic.

            First off, make sure your grill is mounted solidly and in accordance with the manufacturer's instructions.  Avoid using camp type grills or the like, which typically have no means to properly mount them on a boat.

            As with your galley stove, burner controls should be two-stage operation when going from ”off” to “on” (to prevent accidental opening of the valve during handling or storage) and should be located at the front of the grill, so you can operate them without reaching over the burner.

            If your grill is fueled by the LPG system, inspect the system as previously discussed.  If it uses portable cylinders, they have to be DOT-approved 2P/2Q 8 ounce units with rim vent release.  Never use or store portable cylinders larger than 8 ounces and these must be stored on the exterior of the vessel such that any leaking gas can flow overboard. 

Most excellent ideas

            Check your LPG system weekly for leaks, or anytime you fire up that stove or grill.  Installation of a marine grade, LPG “sniffer” or fume detector is also highly recommended.  If you have one installed, ensure the gas sensor is mounted as low as possible and near the range (where leaking gas is likely to accumulate) and that you test sensor operation on a regular basis.  Other safety upgrades should include installation of smoke and CO detectors.

            After cooking, leave one burner ignited and turn off the solenoid or tank valve. When the burner goes out, close the burner valve – this empties the line of gas and prevents leaking should a burner valve fail to seal.  It’s also a good idea to close the tank valve in addition to the solenoid valve when the system is not in use, particularly if you plan on leaving the vessel for an extended period of time (the solenoid should always be closed when the system is not in use).