Features March 2014 Issue

Some Propane Dos and Don’ts

LPG can spell danger if not properly installed and maintained.

lpg locker on boat
Only LPG equipment should be stored in an LPG locker to ensure that the systemís e not damaged by other gear.

Thereís nothing more satisfying than capping a pleasant day on the water with a good meal, be it burgers and dogs on the grill or some fancy, culinary extravaganza whipped up by the galley wizard. Most marine stoves and grills use liquefied petroleum gas (LPG). Itís efficient, relatively cheap, and widely available. Itís also highly explosiveóparticularly with regards to boat installationsówhich makes proper installation and regular inspection so critical in onboard systems.

LPG, a combination of propane and butane, is a gas that changes to a liquid form when pressurized, a trait that allows for easy storage in its concentrated, liquid form. Once this pressure is removed, it changes back into a gas for use in stoves, grills, and the like.

lpg locker meeting American Boat and Yacht Council safety standards
The Hunter e33ís LPG locker comes close to meeting American Boat and Yacht Council safety standards, but the bilge pump handle on the lockerís inner lid means itís not a dedicated storage space.

One downside of LPG is that itís heavier than air, which means it tends to ďflowĒ likewater, seeking the lowest possible point. This typically isnít a problem with shore installations, as there tends to be more airflow to help disperse leaking gas; however, boat installations are another matter. A boatís 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, but just because you canít smell gas doesnít mean it isnít there; the gas can remain after the odorant has dissipated.

The goal of any LPG system inspection is to prevent (or locate) gas leaks. In this article, weíll cover basic LPG system installations and inspections, however always seek professional advice from a certified LPG installer if youíre unsure about any aspect of inspecting or maintaining your LPG system.

Fuel cylinders and storage

All LPG cylinders must meet Department of Transportation (DOT) or American Society of Mechanical Engineers (ASME) requirements. You can verify whether a tank is acceptable by looking for a stamp from one of these organizations near the tank valve. LPG storage tanks can be mounted on deck or in a dedicated storage locker; however, they must be properly secured in an upright or horizontal position, depending on the design of the tank.

Tanks designed to be mounted vertically should never be installed in a horizontal position, which could allow liquid LPG to flow through the regulator and into the system, causing flare-ups and all manner of nasty things. The above applies to all tanks, regardless of their status (full, empty, disconnected reserve cylinders, etc.).

Cylinders mounted on deck have to be located in a well-ventilated area where leaking gas will flow directly overboard; they must be readily accessible and be 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.

According to the American Boat and Yacht Council (ABYC), dedicated LPG storage lockers must be vapor tight to the vesselís 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 shutoff valve during an emergency.

LPG storage locker installation

LPG lockers are required to open directly to open air. However, an after-market, standalone locker like those Trident Marine sells can be located inside a cockpit locker if they are mounted so that the LPG locker lid canít be opened without opening the cockpit locker first. All LPG lockers must also have a dedicated drain at the bottom that vents directly overboard; the drain must be a minimum of a half-inch in diameter.

An LPG locker must be a dedicated space. That means all non-LPG system itemsóshackles, tools, etc.ómust be removed as they can easily damage system components. When inspecting the locker, check the bottom, sides, and seams for damage (corrosion, cracks, holes) that could allow gas leaks into the boat interior.

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

A note of caution about external, stern-rail mounted LPG lockers: Most stern rails are not designed to withstand the loads induced by waves breaking over the external locker, so storing your LPG tank on the stern rail runs the risk of losing the rail in foul weather.

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 is mounted so you can operate it without reaching over the top of any open flame (such as a stove burner).

For a corrosion-resistant solenoid valve, David Anderson of Sure Marine Service, recommends using one made of marine-grade stainless steel. He said that the common cadmium-plated steel solenoids will rust in short order on a boat.

LPG cylinder storage locker ventilation
LPG cylinder storage locker ventilation canít be connected with other piping; here, a siphon vent for the engine exhaust has been Tíd into the LPG storage locker vent hose.

Fuel lines

Copper hose is used throughout the world in most LPG installations, but flexible, high-pressure hose is another option worth considering. Both types have their pros and cons: Flexible hose allows for gimballing stoves and resists vibration better than copper, but copper withstands chafing (and rat gnawing, see sidebar) better than flexible hose. Installations that use flexible hose should include chafe protection.

Whether you use copper or flexible hose, itís imperative that you visually inspect lines for cracks, brittleness, kinks, and chafing, ensuring each is protected by grommets at bulkheads, partitions, or deck penetrations. For copper lines, in addition to chafe protection, 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.

Check the outer jacket of flexible hose for markings that indicate compliance with Underwriters Laboratory UL21 LP Gas Hose. Verify that all end fittings are permanent types such as a swaged sleeve or sleeve and threaded insert; hose clamp fittings are a big no-no.

Finally, each appliance (galley stove, cockpit grill, etc.) has to have its own dedicated supply line, with each one originating from inside the propane locker or tank enclosure at the solenoid valve. The supply line must be a continuous run, with no breaks, connections, or Ts in order to reduce the possibility of leaks.

storing flares in lpg locker
In our opinion, an LPG locker is a particularly poor place to store flares, as this boat owner was inclined to do.

Regulators, gauges, Leak Tests

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

LPG systems are also required to have a pressure gauge installed on the cylinder side of the pressure regulator. This gauge allows you to quickly and easily check the system for leaks using a ďleak down test.Ē To conduct a leak down test, turn on an LPG appliance (the stove or grill), then close all the burner valves but leave 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 you must inspect the entire system before using any connected appliance.

Check your LPG system regularly for leaks or anytime you fire up that stove or grill. Leaks can occur anywhere in the system due to chafe or physical damage to supply lines or other components, but they typically occur at fittings and connections. To locate leaks in the system, you can use leak detection fluid or concoct a detergent-water solution. Liquid dishwashing soap mixed with water will produce the most bubbles. Donít use solutions containing ammonia, which will attack brass fittings, and unless you want top billing at the Darwin Awards, never use a flame to check for LPG leaks.

failed marine grill propane system
This system fails to meet ABYC standards for LPG system installations. The cylinder is not secure, thereís no shut-off valve operable from the vicinity of the LPG appliance nor is there a pressure gauge. Another no-no: The tank is in close proximity to openings into the vessel interior.

Mix the soap-water solution in a spray bottle and stream spray (donít mist) it onto hoses, connections, and other parts of the system. You can also use a sponge or rag to apply the solution, but weíve found a spray bottle to be fastest, and it can get to hard-to-reach places. If you see bubbles, thereís a leak.

Installation of a marine-grade LPG ďsnifferĒ or fume detector is also highly recommended. If you have one installed, be sure that 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 desirable safety upgrades include installing smoke and carbon-monoxide detectors.

Best practices when cooking with LPG is to leave one burner ignited after cooking and turn off the solenoid or tank valve. When the flame goes out, close the burner valve; this empties the line of gas and prevents leaking should a burner valve fail to seal. Itís also a good idea to close the LPG tank valve in addition to the solenoid valve when the system is not in use, particularly if you plan on leaving the boat for an extended period of time. (The solenoid should always be closed when the system is not in use.)

Comments (3)

I have used propane stove/oven fuel on my boats for the past 30+ years. Safety is always a concern. I have a pressure gauge between the solenoid and the tank. The gauge is used to pressure test the propane line regularly by pressurizing the system, assuring the stove and tank valve are both off with them solenoid is open then noting the initial pressure reading on the gauge. If the pressure holds for 15 to 30 minutes the system integrity is not compromised. I also check the integrity of the tank valve / solenoid by pressurizing the propane supply line with the solenoid closed and re-pressurizing the line between the tank valve and the solenoid then keeping an eye on the pressure gauge to see if the pressure holds. I have seen first hand what a propane explosion can do to a boat. Propane is the best and most efficient stove fuel to use on a boat. I will continue to use propane for stove fuel but with extreme respect and caution.

Posted by: BRUCE W | March 21, 2014 5:37 PM    Report this comment

I got tired of having to search for the large wrench needed to undo a POL valve and change bottles, and purchased a quick-connect pigtail that allowed me to change the supply bottle very quickly. Unfortunately, the QC pigtail fittings also contain an excess flow limiter that can cause problems when you open the solenoid, if your supply hose is too long. I noticed that occasionally, in the morning, I could not get any gas flow when I went to boil water for the morning tea. A trip out to the propane locker revealed no issues, and if I just shut the valve, waited a bit, and re-opened it slowly, full flow was restored. After three of these early AM trips in cold weather I went back to the POL connector, which does not have an excess flow limiter.

Posted by: rxc | March 9, 2014 8:47 PM    Report this comment

Minor issue, leaving the burner on and turning off the solenoid drops the pressure to atmospheric but the line still contains propane. I was hoping the article would discuss using large tank and hose with outdoor grill as 1 lb tanks get expensive. Comments on a save method would be good to share

Posted by: michael w | March 2, 2014 7:21 AM    Report this comment

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