A Boaters Guide to Propane Here’s all the information you need to survey your boat’s LPG system and appliance installations, including warning label details and quick-reference checklists for ABYC standards’ compliance.
For many boat owners, petroleum gas (LPG) is the favored fuel for galley stoves, cabin and water heaters and refrigerators. LPG’s high calorific value and worldwide availability make it the popular choice. LPG is composed of propane, propylene and butane gasses. It’s a gas at normal room temperature and atmospheric pressure, but it liquefies when pressurized, and vaporizes again when the pressure is released. This two-phase characteristic is what allows LPG to be stored in its convenient, concentrated form. Aromatic Code LPG is non-toxic and invisible, but it can displace the air necessary to sustain life. The law requires commercially available LPG to contain an odorant that lets you know there’s a gas leak. Even if you can’t smell that distinct odor, you should know that leaking gas could still be present since the odorant can dissipate even though the gas itself remains. Released from its liquid state, LPG is heavier than air and will tend to sink to the bottom of an enclosed compartment. If mixed with air in certain proportions and confined, it will explode if ignited. (The lower explosive limit is between approximately 2% and 10% gas by weight in the air mixture.) Any fuel that burns with a flame consumes oxygen and gives off both carbon dioxide (CO2) and water vapor. In a tightly sealed boat cabin, the available oxygen can be rapidly depleted. This sets up a potentially deadly reaction since insufficient oxygen results in incomplete combustion and, instead of producing CO2, you get carbon monoxide (CO). This combination of oxygen depletion and carbon monoxide buildup can be fatal. [Ed: A discussion on gas detection systems and the dangers of carbon monoxide appears in DIY 2001-#1 issue.]
Fine Tuning As a marine surveyor, I find LPG systems in many of the boats I inspect don’t meet American Boat and Yacht Council (ABYC) safety standards. While most boat owners recognize the hazards involved -– explosion, fire, oxygen depletion and carbon monoxide -– they are often unaware of the standards that apply to LPG installations and appliances. Below are ABYC recommendations for LPG systems, appliances and installations. Quick reference checklists appears below. Cylinders LPG cylinders must comply with Department of Transporta-tion (DOT) or American Society of Mechanical Engineers (ASME) requirements. Look for the DOT or ASME stamp near the valve. Install all LPG cylinders on the boat’s exterior or in a dedicated locker where escaping gases will flow directly overboard. Secure each cylinder for sea conditions, and provide protection from weather and mechanical damage. With an exterior installation, it’s better to mount cylinders aft than forward where seawater or spray can cause corrosion. Aluminum cylinders resist corrosion better than steel cylinders, but are twice the cost. In the harsh marine environment, they are well worth the extra expense. Be sure you can access cylinders quickly without the use of tools. You may need to close the valves manually in an emergency, and you don’t want to be hunting for a screwdriver or a key to the locker. Also, you must post a legible, waterproof warning sign (Figure 1) in the immediate vicinity of the cylinders. If your boat has a gasoline engine, you must also post the gasoline vapor warning sign (Figure 2). Lockers In ABYC-speak, a “dedicated locker” is used for storing LPG cylinders, regulators, valves and piping, and absolutely nothing else. It should be made of corrosion-resistant material, with a top that opens directly to the atmosphere so any escaping gas will flow overboard, and mounted above the boat’s static waterline. Recently, ABYC revised its A-1 standard, Marine LPG Systems, to recognize the LPG lockers that can be installed within a larger cockpit locker. These are popular aftermarket lockers often used to create LPG cylinder storage on boats that did not incorporate the provision originally. If you have one of these, locate it as close to the top of cockpit locker as possible so that you cannot open the LPG locker without opening the larger one. To keep out seawater and rain, and to prevent loss or accidental opening of the cover, the LPG locker’s cover should be gasketed and latched securely. The locker itself must be vapor tight to the boat’s interior. Locate piping exits near the top of the locker and seal them with flexible grommets or other sealant. Locker Vent System The locker’s vapor drain must be in the bottom of the locker, and must be installed to prevent any escaping gas from entering the boat’s exterior. The vent system cannot be connected to a cockpit drain or bilge-pump discharge line. It must run directly from the locker drain to the overboard outlet. All components of the vent system require at least 1/2” (12mm) inside diameter to minimize clogging. The vent outlet must be above the static waterline and at least 20” (50.8cm) from any opening to the interior to keep escaping gas from entering the boat. The hose run must be straight with no low spots or pockets (or loops) that could trap water and block the flow of escaping gas.
Multiple Cylinder Systems Systems with multiple, connected cylinders need a manual shut-off valve or automatic check valve at the manifold so each cylinder can be isolated from pressure feedback from the other. This is in addition to the valve on the cylinder itself. Pressure Gauge Each system requires a LPG pressure gauge on the cylinder side of the regulator to provide a quick and easy way to test for leakage. The face of the gauge must be fully visible with the cylinder in place. Perform the three-minute leak test described in Figure 1 every time you open the system. Pressure Regulator Each LPG system must have a pressure regulator designed for use with LPG. If your LPG cylinder is stored on the exterior of your boat, make sure you locate the regulator’s relief valve discharge, like the locker vent discharge discussed above, at least 20” (50.8cm) from any opening to the boat’s interior. Shut-Off Valve There must be a “readily accessible” manual or electrically operated (solenoid) shut-off valve (remember, no tools allowed) that is operable within reach of the appliance in the event of an emergency. If the cylinder shut-off valve is accessible to the appliance, a separate shut-off valve on the supply line is not required. In either case, you should be able to operate the valve or its control without reaching across or through any flame and without risk of being injured in the process.
Fuel Lines LPG fuel lines are either copper tubing or flexible hose. If your boat uses tubing, check for long nut flare fittings; short nut fittings, commonly used in refrigeration systems, are more susceptible to failure from vibration. Don’t even consider using copper tubing unless it’s specified for LPG use. Also, a copper line should never double as an electrical ground. If your system uses hose, it must be marked to indicate its compliance with Underwriters Laboratory’s UL21 LP Gas Hose. No hose clamps here, only permanently attached end fittings, such as a swaged sleeve or sleeve and threaded insert. Support piping using corrosion-resistant (and galvanically compatible if copper tubing is used) clips, straps or other means. Where piping passes through bulkheads, decks or lockers inside the boat, drill oversized holes and insert close-fitting grommets, PVC tubing or other protective material.
Ignition Protection Electrical sources of ignition must be ignition protected to prevent sparks from escaping when activated in an area where LPG or other ignitable gas concentration is present. It’s a critical safety feature for all electrical equipment located in closed compartments. Electrical equipment located in accommodation spaces and compartments open to the outside atmosphere that contain an LPG appliance, cylinder, fitting, valve or regulator are not required to be ignition protected. “Open to the outside atmosphere” is a space with at least 38 sq.cm (15 sq.in) of open area per cubic foot of net compartment volume. The solenoid valve installed in the LPG locker and any other electrical equipment that occupies closed compartments with LPG equipment must be labeled “Ignition protected.” If you don’t see a label, check the owner’s manual or contact the manufacturer for verification. If you can’t prove that protection exists, replace the device. It’s cheap insurance. Appliances For Cooking And Comfort Where systems fueled by volatile gas are concerned, there is no room for cost-cutting. Adapting appliances intended for household, recreational vehicle or camping use to a boat is a recipe for disaster. The LPG appliances used on your boat must be designed for safe operation and built with materials that can withstand the rigors of the marine environment. No LPG appliance should be installed in compartments containing internal combustion engines (gasoline or diesel), their fuel tanks or fuel system fittings. Onboard cooking stoves, heaters and other LPG appliances, all system accessories and fuel supply must be installed to prevent upset, displacement or any strain. Post operating instructions at each LPG appliance. The warning sign in Figure 3 must be plainly visible from the vicinity of galley stoves, as applicable. Gasoline vapor (Figure 2) and oxygen depletion (Figure 3) warnings must be posted at each appliance as well.
Burner controls must be the push-turn or other two-step operation type when going from the off to on position to minimize the chance of accidental operation. You should also be able to operate burner controls without reaching over an open flame. LPG appliances that function without frequent attention by an operator pose special concerns. Thermostatically-controlled equipment like refrigerators, cabin heaters and water heaters operate unattended. Any malfunction resulting in incomplete combustion can be fatal if it goes unnoticed. These appliances are required to have a sealed combustion chamber. In a sealed combustion system, the air needed for combustion is drawn from the outside of the boat and the byproducts of combustion are exhausted to the outside. Air inside the boat is not consumed, so oxygen levels remain constant, and there is no contamination of interior air by exhaust gasses. Only sealed systems may incorporate pilot lights or other automatic ignition devices. An LPG cooking stove is an example of an attended appliance. During normal operation (cooking) a stove is frequently attended by the cook. Stoves are not required to have sealed combustion chambers, and could not do their work if they did because the flame produced by the fuel is used as the heating element. These appliances can have pilot lights or other automatic ignition devices. Non-sealed combustion system appliances require an oxygen-depletion sensor that cuts off the fuel supply to the appliance if the oxygen level in the space falls below 95% of normal. Check the owner’s manual to determine if your attended LPG appliance is equipped with this sensor. Flame failure devices are required on all burners and pilot lights on both unattended and attended appliances to prevent gas from flowing when a flame is not present.
Cooking appliances with integral cylinders, such as camp stoves and externally mounted grills, are common onboard boats. These stoves are convenient and good alternatives to alcohol cookers, but don’t confuse them with “camp” stoves that use a 14-ounce fuel cylinder. Stoves approved for marine use must be fueled by DOT-approved 2P/2Q 8-ounce cylinders with rim vent release. Don’t stow or use any LPG cylinders with more than 8oz of fuel capacity. Use the stove in a ventilated location, out of the weather and the risk of damage. Stow unattached reserve cylinders on the boat’s exterior where escaping gas will flow directly overboard. [Ed: For instructions to build a holder for LPG canisters, see DIY Projects, 2000-#3 issue.] Externally mounted grills and camp stoves with 8oz or larger LPG cylinders must be labeled as follows: “Do not use this appliance inside the boat or in any enclosed space.” Also, post the oxygen-depletion warning sign (Figure 4) adjacent to all fuel-burning stoves with integral cylinders. If your boat’s LPG system and appliances do not meet current ABYC standards, make the necessary repairs or upgrades for your own safety. Consult the references listed below for additional information. Knowledgeable marinas, boatyards and marine chandleries typically maintain a copy of the ABYC standards for staff and customer reference. You can direct specific questions concerning LPG safety standards to ABYC’s technical staff at www.abycinc.com or call 410/956-1050. About the author: Susan Canfield is an accredited marine surveyor with Marine Associates, Inc. of Annapolis, Maryland. She is a member of the Society of Accredited Marine Surveyors and the American Boat and Yacht Council.
Warning Signs Obtain required warning signs from equipment manufacturers, or copy and laminate those illustrated below, and mount in locations as specified in this article.
Liquefied petroleum gas (LPG) is flammable and explosive. Follow these instructions to avoid injury or death from fire or explosion. • This system is designed for use with liquefied petroleum gas (LPG/propane /butane) only. Do not connect compressed natural gas (CNG) to this system. • Keep cylinder and/or solenoid valve(s) closed when boat is unattended and when appliances are not in use. • Close cylinder valves immediately in any emergency. • Keep empty cylinders tightly closed. • Close all appliance valves before opening cylinder valve. • Apply ignition source to burner before opening appliance valve. • Test for system leakage each time the cylinder supply valve is opened for appliance use. Close all appliance valves. Open solenoid shut-off valve, if installed. Open, then close cylinder supply valve. Observe pressure gauge at the regulating device, and see that it remains constant for not less than three minutes before any appliance is used. If any leakage is evidenced by a pressure drop, check system with a leak detection fluid or detergent solution that does not contain ammonia. Repair before operating system. Never use flame to check for leaks! Gasoline vapors are explosive. Open flame appliances can ignite gasoline vapor causing death or injuries from fire or explosion. Turn off all open flame appliances when fueling. Liquefied petroleum gas (LPG) is flammable and explosive. Follow these instructions to avoid injury or death from fire or explosion. • This system is designed for use with liquefied petroleum gas (LPG/propane/butane) only. Do not connect compressed natural gas (CNG) to this system. • Keep cylinder and/or solenoid valve(s) closed when boat is unattended and when appliances are not in use. • Close cylinder valves immediately in any emergency. Keep empty cylinders tightly closed. • Close all appliance valves before opening cylinder valve. • Apply ignition source to burner before opening appliance valve. • Test the system for leakage in accordance with the instructions required to be posted in the vicinity of the cylinder each time the supply valve is opened for appliance use. Never use flame to check for leaks! Open flame cooking appliances consume oxygen and produce carbon monoxide. To avoid asphyxiation, injury, or death from exposure to carbon monoxide, maintain open ventilation when using these appliances. Do not use this appliance for comfort heating. LPG APPLIANCES The information below includes requirements applicable to galley stoves or cabin heaters fueled by LPG. Other fueled appliances may have additional requirements. Installation • Not in space containing internal combustion engines, their fuel tanks or fuel system fittings. • Secured to prevent upset, displacement or strain on system and connections. • Operating instructions posted at appliance. • LPG warning sign at galley. • Oxygen-depletion warning sign. • Gasoline vapor warning sign (if applicable). Controls • Two phase, e.g., push-turn. • Operable without reaching over open flame. Burners • Operate safely at pitch, roll and heel angles up to 30° from horizontal. • Sealed combustion system if unattended. • No pilot lights or automatic ignition devices if non-sealed combustion system. • Exception: Pilot light that operates only when oven is operating. • Oxygen-depletion sensor if non-sealed combustion system. • Flame failure devices on all burners and pilot lights. Cooking Appliances with Integral LPG Cylinders • DOT approved 2P/2Q cylinders with rim vent release. • No more than 8oz fuel capacity if used or stored inside boat. • If cylinder attached, stored in ventilated location protected from weather and mechanical damage. • Unattached cylinders stored on boat’s exterior, where escaping gas will flow directly overboard. • Warning sign for externally mounted grills/galley stoves with fuel cylinders of more than 8oz (if applicable). • Oxygen-depletion warning sign (fuel burning stoves other than externally mounted grills) LPG SYSTEM Use this checklist to determine if your boat’s LPG system complies with current ABYC standards. Cylinder(s) • Located on boat’s exterior, where escaping gases flow directly overboard or in a dedicated locker. • DOT/ASME compliant. • Secured for sea conditions. • Protected from weather and mechanical damage. • Accessible without tools. • LPG warning sign. • Gasoline vapor warning sign (if applicable). Locker • Not used for storage of other equipment. • Top opening directly to outside atmosphere. • Corrosion-resistant material. • Located above static waterline. • Gasketed cover; tightly latched. • Vaportight to boat’s interior. • Vented at bottom. Vent system • Minimum 1/2” (12mm) inside diameter (all components). • Dedicated; not connected to other piping. • Led outboard through hull to point below locker bottom and above static waterline. • Outlet at least 20” (50.8cm) from any opening to boat’s interior. • No low spots or loops that could trap water. Pressure Regulator • Designed for use with LPG. • Relief valve discharge at least 20” (50.8cm) from any opening to boat’s interior. Shut-Off Valve • Manually or electrically operated. • Operable from vicinity of appliance in event of fire. • Operable without reaching over open flame. Fuel Lines • Continuous from regulator or solenoid valve to appliance or flex section if appliance is gimbaled. • Annealed copper with long nut flare fittings or LP Gas Hose with permanently attached end fittings. • Metallic fuel lines (if installed) not used for electrical ground. • Flexible LPG hose section (if gimbaled stove). • Supported by corrosion-resistant clips, straps or other devices designed to prevent damage to lines. • Installed so bulkheads will not cut, abrade or damage lines. • Protected by non-abrasive grommets, sleeve or sealant where run through decks or bulkheads. Multiple Cylinder Systems • Manual shut-off valve or automatic check valve at manifold. Pressure Gauge • On cylinder pressure side of regulator. • Dial fully visible. • System passes leak test. Ignition Protection • Electrical devices in closed compartments containing LPG appliances, cylinders, fittings, valves or regulators are ignition protected. • Exceptions: (1) Accommodation spaces and (2) compartments having at least 15 sq.in (38 sq.cm) of open area per cubic foot of net compartment volume exposed to the atmosphere out side the boat. |
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