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Surveyor's Notes
Boat Maintenance and Safety
By Michael Scalet & Vince DiLeo
Society of Accredited Marine Surveyors
Cooking with Gas
LPG Marine Systems
Many boats rely on LPG (propane, butane) as a source of heat. Many galleys are fitted with stoves and ovens that use it as a source of energy. It is also used to power heaters. Why? It lights instantly. Just turn on the safety valve, light a match, and it's burning. No priming is necessary if there is fuel. The flame is hot and extremely clean. Stoves require very little maintenance other than a monthly check on the valves and connections. Butane can be put in a propane tank but not the other way around, so get a propane tank and you will be set. One twenty-pound tank can supply cooking fuel for as long as three months. A tank full costs between three and six dollars (depending on your location). However, LPG must be used with great care.
Often surveyors give reports to boaters that make all types of recommendations on what should be done to a system to insure its safety. However, many boaters just brush it aside because they don't understand the inherent dangers of LPG. Let's take a look at this gas and why these surveyors are so intent on modifying a system.
As most of you know, LPG is heavier than air. So if you have even a slight leak in any part of the system gas will escape and settle in the bilge. Although the gas contains an odorant, the odor can be difficult to detect when mixed with air and at differing volumes. A spark from a bilge pump or any non-ignition protected devise and odds are you will not even get to see your boat sink! This is why one should understand how to create and maintain a secure LPG system.
Let us start at the source, the tank. The American Boat and Yacht Council (ABYC) has a laundry list of recommendations for the cylinder installation. The major objective is to not allow a leak from the tank to escape into your bilge as mentioned above. You may keep the tank where escaping gases flow directly overboard and the valves and gauges are protected from weather. This is not practical if you are going off shore since it is virtually impossible to secure it for inclement seas. So if you are to keep it on board you must have a dedicated locker which should be:
¨ Vapor tight to the interior.
¨ Located above the water line.
¨ Be corrosion resistant.
¨ Have a gasket cover that latches tightly.
¨ Opens directly to atmosphere outside the boat from the top.
And it should have a vent at the bottom which:
¨ Leads directly outboard and exits below the bottom of the locker but above the waterline.
¨ Is located 2' from any thru-hull leading back into the boat.
¨ Is located 2' from any engine exhaust discharge under the vent.
¨ Has a diameter greater than or equal to 1/2".
If that is not enough to make you change to a microwave there is much more. The tank must be installed with a pressure regulator and gauge. There should also be relief valve, which discharges in the locker or overboard. Now we can continue down the system to the fuel lines.
The lines should be annealed copper tubing with permanently attached end fittings. The tubing should be connected by flare fittings. Metal to metal compression sleeve type are not considered leak proof and should not be used. The lines should be protected and yet accessible for inspection. Of course if your stove is gimbaled it should have a flexible section to allow it to rock and roll. Had enough yet? Well, please stay with us because this information could save your life.
¨ Fuel supply lines that pass through bulkheads should be protected from cuts, abrasion and damage.
¨ Fuel supply lines should be continuous lengths of tubing, piping or hose from the regulating device, solenoid valve or leak detector to the appliance or too the flexible section at the appliance.
¨ LPG fuel supply lines shall not be used for an electrical ground.
After inspecting the installation of your LPG lines it is important to test the system. The system should be tested after installation, but prior to its connection to the regulator and appliances. Before we talk about testing a LPG system here are a few NEVER DO's!
¨ Never use a flame of any sort to check for leads. This may seem obvious, but you never know.
¨ Never use solutions containing ammonia. Ammonia, which is present in soaps and detergents, attacks brass fittings. Undetectable at first, in a matter of months these fittings may develop cracks and leaks.
Now, here are the American Boat Yacht Council (ABYC) guidelines for testing the fuel system.
¨ Pressurize the system with not less than 5 psig (34.5 kpa) of air.
¨ The cylinder valve should be checked for leakage at its connection to the cylinder by application of a leak detection fluid prior to connection to the system.
¨ With appliance valves off, open the cylinder supply valve. Close the cylinder supply valve. Watch closely the pressure gauge reading. The pressure indicated should remain constant for not less than three minutes. If a drop in pressure indicates any leakage, check the entire system with a leak detection fluid to locate the leak. Test solutions shall be non-corrosive and non-toxic. Remember to make all repairs before introducing LPG fuel into the system.
One final recommendation to safe guard yourself is to obtain a "sniffer". It is a device that will detect small amounts of gas before they can reach an explosion point. Make sure all the connections are ignition protected so it does not ignite the fumes as it detects them! If the alarm sounds shut of the valve at the tank, a solenoid if installed and all the appliances.
Marine LPG systems are more complex than your propane stove at home. If you have questions about your boat's LPG system call a marine surveyor. They know guidelines and will find the answers to all your questions. This is not a system you'll want to jury rig. Good food conveniently prepared is one of the joys of life and LPG is one fuel source you can use to prepare your gourmet meals, however it is very important that the properties of Liquefied Petroleum Gas (LPG) be understood and that safe practices for its use be followed.
Happy sailing and Bon Appetite!
Michael Scalet of TransPac Marine Surveying and Vince DiLeo of Admiralty Marine Services, LLC www.admiraltyservices.com are practicing marine surveyors in Northern California. They are members of the Society of Accredited Marine Surveyors, American Boat & Yacht Council, and Boat/US Technical Exchange. In addition to graduating from Chapman School of Seamanship they hold advanced degrees from Rutgers and San Francisco State Universities respectively. If you are considering buying a boat, refinancing, or insuring an existing boat you probably have questions. They have encountered most and likely have the answer. In the event that they don't, they will research it for you or point in the right direction.
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