Cooking Fuels

A clean look at the “dirty” half dozen

By Theresa Fort

Article taken from Good Old Boat magazine: Volume 3, Number 2, March/April 2000.
This and other cooking aboard articles are also available in the Good Old Boat Galley Book.

Pros and cons of the six main fuels for galley stoves

When it comes to choosing a marine stove fuel there is rarely anyone completely
happy with the choice. All fuels have a “dirty” side to them, and some
sides are deadly as well. Alcohol is heating-impaired. Kerosene is maintenance-dependent,
and a mess if spills occur. Diesel is hot and has sooting problems. Electricity
is power-hungry and generator-dependent. Compressed natural gas (CNG)
is explosive and expensive, as well as hard to find. And what about liquefied
petroleum gas (LPG)? The potential for a massive explosion aboard your
good old boat gives LPG both a deadly and a “dirty” side.

After talking to more than 30 marine stove owners about their fuel and
stove choices, I learned that, like me, almost every one of them had learned
to cook and live with whatever stove and fuel came with the boat when
they bought it. But, even though it was chance that decided it, most owners
were happy with their stoves and fuels.

As the years go by, however, good old boats need refitting. We may need
to replace our stoves. Then when it comes to fuels, choosing one of the
dirty half dozen is unavoidable, and this time it won’t be chance that
decides. We are wrestling with this decision aboard Lindsay Christine,
our Mercator Offshore 30. Our propane stove is more than 20 years old.
And it looks it, at least what you can see of it, because most of it has
rusted away. In the hopes of making the “right” decision, I did extensive
research and asked many boaters about the marine stoves and fuels they
use.

What follows are some pros and cons of marine stove fuels from my own
research and some advice from the experts – other stove owners – to help
you decide which is the best choice for you.

Heat vs. cost

Average
Heat Content of Marine Stove Fuels
Fuel
Type
Btu/lb.
Btu/
significant unit
Cost
Cost/
5,000 Btu
Alcohol
11,935
80,919
Btu/gal.
$9/gal.
$55.61
CNG
23,601
1,000
Btu/ft.
$.16/ft.
$77.38
Diesel
19,557
139,400
Btu/gal.
$1.30/gal.
$4.66
Kerosene
19,800
134,950
Btu/gal.
$2.07/gal.
$7.67
LPG
21,560
21,560
Btu/lb.
$.50/lb.
$11.60
Electricity
3,412
Btu/kwh
$
.10/kwh
$14.65

The heat output of fuels is determined by test. The table on the next
page shows approximate heating values – approximate because, with the
exception of electricity, all of these fuels are mixtures, and their exact
content varies from source to source.

One Btu, or British thermal unit, is the amount of heat energy needed
to raise the temperature of 1 pound of water 1°F, starting at 60°F. One
Btu is also equivalent to 252 calories, and 1 calorie is the amount of
energy needed to raise the temperature of 1 gram of water 1°C.

The Btu/lb. column in the table offers a way to compare all fuels (except
electricity) with each other. Btu/lb. would only be a significant figure
of merit, however, in cases where the major consideration was the weight
of the fuel load. If you are doing a serious weight comparison, you will
want to include the weight of all parts of the cooking system, including
the tanks, plumbing, and stove.

Most sailors will care more about the cost and availability than about
the weight difference. The column showing Btu per significant unit is
provided to show the heat content of the unit of measure in which the
fuel is normally purchased.

The cost per 500,000 Btu shows how significant the difference is between
various fuel costs. For purposes of comparison, 500,000 Btu may be taken
to be (very roughly) the heat required to cook for four people for 90
days. If you live aboard your boat, multiply that figure by four for an
estimate of annual cost. If you sail in a northern climate on weekends
and get in a two-week vacation, your annual fuel requirement will likely
be only about half of the 500,000 Btu shown.

Generally speaking, the cost difference between these fuels for weekend
sailors is not significant enough to be the reason for changing fuel types,
because the cost of new equipment is high relative to the cost differences
between fuels. Liveaboards and long-ra nge cruisers may find the cost
differences more interesting.

Fuel availability

Availability
of Fuels
Inside
the U.S.
Outside
the U.S.
Alcohol
Yes
Random
CNG
Random-Rare
Rare
Diesel
Yes
Yes
Kerosene
Yes
Yes
LPG
Yes
Yes

Here is a table showing the availability of fuels – excluding electricity,
since electricity is generated by using another fuel. I used the word
random to describe the availability of CNG in the U.S. because, even with
a long list of available stations, I had great difficulty finding a place
that really did refill CNG cylinders in Florida, where I live. But I’ve
been told it’s much easier to find in other parts of the country where
EPA standards have forced the use of CNG as a motor fuel and where natural
gas is a common fuel for heating.

Auto-ignition temperature

The table on the next page shows the characteristics of fuels, also excluding
electricity. It gives the auto-ignition temperature of each fuel. This
is the temperature at which a fuel will automatically ignite without a
spark or flame. The flash point, on the other hand, is the temperature
at which the fuel will ignite when there is oxygen and a spark for ignition.

Stove fuels one by one

Alcohol

Denatured alcohol can

Alcohol fuels for stoves are generally composed of ethanol, methanol (added
as a denaturing agent), methyl ethyl ketone, acetone, and water. The exact
percentage of these components varies rather widely from one supplier
to another. Nigel Calder, in his book, Boat Owner’s Mechanical and Electrical
Manual, states that the best fuel for stoves is ethanol. For practical
purposes, this would be a fuel like Tru Heat, which is 92 percent ethanol,
5 percent water, and 3 percent methanol. It has only trace amounts of
other compounds, such as methyl isobutyl ketone, ethyl acetate, and rubber
cement. In contrast to this fuel, Soot-Free, the fuel endorsed by Origo
for use in their stoves, is not a high-ethanol-content fuel. Soot-Free
contains roughly 71 percent ethanol and 20 percent methanol, as well as
methyl ethyl ketone, acetone, and water.

You can also buy suitable fuel in paint and hardware stores labeled as
“denatured alcohol.” Kleen Strip is one brand that notes on the container
that it is suitable as a shellac thinner and as marine stove fuel.

One test Nigel suggests is to pour a sample of the fuel into a clean (oven-proof)
dish and burn it. If there is any residue after the fuel is completely
burned, it’s unsuited for use as a stove fuel. In addition, stove-fuel
vendors will send you a Material Safety Data Sheet (MSDS) for their products
listing the chemicals in the fuel by percentage.

Alcohol has been advertised to be the perfect environmentally correct
fuel because it is mostly produced from renewable resources (plant matter).
It is a relatively safe fuel because of its low volatility. This makes
it safer than other fuels in the closed environment of a boat. Alcohol-stove
owners like the fact that there is no hauling of heavy and cumbersome
storage tanks, that fires can be extinguished just by adding water to
the fire or fuel, and that it is a clean-burning fuel.

But it’s not the perfect fuel. Some people say the sweet smell of burning
alcohol makes them nauseous. It’s more expensive per Btu than all the
other alternatives except CNG, averaging $9 a gallon across the U.S.,
and its availability is irregular outside of the U.S. and Canada. The
price of alcohol outside the U.S. is also quite high.

There are two basic types of marine stoves that use alcohol as a fuel,
pressurized stoves and non-pressurized stoves. Each has advantages and
disadvantages.

Pressurized alcohol

I chuckled as I read LaDonna Bubak’s description of lighting her
pressurized alcohol stove. She sails her boat out of Portland, Ore., and
writes:

“(First you) have to fill a small tank, pump it up to pressurize it .
. . preheat the burner by allowing a puddle of fuel to develop, light
it, jump back so flames don’t singe eyebrows, extinguish (any) flaming
curtains, etc., then, when the puddle-flame almost dies, you turn on the
burner and hope it catches.” A lost memory flashed into my mind. It was
my first and only attempt to light the pressurized alcohol stove aboard
our Catalina 22. As flames shot up above my head and within reach of the
cabintop, I heard the kids approaching. They were arguing about whose
idea it was to have lunch aboard Gypsy Rose. Trembling, I made sure the
burner was off, then nervously searched for something with which I could
extinguish the flame. There was no water. Gypsy Rose was in our driveway.
I found a pot lid that had fallen on the cabin sole in the confusion of
the flare-up. The fire went out as I covered it. I took a deep breath.
Amie arrived first with Alex close behind, full of spit and vinegar.

“Mommy, tell Amie that I thought of it first! Here’s the soup . . . ”
Then there was silence as they both watched me pack up everything and
start to close up the boat. “Mommy, are you OK?” I vowed never to light
that stove again as I replaced the tarp and walked back to the house.
I had no idea that this experience was almost normal for lighting a pressurized
alcohol stove until I talked to other boaters about their stoves.

A few of the boatowners I questioned were happy with their pressurized
alcohol stoves, but the majority were looking to replace them. Many were
not comfortable using the oven because of concerns with priming and flare-ups.
A few owners commented on being bothered by the sickeningly sweet smell
of the alcohol and the paleness of the flame, which makes it almost impossible
to see in bright light.

The real danger of flare-ups seems to come from failing to light the burner
on the first try. After the first try, the burner may not be hot enough
to sufficiently vaporize the fuel by the time all the fuel in the priming
cup has been burned. So the chef opens the control knob to allow more
fuel into the priming cup, and the fuel ignites sending flames sky high.
While the burner was not hot enough to vaporize the fuel the first time,
it was hot enough to ignite the liquid alcohol added again. If the stove
is gimbaled at the time of lighting, flames can splash onto other parts
of the boat and the cook. According to Optimus International, the best
advice is to let the burner cool off before filling the priming cup with
fuel again.

Pressurized alcohol stoves are not maintenance-free. The customer service
department of Kenyon Stoves explains that severe pulsing of a burner or
a glowing red cap during operation are caused by dirt and scale buildup
in the filter and burner body. The burner should be stripped of all removable
parts, cleaned, and rebuilt.

With Kenyon alcohol stoves, a wick in the center of the burner is lit.
Pressure builds up in the burner as the available fuel heats up, causing
alcohol vapors to be released into the burner to be used. Regardless,
most alcohol burners work in the same way and require the same maintenance.

One stove owner, known as “Captain Key West,” from Key West, Florida,
commented that he thought the bad press about pressurized alcohol stoves
comes from the fact that they need to be maintained to work well, especially
after many years of use. He writes, “I think many people disenchanted
with alcohol stoves may have based their opinions on only having used
poorly maintained stoves. I used to be surprised how alcohol stoves got
a bad “rap” since mine worked great for many years before it started getting
“fussy.” Now, I realize many users are not aware that these stove are
not maintenance-free. They buy a used boat, never can get the stove to
work right, then complain about how poor alcohol stoves are. They’re not
listening to their stoves which are begging for maintenance!”

I know I never gave my pressurized alcohol stove a chance after that first
lighting.

Non-pressurized alcohol.

Characteristics
of the five liquid or gaseous marine stove fuels
Alcohol
CNG
Diesel
LPG
(Propane)
Kerosene
Methanol
Ethanol
Toxic to skin
Moderate-high
Slight
No
Moderate
No
Moderate
Toxic to lungs
Moderate
Slight
No
Moderate
No
Moderate
Specific gravity
1.11
1.59
0.55
lighter than air
>4
1.52
>4
Auto-ignition
temp
867
793
1,000
-600
850-950
410
Flash Point
52
55
-300
165
-100to
-150
100
Luminous flame
No
Faint
Yes
Yes
Yes
Yes
Source
Natural
gas &
other hydrocarbons
Grain,
biomass
Natural
Gas
Petroleum
Natural
gas, petroleum
Petroleum,
coal, shale

Non-pressurized alcohol stoves are quite popular. The Origo brand stoves
have helped to keep alcohol in fuel-option lists for boaters. All non-pressurized
alcohol stove owners I questioned are happy with their stoves. Some even
commented that they cook faster than pressurized alcohol stoves and claimed
speed close to propane. But the fuel is expensive.

These non-pressurized stoves use a wicking action to deliver fuel to the
flame, instead of pressure, making them very safe, with no flare-ups.
The fuel is stored in canisters under the cooktop. The canisters contain
nonflammable wadding with a shield-type cover that closes over the canister
to extinguish the flame, somewhat like cooking with Sterno.

These stove users/experts seem to agree that non-pressurized alcohol stoves
are the way to go if you are interested in using alcohol as a marine stove
fuel. In fact, two of the pressurized kerosene stove owners are switching
to non-pressurized alcohol with their next refit.

Safety considerations (alcohol)

While it is true that alcohol fires can be put out with water, sometimes
the water displaces the alcohol, and the fire continues to burn.

  • Fill the fuel tank no more than three-quarters full to allow space for
    increased air pressure.
  • Before lighting and throughout the burner’s use, pressure in the storage
    tank needs to be around 7 pounds per square inch (psi).
  • Once you have successfully lit the burner, run it on a low setting until
    the burner gets really hot; then it can be adjusted for your cooking.
    Turning the valve all the way open will put out the flame, because there
    is a cleaning needle that comes out when you turn the knob all the way
    counterclockwise.
  • Never refill the priming cup or stove while the burner is on or even
    hot. The alcohol in the container may ignite.
  • Clear the area above and around your stove of any flammable objects,
    including your eyebrows, before priming your stove.

Special hints (alcohol)

Tru Heat stove alcohol bottle

  • Experienced users of alcohol stoves recommend that you use heavy cookware
    to reduce the scorching that can occur if the burner has a hot spot.
  • On pressurized stoves, cook and bake using a strong flame to reduce
    chances of the flame’s dwindling and being blown out.
  • Most owners agree that it helps to use the stove manufacturer’s fuel
    because it burns more cleanly.
  • One owner uses a contact-solution bottle to hold alcohol for the priming
    process. It give you better aim and more control over the amount released.
  • Pressurized alcohol stoves can be converted to kerosene by replacing
    the burners. As a caution though, one stove owner commented that he was
    witness to one such conversion exploding aboard a friend’s boat. Make
    sure the conversion is done correctly.
  • Several owners use small bicycle pumps with pressure gauges to pressurize
    the fuel tank to the proper pressure. Ferenc Maté’s book, Shipshape: The
    Art of Sailboat Maintenance, explains the use of a bicycle pump for pressurized
    alcohol and pressurized kerosene stoves. He suggests getting rid of the
    pump that came with the stove and finding a valve from a bicycle tube.
    Solder this valve into a washer and use the nut that came with the tank
    to thread it into place with a small rubber gasket between.
  • Dan Spurr, in his book, Upgrading the Cruising Sailboat, recommends
    putting a pot on the burner when priming. It will partially contain the
    flames and provide a darkened area which enables you to see the flames
    better.

Compressed Natural Gas

There’s a lot of technical merit to compressed natural gas, but its popularity
has never developed. Natural gas is a mixture of hydrocarbons – mainly
methane (CH4) – and is produced from gas wells or in conjunction with
crude-oil production. It’s a very clean-burning fuel and burns hotter
than alcohol. It also has an advantage over LPG in that it is lighter
than air. So it is a much safer gas. Any leaks tend to rise to the cabintop
and escape through any point that has an opening to the outside. But vapors
could still build up in areas of the cabin that have poor ventilation,
so care should be taken to have good airflow aboard. I know of one boatowner
who has had trouble-free use of his CNG stove for the last 16 years.

CNG’s disadvantages are much the same as LPG’s. It’s a highly volatile
gas stored under pressure, much higher than LPG. CNG is stored at 2,250
psi, compared to LPG’s 150 to 180 psi. The cylinders are heavier and more
cumbersome because CNG requires a thicker-walled tank. The tanks also
require recertification periodically. CNG also costs more per Btu than
LPG. I found the price of a refill in Florida to be between $10 and $16
for 84 cubic feet.

But the biggest drawback seems to be the lack of availability outside
the U.S., as well as in some areas within the U.S. A special quick-release
fitting can be bought through Corp Brothers, Inc., to allow you to fill
your tanks from a utility-company or automobile-station pump, when found.

Safety considerations (CNG)

A good-quality, spark-proofed alarm and sniffer should be installed aboard any boat with a compressed natural gas stove.

  • CNG cylinders should be stored away from the cabin in self-contained
    storage lockers that are vented overboard above the waterline, with venting
    at the compartment’s highest level. Or they may be stored outside on deck.
  • Cylinders should never be painted a dark color. In direct sunlight a
    cylinder could absorb enough heat to cause it to rupture.
  • CNG and LPG cannot be interchanged without modification to the stove.
  • CNG burned in LPG stoves will produce only about half of the designed
    output.

Diesel

Stove fuel container

Diesel is a high-energy fuel that is not volatile. It does not give off
flammable fumes, and it is inexpensive and available worldwide, especially
in areas of commercial fishing. There are pressurized and non-pressurized
diesel stoves. Pressurized diesel stoves are operated much like kerosene
and alcohol stoves. Non-pressurized “drip pot” diesel stoves use a metering
valve to deliver fuel to a drip-pot-style combustion chamber. The burner
can be fed by gravity or by a pump. The drip-pot-type stoves are quite
popular on commercial fishing boats and aboard yachts in northern regions.

They are known for producing a dry heat because they draw in moist air
from the cabin for combustion and expel it through the chimney as flue
gas. For boaters living in cool climates most of the year, this means
a warmer and drier boat. Drip-pot diesel stoves can also be used to produce
hot water when a water coil is added to the stove. Another advantage is
the fact that you will only be using one type of fuel if your auxiliary
engine is diesel.

A downside for drip-pot diesel stoves is that they tend to heat the cabin
as well as the food. They are slow to warm up and cool down because they
are made of heavy cast iron. With a constant oven temperature of 350°F,
a cabin can get quite warm in the tropics. Sooting and down drafting can
also be problems when a drip-pot diesel stove is not properly adjusted
or if poor-quality fuel is burned. Installation of the drip-pot variety
can be quite difficult just because of the weight of the stove itself.
And, because of their weight and the chimney required, drip-pot diesel
stoves cannot be gimbaled. It would be best to install one athwartship.
Since the flue removes combustion products from the cabin, the build-up
of carbon monoxide gases is not a concern as long as the stove is working
properly and outside make-up air is brought into the cabin.

Special tips (diesel)

The key to being happy with your diesel stove is to learn how to operate
and adjust it. Understanding how your stove works, and adjusting it properly,
will save your sails (as well as the rest of your boat) from soot. Jeannie
and Jack, aboard their Columbia 50, Terri Knot, had terrible sooting problems
with their diesel stove on their trip to Alaska. After several phone calls
to the manufacturer, they were finally able to adjust it properly. They
are pleased with the heat it generated while cruising in the cool north.
But Jeannie commented that it would have made the trip more enjoyable
if they could have worked out the stove’s idiosyncrasies before their
trip.

  • Filtering your diesel fuel with a “Baja” filter will increase the efficiency
    of your stove and reduce sooting. If you don’t have a very fine filter
    of this type, you can also filter fuel to some extent using panty hose.
  • If you are planning on cruising in tropical climates with a diesel stove,
    consider bringing along a small cook-top that uses an alternate fuel –
    such as propane, butane, or alcohol – to reduce heat in the cabin.
  • Diesel stoves will burn cleanly with sufficient draft. Make sure your
    flue is the proper length and diameter. It is important that the flue
    be installed without any bends to restrict the air flow. Make-up air must
    be allowed into the cabin for the stove to have proper draft.

Electricity

For those boaters who have an alternating current (A/C) generator, or
who find themselves close to shorepower quite often, electricity may be
the answer. It is highly efficient, there are no problems about storage
and fumes, and the fact that you may already have shorepower aboard your
boat makes it easy to install. If your electrical cooking appliances include
a microwave, it will speed up cooking times, helping you to use less energy.
It will also conserve vitamins during cooking, and it will not heat up
the cabin. Because electricity is a dry heat, it will also mean a drier
cabin, something that helps with all boats.

But, if you will be relying on a generator to power your stove, there
will be an increased need for diesel or gas, depending on your energy
source. Increased use of your generator also means increased wear and
maintenance, increasing the total expense of this type of fuel. The noise
of having to run the generator or engine each time you use your electric
appliance can also be a disadvantage.

Special tips (electricity)

  • Make sure all wiring is accessible so you can check for corrosion periodically.
    If some of the wires are hidden or difficult to get to, it will be a tedious
    job to find the cause of a malfunction.
  • Proper maintenance of your generator is a necessity when relying on
    electricity for your cooking. Consider having a small back-up stove aboard.
  • If you will be running your generator in quiet anchorages, consider
    anchoring farther away from other boaters. It will go a long way toward
    improving relationships with those who are living without generators.
  • Try to combine stove needs with battery charging to enable you to run
    the generator less frequently.

Kerosene

Kerosene can

Kerosene, also called paraffin outside the United States, is a colorless,
thin oil. It’s less dense than water, and it’s made of a mixture of hydrocarbons
commonly obtained from the fractional distillation of petroleum. As with
alcohol, there are pressurized kerosene stoves and non-pressurized kerosene
stoves. Pressurized ones function much like pressurized alcohol stoves.
Kerosene burns hot – much hotter than alcohol. It is inexpensive and widely
available in the U.S. as well as overseas.

Eric Freeman, who sails Blackguard, an old Seawolf ketch, in northern
Washington state, commented that kerosene is easy to find, being available
anywhere jets fly. Kerosene is not as volatile as alcohol and can be easily
stored. Because kerosene – like alcohol and diesel – doesn’t have to be
under pressure, it is easy to be aware of how much fuel you have left.
A well-maintained and properly running stove is odorless and soot-free
without any flammable fumes to worry about.

But kerosene stoves can be hard to light. These stoves require priming
with alcohol, a tricky business. They can also have a sooting problem
if the burners are not adjusted properly. They can smoke liberally when
firing up and smell terrible. Spills take a long time to evaporate and
can be a problem because they will soak into cushions and be a fire hazard
for a long time.

Non-pressurized kerosene stoves are often discussed with diesel drip-pot
stoves since they are so similar. Kerosene can be burned in a diesel stove
and is the cleaner of the two in that application. The advantages and
disadvantages of non-pressurized kerosene stoves are the same as those
for diesel stoves. Like diesel stoves, kerosene drip-pot stoves cannot
be gimbaled and are usually made of heavy cast iron with a flue.

Special tips (kerosene)

  • It’s important to buy the best-quality kerosene possible to reduce the
    chances of clogged burners. Good-quality kerosene is colorless and as
    clear as good drinking water.
  • You can check the quality by burning a small puddle in an ovenproof
    dish. Any gooey remainders mean a poor-quality fuel for your stove.
  • Filter your kerosene through a “Baja” filter to eliminate particulates.
  • Keep a small spray or squirt bottle of alcohol (like a contact solution
    bottle) close by to use when priming the burner.

Liquefied Petroleum Gas

LPG is a gaseous paraffin hydrocarbon, extracted from crude petroleum
or natural gas, containing propane and butane. Most LPG produced and sold
in the U.S. is primarily propane. It seems to be the fuel choice for a
large number of marine-stove owners, especially international cruisers.
They seem drawn to it because it is cheap, burns hot and clean, and has
world-wide availability. I found the average price to fill a 20-pound
cylinder was $10, which lasts our family of four an average of three months
while traveling. But, it has some major drawbacks that can make it a very
dangerous fuel to have aboard.

LPG is highly explosive and heavier than air. Any leaks in the system
can go undetected, sinking into bilges and creating a very dangerous situation.
And, on stoves without thermocouples, it is too easy to leave a burner
on accidentally after the flame goes out, leaving an explosion waiting
to happen when the cook goes to re-light a burner.

Thermocouple-controlled solenoid valves control the flow of gas on some
stoves. When heated, the dissimilar metals in the thermocouple generate
electrical current that causes the solenoid valve to open. When the thermocouple
cools, it does not generate the electrical current and thus the valve
closes, cutting the supply to the burner. This is why, upon lighting your
burner, you need to hold the valve open for at least 30 seconds to allow
the metals to become warm enough to generate the electrical current which
will hold the solenoid valve open.

LPG (as well as CNG) requires constant vigilance in its use and storage
on board. All crewmembers should check and re-check to make sure all switches
and shut-off valves are in the proper position. LPG’s high volatility
also creates a transportation problem. Transporting cylinders to be re-filled
can be difficult. The thick-walled cylinders are heavy and cumbersome.
These cylinders, like CNG cylinders, have to be re-certified after several
years. The date of the next re-certification should be stamped on the
cylinder. Due to safety concerns, many buses and taxis will not allow
usually outside of town in order to reduce loss of life and property should
there be an explosion. This makes them difficult for cruisers to reach
without transport.

Though propane and butane are usually lumped together and called LPG for
simplicity, they have a few differences.

Butane

This gas liquefies at higher temperatures than propane
does. At extremely low temperatures, butane’s evaporation rate will be
so low that the stove will not operate. But butane can be stored in a
propane container.

Propane

In extremely cold conditions, propane can be used
when butane would fail to evaporate. Propane can be used interchangeably
with butane. But propane cannot be stored in butane cylinders because
it has a higher cylinder pressure.

Safety considerations (LPG)

Marine
Stove Fuel Survey Results
Fuel Happy Safe Feel limited
in use
High fuel
price
Alcohol
(pressurized)
Yes:
1
No: 3
Yes:
1
No: 3
Yes:
2
No: 2
Yes:
3
No: 1
Alcohol
(non-pressurized)
Yes:
6
No: 0
Yes:
6
No: 0
Yes:
1
No: 5
Yes:
3
No: 3
CNG
Yes:
1
No: 0
Yes:
1
No: 0
Yes:
0
No: 1
Yes:
1
No: 0
Diesel
Yes:
1
No: 0
Yes:
1
No: 0
Yes:
0
No: 1
Yes:
1
No: 0
Electricity
Yes:
2
No: 0
Yes:
2
No: 0
Yes:
0
No: 2
Yes:
2
No: 0
LPG
Yes:
15
No: 0
Yes:
1
No: 14
Yes:
0
No: 15
Yes:
15
No: 0
Kerosene
(pressurized only)
Yes:
2
No: 1
Yes:
3
No: 0
Yes:
0
No: 3
Yes:
3
No: 0

For excellent instructions on the proper installation of an LPG system,
read Chapter 14 of Nigel Calder’s Boatowner’s Mechanical and Electrical
Manual.

  • It is a good idea to install a good quality sniffer that will sound
    an alarm when vapors are detected. But be sure it is spark-proofed so
    that turning it on will not ignite any vapors already present.
  • LPG cylinders should be stored away from the cabin in self-contained
    storage lockers that are vented overboard above the waterline, with venting
    at the compartment’s lowest level. Or, they may be stored outside on deck.
  • Cylinders should never be painted a dark color. In direct sunlight,
    a cylinder could absorb enough heat to cause it to rupture.
  • Install a lighted manual switch at the stove with a solenoid valve to
    shut off the gas at the tank when the stove isn’t in use.
  • LPG cannot be interchanged with CNG (compressed natural gas) without
    modifications to the stove. Propaneburned in a CNG stove will produce
    extremely high flames and dangerous overheating of the appliance.
  • When re-filling cylinders outside the U.S., make sure the LPG has a
    smell to it. It is not safe to have LPG (or CNG) aboard if it is odorless.
  • Be careful not to have your cylinders filled beyond 80 percent capacity.
    There should be two weights stamped into your cylinder, the empty weight,
    called tare weight, and its net fill weight, the safe weight of LPG that
    can be added. Upon weighing your filled tank, it should not weigh more
    than your tare weight plus your net fill weight. If it has been overfilled,
    some of the gas will need to be vented carefully away from flames and
    sparks. An overfilled cylinder is a terrible danger aboard your boat.
    Increases in the ambient temperature could cause a rupture of the cylinder
    or could cause liquid LPG to be pushed into the low-pressure lines, a
    very dangerous situation that would ruin, at the least, an oven’s thermostat.

Special tips (LPG)

Debbie Lyons shuts off propane

Debbie Lyons, reaches through the portlight to shut the propane off at the tank aboard Rhiannon.

Having an easy shutoff valve close to the storage cylinder helps reduce
dangers. Aboard Rhiannon, Debbie Lyons, of Seattle, stores her propane
cylinder on deck near an opening portlight over her sink. She only has
to open the portlight to shut off the propane right at the tank. She shuts
off the propane at the cylinder as her cooking is completed and when the
flame dies, signaling that all the propane has been used in the lines,
she turns off the burner. Before lighting, as a double check, she makes
sure that all burners are turned off first. (Make sure the portlight will
not allow LPG to drain into the cabin if there is a leak at the cylinder.)

Hunting for leaks is required maintenance for propane stove owners. It
is a good idea to periodically apply soapy water to all tubing connections
in your installation. Bubbling signals a leak that should be immediately
fixed. Also use your nose for finding leaks. As with CNG, an odor has
been added to LPG. Never use a flame to test for leaks.

To check the level of your propane tank, boil a cup or so of water and
pour it on the outside of your propane tank. Right afterward, feel for
the level of much cooler propane in the cylinder.

Propane and CNG are serious materials to have aboard a boat. The ABYC
(a voluntary boat construction standards organization) recommends that
the following label be placed near LPG fuel tanks:

Caution

  1. This system is designed for use with liquefied petroleum gas (LPG)
    only. Do not connect compressed natural gas (CNG) to this system.
  2. Keep cylinder valves and solenoid valves closed when boat is unattended.
    Close them immediately in any emergency. When on board, cylinder valves
    or solenoid valves shall be closed when appliances are not in use. Keep
    empty cylinder valves tightly closed.
  3. Close appliance valves before opening cylinder valves.
  4. Test for system leakage each time the cylinder supply valve is opened
    for appliance use. Close all appliance valves. Open, then close, cylinder
    supply valve. Observe pressure gauge at the regulating valve 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 which does not contain
    ammonia and repair before operating the system.
  5. Never use flame to check for leaks.

At the end of the ABYC standard on LPG systems is the following note:

  1. Never use flame to check for leaks!
  2. Never use solutions containing ammonia. Ammonia, which is present
    in soaps and detergent, attacks brass fittings. Undetectable at first, in a matter months these fittings may develop cracks and leaks.

Ammonia which is present in some soaps also attacks copper tubing in the
same way. In fact, it is the copper in the brass that is attacked by the
ammonia.

Watch out for CO

With electricity as the exception, it’s important to make sure that the
galley has sufficient oxygen to keep the stove working properly. A deficiency
of oxygen causes any fuel to burn improperly, resulting in an output of
carbon monoxide, rather than carbon dioxide.

For this reason, a carbon-monoxide detector is a worthwhile investment.
We have one aboard our boat that saved our lives in Alaska. One night
after having hot cocoa before bed, we accidentally left the pilot light
in our oven on. Even with a cracked hatch, there was not enough oxygen
inside the cabin. We were slowly awakened when our CO detector went off,
releasing a mind-boggling blare of noise that just barely woke my husband,
Chuck, and me. The kids were sound asleep with the detector right above
their heads. We were able to get the kids and ourselves out of our cabin
in time, with only headaches to complain about. The fresh air never felt
better. Now we make sure the CO detector always has a good battery.

Decisions, decisions

In Jimmy Cornell’s book, World Cruising Survey, the most popular cooking
fuel was LPG. In fact, 138 boaters chose LPG with the other fuels barely
showing up: 17 others chose kerosene; two chose diesel; one chose alcohol;
and two chose electricity. LPG was the most popular choice among the people
I talked to, as well. But I found many more owners who chose alcohol than
Jimmy did. This is probably because I talked to coastal cruisers and weekend
boaters. I also talked to only 32 stove owners. For what it’s worth, refer
to the chart of my findings on Page 53.

Which to choose?

After weighing all of the pros and cons of the dirty half-dozen, I still
haven’t made up my mind about which to choose. But our plans for cruising
outside the U.S. have ruled out CNG and alcohol. And electricity won’t
work aboard our boat without a generator. LPG is at the top of our list,
but I hesitate because of memories of singed arms, flames in my face lighting
our oven, and waking up to our carbon monoxide detector blaring. All these
are memories from forgotten pilot lights and burners not turned off completely.
It makes me gun-shy. I know the safety mechanisms on the new LPG stoves,
as well as a proper installation, will take care of those problems. But
should I choose to have our family depend on that?

Then there’s kerosene and diesel to consider. Decisions, decisions. Maybe
we could buy a new good old boat with a stove already installed so I could
leave this decision to chance. Maybe I’ll make Chuck decide.

Theresa Fort

Theresa Fort
and her family of four have lived and cruised aboard
Lindsay Christine, a Mercator Offshore 30, since 1995. In another life long, long ago and far away, Theresa was a home economist with a specialization in consumer education. After receiving her BA in home economics at the University of Montana, she went on to become a master food preserver with the co-operative extension office in Montana.

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