Electroshock Drowning is a topic in which myself and many others have been very vocal about these past few years and I have written about it many times in my magazine articles. It is a phenomenon which has been occurring in fresh water marinas, cottage docks and anywhere boats are moored and plugged into shore supplied AC (alternating) electrical current. It occurs when AC current, by way of faulty electrical wiring or appliances either on board the boat or on the dock leak current into the water and if persons or animals (yes pets and wildlife are susceptible to this too) are in the water nearby, the current travels through their bodies causing paralysis and even death.
Here is the equation: AC electrical power is supplied to boat shore power systems typically in the range of 15-30 amps …… .6 of an amp of electrical current is enough to stop your heart almost instantly if it travels through your body in an effort to reach ground.
How does this occur: It occurs when, through a wiring fault or a fault with an AC appliance allows stray current to travel through the boats DC ground circuits which include underwater metallic components such as the prop shaft or stern drive. Think of your boat when plugged into shore power as similar to a hair dryer plugged in and floating in the bathtub. This in effect electrifies the water in the immediate vicinity of the affected boat. Anyone swimming nearby can be affected by this as the electrical current moves from the charged water to ground. If you remember your basic electrical theory electricity always moves from the source to ground and if your body gets in the way it will pass right through you and your heart.
Another point that you need to be aware of is that this occurs mostly in fresh water situations, much more so than in salt water. This is because salt water is a better conductor than fresh water and any current dissipates rapidly after it enters the water. In fresh water it remains at a concentrated level in the immediate area surrounding the boat. And when you take into consideration that the high salinity levels of the human body actually make it a better conductor than the water itself, just by being in the water we actually provide the best path for the current to move to ground.
This is a very brief overview on how this can occur and is occurring. I will have much more to say in future posts. For more on this I invite you to visit a couple of websites dedicated to this phenomenon. I will add them to my links page as well.
http://www.electricshockdrowning.org/ This site is operated by Kevin Ritz who has a very deep connection to this issue.
http://www.boatus.com/seaworthy/magazine/2013/july/electric-shock-drowning-explained.asp A very good article by Boat US which offers a very good description on how to inspect for electrical leakage aboard boats.
http://www.boatingmag.com/how-to/electric-shock-drowning-prevention More good information.
I was asked how to determine the battery size (capacity) for a typical engine starting battery. To that end I have come up with some information on how to do just that.
Starting Battery Ratings: Marine Cranking Amps (MCA) or Cold Cranking Amps (CCA). 1 CCA = 1.3 MCA. The ratings are calculated by the same process just at different ambient temperatures.
Minimum Size for Starting Battery: Engine Displacement (in cubic inches) X 2 (Cranking Requirements) X4 (Reserve Capacity) = Required Battery Size (CCA)
I should note that this calculation will give you the minimum size requirement for a starting battery and I sure won’t hurt to increase the size somewhat. I an also a fan of using a deep cycle rated battery as your starting / reserve.
In this post we are going to take a look at what constitutes a proper and safe Marine LPG (Liquefied Propane Gas) installation. As a surveyor I encounter many improper and unsafe LPG installations and to be truthful very few proper ones. When you consider the fact that this stuff has the ability to cause fatal injuries or completely destroy your vessel serious attention needs to be paid to these installations. LPG on sailboats is used mainly for cooking and cabin heat but occasionally it is also utilized in refrigeration and hot water heating systems. It is manufactured as a by-product of natural gas production and gasoline refinement. At atmospheric pressure it is in a gaseous state but under moderate pressure it becomes a liquid making it easy to store and transport. It also naturally odorless but the strong pungent smell related to propane is the result of a chemical added to facilitate leak detection.
The downside to propane gas is that it is highly flammable and being heavier than air it collects easily in the bottom of any enclosed area such has boat cabins and bilges. It is for these reasons that it needs to be handled and treated carefully. The ABYC (American Boat and Yacht Council) has a long list of standards pertaining to marine LPG installations and we’ll take a look at those next. Here’s the condensed version.
1. All LPG storage tanks, shut off valves, pressure gauges and regulating equipment should be ignition protected, secured for sea conditions and enclosed in a dedicated, sealed locker with a gasketed lid equipped with a mechanical latch. Nothing else should be stored in this locker. It should be situated above the hull waterline and vented out the bottom to flow overboard.
2. The gas supply line should be of approved hose and have a pressure gauge installed between the tank and pressure regulator / line shut off valve to facilitate leak testing of the system. To do this you simply open the tank valve (with the line valve in the “on” position), then close the valve and watch the gauge. If a leak does exist the gauge pressure will drop. The system should hold pressure for at least three minutes. The line shutoff valve mentioned above can be manual but is usually an electric solenoid installed at the pressure regulator with the on / off switch being located within easy reach of the appliance without reaching over the appliance. The only time that this devise is not required is if the tank valve itself is within easy reach of the appliance.
3. All feed line splits (to facilitate multiple appliances) should be located inside the storage locker itself and a separate line be run to each appliance.
4. Where the feed line(s) exit the tank storage locker there should be an air tight seal between each line and the locker wall.
5. An LPG leak detection system should be installed in the vessel’s living quarters.
Just in case you think that these standards are overkill let me share with you a story told to me about a year ago by an ABYC training instructor at a course I attended. There was a reported case of a late model 36 foot sailboat anchored on an inland lake in the US. It was a cool evening and the vessel’s full cockpit enclosure was in place. The boat had an LPG installation that met all of the standards listed above with one exception. The tank storage locker did not have a sealed lid, meaning that no gasket was installed and there was no latch. A leak developed at the pressure gauge and a considerable amount of LPG gas made its way from the locker, through the cockpit and into the main saloon. The operator noticing the smell immediately switched on the cabin lights one of which had a loose wiring connection causing a spark and igniting the gas. Amazingly enough he wasn’t hurt but did hear a loud “Whump”. He then went up on deck only to find that the entire hull to deck joint had separated and the deck was literally “ballooned” upward. So you can see this stuff really needs o be treated with respect.
I also want to comment on another issue I frequently encounter with regards to LPG installations. This is all of the small tanks I see strapped to stern rails and flexible hoses connected to portable barbecues. These installations literally don’t meet any of the standards I’ve listed above. The tanks generally are not secure and there is no way to leak test the systems. While the chances of gas migration into the vessel’s living areas may be reduced there’s nothing preventing a leak from setting body parts or your skivvies on fire when you light the appliance. Be careful!
So you can see that while LPG, as a cooking or heating fuel can make our cruising lives much easier it can also be very dangerous if not handled properly. Refer to the above list and ensure that your installation meets all of the criteria I’ve noted. If you’re unsure of any of this I suggest that you contact a knowledgeable professional and have your system inspected. Any ABYC Standards certified marine surveyor or technician should be glad to assist you.