Professor Diesel
PRINT DIGITAL Maintenance How to Prevent Boat Fires By Capt. Richard Thiel Where There's Fire, There's Smoke
Think that red tank in your Engine Room will protect you from fire?
There's a good chance it won't.
Complacency kills. I learned that rule in aviation school, and it's proven true time and again in other fields, including boating. A captain's worst enemy is that comfy feeling that he's covered all the bases, which is why the best skippers are the twitchy ones - they're constantly flitting around, checking and rechecking.
The rule certainly applies to shipboard fire. While the odds of one happening are small, the possibility exists and the consequences are dire. If you believe you're covered because you've got a fire-suppression system in your engine room, think again. You may be at much greater risk than you thought.
Fire-suppression systems come in two flavors: engineered and pre-engineered. With the former, a specialist usually examines engineering drawings, perhaps tours the vessel under construction, and then formulates a system tailored to that vessel. This is costly, which is why engineered systems are typically found only on large, expensive vessels. Most production builders rely on less expensive pre-engineered systems. The builder supplies the manufacturer with engine-room dimensions and the manufacturer recommends a system based on cubic footage and ships it to the builder for installation.
Alas, a boatbuilder's principal priorities don't always include finding the best spot for a big red bottle. Just ask Capt. John McDevitt, an expert in fire prevention who serves on a host of advisory panels, including the American Boat and Yacht Council, International Association of Marine Institutions, National Fire Protection Association, Society of Accredited Marine Surveyors, and others. In those capacities, and as a delivery captain with a 100-ton masters ticket, he's made something of a pastime of collecting photographs of - to put it gently - non-complying installations. Some are shocking in their incompetence.
The guidelines for placement are actually simple: The combination outlet nozzle/sensor, usually at the top of the bottle containing the agent, should be as high in the engine room and as far away from natural and mechanical ventilation sources as possible. That's because the sensor is triggered by temperature - typically 175 degrees Fahrenheit - and the hottest air is at the overhead, and because fresh air naturally reduces ambient temperature. The paradox is that ERs are designed to maximize the supply of fresh air to the engine(s), so sensor placement is critical. But even with optimal positioning, a fire some distance from the sensor may not immediately trigger the system.
And it might not trigger it at all. McDevitt lays out this common scenario: At cruising speed, a fire breaks out but smolders because the mains are consuming most of the available oxygen. The fire's generating little heat but enough smoke so that the engines start to misfire. Noticing this, the helmsman throttles down, freeing up lots of fresh air for the fire, which now grows quickly. By the time the temperature at the sensor reaches 175 degrees, it's a blaze. The system may or may not trigger in time, depending on whether it has been properly positioned. If it hasn't and the fire's not too advanced, someone will have to fight it manually. If it has, it's time to get in the water.
You should examine the location of your system to make sure it is as high and out of the way of fresh air as possible. But McDevitt says that your larger goal should be giving yourself the earliest possible warning of fire, and the best way to do that is to add a smoke alarm to your engine room. He has six on his boat, in the ER and elsewhere, including at the helm.
Of course you'd never hear a smoke alarm go off in the ER, which is why McDevitt uses the First Alert One Link system of multiple networked alarms. When one triggers, all sound off and indicate which is the source of the smoke, providing an alert long before ER temperature reaches 175 degrees. You can then fight the fire relatively easily with a handheld without having to activate your fixed system - if you have the right handheld. Petroleum fires are Class B, so your extinguisher must include this rating, but it should also be big enough. A typical two-pound extinguisher gives you roughly 15 seconds of discharge, not nearly enough to fight most petroleum fires. For an ER fire, you need multiple large extinguishers, placed where you can reach them.
You also need to maintain your system: Inspect the bottle monthly for frayed wires, corrosion, improper gauge reading, and proper movement of the manual activation cable. Have an authorized technician examine the bottle annually, and every 12 years, you must have the bottle hydrostatically tested. Finally, if you have an older Halon system (Halon was outlawed in 1993), you'll eventually have to replace it - it can't be recharged. When you do, you'll need half again as much agent, which means a bigger bottle, to get the same protection. And by all means don't be complacent. Make sure your fixed system is installed correctly before you find out the hard way that it wasn't.