Every engine room machinery system requires a specific procedure for starting and stopping it. Marine Boilers being one of the most important systems on board ships, requires special care and attention during operation and maintenance. Inability to do so leads to major failures and accidents, which can not only be life-threatening but also cause huge damage to the ship’s property.
Mentioned below are 10 boiler operating mistakes that can lead to heavy loss of life and properly on board ships:
Starting a Boiler Without Pre-purging the Furnace
Marine Boilers come with an automation system of starting and stopping consisting of programmed pre-purging and post-purging of the furnace before the burner is fired.
Never ignore or isolate this safety feature. If the boiler has to run manually, it must be pre-purged by means of FD fan for at least 2 minutes. Avoiding this step can lead to blowback and even explosion.
Ignoring Furnace Blowback
Several accidents in the past involving furnace blowback have led to fatal situations on board ships.
Still marine engineers often overlook this danger and fire furnace even when the first attempt ends with flame failure and blowback. One of the reasons for this is stated above i.e. no pre-purging of the furnace.
Bypassing Safety and Alarm
This is a common practice among seafarers, who bypass some of the safety or automation sequences to shorten the operating procedure of boilers. Such systems are installed to ensure safety of ship personnel and thus should never be missed.
No checks on Boiler Refractory
Marine Boilers’ refractory provides better heat-exchanging efficiency and closes/seals gaps to restrict fire, heat, ashes etc. inside the boiler.
Regular inspection of the boiler refractory is important as damaged refractory would expose the boiler shell to flame and heat, leading to bulging or even cracking of the boiler shell.
Dirty Gauge Glasses
Gauge glasses installed on the boiler are the only physical means to check the water level of the boiler.
Every engineer knows the procedure to blow the gauge glass to avoid any kind of blockage. Neglecting this can lead to wrong water level indication and heavy damage to boiler tubes.
Pilot Burner Check
Many engineers remove the pilot burner to check the electrode spark. Such practice can lead to electrical shock and even fire if the surroundings are not properly cleaned or the pilot burner is kept on an oily floor plate with rags.
The best way to check the pilot burner operation is to fit it in place and watch the firing from the boiler inspection manhole located opposite of the burner.
No Clean-up After Burner Maintenance
When any maintenance work is done on the burner assembly (pilot or main burner) and the surrounding area is not cleaned before trying out the boiler, there are high chances of fire and explosion as blowbacks are normal during starting-up after maintenance.
Oil spilled inside the furnace and over the burner assembly can add more to this blowback, converting it into an explosion.
Thermal Shock: Never fire a boiler continuously when starting from cold conditions to avoid thermal shock. Thus in cold conditions, boilers should be started by following an intermediate firing pattern, for e.g. 2 minutes of firing followed by 10 minutes of break.
Also, once the boiler starts to warm up the “break” time gradually decreases and the “firing” period increases simultaneously
Wrong Operation of EGB Circulating Pump
Exhaust gas boiler (EGB) normally comes with a water circulating pump. It is important to start this pump well ahead, at least 2 hours, of starting the main engine and to be stopped 12 hours (the time may reduce depending upon the capacity of the boiler and the geographical condition) after stopping the main engine to avoid thermal shock and EGB fire.
Cleaning of EGB tubes
The exhaust gas boiler (EGB) tubes are arranged in the passage of exhaust gases, which heats the water in the tubes. If these smoke tubes are not cleaned regularly, it can lead to soot deposits over the tubes and during low load operation or improper combustion oil can mix up with the soot. When ignited, the soot can lead to major soot fire followed by hydrogen or iron fire.