Fuel leaks and unshielded hot spots in engine rooms

Technology

November 2022 Safety

Published on 03 Nov 2022

Introduction

Every year, fires on board ships lead to loss of lives and severe damage to ships. Most fires originate in the engine room (ER) due to an atmosphere that is conducive to fire. The three ingredients for a fire - fuel, oxygen and a source of ignition - exist in abundance in the ER. This atmosphere does not only start the fire but also feed and intensifies it. Preventing fire ignition is as critical a part of fire safety as detecting and fighting it is.

How do most engine room fires start?

Data for 2017-2021 period for fires and explosions on ships indicates that nearly 60% of fires originated in the ER. Nearly two thirds of these fires started in the main and auxiliary engines or their associated components, like turbochargers. Most fire incidents occurred due to failure in a flammable oil system, mainly in the low-pressure fuel oil piping. The resultant spray of oil onto an unprotected hot surface ignites a fire.

Case study

A copper pipe on the fuel oil pressure gauge for one of the auxiliary engines fractured. A missing metal spray shield allowed the fuel oil spray in the vicinity. It sprayed onto the unprotected hot surfaces of the nearby turbocharger and exhaust system, at a temperature of more than 400°C. The resultant fuel ignition caused extensive damage to all AE and power distribution cables.

An investigation showed that the fractured copper pipe had a lower wall thickness compared to the original design. The pipe assembly on the other three AE appeared to be from the original installation and comprising of a steel pipe. The crew removed the spray shield during maintenance and did not re-install it. Insulation was inadequate on the other three AE as exposed sections around the exhaust manifold and turbocharger were visible. The main cause of the fire was inadequate heat shielding arrangements on the AE, which did not meet the relevant SOLAS regulations.

Pipes in the engine room on the ship covered in smoke.
Copper piping and connections

In the above case, there are two main aspects that need to be highlighted:

  • Leakage of flammable oil.
  • Inadequate protection to prevent highly flammable fuel from coming in contact with a source of ignition.

Leakage or spray of fuel due to a failure in the oil system

Some of the most common causes of fuel sprays from low pressure piping systems:

  • Not using original parts like piping, piping connections and other associated components, such as o-rings.
  • Not tightening the piping connection to the required torque. Vibrations can cause it to loosen over time.
  • Incorrect assembly after maintenance.
  • Overtightening causing breaking of bolts for flanges or filters with time.
  • Fatigue fracture of pipes. Pipes are typically not well supported along their entire length and undergo excessive stress due to vibrations. Failure to reinstall the holding brackets after maintenance is a common cause.
  • Loosening of FO filter covers and displacement of the spindle from the top cover.
  • Degradation of rubber hoses due to excessive heat in the ER leading to its rupture.

Oil coming in contact with hot surfaces

Some common issues with insulation are:

  • The quality may differ from yard to yard
  • Deterioration with age
  • Improper re-installation after maintenance
  • Getting soaked with oil over a period of time due to minor leakages.

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Note: Physical barriers may not have been part of the original design and therefore not fitted. Where fitted, crew may not re-install it after maintenance or can be misplaced with time.

Age of the ship

One factor to consider when assessing fire risks in the ER is the age of the ship. The risk of leakages from machinery may increase as ships get older. Some of the main issues that can increase the risk of fire in the ER on older ships:

  • Protection of hot surfaces may degrade, providing inferior insulation and increasing the risk of fires.
  • Cuts to maintenance and safety budgets as older ships near the end of their service life.
  • Frequent changes to ownership and management can directly impact the consistency of maintenance.

Typical hotspots in the engine room

The temperature in some areas in the ER can easily exceed 500°C, which can be above the oil’s auto ignition temperature. Some of the areas that can act as source of ignition are:

  • Exhaust manifold, pipes and associated flanges.
  • Exposed areas of boilers.
  • Turbochargers.
  • Indicator valves on cylinders.
  • Heater for purifier units.
  • Electrical wires / components and switchboards. Melting or smouldering of cables can also contribute to the transmission of heat.

Frequency of engine fires

One of the main concerns is an increase in the frequency of both main and auxiliary engine fires. The highest frequency of fires on main and auxiliary engines is seen on passenger and container ships. Within the container ship segment, the highest frequency is for feeders (<3,000 teu).

Age as a factor

As seen above, the age of the ship is a major factor when assessing fire risks in ER. Older ships are more prone to fires originating in ER and frequency peaks for ships between 25–30 years age. The CIC by PSC MoUs on ‘Fire Safety Systems’ showed that the rate of detention increased for older ships.

Frequency of engine fires

Recommendations

Following three key recommendations can help to reduce the risk of ER fires:

Identifying sources of leakages

  • PMS must include checks on:

- Fuel and lube oil pipes for loose fittings.

- Missing bolts on flanges.

- Condition of non-metallic hoses in areas where the temperatures can exceed the oil’s ignition point.

- Locations from where oil can spray onto hot surfaces.

  • Regularly carry out assessments to identify potential sources of leakages.
  • Check whether the components of the oil piping system are original and meet the manufacturer’s specifications. This is particularly important when taking over a second-hand ship.

Mapping hot surfaces using thermography

It is recommended to use thermography onboard for detection of hot surfaces and for checking insulation during normal operations. Periodically carry out thermographic examination of the ER and electrical installation with engines and electrical equipment running.

Shielding hotspots

Insulation: Carry out regular checks of material used to insulate high temperature surfaces as it may degrade over time or become oil soaked. Even if the insulation appears in good order, there may be hidden inadequately insulated areas and hot spots that could start a fire if in contact with oil.

Spray shields: Regularly check the position and condition of spray shields for both high and low pressure flammable oil lines. In addition, check drainage arrangements and alarms for jacketed fuel oil pipes. Consider installing spray shields for areas identified as potential ‘sources of oil leakage’ where spray shields were not included in the original design. Pay particular attention to proper refitting of spray shields and insulation materials immediately after maintenance.

(Source: ABS; Gard P&I)

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