Exam Question
(a) State why double walled fuel pipes are employed for high pressure fuel lines. (6)
(b) Sketch and describe such a double walled pipe arrangement and show how high pressure pipe failure is indicated. (10)
Class 4 (4th Engineer)
MEKM
📅 Apr 2023
Reference Answer
### (a) Reasons for Employing Double-Walled Fuel Pipes for High-Pressure Fuel Lines
Double-walled fuel pipes are a critical safety feature mandated by international conventions (such as SOLAS and MARPOL) and Classification Societies (e.g., LR, DNV, ABS) for high-pressure fuel lines, particularly those carrying flammable liquids near hot surfaces within the machinery spaces. Their employment is driven by several paramount safety, environmental, and operational considerations:
* **Prevention of Fire and Explosion Hazards:**
* **Spray Ignition:** High-pressure fuel (especially heavy fuel oil, HFO) leaking from a single-walled pipe can atomize into a fine mist. If this mist impinges upon hot surfaces (e.g., exhaust manifolds, turbochargers, steam pipes, electric heaters), which routinely exceed the auto-ignition temperature of fuel oil (typically around 250-380°C), it can instantly auto-ignite. This leads to a severe engine room fire, posing an immediate and catastrophic threat to the vessel, crew, and cargo.
Double-walled fuel pipes are a critical safety feature mandated by international conventions (such as SOLAS and MARPOL) and Classification Societies (e.g., LR, DNV, ABS) for high-pressure fuel lines, particularly those carrying flammable liquids near hot surfaces within the machinery spaces. Their employment is driven by several paramount safety, environmental, and operational considerations:
* **Prevention of Fire and Explosion Hazards:**
* **Spray Ignition:** High-pressure fuel (especially heavy fuel oil, HFO) leaking from a single-walled pipe can atomize into a fine mist. If this mist impinges upon hot surfaces (e.g., exhaust manifolds, turbochargers, steam pipes, electric heaters), which routinely exceed the auto-ignition temperature of fuel oil (typically around 250-380°C), it can instantly auto-ignite. This leads to a severe engine room fire, posing an immediate and catastrophic threat to the vessel, crew, and cargo.
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