MDE Unit 5 Q5

A scroll metering fuel injection pump is a type of jerk pump that utilizes a helical scroll to control fuel delivery.

1. Jerk-type or Plunger-type Fuel Injection Pump – Working and Animation – YouTube

How it works:

• Plunger and Scroll: The pump has a plunger with a helical groove (scroll) machined into it.   1. Jerk-type or Plunger-type Fuel Injection Pump – Working and Animation – YouTube www.youtube.com
• Fuel Delivery: As the plunger rotates, the scroll progressively opens and closes the fuel delivery port, controlling the amount of fuel injected.
• Injection Timing: The timing of fuel injection is determined by the position of the plunger in relation to the fuel delivery port.

Key advantages:

• Precise fuel metering: The scroll design allows for accurate control of fuel delivery.
• Smooth injection: The helical shape of the scroll contributes to smoother fuel injection.
• Compact design: Scroll pumps can be relatively compact compared to other types of injection pumps.

While scroll metering pumps offer advantages, they have largely been replaced by more advanced electronic fuel injection systems due to limitations in precision and control compared to modern technologies.

While the scroll mechanism is primarily responsible for metering fuel in a scroll metering fuel injection pump, the delivery valve also plays a crucial role.

The primary function of the delivery valve is to prevent the backflow of fuel.

Once the fuel is injected into the high-pressure line, the delivery valve closes to maintain the pressure and prevent fuel from returning to the pump. This is crucial for ensuring accurate fuel delivery and preventing fuel leakage.  

1. KR20060117567A – The delivery valve with back pressure function of fuel injection pump for diesel engine – Google Patents

Additionally, the delivery valve contributes to the precise timing of fuel injection by controlling the pressure build-up in the fuel line.

In essence, the delivery valve acts as a seal to maintain fuel pressure and control the injection process, working in conjunction with the scroll mechanism to ensure accurate fuel delivery.

To mitigate the risks associated with a high-pressure fuel pipe failure, several safety measures are employed:

Containment Systems:

• Jacketed Piping: High-pressure fuel lines are often encased in a secondary outer pipe. This containment system can capture leaking fuel, preventing it from spreading.
• Drip Trays: These are placed beneath potential leak points to collect any spilled fuel.
• Fire-Resistant Materials: Components in the vicinity of high-pressure fuel lines are often made of or covered with fire-resistant materials to minimize fire hazards.

Safety Devices:

• Pressure Relief Valves: While not directly preventing spraying, these valves can help to reduce pressure buildup in case of a blockage or failure, potentially reducing the severity of a leak.
• Quick-Closing Valves: Some systems incorporate valves that can be rapidly closed to isolate a damaged section of the fuel line.

Design Considerations:

• Redundancy: In critical systems, redundant components or backup systems can be used to reduce the risk of catastrophic failure.
• Material Selection: High-quality materials resistant to fatigue and corrosion are used for fuel lines to minimize the risk of failure.
• Installation and Maintenance: Proper installation and regular inspection of fuel lines are crucial to prevent leaks.   1. Lessons Learned from fuel oil leakage accident onboard – SAFETY4SEA safety4sea.com

By implementing these measures, the risk of fuel oil spraying in case of a high-pressure pipe failure can be significantly reduced, enhancing safety and protecting personnel and equipment.