Everything you need to know about boiler blow down and surface scum

Aboard every seafaring vessel, the marine boiler is one of the most important piece of equipment and for some of the vessels is the beating heart of the ship’s power generation and propulsion. Maintaining the boiler’s efficiency and safety is of paramount importance, and two key processes that ensure this are blowdown and surface scum removal. In this article, we will explain the significance of these operations, their proper execution, and the essential safety precautions for marine engineers.

What are marine boilers blow down and surface scum and why are they important?

Marine boilers blow down and surface scum are two methods of removing impurities from the boiler water. Boiler water is the water that circulates inside the boiler tubes and generates steam for various purposes on board, such as propulsion, heating, electricity, etc. Boiler water needs to be treated with chemicals to prevent corrosion and scale formation in the boiler tubes.

If you are interested to read more about “Boiler feed water system, water sampling and treatment systems”, please follow THIS LINK.

However, even with proper treatment, some impurities may still remain in the boiler water due to evaporation, leakage, contamination, etc. These impurities can affect the quality and quantity of the steam, reduce the efficiency and safety of the boiler, and damage the boiler components. Therefore, it is important to remove these impurities periodically by performing marine boilers blow down and surface scum.

The Importance of Marine Boiler Blowdown and Surface Scum Removal

• Efficiency and Heat Transfer: Over time, impurities accumulate in the boiler water, leading to decreased efficiency. Blowdown and surface scum removal help maintain the purity of the boiler water, ensuring optimal heat transfer. This, in turn, results in efficient steam production and reduced fuel consumption.

• Corrosion Prevention: Impurities like salts and minerals can cause corrosion within the boiler. Regular blowdown reduces the concentration of these impurities, thus protecting the boiler’s critical components from damage and extending its lifespan.

• Scale and Sludge Control: Blowdown helps to prevent the buildup of scale and sludge on the boiler’s heating surfaces. Scale and sludge insulate the heat transfer surfaces, making it harder for heat to pass through and leading to overheating and damage. Proper blowdown is crucial to control these issues.

• Safety: Maintaining the boiler’s water quality is essential for safety. High impurity levels can lead to boiler explosions or other dangerous incidents, making proper blowdown and surface scum removal critical for the safety of the vessel and its crew.

The Proper Way to Perform Blowdown and Surface Scum Removal

• Frequency: Blowdown should be conducted at regular intervals, typically once or a few times each day. The frequency depends on the quality of the feedwater and the operating conditions of the boiler. It’s essential to consult the boiler manufacturer’s guidelines and the vessel’s specific requirements.
• Procedure: Marine boilers blow down and surface scum are done by opening valves that drain water from different parts of the boiler. Blow down is the process of draining water from the bottom of the boiler drum or the mud drum. Blow down removes the sludge or sediment that accumulates at the bottom of the boiler due to gravity separation. Sludge consists of solid particles such as rust, sand, dirt, etc. that can cause erosion or blockage in the boiler tubes.

Surface scum is the process of draining water from the top of the boiler drum or the steam drum. Surface scum removes the foam or oil film that forms on the surface of the boiler water due to agitation or contamination. Foam consists of bubbles that contain steam or air that can reduce the heat transfer or cause carryover of impurities into the steam. Oil film consists of oil droplets that can cause fouling or corrosion in the boiler tubes. Surface scum is usually done continuously or when the pH or dissolved oxygen of the boiler water exceeds a certain limit.

• Monitoring: Continuous monitoring of the water’s chemical composition and impurity levels is crucial. Regular testing ensures that blowdown and scum removal are done effectively, preventing issues associated with excessive or insufficient removal. If you are interested to read more about “Boiler chemical dosing and control”, please follow THIS LINK.

What is the role and safety precautions of onboard marine engineers regarding marine boilers blow down and surface scum?

The role of onboard marine engineers is to perform marine boilers blow down and surface scum according to a planned schedule or as per need. The marine engineers should also maintain records of these operations and analyze the feed water and boiler water quality for any deviation or improvement.

As part of the safety precautions, those are, but not limited to:

• Training: Marine engineers must receive thorough training in boiler operations, blowdown, and surface scum removal procedures. They should understand the equipment, the importance of these processes, and the potential risks involved.
• Personal Protective Equipment (PPE): When conducting blowdown and scum removal, engineers should wear appropriate PPE, including eye protection, gloves, and heat-resistant clothing to safeguard against hot water and steam.
• Pressure and Temperature Control: Engineers must be aware of the boiler’s pressure and temperature limits. Overly aggressive blowdown can lead to excessive stress on the boiler, while insufficient blowdown can compromise water quality.
• Emergency Protocols: It’s essential for engineers to be well-versed in emergency response procedures in case of boiler malfunctions or accidents, ensuring the safety of the crew and the ship.
• Communication: Effective communication among the engineering team is vital. Engineers must coordinate and share information about boiler conditions and blowdown operations to prevent misunderstandings and accidents.

In conclusion, marine boiler blowdown and surface scum removal are not mere routine tasks; they are essential processes that ensure the efficient and safe operation of a vessel’s boiler. Marine engineers play a pivotal role in carrying out these tasks, following established procedures and safety precautions. Properly executed blowdown and surface scum removal contribute to a longer boiler lifespan, reduced fuel consumption, and, most importantly, the safety of the crew and the vessel. In the challenging environment of the open sea, these operations are the linchpin to reliable and safe maritime operations.

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Source and References:

• YouTube video training: weareboilers