Firefighting Enclosure Load Bearing Points

In the context of firefighting within enclosures, such as buildings or industrial spaces, identifying load-bearing points is crucial to ensure the safety of both firefighters and occupants. Load-bearing points refer to structural elements that support the weight of the building, including walls, beams, columns, and foundations. Understanding the location and status of these points helps prevent structural collapse during firefighting operations.

Here’s an overview of how load-bearing points relate to firefighting in enclosures:

1. Structural Integrity Concerns

• Heat and Fire Impact on Load-Bearing Structures: Fire can weaken load-bearing elements, especially if they are made of steel or wood. Prolonged exposure to heat can cause steel beams to warp or lose strength, and wooden beams can char and eventually burn through. Concrete can crack due to thermal stress.
• Potential for Collapse: If load-bearing points are compromised by fire, there's a significant risk of a structural collapse. Firefighters need to assess these risks quickly before entering or continuing operations inside a burning structure.

2. Firefighting Tactics Regarding Load-Bearing Points

• Pre-Incident Planning: Firefighters should have knowledge of building layouts, including load-bearing points, through pre-incident plans or building blueprints. This helps identify vulnerable areas before they enter a hazardous environment.
• Thermal Imaging: Firefighters often use thermal imaging cameras to detect the spread of heat, which can indicate compromised load-bearing structures before they are visibly damaged.
• Ventilation Control: Ventilation must be controlled carefully in relation to load-bearing points. Improper ventilation can intensify the fire and increase heat stress on key structural elements.

3. Building Materials and Fire Resistance

• Steel Structures: Steel loses much of its strength at temperatures above 1,000°F (538°C), so firefighters need to be cautious when engaging in structures primarily supported by steel.
• Wooden Structures: Wood burns, but certain engineered wood products or treatments offer improved fire resistance. Nevertheless, prolonged exposure to fire can severely weaken these load-bearing elements.
• Concrete Structures: Concrete is more fire-resistant than wood and steel, but it can crack and spall under high heat, potentially exposing internal reinforcements like rebar, which may be vulnerable to failure.

4. Fire-Resistant Design

Some buildings are designed with fire-resistant structural components that protect load-bearing points from direct exposure to flames. This can include:

• Fire-rated walls and ceilings
• Intumescent coatings on steel beams that expand when heated, providing insulation.
• Compartmentalization to contain fire spread, keeping critical load-bearing points away from the fire.

5. Search and Rescue Operations

Firefighters conducting search and rescue operations must identify load-bearing points to navigate safely. These points can serve as reference points for locating individuals or understanding the stability of the structure while moving through it.

6. Collapse Zones

• Firefighters establish collapse zones around areas with compromised load-bearing points to avoid injury or fatalities in the event of a structural collapse.
• The collapse zone distance is generally 1.5 times the height of the structure, as a conservative measure.

1. Fire’s Impact on Load-Bearing Structures

Different types of load-bearing structures respond differently to fire, depending on the material, fire duration, and intensity. Here’s a closer look at common structural elements and their behavior under fire conditions:

Steel Structures:

• Fire Response: Steel is a strong material but has poor heat resistance. At temperatures above 500°C (932°F), steel begins to lose its structural strength, and by 1,000°F (538°C), it can lose up to half its strength. Since steel is often used in critical structural elements such as beams, columns, and trusses, weakening of these components can lead to a sudden collapse.
• Fireproofing Methods:Steel structures are often coated with intumescent paint, which expands when exposed to heat, forming an insulating layer that delays heat transfer.Fireproofing boards or sprays can also be applied to steel beams to improve fire resistance.

Wooden Structures:

• Fire Response: Wood is combustible, and its behavior in a fire depends on its thickness and type. Heavy timber can char on the outside, which actually insulates the inner layers and allows the structure to maintain strength for some time. However, lightweight wood trusses or engineered wood products (like plywood or particleboard) can burn through quickly and cause early collapse.
• Fire-Rated Wood Construction: Some buildings use fire-retardant-treated wood (FRT wood) that is chemically treated to resist ignition and slow the spread of flames, providing additional time for evacuation and firefighting efforts.

Concrete Structures:

• Fire Response: Concrete is non-combustible and highly resistant to fire, but it can spall (break apart) when exposed to extreme heat. Spalling occurs when the moisture within the concrete expands and causes surface pieces to break off explosively. Additionally, the steel reinforcement (rebar) inside concrete can heat up and weaken the structure if exposed for long periods.
• Reinforcement Protection: To protect the rebar and avoid concrete failure, thicker concrete coverings are used in construction to insulate the steel from fire.

2. Firefighting Tactics Regarding Load-Bearing Points

Pre-Incident Planning:

• Pre-Planning: Fire departments often collaborate with building owners to create pre-incident plans. These plans include details about the building’s structure, including load-bearing walls, support columns, and fire-rated features like doors and walls. Knowing the layout and load-bearing points of a structure in advance allows firefighters to enter and fight the fire safely and effectively.

Size-Up and Risk Assessment:

• Initial Size-Up: When arriving at the scene, firefighters perform a 360-degree size-up of the structure to assess fire conditions, potential entry points, and risks to load-bearing structures. They look for signs of structural weakening, such as sagging floors, bowing walls, or cracking sounds, which may indicate impending collapse.
• Interior Assessment: While inside, firefighters use thermal imaging cameras (TICs) to detect areas of extreme heat. This technology helps them identify sections where fire may be compromising the load-bearing elements hidden behind walls, ceilings, or floors.

Ventilation and Fire Spread:

• Ventilation Control: Improper ventilation can lead to flashover (where the entire room ignites suddenly) or backdraft (an explosive re-ignition of fire when oxygen is introduced). Both of these events can drastically increase heat and fire intensity, putting further stress on load-bearing structures. Firefighters must be cautious in creating vent openings, ensuring that fire doesn’t rapidly expand and affect critical structural points.
• Compartmentalization: Many buildings are designed with fire-rated walls and ceilings to create compartmentalization, which slows fire spread and gives firefighters more time to protect load-bearing elements. Firefighters need to identify these compartments and prevent the fire from breaching them.

3. Collapse Indicators in Load-Bearing Structures

Firefighters are trained to recognize early warning signs of structural failure, which can include the following:

• Sagging or Bowing: Load-bearing walls, floors, or ceilings that start to sag or bow outward under the weight of a building signal potential collapse.
• Cracking and Popping Noises: Audible cracking sounds or popping can indicate that structural members, especially wood or steel, are under stress and might soon fail.
• Discolored Walls: When fire behind a wall causes discoloration or bubbling paint, it indicates that load-bearing walls may be compromised by intense heat or fire.
• Falling Debris: Small pieces of ceiling tiles or chunks of plaster falling from above may signal weakening of overhead load-bearing beams or trusses.

4. Establishing Collapse Zones

In situations where the fire has compromised load-bearing points or the building’s integrity is uncertain, firefighters establish collapse zones around the structure. The collapse zone typically extends 1.5 times the height of the building to protect firefighters from debris in case of a sudden collapse.

For example:

• A 20-foot tall building would have a collapse zone of 30 feet from its perimeter.

Firefighters remain outside these zones unless absolutely necessary, reducing the risk of being caught in a structural failure.

5. Fire-Resistant Design and Materials

Modern building designs often incorporate fire-resistant features to protect load-bearing points and minimize the risk of structural collapse. These include:

• Fire-Resistant Walls and Ceilings: These barriers are built with materials like gypsum board, concrete, or fire-rated insulation to contain fire and protect critical load-bearing elements.
• Intumescent Coatings: Intumescent paints are applied to steel or wooden load-bearing elements. When exposed to high temperatures, these coatings expand to form an insulating char layer that protects the structural element underneath from heat.
• Automatic Fire Suppression Systems: Buildings often use sprinkler systems and standpipe systems to control fire spread early on, protecting structural points from excessive heat.

6. Post-Incident Considerations for Load-Bearing Structures

After a fire has been extinguished, a thorough structural evaluation is required to assess the condition of load-bearing points. Engineers and safety experts inspect critical areas to determine if they need reinforcement, repair, or complete replacement. Some specific evaluations include:

• Checking for Heat Damage: Steel members may need to be replaced or strengthened if exposed to prolonged heat, while concrete may require patching or full reconstruction if spalling has occurred.
• Wood Charring: In wood-framed buildings, the depth of charred wood may be measured to determine if it has compromised structural integrity.

Based on the two General Arrangement Drawings (GADs) provided, let’s focus on identifying the load-bearing points of the diesel engine-driven fire pump enclosure and their significance in firefighting operations.

Key Load-Bearing Points in the Enclosure:

1. Carbon Steel Baseframe (200 mm height): Purpose: The baseframe serves as the primary load-bearing structure of the enclosure, supporting the diesel engine, pump, fuel tank, and other heavy components. Importance in Firefighting: This base ensures that the entire firefighting system remains stable even under dynamic conditions (e.g., during pump operation). Its integrity is critical for keeping the equipment operational during a fire. If the baseframe is compromised by heat or fire, the entire structure could be destabilized.
2. Skid Fixing Points: Purpose: The skid fixing points are the locations where the enclosure is anchored to the foundation or the ground. They prevent movement or vibration that could occur due to the engine and pump's operation. Importance in Firefighting: The integrity of these points is crucial for ensuring that the enclosure doesn't shift or collapse, especially when exposed to fire or during high-pressure firefighting operations. Any fire damage near these fixing points could lead to structural failure, posing a risk to both the enclosure and nearby personnel.
3. Lifting Lugs: Purpose: Lifting lugs are designed to bear the weight of the entire enclosure when it's being transported or installed. They ensure the system is lifted without causing damage to the structural elements. Importance in Firefighting: Although primarily used during installation, these lugs also represent reinforced load-bearing sections of the enclosure. In extreme firefighting conditions, if parts of the structure fail, the lugs may act as secondary support points.
4. Vertical Pump VAB 180/6 and Diesel Engine: Purpose: These heavy components (such as the pump, engine, and their mountings) are integral to the functionality of the fire pump system. The vertical pump, with a duty capacity of 228 m3/h, is mounted on the baseframe and constitutes a significant portion of the load. Importance in Firefighting: Maintaining the integrity of the load-bearing points that support these critical components is essential. If the structural support for the pump or engine is compromised by fire, it could lead to a catastrophic failure of the firefighting system itself.
5. Exhaust Gas Silencer and Electric Fans: Purpose: These components are part of the enclosure’s ventilation and exhaust systems, mounted to the structure to manage airflow and reduce noise. Importance in Firefighting: The load-bearing capacity of these mounting points ensures that ventilation continues to function during firefighting operations, preventing overheating and ensuring safe engine operation. Failure of these points could lead to heat buildup, affecting the overall structural stability of the enclosure.
6. Fuel Tank and Fuel Tank Supports: Purpose: The fuel tank is mounted to the structure and provides diesel for the engine. It must be securely fastened to avoid spillage or movement. Importance in Firefighting: Load-bearing points around the fuel tank are especially critical because, in a fire, any failure could lead to fuel leaks, potentially exacerbating the fire. Proper load support ensures the tank remains secure, minimizing fire risk.

Firefighting Considerations for Load-Bearing Points:

1. Fire and Heat Exposure: Risk: If the enclosure’s carbon steel baseframe or skid fixing points are exposed to extreme heat, the metal could weaken, reducing the structural integrity of the enclosure. Response: The firefighting team should avoid excessive water directly onto load-bearing points that are heated, as sudden cooling could cause thermal shock and fractures in the metal. Instead, indirect cooling techniques should be used.
2. Ventilation and Cooling: Risk: Overheating of the engine or pump could occur if the exhaust gas silencer or electric fans fail due to damage to their mounting points. This could cause equipment failure or fire spread. Response: Proper ventilation should be maintained during firefighting. Ensuring these load-bearing mounts are intact is essential for equipment operation under fire conditions.
3. Structural Collapse Prevention: Risk: If the baseframe or skid fixings give way due to fire damage, the entire enclosure could collapse. This would not only halt firefighting operations but also pose a direct threat to firefighter safety. Response: Firefighters need to assess the condition of the structure's load-bearing points before entering the enclosure. Thermal imaging cameras can be used to evaluate the temperature around critical load points, and the establishment of collapse zones (1.5 times the height of the structure) ensures personnel safety in case of failure.
4. Noise and Structural Monitoring: Risk: The 85 dB(A) noise level from the enclosure, combined with the sound of firefighting operations, may mask structural failures like cracking or shifting of load-bearing elements. Response: Continuous monitoring of both sound and visual cues (e.g., sagging components, metal deformation) should be part of the firefighting strategy to detect early signs of load-bearing failure.

Summary of Load-Bearing Points:

• Baseframe: Main load-bearing structure that supports all equipment, must remain intact for safe operation.
• Skid Fixing: Anchors the entire system to the foundation, preventing dangerous shifts during firefighting.
• Lifting Lugs: Provide additional structural integrity and are key during installation and possible recovery.
• Engine and Pump Mounts: Must remain stable to ensure the firefighting system can function effectively.
• Ventilation and Exhaust System Mounts: Essential for preventing overheating during firefighting operations.

By focusing on these load-bearing points in the diesel engine-driven fire pump enclosure, firefighters can ensure that the system remains operational during a fire and avoid structural collapses that could endanger lives and firefighting effectiveness