Blast Resistant Modular Building (BRM) Prices
The price of a blast resistant modular building is not set only by the size of the structure, its total weight or the amount of steel used. The design blast load, the purpose of the building, the target performance level, the number of doors and windows, the mechanical systems, the interior fit-out and the transport and installation conditions all directly affect the cost.
Blast Resistant Module (BRM) systems are designed to protect personnel and critical equipment in refineries, petrochemical plants, energy facilities, defense industry campuses and industrial areas where there is a risk of explosion.
These buildings are not a heavier version of a standard cargo container. The walls, roof, floor, main load-bearing system, connections, doors, windows, ventilation openings and foundation connections must work together against the defined blast load.
Design Blast Pressure and Impulse
The most important technical input that determines the price of a BRM (blast resistant modular building) is the blast load the structure has to withstand. This load should not be expressed by a pressure value alone.
A technical evaluation considers the following data together:
- Peak blast pressure
- Impulse value
- Positive phase duration
- Location of the blast source
- Distance of the structure from the blast source
- Direction of the load
- Design loads on the different faces of the structure
Impulse is one of the basic parameters that shows how long the blast pressure acts on the structure. Two blast scenarios with the same peak pressure can produce different dynamic responses in the structure because of different impulse values.
The front, rear and side walls of a BRM, and its roof and floor, may not be exposed to the same load. The position and orientation of the building within the facility can change the design load used for each face.
For this reason, comparing prices on a single value such as “a 10 psi BRM” is not sufficient.
Purpose of the Building and Number of Occupants
The purpose for which the blast resistant modular building will be used determines both its structural design and the scope of its interior equipment.
The number of people inside affects the usable area, the escape arrangement, the number of doors, the ventilation capacity and the emergency needs.
The design and equipment requirements of a control room with permanent staff are not the same as those of a technical BRM that only houses equipment. The same applies to blast resistant containers, blast resistant storage rooms and offices.
Target Structural Performance Level
The performance expected of the structure after an explosion must be clearly defined at the start of the project.
In some projects the main goal is for the structure to deform in a controlled way and protect the people inside. In more critical applications it may be required that the structure remains usable after the blast or that critical operations are not interrupted.
Performance expectations that can affect cost are:
- Preserving life safety
- Preserving structural integrity
- Limiting permanent deformation
- Protecting critical equipment inside
- Keeping doors and escape routes usable
- Continuing operations after the blast
- Limiting the risk of secondary fragmentation
“Blast resistant” on its own is not a sufficient definition of performance. The permitted damage level and acceptance criteria must be stated clearly in the technical specification.
BRM Dimensions and Modular Configuration
The length, width and height of a BRM affect the total cost. But not only the total area matters. The geometry of the structure and the module layout are also important.
In addition to single-piece 20 ft or 40 ft modules, wider and longer project-specific structures can also be designed. A larger interior usable area increases roof and floor spans and may require the load-bearing system to be re-sized.
Load-Bearing System and Structural Weight
The wall, roof and floor system of a BRM is designed for the dynamic responses that occur under the blast load. The steel thickness and load-bearing profiles to be used must be determined as a result of engineering analysis.
Using more steel does not always mean a better design. The aim is to create a structural system that meets the defined performance safely and can be manufactured.
An over-heavy design can increase manufacturing, transport, crane and foundation costs. An inadequate design, on the other hand, is a direct safety risk.
Doors, Windows and Other Openings
Every opening in a BRM affects the load transfer and the protective shell of the structure. Doors and windows should therefore not be treated as architectural elements added afterwards.
The openings that affect cost are:
- Blast resistant personnel doors
- Equipment entry doors
- Emergency exit doors
- Blast resistant windows
- HVAC openings
- Cable and pipe penetrations
- Ventilation louvres
- Drainage and services penetrations
An increase in the number of doors and windows affects not only the product cost but also the structural reinforcement and connection details around the openings.
The performance of doors, windows and louvres must be compatible with the overall performance target of the BRM. A blast resistant structural shell does not mean that a standard door or window will provide the same protection.
HVAC, Pressurisation and Mechanical Systems
In BRMs occupied by personnel, ventilation and air conditioning systems are a major cost item. The HVAC system should be evaluated not only for interior comfort but also for the continuity of the protective building shell.
In petrochemical and chemical plants, there may be fire or toxic gas risks in addition to the explosion hazard. Focusing only on structural blast resistance may therefore not be enough. API RP 752 addresses permanent buildings in process plants, and API RP 753 addresses the management of hazards associated with the siting of portable buildings. Whether the building is classified as permanent or portable, its period of use and the plant layout should be clarified at the start of the project.
Fire, Ballistic, Gas-Tight and Corrosion Requirements
In some BRM projects, other protection levels are required in addition to blast resistance.
These may include:
- Fire resistance
- Ballistic protection
- Gas tightness
- NBC/CBRN filtration
- Resistance against forced entry
- High corrosion resistance
- Coating suitable for marine environments
- Extreme hot or cold climate conditions
Combining several performances in the same structure can change the wall system, the door and window configuration, the seals, the coating and the mechanical installation.
Blast resistance does not by itself provide fire resistance or gas tightness. Each property must be evaluated separately against its own specification, standard and acceptance criterion.
Interior Layout, Electrical and User Equipment
When the price of a BRM is calculated, it must be stated clearly whether the building will be delivered as an empty steel shell or ready for use.
Analysis, Quality Control, Transport and Installation
The last major part of the cost of a BRM is the scope of engineering verification and of manufacturing and site services.
Depending on the project, the following work may be requested:
- SDOF or finite element analysis
- Structural calculation and design report
- Third-party technical verification
- Material certificates
- WPS/PQR and welder qualifications
- Weld map
- Non-destructive testing
- Dimensional checks
- Inspection and test plan
- Factory acceptance tests
- Site acceptance tests
ARSDEF’s BRM Design Approach
ARSDEF treats blast resistant modular buildings not as standard container products but as integrated security structures developed specially for each project.
In the design process, the walls, roof, floor, load-bearing system, connections, doors, windows, louvres and foundation connections are evaluated together. The structural solution is determined on the basis of the design blast load, purpose of use, number of occupants, target performance and site conditions.
Carrying out engineering, manufacturing and site work in step with each other matters not only for safety performance but also for cost, delivery time and ease of installation.
To learn more about ARSDEF’s blast resistant modular solutions, contact us.