Design of automatic gas fire extinguishing system for premises
Our design department has developed working documentation for the installation of an automatic gas fire extinguishing system.
General Principles of Gas Fire Extinguishing System Design
Brief characteristics of the protected premises.
The data center machine room is protected by an automatic gas fire extinguishing system. Room height is 3.8 m. There are no suspended ceilings or raised floors. The room is dry with humidity up to 60%.
Temperature ranges from +20 to +23°C. The room is equipped with a split-system air conditioning system. The main fire load in the protected premises is electronic equipment and cable wiring. There is no dust or aggressive environments in the protected area.
Purpose and Application of Gas Fire Extinguishing System
The automatic gas fire extinguishing system is designed to detect and localize fire in the protected premises. Signals about fire occurrence and system status are transmitted to the existing control panel located on the first floor of the building in a room with 24/7 monitoring.
System composition.
The system includes:
- Existing control panel
- Fire alarm control unit
- Gas fire extinguishing system for machine room - direction #1
- Additional equipment.
Direction #1 system belongs to the class of volumetric extinguishing installations with modular storage of fire extinguishing agent, with electric activation from start impulse.
Fire Extinguishing Agent Mass Calculation
Calculation of fire extinguishing agent mass was performed according to the methodology outlined in the fire safety standards and is presented in the accompanying documents, Calculations section, Appendix A.
Hydraulic Calculation
Hydraulic calculation for this modular installation was performed by the equipment supplier and is presented in the accompanying documents, Calculations section, Appendix B.
Pressure Relief Opening Area Calculation
Calculation of pressure relief opening area was performed in accordance with fire safety standards and is presented in the accompanying documents, Calculations section.
Fire Extinguishing Agent Discharge Delay Time
Calculation of fire extinguishing agent discharge delay time into the protected premises, required for personnel evacuation and engineering systems management, was performed according to safety standards and is presented in the accompanying documents, Calculations section, Appendix D.
Main Design Solutions
Technical part.
The fire extinguishing agent used in the system is Novec-1230.
Fire extinguishing agent storage is provided in a gas fire extinguishing module. The module consists of a cylinder and valve-actuating device. The valve-actuating device has a pressure gauge, electric activation device, local activation device, safety pin for local activation and safety membrane.
The module is connected to the distribution pipeline through a high-pressure hose. A universal pressure switch is installed on the distribution pipeline. According to fire safety standards, the project provides for 100% reserve of fire extinguishing agent in a module of similar type. Nitrogen is used as pressurization gas. Pressurization pressure in the module is 24.8 bar. Electrical activation parameters: DC voltage U=24V±2, current I=0.2A.
Control of fire extinguishing agent mass during module filling is performed by weighing, and leakage during operation is controlled by the pressure gauge installed on the module's valve-actuating device.
The modular fire extinguishing installation includes:
- Module with fire extinguishing agent
- Distribution pipeline with discharge nozzles-sprayers
- High-pressure hose for connecting distribution pipeline to the module
- Electrical control system.
Distribution pipeline is executed according to fire safety standards requirements from steel pipes. For connection of distribution pipeline elements, welding and threaded connections made from similar material are used. For uniform distribution of fire extinguishing agent in all spaces of the protected premises, jet nozzles are used in the project.
Electrical Part
Based on room characteristics, type of fire load, and fire development features, the project provides for room protection using smoke detectors.
For signal reception, existing control panel and fire alarm control unit are used.
Main elements of the gas fire extinguishing system include:
- Signal-start unit
- Smoke fire detectors
- Manual fire detectors
- Magnetic contact detectors
- Visual indicators
- Pressure switch
- Visual-audible alarms
- Redundant power supply
- Control panel
The existing security and fire control panel is designed to work as part of security and fire alarm systems to monitor status and collect information from system devices, maintain event protocol, indicate alarms, control arming and disarming, and manage automation. The panel combines connected devices into one system, ensuring their interaction.
In the system, it performs the function of a central controller, collecting information from the connected fire alarm control unit and controlling it automatically or by operator commands. The fire alarm control unit monitors the status of its alarm loops with connected detectors, and control output circuits for visual and audible alarms. The control panel manages the fire alarm control unit and its outputs, and also controls status display on technical security system workstations.
The fire alarm control unit is designed for:
- Protection of one fire extinguishing zone
- Automatic fire extinguishing system control in automatic and remote modes
- Reception and processing of signals from automatic and manual passive, active loop-powered and four-wire fire detectors
- Control of audible and visual alarms
- Management of engineering equipment by switching off ventilation systems
- Reception of commands and issuance of alarm notifications via RS-485 interface
- Monitoring of fire extinguishing system control circuits, visual and audible alarms
- Monitoring of automatic fire extinguishing system serviceability
Reception of notifications from:
- Door status sensors
- Pressure switches
- Manual start sensors
- Electronic identifier readers
- Issuance of "Fire" and "Malfunction" notifications to the fire department panel.
The control-start unit is designed to work as part of security and fire alarm systems and access control together with the control panel or personal computer.
Manual fire call points are used in fire alarm systems and automatic fire extinguishing systems, designed for manual formation of fire alarm signal or activation of fire automation systems.
Detector power supply is provided from the alarm loop of control panels, providing voltage in the loop up to 30V and limiting current through activated detectors at no more than 25mA.
Visual fire alarm "Gas! Do not enter" is designed for external installation outside premises and installation inside industrial enterprises, civil buildings and structures for visual fire alarm or other emergency situations.
Visual-audible alarm "Gas! Leave!" is designed for use as information indicators, signs, display boards installed inside premises.
Remote optical signaling device is designed for formation of optical signals displaying electrical modes in fire and security-fire alarm loops.
Operating Modes and Algorithm
Operation in automatic mode
When two automatic fire detectors activate in the protected premises, the control unit outputs signals:
- To activate warning visual-audible alarm in the protected premises with displays "Gas! Leave!", "Gas! Do not enter!", Siren
- To open the valve of the module's valve-actuating device with start time delay necessary for people evacuation from the premises and management of object's engineering systems, switching off air conditioners by closing corresponding contacts of the control unit
- To activate visual and audible signaling in the security room about fire occurrence.
Operation in remote mode.
Fire extinguishing activation is performed from the remote start button of the manual fire detector. Further interaction of system parts is similar to automatic start mode.
Remote start of fire extinguishing is provided for cases of automatic start disconnection or failure, as well as for cases of visual fire detection by personnel before fire detector activation. Before performing start, all people must be evacuated from the premises.
Local start
Local start from modules according to fire safety standards is blocked and sealed.
Automatic Mode Operation Algorithm
When one fire detector activates, the control unit receives "attention" signal. The device activates visual and audible signaling, and also displays the number of fire extinguishing direction where the detector activated.
When two fire detectors activate in the protected premises, the following operation algorithm occurs:
- On control units, visual and audible signaling activates, and the number of fire extinguishing direction where detectors activated is displayed
- The control unit outputs signal to activate warning visual-audible alarm in the protected premises with display "Gas! Leave" and siren
- The control unit outputs signal to open the valve of the module's valve-actuating device with delay necessary for people evacuation from the premises and management of object's engineering systems
- After delay time, fire extinguishing agent discharge occurs, visual display "Gas! Do not enter" activates, pressure switch activates, the number of direction where gas discharge occurred is displayed
- If there is no signal from pressure switch or signal to open the module's valve-actuating device failed, the control unit lights "Malfunction" indicator, the number of direction with indication of malfunction type is displayed.
Fire extinguishing activation in remote mode is performed from the remote start button using manual fire detector. Further interaction of system parts is similar to automatic start mode.
Premises Preparation
According to fire safety standards, the leakage parameter of the protected premises enclosing structures should not exceed normative values.
Technologically unjustified openings must be eliminated, cable penetrations and air conditioning system route penetration points must be sealed using fire-resistant foam.
Integration with object's engineering systems.
Regarding integration of fire extinguishing system equipment with object's engineering systems, in case of fire, the following is provided:
- Output of control signals via dry contact from control unit
- Output of status signals, dry contact "FIRE", "Malfunction" from control unit
- Output of control signals via dry contact from signal-start unit to switch off air conditioning system.
Power Supply and Grounding
According to electrical installation rules, automatic fire extinguishing installations in terms of power supply reliability are electrical consumers of 1st category. System power supply is provided from one AC source with automatic switching in emergency mode to backup power from control unit battery packs, ensuring normal operation for 24 hours in standby mode and 3 hours in "alarm" mode.
Power consumption from AC network is no more than 0.15 kW. System equipment, including distribution pipeline, is grounded according to requirements using the existing common grounding loop. Resistance of grounding device used for equipment grounding should be no more than 4 Ohms.
There should be no disconnecting devices and fuses in grounding and neutral conductor circuits. Connection of grounding and neutral conductors to equipment parts should be performed by welding or bolted connection.
Composition and Placement of Elements
Technical Part
Gas fire extinguishing module is installed in the protected premises. Distribution pipeline with discharge nozzles is laid under the ceiling of the protected premises.
Exact location of the module is determined considering location of existing equipment. Equipment placement is shown on the technological equipment layout diagram.
Electrical part
- Control unit. Installed in the protected premises on the wall, at height of 1.5 m from finished floor level
- Signal-start unit. Installed in the protected premises on the wall, at height of 1.5 m from floor level next to control unit
- Redundant power supply. Installed in the protected premises on the wall, at height of 1.5 m from finished floor level next to control unit
- Smoke detectors. Installed in working space on the ceiling of protected premises
- Warning visual and audible alarm devices installed inside and outside the protected premises
- Manual fire detectors. Installed at entrances to protected premises at height of 1.5 m from floor level
- Electronic identifier reader. Installed at entrance to protected premises next to manual fire detector, from the main entrance side.
Installation of fire detectors should be performed according to manufacturer's instructions and fire safety standards. Equipment placement is shown on the electrical equipment layout diagram.
Cable Route Installation
Cable network is executed with fire-resistant cables, laid along walls and ceilings in electrical conduits.
Fire alarm loops should be laid at distance of at least 0.5 m from power and lighting cables and wires. Cable installation to equipment installed outside the protected premises should be performed in electrical conduit inside the premises.
Measures for organization of installation and commissioning works.
Installation, adjustment, testing and commissioning of the system is performed according to requirements of technical standards.
System installation works are performed in the following sequence:
- Pipeline, module and electrical equipment installation works
- Cable route installation
- Individual and complex adjustment of the system.
Strength and tightness testing of discharge device is not performed as it is certified by the manufacturer as part of the module.
Commissioning works are conducted for electronic equipment of the system and include the following types of works:
- Checking system components, batteries, detectors etc.
- Control unit adjustment - static, dynamic
- Complex testing of the system in operating modes and commissioning.
Installation and commissioning works are performed by different teams.