Transformer Deluge Systems
How Do Transformer Fires Ignite? Common causes of transformer failure: Weather-related events such as lightning Short circuits in electrical equipment The most common cause is breakdowns in the insulation system
Implications of a Transformer Fire Destruction of equipment such as: Overhead conductors Buses Cable trays
Implications of a Transformer Fire Transformers can rupture during a failure, releasing oil into the area Risk is amplified substantially Fire can spread to other areas of the facility Oil can overflow from the collection basins if discharge is not calculated correctly or containment pits are not the appropriate size
Implications of a Transformer Fire Plant is taken offline, resulting in revenue losses Lives of employees and building inhabitants are put at risk
Why are Effective Fire Protection Systems Important for Transformers? Implementing and maintaining an effective fire protection system for transformers should be a priority for power generating facilities for many reasons: Loss prevention controlling transformer fires can prevent the loss of millions of dollars that is associated with the destruction of adjacent equipment and unplanned outages Life safety fire protection systems can help protect on-site employees from the hazards of potentially violent and explosive transformer fires Industry requirements NFPA, insurance and even environmental authorities in some instances require facilities to take specific measures to meet fire protection standards for transformers
What is a Deluge Water Spray System? NFPA-850: Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations Identification of and Protection Against Hazards - Transformers Oil filled main, station service and start-up transformers not meeting the separation or fire barrier recommendations or as determined by the Fire Protection Design Basis should be protected with automatic waterspray or foam-water spray systems.
What is a Deluge Water Spray System? NFPA-15: Standard for Water Spray Fixed Systems for Fire Protection Defines a water spray system as: an automatic or manually actuated fixed pipe system connected to a water supply and equipped with water spray nozzles designed to provide a specific water discharge and distribution over the protected surfaces or area.
What is a Deluge Water Spray System? NFPA-15: Standard for Water Spray Fixed Systems for Fire Protection Design of systems can vary considerably Must consider the nature of the hazard and basic purpose of protection There are a wide variety of nozzles with different spray characteristics It is essential that the designer understand the limitations and capabilities of the systems Design density is typically.25 GPM over the entire surface area of the transformer
How Does a Deluge System Work? Water is released through open nozzles Deluge Valve The Deluge Valve is an integral part of a deluge system Specialty fire protection valve Holds water supply back behind a clapper or diaphragm Water is released via an electric or pneumatic detection system
How Does a Deluge System Work?
Where to Begin? What is the available water supply? Fire pump flow test Hydrant flow test Available pressure and flow at the base of the riser Determine the location of existing transformer deluge valves and routing of existing feed mains
Where to Begin? Consider existing pipe stand foundations Will the existing locations suit new transformer dimensions? Are they reusable? (Consult with Plant Structural Engineers) Are there currently or will there be fire walls to isolate each fire area?
Where to Begin? What is the ground below the transformer? Absorbing pit with stone fill or Non-absorbing with exposed concrete containment Obtain any specific electrical clearance requirements based on Basic Impulse Level (BIL) as specified in NFPA-15 or other specific requirements defined by Owner
Design of Deluge Systems - Nozzles The layout of nozzles is based upon spray characteristics: Angle of spray and associated positioning angle Orifice size (how much water can be sprayed out of each nozzle
Design of Deluge Systems - Nozzles Nozzles are positioned to provide complete water spray impingement on all exposed exterior surfaces, such as: Radiators Conservator tank Electrical cabinets, etc Water spray should not envelop energized bushings or lightning arrestors by direct impingement.
Typical Nozzles
Spray Pattern Design
Design of Deluge Systems Pipe Support Pipe support options Can fire walls or other structural elements be utilized for support? Are there existing foundations for pipe stands or are new ones required? Must locate stands to avoid interferences with cabinets, door swings, etc.
Design of Deluge Systems Piping Layout Piping Layout Considerations Transformer height dictates how many rings are required Rings are typically located around the transformer with the possibility of additional piping between transformer casing and radiators Avoid locating piping within cabinet door swings Design with consideration for future maintenance access
Design of Deluge Systems Piping Layout Piping Layout Considerations Avoid running piping across the top of the transformer tank Determine electrical clearance requirements and locate piping the proper distance Route piping so that it facilitates automatic draining through open nozzles Determining the connection to mains Designing for effective drainage
Design of Deluge Systems - Bracing Bracing: significant forces are incurred when a deluge valve trips Piping must be braced to resist these forces. Bracing is usually provided at: Corners of the main loop Drops and/or rises more than 4 Bracing consists of pipe clamps and swivels attached to steel bracing pipe
Design of Deluge Systems - Detection Electric Detection Can an existing releasing panel be utilized or is a new one required? Which type of electric detection is to be utilized? Spot Type Heat Detectors Linear Protect-O-Wire Protectowire Linear Heat Detector VERTICAL DETECT-A-FIRE UNITS (Hexagonal Head) Spot-Type Electric Detection
Design of Deluge Systems - Detection Pneumatic Detection Utilize dry pilot sprinkler head Air supply plant air or local air compressor? Which type of electric detection is to be utilized? Implementing Alarm Systems Manual Release stations to be provided at hazard area? New Notification Appliances such as horn/strobe units to be used? Dry pilot sprinkler
Design Drawings and Documentation Preparation of material data sheets for Owner s approval of equipment to be utilized Development of a preliminary design drawing showing nozzle locations, pipe routing and support locations along with initial detailing Hydraulic calculations are performed for pipe sizing
Design Drawings and Documentation Electrical drawings showing detection and alarm devices along with preliminary wiring diagrams In some instances a partial design is submitted for Owner review and comments Owner comments would then be incorporated into the design package submittal for approval
Design 3D Animation
Pre-Construction Planning Scheduling Assist owner in schedule development to be sure all activities are captured and correct durations are utilized
Pre-Construction Planning Scope Meet with Project Manager to verify scope and ensure all aspects of construction are discussed so that everyone is on the same page Identify and plan for any required pre-outage work Verify that the Owner is aware of items and services that are expected to be Owner-provided: Materials and equipment Labor and services such as electrical install, painting, excavation and backfilling, etc. Construction-related requirements such as aerial lifts, scaffolding, laydown requirements, job trailers, etc.
Pre-Construction Planning Safety Prepare a job safety analysis for specific work activities Review installation sequence in detail with Owner s project manager and field superintendent
Installation Coordination with other activities: Access to work areas Scaffolding erection Aerial lift usage
Installation Pre-job briefing: Work activities change Safety concerns Weather Jobsite working conditions change due to the type of activities being undertaken by others
Installation Typical installation sequencing Demolition of existing piping May require partial demolition prior to existing transformer s removal Other piping may need to be removed after the transformer is removed Installation of pipe stands Coordinate with the rigger for efficient installation Install as many as possible before the new transformer is rigged
Installation Typical installation sequencing Installation of main loops and feed mains Coordinate with the rigger for efficient installation One or more sides of loop may be able to be installed prior to the new transformer being rigged into place Installation of vertical nozzle piping and swing joints Some nozzle piping may be made on to loop piping on the ground to facilitate lifting into place with a crane. Piping is installed with plugged nozzle outlets to facilitate hydrostatic testing
Installation Typical installation sequencing Hydrostatic testing of all deluge piping at 200 psi Remove test plugs and install and orientate nozzles Install bracing Install linear heat detection and/or conduit that may be attached to deluge piping Detection system terminations are made at releasing control panel
Installation Perform the spray test, also known as a performance test: Typically initiated through detection system All nozzles are viewed to assure there are no obstructions Water spray patterns are verified to assure that all surfaces are adequately protected Pressure reading is observed at remote nozzle to verify system is putting out the required pressure determined from hydraulic calculations
Inspection, Testing and Maintenance Developing a comprehensive inspection, testing and maintenance program is essential to: Ensuring systems are optimally functional when they are needed in a fire Maintaining compliance with industry, insurance and corporate standards Maximizing the life cycle of fire protection systems
Inspection, Testing and Maintenance A deluge system s ITM program should be developed in accordance with NFPA 25: Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems Detection system ITM should follow the requirements set forth in NFPA 72: National Fire Alarm and Signaling Code Documentation of all ITM work should be meticulously maintained and readily available for review by the AHJ
Inspection, Testing and Maintenance Critical elements of an ITM program include: Annual tripping of deluge valve at full flow Observation of water discharge patterns to confirm proper positioning and absence of obstructions Verification of water flow alarms Pressure readings at the remote nozzle and deluge valve to ensure hydraulic design requirements are met
Inspection, Testing and Maintenance Critical elements of an ITM program include: Annual operation of annual actuation devices Cleaning of interior of deluge valve during annual testing Draining of system low points Internal inspection of strainers every five years at a minimum
Summary A transformer fire is not a frequent occurrence but the impact is tremendous In a fire the transformer will likely be destroyed immediately but damage to adjacent equipment/structures can be mitigated The consequences of an uncontained fire include: Costly damage to the facility Loss of revenue due to an unscheduled outage Compromising the safety of facility inhabitants
Summary Fire protection systems can be effective in minimizing damage if: Design Operation Construction Inspection, Testing and Maintenance are properly executed by an experienced professional with the required experience.
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