Combined Impulse Storm-A(S) systems (ISAS)
for firefighting ocean oil terminals
Impulse Storm-A(S) systems (ISAS)
for firefighting high voltage power transformers
Power utilities have installed power substations in their distribution grids to accommodate the ever-increasing demand for dependable power with their rows of large high voltage power transformers. Many precautions are taken to safeguard them against failure because when all power fails, customers complain, revenues are lost and medical emergencies can even happen.
One of the risks these large transformers are subjected to is fire. Although the manufacturers of these oil filled transformers are building them with many imbedded safety features, when they fail they often produce very large fires that are very hard to extinguish and provoke environmental damages by the release of thick black toxic smoke and spilling of transformer oil. This is why more and more utilities are installing fire protection systems to protect their investment and to prevent such fires. Containment curbs and runoff water catch basins are also built around the transformers to prevent oil spills in case of problems.
When they are protected, most high voltage power transformers are with a deluge sprinkler system and designers use NFPA-15 as a guide to design a system that will cool off the transformer and eventually, extinguish the fire. Typical design calls for a grid of open type deluge/spray nozzles to be installed all around the transformer. A typical system will use about 44 of them and will be designed to spray about 500gpm of water for a duration of one (1) hour. That is a lot of water!
NFPA-850 for Power Plant Design goes even farther, requesting water spray duration to last a full two (2) hours! But minimum provisions for drainage are specified to be only large enough to contain the spill from the largest single container of any flammable or combustible liquid in the area and for fixed fire suppression systems operating for a minimum of 10 minutes!
A lot of power substations are located in remote areas, or on the outskirts of towns where water is often not readily available in these large quantities. Water reservoirs have to be built (often underground) to accommodate this large demand. They require an initial investment that is fairly high for the utility company and they also need regular maintenance, factors that are rarely included in the fire protection contractor’s proposal.
Even when water is available in these quantities, powerful fire pumps will be needed to provide water at a sufficiently high pressure to achieve the goals of the fire protection system. Infrastructure costs for the utility company rise rapidly, to the point where some of them don’t protect their transformers at all and will simply provide passive protection measures such as firewalls.
Then, when a fire happens, so much water is discharged by the fire department on the flaming transformer to cool it and control the fire that soon, the curbs built around it overflow and hot transformer oil is spilled around, compounding the problem with the possibility of burn back and now creating an environmental.
A solution to these problems is now available using ISAS systems with integrated neutral gas and water fog or AFFF foam system for fixed piping network.
This system ISAS is designed for emergency cooling and extinguishing fires on transformers using a technology spraying fine dispersed water. Neutral gas generators are used to create the effect of fine water and water mist.
The system consists of special tanks (ISAS module) which contain not less than 7,500 liters of water and built-in neutral gas generators (4). Spraying is carried out through a fine water pulverization system installed around the transformer.
ISAS module must be located in the immediate vicinity from the transformer (the place is determined together with the customer). ISAS module can be located on the ground or can be completely hidden underground to create space around the transformer. The location of the module does not affect its work.
Each ISAS module can operate in two modes:
– Emergency cooling mode, water consumption rate is from 20 to 200 liters per second
– Fire extinguishing mode, water consumption rate is 300 liters per second.
The number of ISAS modules around each transformer is determined together with the customer. The total number of modules cannot be less than the number of transformers.
At the request of the Customer, ISAS modules can be connected with a ring pipeline. This pipeline system can be freely connected to fire hydrants located anywhere. The integrated ISAS system can use all its power to extinguish a fire only on one or several transformers. Fire extinguishing mode through hydrants is also possible. Modules operation takes place sequentially in this case.
Due to the possibility of ISAS system to support the constant pressure in the pipelines during its operation, the levels and locations of pipelines and modules do not affect the efficiency of the system and can be defined by the Customer to achieve maximum comfort during operation and maintenance of transformers.
ISAS system has no electric valves and other electrical actuators. It is completely independent on external power sources and eliminates the possibility of failure of mechanisms that are bound to external electrical interference as a result of an accident on the transformer.
The system can be adapted for extinguishing with foam.
ISAS system is guaranteed to execute:
1. Start water feed in a fire extinguishing mode not exceeding the timeframe of five seconds after the fire source determination in an automatic mode. This timeframe will not exceed 3 seconds in case of a manual start-up.
2. Execute fire extinguishing or emergency cooling at any time during 10 years the least at the absence of external sources of electricity and water.
3. Perform its work in case of global disaster or accident at the transformers station and electrical network with a large number of electrical interference.
The principles of the system operation
The launch of the ISAS module in the automatic mode is conducted by sending a low power electrical signal or manually by pressing a button or pulling the operation ring.
In the automatic mode, the signal to start the system is sent by special autonomous thermal sensors that automatically generate an electrical signal. Sensors are 100% independent on external sources of electricity. The sensor is completely protected from external electrical noise.
Remote manual start is also possible.
After starting the pressure generator, neutral gas (fire aerosol) is supplied into the module case and this starts the displacement of water into fine sprays or into the water pipes. The capacity of gas and pressure in the housing is automatically maintained at the same level regardless of the amount of displaced water. For emergency pressure release, each ISAS module contains pressure release valves (3).
The pressure level in the system during operation shall be determined during the module charging procedure with pressure generators and can be any in the range from 0.2 to 2 Mpa.
After starting the module all water is displaced and pressure generator resource is completely consumed. Recharging the module is conducted by trained personnel of the customer and it takes less than one hour.
Each module in the system can be used locally to extinguish a fire on the transformer next to which it is installed or as a part of the whole system for extinguishing a remote transformer using the capacity of all modules.
Constantly maintained pressure of the neutral gas allows the creation of highly effective thin streams of fine water (fire extinguishing mode) or water mist (emergency cooling). This cannot be created with the help of pumping stations and without the use of compressed gas.