This part consists of water based fire protection system called hydrant system in thermal power plants.
Flow scheme for a typical 660 MW unit

Hydrant System:

The fire water ring main network of hydrant system piping shall consist of:

• Isolation gate valves are installed on RCC pedestals above the ground to be protected.
• Hydrant Valves (External/Internal)
• Hose cabinets
• couples
• Branch pipe
• Nozzles and water monitor with all accessories.
• The Other is accessories like MS painted hose box shall be provided as per TAC.
• External hydrants shall be located in hose houses or hose boxes around the buildings and internal hydrants shall be provided by above ground mains at each landing floor of the “hose box” stairs.

Fixed Water Screens (open air type) will be accommodated:

• ESP regions,.
• Evaporator house.
• Tall structure.
• Coal store region.
• Shelter building.
• Intersection tower/move towers and.
• Different regions in the coal transport where water can’t reach.
• from hydrant framework.

Hydrant System Requirements:

Hydrant framework necessities will be planned remembering the accompanying parts of plan in accordance with the TAC prerequisites:

• The hydrant network shall be sized to ensure that a pressure of approximately 3.5 kg/cm2 is available at the hydraulically remote point (according to TAC) in the system with the hydrant pump and the hydrant pump rating. Excludes closed pump capacity and head flow.
• The velocity in the hydrant main should not exceed 5.0 m/s.
  At least two hydrants shall be provided with separate ring mains for main plants.
• A distance of 45 meters shall be provided for each outdoor hydrant. In case of TG halls, mill bays, boilers and other areas, internal hydrant/landing valves shall be provided at a distance of 45 meters and at a distance of 30 meters on each floor.
• A building shall be considered protected by a hydrant if the hydrant is within 15 meters of the building.
• Each landing valves and external hydrant valves connected to main plant like transformer yard, TG building and boiler area are to be provided with hose box.
• Each ring shall be terminated with isolation valve and blind flange at all corners to enable future expansion/modification.
• The firewater booster system pump head shall be designed for the highest point farthest from the boiler and shall be pressure tested at this elevation.
• All landings in boiler staircases, turbine buildings and other multi-storied structures, transfer points/junction towers of coal handling plant, crusher house, bunker floors and other auxiliary buildings/non-plant buildings shall be provided with landing valves with hose box. Rails.

Spray System:

The spray system works automatically. The Deluge valves are being operated and controlled by fire detection devices i.e. quartzite bulb detectors or any other means of fire detection. The system can be pressurized up to the deluge valves.
It covers all transformers area, turbine and its auxiliaries, all oil storage tanks, cooling units and purifier units. The equipment used in the whole system is spray pump, pressure control unit, various types of valves and strainers. There are two methods of spray systems:

1. High Speed Water splash framework (HVWS framework).

2. Medium Speed Water splash framework (MVWS framework).

1. High Speed Water splash framework (HVWS framework):

HVWS shall be designed as per TAC regulations. HVWS shall consist of the above group piping, associated fittings, deluge valves, isolation gate valves, spray nozzles, quartzite bulb detectors and pressure switches. The HVWS system shall be equipped with automatic detection, control and extinguishing of any fire outbreak. This system will hydraulically allow the deluge valve to be opened so that water can be sprayed onto the equipment/area through projector nozzles in the form of a solid conical emulsifying spray.

Isolation gate valve and Y type strainer shall be provided upstream and downstream of deluge valve. A fast acting butterfly valve shall be provided as a bypass to the deluge valve, so that the valve can be kept closed and operated manually in case of deluge valve failure.

According to TAC the pressure at the most hydraulically remote point in the network for external transformers should not be less than 3.5 bar.
Spray nozzles should be positioned such that their spray nozzles overlap each other.

Areas covered under HVWS are:

According to TAC the pressure at the most hydraulically remote point in the network for external transformers should not be less than 3.5 bar.
Spray nozzles should be positioned such that their spray nozzles overlap each other.

• All oil-filled generator transformers and surrounding areas.
• Auxiliary transformers of the unit.
• Unit transformers.
• Auxiliary transformers related to the station.
• Standby Maintenance Transformers.
• A bus reactor.
• CHP auxiliary transformers.
• AHP auxiliary transformers.
• the Station is transformer (transformer rating 10 MVA and above).
• All types of oil storage tanks.
• Oil cooler and purifier unit.
• Boiler Burner and its Peripherals.
• Turbine lube oil storage tank and turbine oil purifier.
• Clean and drain oil tanks.
• Boiler feed pump lube oil tank, cooler, consoles etc.
• Turbine oil canal pipelines in main plant.
• Fuel oil pressurizing and heating units.