POWER PLANT: Foam system for fuel tanks farm area

 

 POWER PLANT

      Foam system for fuel tanks farm area

 

  The main foam network shall be intended to serve the fuel tanks farm area.

     Feeding of this network shall come from the foam-generating unit located in each firewater pumping station.

    Arrangement of piping and valves of foam network shall allow both modes of operation: interconnected or split sub-networks.

     The protection by foam of the tanks farm area shall include:

 -         foam boxes located at the top of each fuel tank and controlled by a valve located outside the dike area,

 foam boxes located all along the top of the walls of the dike areas and controlled by valves located outside the dike area,

-         foam hydrants around the fuel dike area,

-         foam guns or foam monitors for the protection of :

 i.          the unloading area,

ii.          The sheltered part of the metering and fuel pumping stations

.

     As above-mentioned, each firewater pumping station shall house its own foam concentrate reserve.

 a]         Foam storage tanks with automatic proportioner shall be provided. The proportioner shall operate from the pressure drop built through an orifice.

 b]         Foam concentrate contained in flexible bags within pressure vessels will be forced out by a small percentage of the main water stream by-passed to the bottom of the vessels.

     Foam concentrate shall be of air type.

     Kind, brand, dosing, and unit cost of the concentrate shall be submitted in the proposal.

     For foam solution, the delivery rate shall be at least on the basis of the NFPA code.

         Water supply to foam system shall be of suitable quality and possible inhibitor or additive to be mixed in the water shall be compatible with the concentrate.

       Foam systems for machine room equipment;

  The other foam system shall protect:

 a]         the fuel skid blocks of the gas turbine units,

 b]         the gas turbine hot parts,         combustion chamber area,  hot bearing, if any,

 c]         The black start diesel gen. set installed in the gas turbo-generator sets buildings.

 d]     The systems shall be of spray type:

e]         automatically actuated for fuel skid blocks and gas turbines,

f]          Manual for black start gen. set.

   The systems shall be designed so as to discharge a foam spray pattern covering any hazardous or already firing fuel spills under, around, and semi-overhead the related equipment.

  Taking into account the simultaneous action of the gas system, the foam is finally intended to cover the lowest parts and, mandatory, any under-floor pipe channel or pit.

  The foam concentrate storage tanks and the foam station shall be independent of the system dedicated to fuel tanks farm

.

  Foam tanks stations shall be suitably distributed throughout the length of each gas turbo generator sets building.

Their location shall be selected so as:

 a]         to be able to deliver real efficient foam as fast as possible,

 b]         to not be subject to hot effect from any neighboring machine,

 c]         To be safely accessible to the firemen in any case of fire, for possible backup manual action.

       Foam hydrants

             Foam hydrants shall be distributed throughout the plant but especially located at suitable vicinity of possible sources of fuel-oil fire.

             They shall be equipped with their own hose box or cabinet.

      Specific protection of the crude-oil floating roofs seal

   In addition to the above foam system, each crude-oil tank shall be equipped with a specific protection of the floating roof seal.

               This system shall be of the automatic type including a network of sprinklers spread out all around the mechanical seal of the roof fed by CO2 bottles located on the roof and pressure monitored.

   In case of fire, the release of CO2 gas and, consequently, the pressure decrease in the bottles, shall actuate a pressure switch, which will announce the fire outbreak.