What is shown in this video is a preparatory phase to the FAT before the completion of the natural gas system that will be installed in the cogeneration plant CCPP EL-TO Zagreb, located in Zagreb (Croatia).
The plant is based on two (2) gas turbines and one (1) steam turbine interconnected with district heating network.
The function of the natural gas interconnecting system is to separate, filter, reduce, heat and measure the flow before supplying the GTs 1 and 2 at the required flow rate and pressure.
The natural gas system will be mainly composed of the following sub-systems/sections:
- Interconnecting sub-system to natural gas network
- Main filtration and dew point heating sub-system
- Gas reduction and metering sub-system
The natural gas system is connected to the main pipeline network at point TP-A1 through a line DN 200.
On the main header immediately downstream the delivery point, an emergency self-actuated shut-off valve is provided in order to shut the gas flow in case of emergency and it will be actuated by the Fire Fighting Control.
Natural gas coming from gas network will be subjected to a first separation and filtration, suitable to remove the entrained particles, and heating for gas freezing prevention. For this aim a double train, each sized at 100% of total flow capacity and composed of Dual Stage Cartridge filter and Dew Point Heat Exchangers, is foreseen.
During normal operation, one set of filtration and heating is operating while the second one is ready to be put into operation.
The complete system is supplied with all valves and instruments for a correct and safe control of the plant.
After its primary filtration and heating, the natural gas will flow through two redundant 100% Reduction and Metering sub-systems to reach the optimum service pressure and to be measured.
The two sub-systems shall be able to allow the automatic change-over of the flow between them.
Each fiscal gas metering and relevant temperature and pressure transmitters for measure compensation will be connected to a dedicated flow computer. Measured data will be locally available and will be sent to DCS.
Each gas metering section will be able to measure 100% of flow rate. However, the stand-by metering device shall be installed in parallel with the possibility of serial operation for calibration purposes (so called “Z” connection).
Each Reduction Station will be equipped with gas pressure regulator with an active reducing valve; a monitor reducing valve will be provided and will operate in case of active valve failure.
- Each monitor reducing valve will integrate inside it the function of Slam Shut-off valve with MIN/MAX function, enclosing the relevant shut-off actuator.
- The SSOVs will be fail-to-close type with manual reset and opening once closed.