Dispensers are second only to
compression equipment as the
most expensive part of a CNG
fuelling station, with gas flow
meters accounting for much of the
high cost . CNG dispensers conform to NFPA‐52, NZS 5425, Oil Industry Safety Directorate (OISD) 179 / relevant international standards. All the electrical and electronic components are mounted in flame/ explosion proof housing suitable for hazardous area classification of Class I, Div 1, Group D
as per NEC or Zone 1, Group IIA/IIB as per IS/IEC specifications. Dispensers are housed in weatherproof cabinet of robust construction and stainless steel (SS 304) material with a tamper proof locking arrangement. Dispensing units have overfilled protection through electronically programmed microprocessors with 2 nos. of pressure limiting device per filling line. Dispensers’ refueling hoses are provided with return vent line hose for safe venting of gas. Dispensers are provided with easily accessible emergency shut off valve on each filling line.Dispensing units have to comply to the Safety, and Weights and Measures regulation requirements.The dispensing pressure can’t be higher than 220 bar at the refueling stations in which the compression is realized at a pressure higher than 220 bar, the pipeline to the dispenser is equipped with a device that limits the pressure to a valve of 220 bars. It also has to be insured with proper equipment, that the maximum established pressure does not exceed the set pressure. For this purpose, after the compression unit at the beginning of the pipelines that deliver the natural gas to the dispensing units, besides the principal equipment of reduction of the pressure, a safety device is installed. This acts before the pressure overcome the maximum established value of set pressure. At the refueling stations in which the compression is realized at pressures higher than 220 bar, the pipeline to the dispenser is equipped with devices for the automatic cut off of the compressors as the pressure becomes higher than 220 bar.
as per NEC or Zone 1, Group IIA/IIB as per IS/IEC specifications. Dispensers are housed in weatherproof cabinet of robust construction and stainless steel (SS 304) material with a tamper proof locking arrangement. Dispensing units have overfilled protection through electronically programmed microprocessors with 2 nos. of pressure limiting device per filling line. Dispensers’ refueling hoses are provided with return vent line hose for safe venting of gas. Dispensers are provided with easily accessible emergency shut off valve on each filling line.Dispensing units have to comply to the Safety, and Weights and Measures regulation requirements.The dispensing pressure can’t be higher than 220 bar at the refueling stations in which the compression is realized at a pressure higher than 220 bar, the pipeline to the dispenser is equipped with a device that limits the pressure to a valve of 220 bars. It also has to be insured with proper equipment, that the maximum established pressure does not exceed the set pressure. For this purpose, after the compression unit at the beginning of the pipelines that deliver the natural gas to the dispensing units, besides the principal equipment of reduction of the pressure, a safety device is installed. This acts before the pressure overcome the maximum established value of set pressure. At the refueling stations in which the compression is realized at pressures higher than 220 bar, the pipeline to the dispenser is equipped with devices for the automatic cut off of the compressors as the pressure becomes higher than 220 bar.
DISPENSER OPERATION -
- Gas from cascade storage system is piped by way of 3 lines (low, medium and high pressure banks) to the dispenser through a combination of filter and valves.
- During r efuelling, the gas flows to the vehicles due to differential pressure between cascade and vehicle’s on-board storage.
- From these banks, the gas passes through mass flowmeter and finally into the delivery hose. The delivery hose incorporates a breakaway coupling, bleed valve, return vent line and refuelling connection.
- As the gas flows, the flowmeter provides an input electrical pulses proportionally to the flow through the dispenser, to the calculator/indicator unit.
DISPENSER COMPONENT -
- FLOWMETER - Flow m easure ment is an important aspect in gas industries since t hese are c a s h registers t hat measure the revenue of t he gas produced by any petroleum companies During the filling process the flow, pressure and temperature of the gaseous fuel being dispensed vary widely
- CALCULATOR/INDICATOR -This electronic device received and process the electrical pulse output from the flowmeter to compute for volume of the gas delivered, its price, totalization, etc.
- BREAKAWAY COUPLING - In the event of an emergency where excessive pulling force is applied to the fill hose, the breakaway coupling pulls apart and the gas flow stops
- NOZZLE, HOSE, BLEED VALVE - Gas passes through 3-way refuelling valve at the end of the fill hose. Gas then enters the vehicle through a coupling. Once gas flow has stopped, the 3-way valve is closed and the gas pressure between the fill valve and the coupling is vented by the exhaust port on the valve. This small amount of gas is vented through the vent hose which is an integral part of the filling hose assembly.
- EMERGENCY SHUTDOWN SYSTEM (ESD) - The emergency shutdown system is activated by an emergency button, manually operated, and located near the local panel of the compressor or near the refueling area and at the station main office. This system performs:
The total isolation of the pipeline to the dispensing units through the valve.
The total isolation of the low-pressure pipeline from the inlet of the compressor.
The total deactivation of all the electrical circuits, with the exception of the ones necessary for the safety system.
DISPENSER TESTING ( Weight & Measurement ) with Provers
K factor - Dispenser Reading - Provers Reading *100 / Provers Reading
