Cylinder packs are arranged with cylinders positioned vertically and equipped with a drainage system to allow the emptying of any liquid that accumulates inside them. Cylinder packs can be installed in full or in part in the compressor room, in a dedicated room or outside on the forecourt, depending on the case in question and the regulations of the destination Country. Reasons for providing cylinder packs on the CNG system:
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• Compressor blow-down volume: all or some of the cylinders are used for decompression when the compressor stops; the number of cylinders and therefore the volume to be dedicated to this purpose depends on the compressor model.
• Damping of pulsations: in systems where there is no storage, it is good practice to provide some cylinders on the compressor discharge to dampen gas pulsations that could be transmitted along the plant piping.
• Storage: in plants with a gas flow rate that varies during the day, providing for the storage of already compressed gas allows to:
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➊ optimise the choice of compressor based on an average value. This avoids having to consider the peak time of sales during which the previously stored gas will be used.
➋ reduce the number of compressor start/stops. Storage can consist of one, two or three sectors (called low, medium and high pressure) depending on how many supply lines are required for the dispensers.
➌ maximise the use of storage by providing more supply lines to the dispensers and therefore storage sectors.
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