200 and 250 bar (200 bar)
Also known as: 250 bar · CBG cylinder pressure · bio-CNG compression pressure
The standard cascade filling pressures for compressed biogas cylinders — 200 bar for older infrastructure and 250 bar for modern high-pressure systems and vehicle dispensers.
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What is 200 and 250 bar?
The 200 and 250 bar pressure points are the standard compressed biogas (CBG) cylinder filling pressures used across India's bio-CNG infrastructure. 200 bar (approximately 2,900 psi) corresponds to the legacy cascade-filling pressure inherited from the early CNG industry, while 250 bar (approximately 3,600 psi) is the modern dispensing pressure used at most new CGD stations and on-board vehicle cylinders. Compression to these levels reduces the volume of biomethane by roughly 200-250 times compared to atmospheric storage, making transport in cylinders or trucks economically viable.
Operationally, CBG compression in Indian SATAT plants follows a multi-stage process:
- Stage 1 inlet: upgraded biomethane at 1-4 bar from the upgrading unit.
- Stage 2: compression to 15-25 bar.
- Stage 3: compression to 70-90 bar.
- Final stage: compression to 250-280 bar for filling.
Inter-stage cooling brings gas back to 30-40 degC between stages to manage compression work and prevent thermal stress. Compressor power demand is significant: 0.30-0.45 kWh per Nm3 of CBG compressed from 1 to 250 bar, accounting for 35-50% of total plant electricity consumption.
Cylinder standards in India follow ISO 11439 and BIS specifications:
- Type 1: all-steel, lowest cost but heaviest (1.0-1.2 kg per litre water volume).
- Type 2: steel liner with hoop-wrapped composite, 25-30% lighter.
- Type 3: aluminium liner fully wrapped in carbon fibre, 50-60% lighter, premium cost.
- Type 4: plastic liner fully wrapped in carbon fibre, lightest, used in fleet vehicles.
Trade-offs at 250 bar versus 200 bar are higher storage density (about 230 vs 185 kg/m3) and longer vehicle range per fill, but higher compression energy, faster wear on compressor valves and rings, and stricter safety regulations under the Petroleum and Explosives Safety Organisation (PESO). Cascade storage systems use multiple high-pressure (250 bar) and medium-pressure (200 bar) bank cylinders to fill customer cylinders efficiently — the high-pressure bank tops off the cylinder while the medium-pressure bank does the bulk transfer, minimising compressor cycling and energy consumption. PESO licensing for CBG storage above 100 kg is mandatory and requires compliance with the Static and Mobile Pressure Vessels (Unfired) Rules.
Common questions about 200 and 250 bar
Plain-English answers to what people most often ask.
Can a 200 bar cylinder be used at a 250 bar station?
Which standard is required for SATAT scheme CBG plants?
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