A CNG cascade is a group of high-pressure cylinders linked by high-pressure piping into a single storage unit. The cylinders sit at fixed spacing on a steel frame, connected with stainless steel tubes, and every cylinder is made and tested to strict PESO guidelines. Cascades supply CNG to vehicles, or carry it from a mother station to daughter booster stations.
Types of cascade
Type 1. All-metal cylinders built to IS 7285, BS 5045 Part 1 or US DOT 3AA, as confirmed by PESO. The heaviest type, but low cost has made them the most popular in India. Common sizes:
- 3000 WL (stationary): 40 cylinders of 75 water litres each, the standard cascade at CNG stations.
- 4500 WL (mobile): the most common cascade for transporting CNG. At 200 bar it holds roughly 630 kg of CNG.
Type 2. Metal-lined cylinders with a partial wrap of glass or carbon fibre in resin. Lighter than Type 1, but more expensive.
Type 3. Metal-lined cylinders fully wrapped in composite (carbon fibre, or carbon and glass fibre), compliant with NFPA 52. Lighter than Type 1 and carry more CNG.
Type 4. Ultra-light cylinders that store the most CNG and can’t corrode. The most expensive, though prices are falling.
Rules for cascades
Cascades are regulated by PNGRB, PESO and other bodies. Among the key rules:
- A cascade can’t be detached from the vehicle transporting it.
- CNG stations must be open to the sky, not housed in a closed room.
- Clearance around the vehicle grows with cascade size: 2 m on all sides for 4,500 WL, 4 m for 9,000 WL and 10 m for 17,500 WL.
- CGD companies may currently use only Type 1 and Type 3 cascades.
Why cascades work
A cascade fills small cylinders without running a compressor. Even with a low-capacity compressor, it lets cylinders be filled in close succession during the long periods storage cylinders need to recharge. Each cylinder has its own isolation and safety relief valves, keeping supply to vehicles safe.
We’ve been awarded testing contracts by major gas companies, including GAIL Gas Ltd. and Indraprastha Gas Ltd.