A scroll compressor is used for HVAC and brake systems in rolling stocks. It works by having an orbiting scroll coupled to a crankshaft that orbits rather than rotates, creating pockets of gas that are drawn in, compressed, and discharged at a higher pressure and temperature. Advantages include being very quiet, small in size, having a simple design with few parts, and requiring low maintenance. Disadvantages are lower capacity, higher cost, and needing to replace the entire compressor element if it fails.

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Scroll Compressor
A scroll compressor is a device for compressing air or refrigerant. In rolling
stocks, scroll compressor is used for HVAC and brake systems.
The orbiting scroll is coupled to the crankshaft and orbits, rather than rotates.
The orbiting motion creates a series of gas pockets traveling between the two
scrolls. On the outer portion of the scrolls, the pockets draw in gas, and then
move into the center of the scroll, where the gas is discharged. As the gas
moves into the increasingly smaller inner pockets, the temperature and
pressure increase to the desired discharge pressure.
Advantages;
– Very quiet.
– It is very small
– Simple design, not so many parts
– Low maintenance (hardly any)
– Oil-free design
Disadvantages;
– Low capacity (flow, liters/minute or cfpm).
– Relatively expensive
– When the compressor-element fails, there’s a very big chance you just have
to buy a whole new element.
– The compressed air gets very hot! Much hotter than compared to other types
of compressors.