Working principles of multistage compressors on board ship

• In a single crank, single acting compressor, the low pressure and high pressure pistons are connected in tandem to a single crank.
• In low pressure stage, when the piston moves down, the atmospheric air is inducted.
• The compressor air from the first stage flows to the second stage through the intercooler.
• The pressurized air is inducted into the second stage.
• As the piston moves up, compression takes place in both stages.
• The high pressure air from the second stage is delivered through the after cooler.

• In a single acting, two crank compressors, the low pressure and high pressure pistons are connected to two separate cranks.
• As the low pressure piston moves down, air is inducted through the air filter.
• When it moves up, the air is compressed and delivered to the second stage through the intercooler.
• The air is further compressed in the second stage, and high pressure air is delivered through the after cooler.

• In Double acting arrangement, the low pressure first stage piston is at the top and the high pressure piston is at the bottom.
• In the first stage, as the piston moves up, air is compressed and the compressed air is inducted into the second stage.
• When the piston moves down, the pressurized air is further compressed in the second stage.
• In the meantime, the low pressure stage inducts fresh air from atmosphere through an air filter. In this way, the process in cyclic.

• In three stage compression, the air is inducted at the first stage, compressed, cooled by the intercooler and delivered to the second stage.
• In the second stage, the air is compressed further and delivered to the third stage.
• In the third stage, air is compressed to the required pressure and delivered through an aftercooler.
• When the piston moves up, air is compressed in the first and third stages, whereas air from the first stage is inducted into the second stage.