These are vertical type reciprocating. In this type of compressor, rider rings and piston rings are not used as in case of horizontal type. In labyrinth piston compressors, an extremely large number of throttling points provide the sealing effect around pistons and piston rods. No contact seals are used. Piston is having labyrinth type piece at the centre called skirt. Cylinder is also
having serration like labyrinths on its inside surface. Piston is not in direct contact with the cylinder and close clearance is maintained in between both. This increases the durability, reliability and availability of the compressor along with its economic operation.
These machines are very popular in the service where total dry operation is required as in case of polypropylene and polyethylene plant. This is unique application where lubricants are not allowed in the cylinders, which is true in case of oxygen compressor, where safety is the most important. It is also employed for applications where the process gas is heavily contaminated with the impurities.
Piston and piston rod are guided by the crosshead and the guide bearing which are located in the oil lubricated crankcase. The oil is supplied by the crankshaft driven lube oil pump
The distance piece separates the gas compressing section from the oil lubricated crankcase. Where process gas can be permitted in the distance piece, then open distance piece type compressors are used. When strict separation of cylinder from the crankcase is essential and at the same time no ambient air is also allowed in the distance piece, then Nitrogen purge is provided. Crankshaft is provided with mechanical seal to prevent the gas leaking in to the atmosphere.
ADVANTAGES:
1. Reliable operation
2. Safe for operation , environment
3. Economical
4. High availability
5. Less floor area is required.
6. As rider rings, piston rings and lubrication is not required the valve life is more.
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