Today I will write about one topic that has taking my time quite a lot, that is reciprocating compressor (for upstream natural gas industry). I get introduced to this beautiful machine in 2006 when I was still a graduate engineer trainee. Now I have involved in 11 reciprocating gas compressors installation and once oversee the operation of 34 recips in Sumatra (total > 26,300 BHP).
So what is reciprocating gas compressors? It is a positive displacement type of compressor, which has pistons and cylinders. Its piston moves back and forth. When it moves back it draws gas into cylinder, and when it moves forward it compresses the gas. It has special valves that open and close using pressure differential and spring mechanism.
The piston moves by a push and pull from a rod, named piston rod. Piston rod moves axially, one of its ends is attached to the piston while the other end attached to crosshead. The crosshead has sliding movement. It is driven by a rod, named connecting rod. The connecting rod is a rod connecting the crosshead and crankshaft. Unlike the piston rod, connecting rod doesn’t move axially. It translates rotating movement of the crankshaft to axial move in the crosshead. The crankshaft itself is a massive metal. It turns by a driver, usually a gas engine or an electric motor.
Here are some pictures to help you understand the mechanism (from Ariel compressor):
Below is two pictures of complete package (both from Conpacksys), showing not only the compressor, but also the driver. First picture is natural gas engine driven and second is electric motor driven.
Here is a better picture of crankshaft, just to give an idea of how massive the metal is (Nuovo Pignone compressor):
Here is my plan for the next writing regarding recips:
- Thermodynamics of Reciprocating Compressor & Sizing
- Standard and Codes (API 618, API 11P, ISO 13631, ANSI NGV 4.8 (CNG)), manufacturers and packagers
- Lubrication, air cooled exchangers and Installation
So stay tuned!