The inertial unbalanced forces and couple are calculated for reciprocating compressor units (integrals or separable) yielding maximum horizontal and vertical forces and couples corresponding to the primary and secondary compressor order frequencies. These forces and couples are required to adequately design the foundation and anchoring system for each compressor unit. Balanced or better balanced reciprocating compressor units are desirable to reduce vibration levels, to minimize long term maintenance and to reduce the frequency of re-grouting.
The primary inertial forces and couples are due to rotating masses (crankshaft throw weights, portion of connecting rods and crankshaft counterweights) and reciprocating masses (portion of connecting rods, crossheads, crossweight balance weights and compressor/scavenging piston assemblies) acting in the direction of the center-of-gravity of the crankshaft and at the frequencies of the crankshaft speed. The secondary inertial forces and couples are due only to the reciprocating masses (portion of connecting rods, crossheads, crosshead balance weights and compressor/scavenging piston assemblies) acting in the line of piston travel.
MLB Engineers' design approach objectives are as follows:
To utilize existing, rearrange existing and/or modify existing crankshaft counterweights to improve the unbalanced characteristics of the compressor unit(s) under study with adjustment of any reciprocating weights such as heavier or lighter crossheads/crosshead shoes, crosshead balance weights/nuts and piston assembly weights.
If satisfactory balance cannot be achieved with existing weights and/or modified existing weights, then new crankshaft counterweights and/or crosshead balance weights are designed.
Provide calculated levels of inertial forces and couples for the existing and proposed crankshaft weight systems with design sketches for any new crankshaft counterweights to be located or manufactured.
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