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Fatigue analysis of helical suspension springs for reciprocating compressors.

Number: pap. n. C2, 1298

Author(s) : BORTOLI M. G. D. de, BOSCO R. Jr, PUFF R.

Summary

The helical suspension spring system has a significant importance on the operation of hermetic compressors, considering the aspects of noise and vibration. Another important point to consider is that, in the moments of start/stop, the internal components (mainly crankcase) must not hit against the housing. In this case, the interaction with the stoppers is very important. Normally a balance between vibration and displacement is aimed through the stiffness of the spring. An increase of the spring stiffness will reduce the kit displacement, but it will increase the transmitted vibration, and vice-versa. Other than the functional aspect mentioned above, the suspension springs must be designed for reliability. The major loading on the springs happens during the compressor start/stop time causing an oscillatory displacement. In this way, the springs must be designed to support the fatigue process where there is a mean load due the kit weight, and an alternative load due to the lateral/torsional motion of the kit. Compressors suspension are usually evaluated at 500,000 cycles of start/stop. It is estimated that this number of cycles represents about 10 or 15 years of the compressor life. The approval start/stop tests are performed in special devices, where each cycle needs some time to reflect on the operating conditions of the compressor. These tests can take more than two months to be done, and it is necessary to have a minimum number of samples to estimate the reliability with an acceptable confidence level. In short, the start/stop approval test is expensive and time consuming. Nowadays, with the necessity of launching products as early as possible (shorter time for project development), it is very important to improve the methodology of designing the suspension system. The objective of this work is to present an improved methodology, based on numerical and experimental analysis, to evaluate the fatigue life of the spring suspension system.

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Pages: 8 p.

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Details

  • Original title: Fatigue analysis of helical suspension springs for reciprocating compressors.
  • Record ID : 30001322
  • Languages: English
  • Source: 2010 Purdue Conferences. 20th International Compressor Engineering Conference at Purdue.
  • Publication date: 2010/07/12

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