Spring Vibration Isolation Foundation Design And Dynamic Analysis Of Offshore Platform Compressor System

Currently offshore platform reciprocating compressor design commonly used method of rigid foundation, This design approach by increasing structural rigidity and improve the natural frequency to achieve structural natural frequency away from the excitation force frequency, avoid the occurrence of resonance. However, compressor unit coupled with structural rigidity deck, causing the compressor group dynamic analysis model complexity, the results are not accurate. In this paper, spring vibration isolation method was put forward, namely through the spring vibration isolator to remove compressor rigid coupling with the deck structure, realize the structure natural frequency away from the compressor excitation frequency, avoid the occurrence of resonance. The main contents as follows:1. Based on the finite element theory to establish finite element model of offshore platform compressor system. Completed the spring vibration isolation foundation structure design work. On this basis, according to the principle of vibration isolation, to spring vibration isolator is designed, including the natural frequency of the spring vibration isolator, the calculation of the spring stiffness and damping. Results show that when the spring vibration isolator of the inherent frequency of 3.5 Hz, spring vibration isolator of the vibration isolation efficiency is 95.3%, rigid coupling between compressor and the deck structure are lifted.2. On the basis of the structural static analysis, carried on the modal analysis for spring vibration isolation system, the results show that the first order natural frequency is 2.6046 Hz, far away from 0.8 times the compressor vibration frequency (16.55 Hz); Close to the compressor vibration frequency of the ninth and 10th order frequency avoid the vibration frequency range of plus or minus 10%, ninth order frequency is 14.586 Hz, less than 0.9 times natural frequency of the compressor system; 10th order frequency is 18.233 Hz, greater than 1.1 times natural frequency of the compressor system. Therefore, the design of the compressor vibration of spring vibration isolation system has good vibration features, avoid the occurrence of resonance.3. In order to analysis the vibration response under the excitation force of the compressor spring vibration isolation system,based on modal analysis conducted harmonic response analysis. Calculated three directions speed response on four key points of compressor foundation, analysis of the results showed:In the exciting force of the elastic response is based on the main skid maximum three directions 3.0696 mm/s; The maximum response values of motor base is 1.7843mm/s; maximum response value of the compressor base is 1.831 mm/s; The maximum response value of the second-skid is 11.728 mm/s; It can be seen, the response values of the four key points far below DNV vibration standards, fully verify the reasonableness of the spring vibration isolator design.4. To test vibration isolation effect of vibration isolation foundation and the vibration response of the compressor key positions, test the compressor vibration in the process of operation, the results show that the spring vibration isolation foundation vibration isolation efficiency can reach 80%; Key position vibration velocity peak value completely satisfy the DNV standard specified value.