CHALLENGES

The Analyzer Team has received a custom design ---Shell and Tube heat exchanger. The pack is designed to take a load of over – for --- and --- systems. This high load demand caused big size -- and operating temperatures and pressure caused high thermal stress. Due to pump mounting on same structure caused heavy vaibration load and structural integrity issues. Since the Heat exchanger is rectangular and a custom design, not much benchmarking currently exists to optimized the heat exchanger system. Apart from that heavy wind, cyclic pressure and Seismic loads make the problem very complex. The Analyzer Team has used ANSYS software to simulate linear ,noliner analysis and optimize the structure of Heat Exchanger. The Analyzer Team simulated the static ,dynamic and thermal load of the Heat Exchanger for operating condition and ensured acceptable stress in Heat Exchanger system. This will ensure strructral integrity throughout the life of the Heat Exchanger.

THE SOLUTION

The initial procedure for analyzing the design included identifying complex loading, defining the material alloys of the various components , fluids, and highlighting the important factors of the ASME design code. Reason of complex loading is various other system like pumps, blower, boiler mounted on same structure or tranfering vibration to HX.  After identifying the critical factors the simulation was then run through the Static analysis. Flow & thermal analysis of the heat exchanger was executed for temperature field mapping. Appropriate frequencies are found with model analysis and study of different vibration source. seismic, Wind, Linear, Non linear, FRF analysis results in material optimization and identifying weak areas. Fatigue anlalysis was done to predict the life of HX for pressure loading and appropriate modifications made for increasing the life. This has reduced stress in critical areas, optimized material for Exchanger and CFD analysis helped in redesigning the Heat Exchanger system and to reduces the size and weight of the heat exchanger.

BENEFITS

• Material
• Life of component

PROBLEM STATEMENT

A well-known engineering company involved in energy and environment got a requirement of optimizing its cooling tower structural components along with resolving its noise and vibration issues. Current design was a frame made up of I beams which was used to support a fan weighing about 1 tonne and Motor gearbox weighing another 2 tonnes. Client had extracted field data of vibration (velocities and displacements) for a existing installation of such frame in a working cooling tower. This data was used as benchmark for developing a new optimized design. At analyzer we used this field data to validate our FEA model of the existing system. As this structure was part of bigger assembly of cooling tower we adjusted different parameters in the FEA model to tune the model with field data.

CHALLENGES

The Frame structure was subjected to simultaneous vibratory forces at different frequencies. Doing a transient dynamic analysis to capture all the loads was time consuming owing to high range of frequencies. We worked out a faster option of combining various harmonic analysis at different frequencies and accordingly validated the model. Since the operating frequency of Fan was very much near to the natural frequencies of fan forced response analysis was conducted on validated model for new optimized frame. ISO 1940 was followed to calculate dynamic excitation forces due to Motors ,Fan and gear box as per balancing grade of the same.

RESULTS

TThe weight of the Frame structure was reduced by about 30% with a better estimated NVH characteristics than that of the original frame by using analysis based design modifications.

Other Projects Executed In analysis of Structures (for details please contact us).

Nose and Vibration Analysis

• Static & Dynamic Analysis of Centrifuge support structure for chemical industry
• Dynamic & Seismic Analysis of Pumps Motor systems support
• Troubleshooting of excessive vibrations in paint emulsifier unit
• Root Cause Analysis of Fuel filter mounting Bracket failure
• Buckling Analysis of Vertical support structure for process vessel
• Lifting Analysis of pressure vessel & big Shelters for BEL