Abqaiq Plants Fin-Fan Tubes Replacement Project

Introduction

Air Cooled Heat Exchangers also known as Air Fin Cooler or Fin Fan heat exchangers utilizes air as the cooling medium. Fin Fan heat exchangers are typically used in application where water availability is obstacle or the desired process outlet temperature can be achieved given the maximum ambient temperature. Also, they are used extensively throughout the oil and gas industry, under high pressure and high temperature conditions, as well as corrosive fluids and environments. The existing Fin Fan heat exchanger are specialized and are normally configured as an A-frame or roof type. Team has decided to replace these existing Fin Fan heat exchanger tube cells due to repetitive failures and leaks.

Problem Identification

The integrity of the equipment decreases with the increase in its age. Consequently, operating cost and repair cost increase. In such cases the replacement of an old item with new one is economically worthwhile. The issues encountered in existing Fin Fan heat exchangers are:

• Repetitive tube failure as the material of construction is not compatible with the operating environment

• The existing type with welded tubes is not commonly available in the market

• The existing type with welded tubes can handle only 11,400 PSI allowable stress at 350 F while seamless Tubes can handle 13,400 PSI allowable Stress at 350 F

Fin-Fan Tubes Assessment:

Based on Engineering Economics Replacement Analysis considering the mean time between failure, maintenance and repair cost and production loss cost, the study reveals that Fin-Fan Tubes replacement is the optimum solution in terms of reliability, cooling efficiency and cost. The methodology adopted to proceed with the tube replacement is:

• Identifying the required upgraded material specifications as per engineering standard to increase equipment reliability and cooling efficiency

• In consequence, material procurement along with technical evaluation ensuring that new Fin-Fan tube bundle fit in place with minor modification

• Receiving material and verification prior the plan of replacement

• Aligning the replacement plan to be within planned Turnaround and Inspection (T&I) outage with the objective of minimizing production loss

New Fin Fan Tube Cells
As part of Abqaiq Plants adoption for the latest technologies that increase plant reliability and overcome obsolescence and equipment chronic issues, total of 12 out of 16 tube cells have been upgraded to alloy 825 and successfully installed. The replacement was completed in-house through aligning the activities to be during the Turnaround & Inspection shutdown window to optimize the plant’s operation and the activities performed are:

• Blots removal including cutting stuck bolts due to equipment aging

• Old tube cells removal through utilizing 200 Ton crane

• New tube cells alignment including drilling holes for new bolts if required

• New tube cells installation

Conclusion
These upgrades enhanced the Abqaiq Plants Fin Fan heat exchanger reliability and efficiency through reducing tube failures. Also, the down time of Turnaround & Inspection has been reduced by 20%. This replacement is part of Abqaiq Plants roadmap to overcome Fin Fan heat exchanger chronic issues and material obsolescence, also enhance equipment reliability, increase mean time between failure and decrease the mean time to repair in addition to the maintenance cost.

Author: Mohanned K. Al-Kabour
Organization: APMD / CSG
Email: mohanned.kabour@aramco.com