Air Compressor Reliability Analysis

By: Dr. Marco Mucino, Alan Ranger

Compression issues increase costs and decrease production

Whitecastle Engineering Ltd (WEL) were recently contracted to undertake a reliability review of air compression issues on an Ethylene Plant in the UK. Continuing problems with the onsite compressors had led to an over reliance upon temporary rented mobile compression units and the situation was only getting worse as down time on the on-site compression packages became ever longer and more regular. WEL reviewed performance data, maintenance records, design data and specifications and conducted specialist thermal modelling and simulations of heat exchanger within the package.

Compressor Issues Identified

Following our review we were able to ascertain that the situation had been caused by a number of differing factors that had come together to cause this out of control state of events, key identified areas of concern that were in need of corrective action were:

The reliance on the OEM to drive the maintenance plan and, indirectly, the risk assessment of their assets generated a vacuum of on-site expertise and resources that had a knock-on effect on the assets reliability and availability.

Negative Cost Implications

This situation had a negative effect on the cost of ownership due to the repeated hire of temporary air compression units to cover downtime of site machinery.

Problems Identified

The reliability of the compressors was mainly affected by considerable compressor screw element performance degradation caused by water ingress and heat exchanger integrity failure and performance degradation caused by the cooling water subsystem undesirable off-design operation. These two caused among several other factors were discovered to be responsible for the regular failure cycle.

Life Time Cycle Cost Reduction

WEL produced a report that outlined a series of corrective actions and defined the available technical alternatives for the optimisation of the system with input from various vendors and then conducted a feasibility analysis to evaluate the technical and economic merits of each option and recommend the preferred solution that would reduce the risk of plant shutdown due to failure of the air compression system by Increasing the reliability and availability of the system and ultimately reducing life time cycle costs.