Jun-2015

Continuously improving machinery performance (TIA)

Through regular inspection and selective or continuous monitoring, traditional maintenance measures are intended to uncover damaged valves or signs of wear in rings and packings.

Hikolaus Lubega
Hoerbiger Compression Technology

Article Summary

Maintenance strategies such as these often disregard the fact that process conditions, loads, operating times and the like have changed, and that reciprocating compressors are subject to changing stresses. The REE service is a methodology for analysing improvement potential.

Audit for reciprocating compressors highlights improvement potential
Operators of process equipment today expect broad-based suggestions on how to optimise their plants. The servicing of compressors – in many instances the core component of a plant – is no exception. Processes change during the life cycle of these machines, necessitating adjustments.

Through regular inspection and selective or continuous monitoring, traditional maintenance measures are intended to uncover clogged valves, signs of wear in seals and bearings, or lubrication problems. Maintenance strategies such as these often do not consider that process conditions, loads, or operating times have changed, and that the reciprocating compressor is subject to varying stresses – not to mention using maintenance as a way to optimise the machine to the new requirements.

Compressor specialist Hoerbiger intends to change this. In October 2012 the company created the service offering known as REE: reliability, efficiency, environmental soundness (see Figure 1). Based on the premise that reciprocating compressors are usually critical process components, so that the productivity and profitability of an entire process plant hinges on their reliability and efficiency, the Austrian compressor equipment manufacturer developed a proprietary methodology for analysing improvement potential.

Systematically uncovering improvement potential
The systematic approach has already proven itself in practice. A refinery operator in the Middle East, for example, had 40 reciprocating compressors analysed, resulting in the identification of energy savings potentials of as much as 10% of total power. In detail, the proposal was to improve the operating concept in general, and specifically compressor control. Following an audit of a fertilizer manufacturer, improvements in lubrication and different cylinder liners were suggested, resulting in less debris and oil contaminating the reactor, and hence extended service life for the catalyst.

During a REE audit, meetings are held to determine the ‘DNA’ of a compressor. The DNA of a compressor has several aspects – the best DNA is the optimum combination of process, compressor, components, maintenance strategy, and mode of operation. On site, compressor specialists learn about the design, operating conditions, and condition of the compressors used in the process. A standardised report summarises the evaluation. The report highlights improvement potential, and an index identifies factors that influence reliability, efficiency, and environmental compatibility on a range from zero (out of operation) to 10 (presently the best configuration in the industry). The Index Tool calculates the potential for improvement.

It is not impossible for the goals of an optimisation process to conflict with each other: if availability is all that is important to an operator, this may come at the expense of efficiency. If efficiency is what is maximised, wear may increase. The goal of the benchmark is to highlight and optimise the effects in all three respects, taking the customer’s requests into consideration. Optimum solutions may even guarantee increased efficiency and higher reliability at the same time.

Operator directly defines optimisation goals
The plant operator ultimately personally evaluates and decides which machines and improvements will be tackled. This decision then serves as the basis for an engineering study which outlines specific solutions and their return on investment. Recommendations range from performance upgrades, through adapting the compressor design to new process conditions, to optimising the entire compressor fleet.

Tools that the specialists have at their disposal include software programs for compressor simulation, and methods for checking the impact of gas pulsations and torsional vibration. In its mission, Hoerbiger draws on data gained over decades of development work, such as information about flow conditions in cylinders and through valves, and the distribution of forces and tribological effects on rings and packings. The database captures the wealth of knowledge gained from more than 55 000 installed compressors.

Even decades-old compressor installations actually never need new machines; instead, a custom upgrade can deliver a considerable increase in reliability and efficiency. This is important, since replacing compressors while plants are operating is not just about investment costs, but also brings issues of safety and time. An upgrade can generally be completed much more quickly than a replacement. REE is designed to boost the compressor’s added value to the operator’s business model, while establishing a continuous improvement process. This is the only way to keep compressors up-to-date, regardless of maintenance measures.   

This short case study originally appeared in PTQ's Technology In Action feature - Q3 2015 issue.
For more information: nikolaus.lubega@hoerbiger.com