Something that we often hear on industrial sites is that Plant Operators don’t have time or focus to optimise for energy efficiency. It’s not that staff don’t want to run an efficient plant, but that priorities are set by the business are skewed toward reliability, throughput and product quality, and therefore they have little time to think about much else.
Our experience, however, is that running an efficient plant will help to deliver the quality, output and reliability results that Business Owners and Operators are seeking.
To do this, several barriers need to be overcome:
- Multiple optimums: There are multiple ‘optimum’ operating points for plant and equipment
- Operator differences: Operators each have their own way of doing things
- Reliability does not equal efficiency: Some ‘conservative’ equipment set points could be compensating for underlying problems.
Multiple optimums
The concept of multiple optimum operating points is well proven in control theory. Without periodic auditing and bottom-up analysis, your systems could be operating in an over-processing state for years. Under-processing gets picked up by system alarms and product quality checks, whereas over-processing may not cause any ‘headaches’ (except in the accounts department) and so tend to continue unnoticed.
Some techniques we use to assess the current energy efficiency of a process are (i) assess the minimum theoretical energy requirements, (ii) compare current operation to manufacturer recommendations, and (iii) compare current operation to industry best practice. This can highlight the gap in performance, which helps to identify the ‘size of the prize’, and how much effort to spend on further optimisation.
Operator differences
It is well known that Operators have a strong influence over plant performance. Despite the wide-scale application of sophisticated control systems, many choices are still made by humans. One good example is the ability for Operators and maintenance staff to change the sequence in which refrigeration compressors, or air compressors are run. This is a recipe for inefficient operation, even though it won’t be compromising reliability. From a total cost of ownership perspective, the most efficient sequencing should be established based on the characteristics of the installed machines, tested and measured, and then locked in by restricting the ability for people to make changes.
Reliability does not always equate to efficiency
Reliability does not equate to efficiency, and some operating modes can in fact can be hiding underlying problems. Over years of plant operation and staff rotations, original setpoints or operational practises may get lost or changed to compensate for other issues. An example is the compressed air pressure required to run a piece of plant. Most plant needs less than 6 barg to operate reliably, but over the years the supply pressure at the compressors is increased higher and higher to compensate for poor air system design. Rather than fixing the underlying problems, energy is wasted. Higher air pressures reduce system capacity, increase the cost of air leaks, and lifts artificial demand.
Conclusion
Energy efficiency is sometimes about the little things. Optimising existing plant is usually the cheapest energy efficiency project with the greatest return, especially when compared to an upgrade of plant and equipment.
At Northmore Gordon, we work with your staff to fine-tune a range of industrial systems to cut out energy ‘fat’ while maintaining plant reliability and operational efficiency.
Get in touch today to find out what approach is best for you.
