Assessment before replacement

While replacing an outdated compressor with a modern equivalent will, in most cases, result in energy savings, it’s important to conduct an assessment, preferably involving a leak detection survey and a data logging exercise, prior to making the initial investment. Not only will this ensure that optimum savings are realised it could even transpire that a new compressor isn’t actually needed at all.

The importance of checking whether there are any air leaks present in the system cannot be underestimated, as in many companies, in excess of 30% of air generated is wasted through leaks.

The cost of leaks

According to the Carbon Trust, air escaping through a single 3mm hole could cost a business around £700 per year in energy costs. However, a typical compressed air system will have more than just one leak – and for a company using 50m3 of compressed air per minute, it is estimated that the annual savings from fixing leaks would potentially be in the region of £63,000. For larger compressed air users the potential savings are even greater.

The good news is that leaks are simple to identify and rectify, and it is cost effective – the average cost of a Mattei leak detection survey for example, is less than ten percent of the overall leakage costs.

It’s also a good idea to re-evaluate the design of the system at this time, as the layout might need to be altered before a new compressor is installed. This is especially important if machinery or production lines have been relocated. Poorly sized pipework, long distances or an excessive number of bends and fittings will all make a compressor work harder, so can have an impact on its efficiency.

It is obviously crucial to iron these issues out before a new compressor is purchased, to ensure it will work to its optimum ability and that energy savings are fully realised. However, selecting the new machine also requires a great deal of consideration, and manufacturers should offer a system assessment involving data logging.

Benefits of data logging

This evaluates compressed air needs and the efficiency of the system by recording and measuring air consumption profiles over a seven day period. This is usually followed by discussions to identify any unusual patterns or planned process changes.

Obviously data logging only provides a snapshot of compressed air activity but, providing it’s a typical week (although allowances can be made if there are higher or lower demands than usual), it is extremely insightful.

Data logging will also determine whether there are highs and lows in the demand for air, or whether requirements are more constant – and hence whether a variable or a fixed speed compressor is appropriate.

Variable speed compressors have been seen as a key solution for companies looking to reduce their energy consumption and cut the cost of producing compressed air (savings are typically 30% or more). However, they aren’t right for every application. They will only save energy if there are true peaks and troughs in the demand for air. This sounds obvious but it’s surprising how many are installed in workplaces with constant demands.

It’s therefore important to avoid simply replacing like for like, especially if air demands have changed since the last compressor was purchased (perhaps because production has increased or decreased), or things are likely to change in the future. It could even be the case that the equipment wasn’t correctly specified in the first place.

Mattei recently found that one company running a 75kW compressor could actually fulfil its compressed air requirements with a 45kW machine, with estimated savings being in the region of £12,000 a year. This compressor only runs for 50 hours a week, so if a similar situation was found in a plant running 24/7 the savings would be considerably more.

Something else to consider is that when choosing a new compressor it’s important to remember that the initial capital outlay actually makes up a very small part of the total lifetime costs of a compressor. The main cost will always be the energy required to produce the compressed air, so Mattei suggest the decision should be largely based on this factor.

Summary

Advancements in compressor design means that replacing an outdated machine with a modern equivalent will more than likely deliver energy savings. However, if a leak detection survey and data logging isn’t carried out beforehand, the case for replacing the machine might be based on misleading figures, and the investment could prove to be an entirely false economy.