The banning of R11 forced engineers to look again at methods for flushing a system. Advanced Engineering technical director Colin Pratt warns against the temptation to cut corners.
BACK when the use of R11 refrigerant was banned, the last problem on the minds of most acr engineers was what they'd use instead when flushing systems.

After all, although R11 was cheap, readily available and easy to use, it had never really been an ideal solution. Because it was extracted as vapour, physical debris like swarf, sludge and carbon deposits were left behind - with the potential to block capillaries and damage the compressor upon recommissioning.

More to the point, though, was that it was very rare to ever need to flush a system. As a precaution against contamination when replacing a burnt-out compressor, perhaps, but not a job you'd perform on a regular basis.

Now, though, the phase-out of R22 and other HCFCs means engineers will increasingly be asked to retrofit existing pipework with new refrigerants. And that translates to an awful lot of flushing between now and 1st January 2015. But what should they use?
'More and more engineers are looking around for a suitable way of flushing a system,' says Colin Pratt, technical director at Advnaced Engineering. 'Making the wrong choice could cause real problems; because when flushing goes wrong, it goes badly wrong,' he warns.

Storing up trouble

Flushing can be slow and tricky to do, and it's no surprise that many engineers treat it as a messy, tiresome chore. It's understandably tempting to cut corners, but it's a big risk.
'At Advanced Engineering we have heard of some contractors turning to compressed solvent-flushing canisters as an apparently quick, clean and easy fix.
'These products push a halogenated flushing solvent through a system, using compressed gas. Some tubing is attached to the system to direct the flow, and the flushing agent is forced through the pipework where the liquid halogenated solvent dissolves the oil and pushes the contaminates along.'

So far, so good - and absolutely ideal for very small systems; but in large or commercial settings, you quickly meet problems, as Coiln Pratt explains: 'On longer pipework runs, the liquid flashes off to a vapour, leaving the contaminants and swarf at the evaporation site. Contaminated oil and all kinds of physical debris lurk in long sections of pipe. It can be difficult to remove but then starts to circulate when the system is recommissioned, causing hidden blockages, damaging new components and ultimately causing compressor burnout which, of course, requires more flushing.
'It's the start of a vicious circle, wasting time, money and - most importantly - potentially ruining a client's trust in their contractor's competence.
'Although it is always tempting to save some mess and a few minutes' work where we can, this is one area where cutting that corner is simply not worth the trouble.' Colin Pratt warns.

Liquid assets

With R11 unavailable and compressed solvents unsuitable, the main option open to the engineer flushing a full scale commercial acr system is a low-density, liquid-based solvent.
'Almost without exception, such products can be slower and more complicated to use than the other methods,' says Colin Pratt, candidly. 'But, unlike the others, they really do work.
'As an example, the market leader, Endoflush, is circulated with a flushing pump until the agent fills the entire system. Because the solvent stays as a liquid throughout, it must removed from the system with particular care. Not only does the majority of the liquid flushing agent need to be removed, but the system then needs to be fully purged with nitrogen before recommissioning.
'However, the very fact that it stays as a liquid throughout the process enables Endoflush to not only dissolve tar and oil-based contaminants, but also push the physical debris out of a system of any size, in a way that is impossible with compressed solvent methods.
'So, it can be a time-consuming and tricky process, and it is essential to follow the instructions carefully. But it's universally compatible, CFC-free and - above all - really does get the system clean, and genuinely protects against contamination.'

A professional approach

With time and cost so critical, Colin Pratt admits that it is no wonder that many engineers find it attractive to risk compressed solvent flushing agents in bigger systems than they can really handle.
'The problem is, as flushing grows more widespread, the resulting issues in system reliability could become a question of reputation for acr contractors generally.
'If we are truly professional engineers, then surely we should take the time to get it right first time and - even if it is a little slow and messy - perform a flush that actually works.'

Advanced Engineering
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