PIPEWORK CLEANING
It is no longer sufficient to assume that serious contamination of the system can be corrected at pre- commission cleaning
Minimisation of risk starts with ensuring the system is installed as cleanly as possible
of water under no load conditions, water treatment chemicals may not reach vulnerable areas of the heating system in the summer period or vulnerable areas of the chilled water system pipework in the winter period. Minimisation of risk starts with ensuring
that the system is installed as cleanly as possible and continues through the pressure testing, pre-commission cleaning and commissioning phases to practical completion and handover into normal operation. It is no longer sufficient to assume that serious contamination of the system can
54 CIBSE Journal November 2011
be corrected at pre-commission cleaning; or that the inhibitors and biocides added after pre-commission cleaning will still be present in sufficient concentration at practical completion. Partial draining and refilling the system for remedial works can allow levels of treatment chemicals to fall below their effective concentration, while bacteriological action can remove nitrite, a common inhibitor, within days. Once the chemical protection is compromised, particularly with high dissolved oxygen levels due to the addition of fresh water, then corrosion will follow. Modern materials can also aggravate the
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