Problems Associated with the Use of Glycols

The operational duties of these smaller boiler systems vary widely, and for HW closed-loop heating systems, where the boiler is periodically offline, or in indirect heating systems where pipework, valves, or final heating units are exposed to chilly winds or icy conditions, some boiler winterization may be necessary. This is usually provided by replacing some of the water with glycols or other heat transfer fluids. 

Typically, the level of glycol required in a HW heating system is only 15 to 25% v/v or so (less than the 35 15% usually employed in cold and chilled-water closed-loop systems). Where glycols are added, the system must be cleaned and flushed first. The system can be partly drained to accommodate the volume of 100% glycol required or alternatively filled with a prediluted mix. If a 20% v/v strength is required, 25% v/v should be specified to allow for inaccuracies in mixing. 

NOTE Glycol selection should also take into account the risk of leaks to the environment and the ultimate safe disposal of the material. Propylene glycol is a safer alternative to ethylene glycol because of its very low mammalian toxicity. 

Where pH levels have dropped below 7.0 due to glycol degradation, there is usually little alternative but to drain, flush, repassivate, and refill with a new inhibited glycol solution. 

3 PROBLEMS OF CORROSION IN HOT WATER AND LOW-PR5ESSURE STEAM HEATING SYSTEMS 

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