It is important to complete a thorough survey of a closed system. You will need to know the volume (or at least a good approximation), the metallurgy, any known problems eg: leaks, corrosion, scale etc.
Usually a closed system will be one of the following – LTHW (low temperature hot water), HTHW (high temperature hot water) or some sort of Chilled system.
Metallurgy and Corrosion
Most products will contain corrosion inhibition for steel and yellow metal, but you should always ask if there is any aluminium present in the system to be treated. Aluminium is difficult to protect as it is amphoteric and will corrode at pH levels above 8.9. It is advisable to keep the system pH around 8.
Chemiteq has a number of inhibitors for hard and soft waters but monitoring should be a key tool, especially where corrosion will be the main issue. This will be in the majority of cases.
Wouldn’t it be good to go to a customer site and know that the chemical you are using is actually working, rather than just relying on inhibitor testing? Shouldn’t you consider adding corrosion coupons to the system so that you can inspect these, and gain the confidence that the metals inside this closed system are being protected? A mild steel coupon should be the minimum requirement, but you could also consider aluminium and copper perhaps. It is usual for such coupons to be inserted on rods into a “bypass rig” (capable of isolation), taking water from the pressure side of a system and returning to the “non pressure” side. These rigs are usually made of mild steel or UPVC and will house up to 4 coupons.
If this is considered to be too complicated, then what about finding a flow tank within the system where you could place some coupons on plastic wire? Remember that this might not be the ideal place because the highest levels of corrosion will be where the highest heat load resides. However, it is very simple to look at your coupon on each visit, take a photo record and show your customer.
If inhibitor and pH levels are in specification then your coupon should be in good condition. If the coupon is showing signs of wear, then at least you can start to troubleshoot what might be wrong with the system and not have your customer tell you he has a failed piece of equipment.
Chemiteq have a wide range of treatment chemicals for closed systems. You will find these under “Closed System Treatments” on the “Products” tab. Our formulations are for use in systems containing aluminium and for multi-metal systems not including aluminium. Cleaning and flushing agents should be considered for use in new systems or “re-commissioned” systems and where appropriate, a suitable biocide may need to be added.
Remember we are always here to offer you the best advice on what chemical to use. Please call us or drop us an email and we’ll get back to you to discuss your requirements.