Asset reliability
Closed-loop and cooling tower management: two systems, two chemistries
Most sites run both an open cooling tower and closed recirculating loops — and they fail in opposite ways. Prosep manages both, each on the chemistry and monitoring discipline it actually needs.
Most sites run both kinds of cooling system, and treat them as if they were one. An open evaporative cooling tower loses water to evaporation, concentrates dissolved solids, and breathes in dust and microbes from the air. A closed recirculating loop does none of that — which is exactly why it gets ignored until it corrodes from the inside.
The two systems fail in opposite ways and need different programmes. Treating both with the same approach guarantees one of them is wrong. Open towers run on the scale, corrosion and microbiological control covered by our cooling water treatment programmes. Closed loops need their own chemistry and their own monitoring discipline — and that is what gets neglected.
The programme
What a Prosep management programme covers
Open and closed circuits each get the chemistry they need, monitored and reported by one team on the same visits.
Closed-loop chemistry
Corrosion inhibitor programmes matched to the loop metallurgy and the make-up water, with the inhibitor reserve monitored and maintained — not dosed once at commissioning and forgotten.
Glycol systems
For chilled, process and low-temperature loops, glycol condition is monitored, inhibitor packages are maintained, and degraded glycol is identified before it turns the loop acidic.
Microbiological control
Closed loops grow biofilm in their stagnant zones. The programme includes microbial monitoring and control appropriate to a closed system.
Cooling tower optimisation
On the open side, cycles of concentration are pushed as high as the chemistry safely allows, scale is held against a measured saturation index, and corrosion and microbiological risk including Legionella are managed.
Monitoring & reporting
Across both system types our engineers sample, dose, monitor, report, and come back — the reserve that was holding, the glycol that was degrading, the cycle that drifted, caught on a visit and written into a report.
Who needs both managed
One survey, both systems, one team
Any site with chilled water plant alongside evaporative cooling needs both managed: data centres running closed-loop precision cooling, food and beverage plants with refrigeration and process cooling, and most large commercial and industrial HVAC installations.
The connecting principle is on how we work: assess each system on its own terms, then run both to stated targets. Legionella on the open side is covered in depth on our Legionella control page.
Related
Where this connects
Cooling water treatment
The open-circuit scale, corrosion and microbiological programme.
Related serviceLegionella control
SANS 893 risk control on the evaporative side.
Related serviceData centres
Closed-loop precision cooling where uptime depends on the water.
Sector pageBuilding HVAC
Closed-loop and tower management for commercial buildings.
Sector pageStandards we work to
On the open side the programme manages Legionella risk to the principles of SANS 893, covered on our Legionella control page. The engagement is the one on how we work: survey what you run, open and closed, then run both to stated targets.
- SANS 893 — Legionella control (principles)
FAQ
Closed-loop & cooling tower questions
Closed loops are sealed, so why do they need treatment?
Because they are not truly sealed. Make-up water introduces oxygen and hardness, glycol degrades and turns acidic, inhibitor depletes, and biofilm establishes in stagnant zones. The result is internal corrosion that fouls exchangers and seizes valves. A maintained inhibitor reserve and routine monitoring prevent a slow, expensive internal failure.
How is a closed-loop programme different from cooling tower treatment?
An open tower concentrates dissolved solids through evaporation and takes in airborne contamination, so it needs scale, corrosion and microbiological control with managed cycles of concentration. A closed loop holds a near-constant water volume, so it needs a maintained inhibitor reserve, glycol management and microbial control. Same site, different chemistry.
How do I know if my glycol system is degrading?
By testing it. Glycol breaks down over time and the degradation products turn the loop acidic and corrosive. Monitoring glycol condition and inhibitor level catches this before it damages the system, which is why it is part of the management programme rather than a once-off check.
Can you manage both our towers and our closed loops under one programme?
Yes, and that is the sensible arrangement. Both are surveyed, each gets the chemistry it needs, and both are monitored and reported by the same team on the same visits, so nothing falls between two suppliers.
Start with a system survey.
A survey of what you run — open and closed — and what each is actually dosed with usually finds at least one neglected loop.