INCORPORATING COLD CHAIN
ASSOCIATIONS implemented. He suggested that such sensors are likely more accurate on ambient water systems and for systems that make use of either elevated or lower temperatures must use more appropriate hardware or take into consideration adjustment factors that may need to be applied. Ultimately, he recommended taking samples for external, third-party laboratory analysis, and comparing water analyses from before and after commissioning and use of the system to identify deviations from the baseline setting.
CASE STUDIES
De Waal then introduced the first case study: a stainless-steel plate heat exchanger installed in a temperature control room at a mushroom produce farm. The issue was excessive water accumulation and ingress into the gas refrigerant compressor unit. Upon cutting the complex, multi-plate unit, One Eighty found brown deposits( rust) and significantly expanded internal passages. The root cause was identified as a freezethaw cycle due to faulty control valves and temperature monitoring sensors, which caused volumetric expansion of trapped water, leading to cracking and leaking in the intricate plate design. While corrosion was present, the primary failure was mechanical due to ice expansion, however the presence of corrosion did raise concern of secondary failure mechanisms that could be prevalent in the existing system. Unfortunately, the complex design meant repair was not feasible, necessitating a full replacement and improved temperature control systems to prevent future occurrences.
THE CASE OF THE FAILING CONDENSER / EVAPORATOR UNIT
Another case study involved a condenser / evaporator unit with a carbon steel shell and copper tubing that suffered rapid corrosion and excessive fouling early in its lifespan, producing ' wet rust ' and necessitating the need to isolate several of the gas line tubes, that repeatedly occurred each time the unit was serviced. The initial key finding was that a degraded galvanised manifold and pipe components in the older closed-loop system were leaching iron into the water. This dramatically increased the water ' s electrical conductivity, causing a runaway galvanic corrosion reaction between the carbon steel and copper tubing that flushing couldn ' t remedy.
This issue was rectified by way of replacing the corroded system with similar stainless-steel materials and polymer piping, but the issue of the continuously corroding heat exchanger kept degrading gradually. It was then discovered that the water source, initially led to believe was being treated through sand filtering and pH control means, was from a reservoir meant for agriculture purposes. The water was periodically tested over the span of 10 weeks, whereby the entire water chemistry history was evaluated. The results thereof proved that the water quality was not intended for use in their existing system, due to the excess of multiple, corrosion driving components that combined had corrosive attacked the metallic components of the closed loop system at an accelerated rate.
The core issue was user error, not a design flaw. The client used untreated agriculture water as the source, which contained microbes and elements outside manufacturer specifications. De Waal emphasised that available water isn ' t always suitable for heat
exchangers, especially closed-loop systems requiring specific water chemistry.
“ I stress the importance of providing clear guidelines and instructions to endusers, especially those operating equipment like wine chillers or cool rooms. It ' s crucial that if the equipment is run outside of the manufacturer ' s or contractor ' s recommended specifications, the end-user assumes responsibility for any failures. This is why I believe service providers need to ensure their clients are fully informed and strictly adhere to operational guidelines, which includes performing regular maintenance to catch issues before they get out of hand,” he said.
A key takeaway from this case was the limitation of relying solely on pH monitoring and basic media filtering systems. While the system ' s pH was consistently within the acceptable range, the electrical conductivity was significantly elevated, a critical indicator that was initially overlooked due to the lack of information provided by the client. This demonstrates that pH is only one piece of the puzzle; a comprehensive water analysis, including electrical conductivity and other aggressive ions like chlorides and sulphates, is vital for predicting and preventing corrosion. The discussion also touched on the challenges of operating in remote sites with limited water options. While simply using available corrosive water is detrimental, solutions exist. In such cases, on-site water treatment systems( though potentially expensive and complex, involving filtration and flocculation) or transporting pre-treated, sealed water in reservoirs for the closedloop system are viable alternatives to prevent long-term damage.
THE CASE OF THE LEAKING JACKET
De Waal presented a final case study of a jacketed mixing tank with severe leakage from its stud welds, leading to disintegrated thermal insulation and operational issues relating to temperature control of the product. Analysis, including microscopic examination, confirmed widespread stress corrosion cracking( SCC) along the jacket wall, particularly near welds, with the classic ' lightning struck ' pattern in the microstructure.
While the stainless steel 316L inner vessel and 304L outer jacket combination is commonly used in the fabrication industry, it ' s susceptible to SCC under specific conditions. The critical factor here was extremely poor water quality sourced from municipal feeds, high in total dissolved solids, chlorides and bicarbonates. This corrosive water, combined with existing manufacturing induced stress, created an ideal environment for chloride pitting and widespread SCC, which worsened as system pressure increased to compensate for leaks and temperature losses.
Additionally, a‘ rainbow pattern’ on external weld sides indicated incomplete pickling and passivation, leaving localised regions vulnerable to corrosive attack due to the lack of the stainless steel’ s protective oxide layer. The key indicators that were noted for this case study was the difficulty of access for postweld cleaning of the stud welds, especially if insulating material became wet and degraded, which inevitably created hidden corrosion hotspots. The presence of zinc oxides also suggested upstream or downstream galvanised piping, though this could not be confirmed at the time. CLA
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