HYDRAULICS 22 HYDRAULICS & PNEUMATICS September 2025 www.hpmag.co.uk The hidden factor in hydraulic heat exchanger performance In cooling and heating applications, pipework is far more than a simple link between equipment and process. It plays a central role in performance, efficiency, and reliability. For temporary hire equipment, selecting the right pipework is especially important — as is knowing the right questions to ask your supplier. In permanent installations, pipework is designed to meet the plant’s exact specifications. Temporary systems, however, often involve different fluids, operating pressures, and the need for rapid installation and removal. In such cases, unsuitable pipe size, material, or layout can reduce efficiency, increase operating costs, and risk unplanned downtime. In process temperature control, the choice of pipework has a direct impact on system performance. The wrong specification can lead to a range of problems. Compatibility issues are common, especially when connecting to a hired system. Compatibility and performance Process media such as oils, solvents, or other thermal fluids may previously have been cooled with refrigerant-based systems. When these are linked to hire units, which typically use water or water–glycol mixtures and may feature different heat exchangers, material compatibility requires careful consideration. Different fluids can react with certain pipe materials and fittings, potentially leading to leaks, failures, or unsafe operation. Additionally, the heat transfer rates between varying fluids and heat exchangers should be taken into account. Incorrect pipe sizing, application, or valve arrangement can compromise the guaranteed cooling or heating output, putting both performance and uptime at risk. Getting the basics right When connecting hire chillers or heaters, it is important to think beyond whether the pipework will simply fit. Material must be matched to the working fluid; steel, stainless steel, or certain plastics are typical for water/glycol systems. Sizing matters: undersized pipes cause high pressure drops, while oversized pipes can lead to low velocity, sediment buildup, and air locks. Layout should be as short and direct as possible; every additional bend or metre of pipe increases resistance. Connections — flanged, threaded, or quick-connect — must be leak-tight and compatible with both the hire equipment and site infrastructure. Insulation is essential in longer-term hires to minimise energy loss and reduce condensation, which can lead to slip hazards and water ingress into electrical systems. Because these are temporary installations, they should also be designed for rapid assembly and dismantling. Flow velocity Flow velocity is another key parameter. High velocity can cause turbulent flow, water hammer, noisy pipework, and cavitation — all of which accelerate internal corrosion and shorten equipment life. Doubling velocity above the recommended limit can even triple erosion rates. If velocity is too low, the risks shift: poor heat transfer, sediment build-up, freezing in cold climates, and reduced chiller efficiency by 10–15%. Low velocity also makes it harder to purge air, raising the chance of airlocks. In ferrous systems, slowmoving or stagnant water can promote internal corrosion, even with inhibitors in place. Flow rate is equally critical. Low flow reduces temperature control accuracy and increases energy use per unit of cooling. Excessive flow can exceed chiller design limits, trigger alarms, or demand more pump energy. In hydraulic systems, efficient heat exchange depends not only on the cooler itself but also on the pipework that connects it. Incorrect pipe sizing, material choice, or layout can undermine cooling performance, increase energy use, and even risk system failure. This article explores why pipework design is critical in process temperature control and how it directly affects the efficiency and reliability of hydraulic heat exchangers, especially in temporary hire applications.
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