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Ensuring optimal performance and longevity relies heavily on maintaining appropriate operating temperatures. Emmegi hydraulic oil coolers, are renowned for their efficiency and reliability in dissipating excess heat generated during hydraulic operations. In this article we delve into the critical task of sizing the correct hydraulic oil cooler, a crucial step in ensuring seamless functionality and preventing potential system failures.
Overheating ranks second on the list of most prevalent issues in hydraulic equipment, with leaks being the top concern. While hydraulic systems offer numerous advantages as a means of power transmission, optimal efficiency isn't one of them.
Efficiency Levels
Consider the following efficiency levels: a single-reduction gearbox boasts an efficiency of 98 to 99 percent, a double-reduction one stands at 96 to 97 percent, and a triple-reduction gearbox is about 95 percent efficient. Even a well-maintained chain drive exhibits an efficiency of 97 to 98 percent.
Now, let's talk about high-performance piston pumps, which achieve an efficiency of 92 percent. If such a pump drives a piston motor, the overall efficiency of this hydraulic drive drops to 85 percent (0.92 x 0.92 x 100 = 85), without accounting for losses through valves and conductors.
Equally important is the fact that a gear pump or motor, when in good condition, operates at 85 percent efficiency. Thus, a gear pump driving a gear motor reaches a best-case efficiency of 0.85 x 0.85 = 0.72, or 72 percent, not considering losses through valves and conductors.
In summary, these efficiency figures underscore the need for an oil cooler in every hydraulic system with a high, continuous power input (and consequently high output power). An oil cooler ensures stable oil temperatures within acceptable limits.
Key Tips for Sizing a Hydraulic Oil Cooler
1. The initial consideration when sizing a hydraulic oil cooler is the system's continuous input power, measured in kilowatts. It's advisable to work in kilowatts as the input power surrendered as heat roughly equates to the same amount of required heat rejection in kilowatts. This simplifies calculations compared to working with horsepower and BTU/h.For example, if a hydraulic system exhibits a continuous input power of 100kW with an 80 percent efficiency, then 80kW is available for useful work at the output, while 20kW is converted into heat. Therefore, the oil cooler must have the capacity to reject at least 20kW of heat to maintain a stable and acceptable oil temperature.
2. The next consideration is the inherent efficiency of the system, which can be challenging to calculate precisely but can be estimated based on the system type and components used.As mentioned earlier, a piston pump driving a piston motor is approximately 85 percent efficient, while a gear pump driving a gear motor is only about 72 percent efficient. Let's assume both systems have a continuous input power of 100kW and account for additional losses in conductors and valves. In this case, the piston pump/motor system would require a cooler capable of rejecting around 25kW of heat, whereas the gear pump/motor system would need to reject approximately 35kW of heat.These percentages should be adjusted upwards if the system includes an accumulator with substantial storage volume or features servo or proportional valves. In fact, proportional or servo hydraulic systems can sometimes necessitate cooling capacity equal to 50 to 90 percent of the input power. For a 100kW input power, this implies a cooler capable of rejecting between 50 and 90kW of heat.
Final Step
Ultimately, the size of the cooler, expressed as a percentage of input power, often involves some degree of judgment based on the considerations above, ideally with a safety margin. It's preferable for the cooler to be slightly oversized rather than undersized, not only for reliability but also to prevent costly issues. While a larger cooler may entail higher initial costs, it typically proves to be a wise investment in terms of system reliability.
Emmegi offers a range of hydraulic coolers and heat exchangers, including ATEX coolers, marinized coolers, AC and DC fan-driven coolers, hydraulic fan-driven air blast coolers, mobile and offline air-blast cooling units, and water-cooled heat exchangers. For further details, visit [Emmegi's product offerings](insert product link here).
VHS Hydraulic Components is an EMMEGI UK distributor. We supply EMMEGI Air Blast Coolers (12V DC & 24V DC), EMMEGI Mobile-S Air-Oil Coolers (12V & 24V DC) and EMMEGI Air-Oil Coolers (415V AC).
To enquire about the Emmegi range, please contact VHS Hydraulic Components on: 0114 276 4430 / E: info@hydraulic-components.net or visit our website at: https://www.hydraulic-components.net/