HYDRAULIC OIL COOLERS

Heat kills hydraulic systems. That’s why hydraulic oil coolers are widely used in a diverse range of agricultural, mobile, manufacturing, and industrial settings. They remove excess heat generated by energy losses in a system, high ambient temperatures and other external sources such as engines, furnaces, and even the surrounding environment.

In fact, coolers are often essential for designing temperature-optimized hydraulic systems that keep oil temperatures within their optimum working range.

A Hydraulic Oil Cooler is quite simply a device used for the cooling of Hydraulic Oil, usually in Hydraulic Power Packs but they can also be used on Power Washers, Engines and almost anything where there is hot oil to be cooled. Some equipment manufacturers use and Air Cooled heat exchanger if their equipment is mobile, some will use a brazed plate heat exchanger but many choose to use a traditional shell and tube oil cooler instead.

In fact, coolers are often essential for designing temperature-optimized hydraulic systems that keep oil temperatures within a limited range. Such circuits are basic prerequisites for cost-efficient operation, as they provide a number of performance, economic, and environmental benefits. These include:

•  Maintaining the correct temperature keeps oil at its recommended viscosity, ensuring mechanical components are properly lubricated and hydraulic devices run at peak efficiency. Letting oil temperature rise beyond recommended limits can reduce the life of a system due to poor lubrication, higher internal leakage, a higher risk of cavitation, and damaged components.
•  Keeping temperatures down also helps ensure the oil and other components last longer. Excess heat can degrade hydraulic oil, form harmful varnish on component surfaces, and deteriorate rubber and elastomeric seals.
•  Operating within recommended temperature ranges increases a hydraulic system’s availability and efficiency, improving equipment productivity.
•  Finally, with more machine uptime and fewer shutdowns, it reduces service and repair costs.

Considering the benefits coolers offer, it’s apparent that accurately sizing them is a paramount concern for design engineers. Undersizing obviously allows higher-than-recommended oil temperatures. But oversizing hurts system efficiency as well, by reducing temperatures below the recommended range and increasing costs with a larger-than-necessary purchase. Here are some tips on selecting the right type and size cooler for a specific application.

Some benefits of using Hydraulic Oil Coolers include:

Considering the benefits coolers offer, it’s apparent that accurately sizing them is a paramount concern for design engineers. Undersizing obviously allows higher-than-recommended oil temperatures. But oversizing hurts system efficiency as well, by reducing temperatures below the recommended range and increasing costs with a larger-than-necessary purchase. Here are some tips on selecting the right type and size cooler for a specific application.

Oil cooling fan helps cool application oil in hydraulic power

Cooler options

Several different types of coolers are suitable for hydraulic systems, with air and water cooled being the most common.

Air-cooled systems dissipate heat with flowing air. This type of cooler operates by forcing cold air over hot fluid inside a heat exchanger’s coil or core. Low running cost and simple maintenance are attractive benefits of air-cooled systems. They also eliminate water-contamination problems and minimize corrosion. Additionally, heat generated from air-cooled systems can be used for other purposes.

On the downside, the upfront expense of an air-cooled system exceeds that of a water-cooled unit. Air-based versions are also larger and generate more noise, so they can degrade the work environment. What’s more, these coolers require ventilation and clean air, and variations in ambient temperature can greatly affect cooling capacity — making steady-state operation more difficult to maintain.

Water-cooled systems use cold water to remove heat, with hot and cold fluids separated by a barrier. Compared to air-cooled systems of equivalent capacity, water-cooled systems have lower up-front costs. They’re also quiet, compact, and do not alter the surrounding ambient temperature. Variations in air temperature have little or no effect on cooling capacity, which allows for greater consistency. Meanwhile, the system’s heated water can be used for other on-site purposes.

Although water-cooled coolers cost less, they generally require clean water. Continuously running water can be expensive, leading to higher operating costs. Other concerns include risk of corrosion and erosion, and increased maintenance. Water-cooled units can also freeze in cold weather, letting water contaminate the oil.

Other cooler types include refrigerated chillers and evaporative cooling towers. In all instances, engineers should first choose the most appropriate type, and then size the unit for the specific application.

Application data

After selecting the type of cooler, the next step is assembling pertinent application data such as maximum system temperature, type of fluid to be cooled, fluid-flow rate, maximum allowable pressure drop of the cooled fluid, and the heat load.

Determining heat load is essential. Many users assume an efficiency for their system, and then derive the heat load. For example, if operating under the premise that a system is 70% efficient, one can assume the remaining 30% of input power is the heat load. Estimating an overall system efficiency produces a heat load figure, but calculating heat load is generally more accurate.

Additional factors

In addition to the above considerations, other application factors are also important. When opting for air-cooled hardware, be aware of altitude, maximum ambient air temperature, and the type of motor driving the fan. Ac, dc, and hydraulic motors are all suitable.

Reliability

Shell and Tube Oil Coolers are simple, with no moving parts and a long established design. This makes for a reliable product but Thermex and Asa have taken it further by introducing a floating tube stack, allowing for Thermal Expansion to occur without putting stress on other components

Performance

Hydraulic Oil Coolers are flexible, this means a choice of connections for our customers but also greater possibilities for our designers to get the most out of our oil coolers. We can do this by increasing or decreasing the number of baffles (which direct the oil flow over the tubes) and changing the number of passes through the tubes keeping the Oil Cooler we select a compact and efficient design.

Ease of Service

One of the biggest benefits of our Hydraulic Oil Coolers is that they are very easy to service. By removing the 4 cap-screws on each end of the cooler you can access any component and change seals, headers or the tube stack without the need for any additional tools. A regular maintenance programme can help an Oil Cooler to remain in operation for over 20 years.

How to Select and Size Hydraulic-Oil Coolers

Air Cooled Heat Exchangers are a type of heat exchanger design commonly used in mobile applications where a liquid coolant supply isn't available such as automotive and construction vehicles. As the name suggests, air cooled heat exchangers provide a cooling solution for fluids using air which is driven through a fin core by an electrical, hydraulic or mechanically driven fan. Air Cooled Heat Exchangers can be supplied to cool a single fluid, such as engine water, or a combination of fluids as part of a cooling pack which can often include 3 fluid circuits cooled by a single fan.

Design of Air Cooled Heat Exchangers and Oil Coolers ensures the most efficient and cost effective heat exchanger solution is always provided. From raw data Manufacturer can design and produce a range of custom-built air cooled heat exchangers for a multitude of applications and operational conditions including

Primary features and benefits include:

• Aluminium plate and bar construction
• Over 200 fin surfaces available including louvered and low-clog options
• All designs are application specific, ensuring efficient and cost effective design
• Minimum batch size of 10 units
• Over 10 years of experience in schedule management and stock management, ideal for large scheduled business.

Selecting a hydraulic oil coolers

Given the necessary data, engineers can then turn to sizing. Coolers can be sized using software programs or by interpolating graphs, both of which are available from cooler manufacturers. Software offers the simplest and quickest solution. Users need only enter the recorded data into the proper fields, letting the software calculate the optimal size.

The heat-rejection capacity of a cooler varies based on the type of fluid, fluid flow rate, difference between the two fluid temperatures, and other factors. Graphs typically express heat load versus fluid flow rate at a given set of conditions.

Often when interpolating graphs, engineers must apply correction factors for parameters like oil viscosity, altitude (for air-cooled), motor frequency (for air-cooled with ac motor) and oil-to-water ratio (for water-cooled without individual curves for various oil-to-water ratios). There may be safety factors to consider as well.

Hydraulic oil coolers images

ASA Hydraulik Hydraulic oil coolers 

COOLBIT hydraulic oil coolers