About 70% of the failures that occur in hydraulic applications are oil related, often the result of improper oil selection, or poor oil performance, says energy and petrochemicals company Shell South Africa product application specialist Peter Thorpe.

Thorpe says that in order to fully appreciate the importance of oil selection, one has to understand the role of the components in a hydraulic oil circuit, and their function. A system’s oil reservoir is important as it allows the oil, dirt, and contaminants to settle, and cool. The filter is important, he says, as nonfilter- able oil can lead to pump cavitation, and the control valves have an extremely important role to play as they control volume, pressure, and the direction of the actuators.

The most important properties of the oil are viscosity, filterability, and additive response, as these properties have an effect on the cooling and cleaning of the system, sealing between surfaces, preventing corrosion, and and preventing wear, he says.

High-performance hydraulic oil must be stable, should not degrade, and should be oxidationally, thermally, and hydrolytically stable. If the oil is hydrolytically unstable, sludges will form, and this may affect the system’s control valves. If the oil is thermally unstable, additive precipitation may occur and viscosity will increase, affecting actuator response. If the oil oxid- ises, acids may build up and corrode the system components.

Shell Lubricants Industry marketing specialist Andrew Evans says that Shell has a range of hydraulic oils that are designed for machines that can operate under different operating and environmental conditions. Thorpe says that the com- pany’s Tellus range of oils, which has been in existence for over 50 years, is continuously reviewed, and the Tellus brand was substantially improved about three years ago.

Recently, Shell Tellus T was reformulated. As a result of these enhancements, he says, the oils now have better thermal, oxidation, and hydrolytic stability, improved wear resistance and filterability, while maintaining their traditional strengths of having excellent surface properties, such as air release, resistance to foaming, and demulsibility, as well as maintaining corrosion resistance and elastomer compatability.

Evans says that specific Shell Tellus oils can be selected for a particular application. He adds that the company is constantly working with its customers in demonstrating the value-added qualities that the lubricants can add to the business of a company. Shell Lubricants South Africa has a value-led sales team, comprising industry experts who work with Shell’s customers to identify areas where ‘true value’ can be added, such as upgrading a particular product.

As it is part of a global network, Shell South Africa has wide-ranging access to the latest technical knowledge, and research and development in hydraulic oils. Thorpe says that the relationship between the different Shell regions is reciprocal, with a continuous flow of information among them.

Evans says that there are certain market drivers that Shell considers when developing lubricants and hydraulic oils, such as the latest developments from the original-equipment manufacturers (OEMs), government bodies that may require oils to be more ecofriendly, or have improved biodegradability or worker safety, and end-users that require the total cost of operations to be lowered through benefits such as improved equipment availability, longer equipment life, and reduced down time. Hydraulic oil is widely used and required in many industries, such as mining, agriculture, and manufacturing. He adds that the importance of lubricants is often overlooked in the local hydraulics industry.

Shell South Africa has three brands comprising the Tellus range, namely Tellus, Tellus S, and Tellus T. The premium brand is called Tellus S, which has a nonash anti-wear additive, and benefits in overall performance. Tellus T, meanwhile, has about a 40% greater viscosity index than Tellus or Tellus S, says Thorpe, giving it a far wider operating range. He says that Shell Tellus T oil is quite often recommended for mobile equipment that operates in harsh environments. He says that one of the most critical aspects of using a high-viscosity index multigrade-type oil is determining the equipment’s temperature operating window. If the oil is too thick, cavitation may occur, and the oil becomes difficult to pump, and if it is too thin, wear will occur.

Shell’s range of hydraulic oil has approvals from certain OEMs, such as Denison, Cincinatti Machine, and Vickers, and meets the requirements of industry bodies such as DIN, ISO, and AFNOR. Shell is one of the leading finished lubricant suppliers and is active in more than 130 countries and territories.