Insight April/May 2026 www.pwemag.co.uk Plant & Works Engineering | 11 damage critical components. Once particles begin circulating through the circuit they create further wear, generating additional debris that progressively worsens the condition of the oil. Contamination control Because of this, contamination control has become one of the most important aspects of hydraulic maintenance. Increasingly, operators are recognising that oil supplied in drums or bulk containers is rarely clean enough to meet the requirements of modern hydraulic systems. Filtering oil during transfer into the machine has become standard practice in many maintenance workshops. Cleanliness levels are normally defined using ISO 4406 particle counting codes. Highpressure hydraulic systems that incorporate piston pumps or servo-controlled valves often require oil cleanliness around ISO 17/15/12 or better to maintain reliable operation. Achieving these levels consistently requires carefully designed filtration strategies. Pressureline filters provide direct protection for sensitive components, while return-line filters capture wear particles before the oil returns to the reservoir. Large hydraulic systems frequently benefit from offline filtration circuits, sometimes known as kidney-loop filtration. These systems continuously circulate oil through a dedicated filter independent of the main hydraulic circuit. Over time this approach can significantly reduce contamination levels and stabilise fluid cleanliness, particularly in systems with large oil volumes. Water contamination presents a different but equally serious problem. Moisture may enter hydraulic reservoirs through damaged seals, poorly protected breathers or condensation forming inside tanks during temperature fluctuations. Even small quantities of water reduce the lubricating properties of hydraulic oil and accelerate chemical degradation. Oxidation of the base oil increases acidity, leading to varnish formation and corrosion of internal components. To prevent moisture ingress, many hydraulic reservoirs are now fitted with desiccant breathers that remove water vapour from incoming air. Improved reservoir sealing and controlled oil storage conditions also play an important role. Where water contamination has already occurred, vacuum dehydration systems are capable of removing both free and dissolved water from hydraulic fluids. These technologies are widely used in heavy industry and offshore installations where large oil reservoirs make complete fluid replacement impractical. Oil analysis programmes Oil analysis programmes provide another valuable tool for maintaining hydraulic system health. Regular sampling and laboratory testing allow engineers to monitor the condition of the oil and detect early signs of component wear. Particle counting reveals contamination levels, while elemental analysis can identify metals such as iron, copper or aluminium that originate from specific components. Monitoring viscosity and acid number provides insight into the chemical condition of the oil itself. Using this information, many operators have moved away from fixed oil-change intervals. Instead, maintenance decisions are increasingly based on the measured condition of the fluid. When contamination is well controlled, hydraulic oils can remain in service for extended periods without compromising reliability. Conversely, early detection of abnormal wear allows maintenance teams to investigate developing faults before they lead to equipment failure. Leakage remains another issue affecting hydraulic system performance. External oil leaks are usually obvious and can pose environmental or safety concerns. Internal leakage, however, is more difficult to detect. As internal surfaces wear within pumps or cylinders, hydraulic oil begins to bypass sealing surfaces. The system may continue operating, but pressure stability declines and efficiency drops. Monitoring pressure behaviour and flow characteristics can reveal the presence of internal leakage. A pump that struggles to maintain pressure under load or generates excessive heat may be experiencing internal wear rather than a simple external fault. Identifying such issues early helps maintenance teams plan repairs in a controlled way rather than responding to unexpected breakdowns. Environmental considerations are also influencing lubrication strategies in the UK. Equipment used in ports, inland waterways and offshore installations must operate with minimal risk of environmental contamination. Hydraulic oil spills can lead to costly remediation work as well as regulatory scrutiny. For this reason, environmentally acceptable hydraulic fluids are increasingly specified in sensitive environments. Many of these fluids are based on synthetic esters that degrade more readily in natural conditions while still providing strong anti-wear performance and oxidation resistance. Standards such as ISO 15380 define performance requirements for biodegradable hydraulic fluids used in environmentally sensitive applications. Renewable energy infrastructure illustrates how lubrication requirements are evolving. Offshore wind turbines rely on hydraulic systems for blade pitch control and maintenance equipment. These systems must operate reliably for long periods in harsh marine environments where moisture and temperature variation can affect fluid stability. Selecting hydraulic oils with strong oxidation resistance and excellent water separation characteristics is essential to ensure long service life. Mobile hydraulic equipment presents different challenges. Construction and infrastructure machinery frequently operate in dusty environments and under fluctuating loads. Maintaining fluid cleanliness in these conditions requires robust filtration, well-designed sealing and disciplined servicing practices. Portable filtration units and onsite oil analysis equipment are increasingly used to support maintenance teams working on remote sites. Energy efficiency has also become a growing concern in hydraulic system design. Hydraulic power remains one of the most effective ways to transmit large forces, but energy losses can occur through internal leakage, fluid friction and heat generation. Maintaining clean oil with stable viscosity helps minimise these losses and allows pumps and valves to operate closer to their intended efficiency. Synthetic hydraulic oils Synthetic hydraulic oils are often used where temperature stability and efficiency are particularly important. Their higher viscosity index allows them to maintain consistent lubrication performance across a wide temperature range, improving cold-start behaviour while maintaining adequate protection at higher operating temperatures. The practical lesson for engineers is straightforward. Hydraulic oil should be treated as an active component of the system rather than a consumable that receives attention only during routine servicing. When contamination is controlled, fluid condition is monitored and the correct lubricants are selected, hydraulic equipment operates more efficiently and components last significantly longer. In industries where reliability is critical and downtime carries significant cost, the condition of the oil circulating through hydraulic systems remains one of the clearest indicators of how well those systems are being managed.
RkJQdWJsaXNoZXIy MjQ0NzM=