Hydraulic power is generated through a combination of oil flow and pressure. Oil flow and pressure is created from a hydraulic pump and transmitted through hoses or tubes, via control valves, to the hydraulic motor or cylinder that will do the work. One of the key advantages of hydraulic systems is to be able to transmit large amounts of power from a remote power source (electric motor or internal combustion engine) to a compact actuator.
Ever since human beings realised the potential of using fluids as a medium for getting work done, hydraulics as a specialised field in applied sciences and technology has kept evolving. Today, hydraulics forms an integral and indispensable part of most construction equipment. The almost incompressible nature of oil along with its ability to withstand pressure aids in transmission of power and force (with multiplication if required ) from one point to another in hydraulic systems. This power and force can then be utilised to do useful work, be it lifting heavy loads, moving it from one place to another, drilling precise holes, digging and excavating the earth etc.
Sachin Nijhawan, Vice President and Business Head, Mahindra Construction Equipment, says, 'Typically, in a hydraulic system we have pump, control valves, cylinders, winch, hydraulic cooler, hoses, tubes and hydraulic tank. We work with global hydraulic suppliers. In all our construction equipment, hydraulics constitutes 30-40 per cent of the entire machine cost.
The evolution of construction equipment (CE) into what we see today largely depends on hydraulics. Shandar Alam, Director- Sales and Service, Vehicle and Hydraulics business - India, Eaton, explains, 'Hydraulic systems in construction equipment have kept abreast of the changing needs and at times have aided the changes in the equipment, causing paradigm shifts in the entire industry from one technology to the next evolved version. The trigger for these changes has always been the inherent limited nature of resources on our planet, be it fuel, materials or most importantly, time. So whether it is moving from a fixed displacement system to a load sensing for better fuel efficiency, use of electro hydraulics for better control, breakthroughs in materials for enabling higher pressure systems, use of advanced computing for predictable and reliable designs with optimum use of materials, the focus has always been on doing more with less.'
Nijhawan, elaborates,'Hydraulics plays a very important role in the construction equipment like what we manufacture. Over the years, hydraulics has become efficient and smarter. Pressure in the hydraulic system has increased which has helped in reducing the size of the actuators and increasing the power-to-weight ratio. More electronic controls have come which makes the system smarter and more efficient.'
Besides the power requirements that vary as per the size of the equipment, the nature of power delivery also varies as per the requirement of the application and the work to be done. For instance, Alam describes,'On wheeled machines, the hydraulic power would be used for steering and work circuit, whereas on the tracked machine, it would also be used for propulsion. In work circuit, one would again have specialised requirements whether it is excavation, levelling of surface, moving a load from one place to the other. So optimum power distribution and power delivery needs to be kept in mind while a hydraulic system is designed for such specialised needs. Besides the actual work to be done, factors to consider also include the typical duty cycle, the number of hours the equipment will be used, the environment and terrain the equipment will be used in.'
Advantages and limitations
According to Alam, the greatest advantage of hydraulic power is its power density. Hydraulic components are able to convert and transmit power with comparatively much smaller space consumption than any existing technology. This has tremendous implications on the equipment footprint and size of the machine. For a given physical volume, both the ability to develop force in linear hydraulic actuators or torque in hydraulic motors is many times larger. Hence, hydraulics continues to be technology of choice for these heavy-duty applications. However, hydraulics does have its share of limitations. Alam adds, 'It is not suitable for transmitting power over large distances as the losses over distances is higher. Hydraulics is also susceptible to contamination and care needs to be taken to prevent wear and tear of precision components. Although control of hydraulic power is much better now with integration of electro hydraulics, it does have scope for further refinements.'
Nijhawan terms hydraulics as the muscle power of any construction equipment, as it plays an important role in the actuation of attachments and performing the intended functions of the equipment like digging, excavating, loading, dozing and grading operations. 'With hydraulics, the source of the energy can be somewhere and transfer of energy can happen through the hoses and tubes and actuate the attachment in other parts of the equipment, this is the fundamental advantage. Handling higher pressure without leakage are challenge to handle with,' he adds.
Satyendra Debdas, General Manager-Industrial Oil Sales and Marketing, Apar Industries, elaborates, 'The various advantages of hydraulic power are high output force, standard component v/s precise control, very complex final movements and fluid circulation ensures heat removal. Pressurised fluids can be transmitted over long distances and through complex machine configurations with only a small loss in power. Multi-functional control - a single hydraulic pump can provide power to many cylinders, motors, or other actuators. It is more advantageous for mobile applications.'
The major components of a hydraulic system are basically hydraulic tank, pump, cylinder, actuators, filter, control valves, pressure regulator and seals. All are very much significant for the smooth functioning of the system. According to Alam the simplest analogy for understanding working of hydraulic system in any machine is through the hydraulic system of the most wonderful 'machine' ever built -the human body. The hydraulic oil is the blood of the system. The hydraulic pump is the heart of the system and needs to be designed as per the size and the pressure required. It provides the required flow to the actuators. The actuators, whether rotary or linear are the limbs of the system that do the actual work of moving things and the machine itself from one point to another. The hoses and connectors are the arteries and veins carrying pressurised or depressurised fluids between the pump and the actuators. The controllers along with the valves are the brains that chose which operation is to be performed. Thus, each and every component in the system is important and needs to be taken good care of not only while designing a system, but also throughout its life for it to work optimally, efficiently and reliably.
Debdas elaborates on the role of oil in hydraulic system, 'The major function of a hydraulic fluid is to provide energy transmission through the system, which enables work and motion to be accomplished. Hydraulic fluids are also responsible for lubrication, heat transfer and contamination control. When selecting a lubricant, consider the viscosity, seal compatibility, base stock and the additive package.'
Since the oil passes through all the above components, the role of oil is also much more significant. There are two significant role of oil, one is its physio-chemical parameters and the other one is its performance parameter. On physio-chemical parameter, the oil should retain its adequate viscosity at different temperatures, maintain its good demulscibility characteristics, should not create any foam, good seal compatibility and cleanliness properties. Whereas on its performance parameter, it should maintain adequate pressure for the cylinder, protect the pump components from wear and tear, fight against oxidation, maintain its VI characteristics against shear load factor, etc.
As a matter of fact, hydraulic oil is the life blood of a hydraulic system. Use of hydraulic fluid with matching properties is the basis of a successful hydraulic system. According to Debdas, over the last 10 years, the development of hydraulic oil has gone for dramatic changes, especially for the construction segment from just a normal R&O + AW type to a more robust value-added type like better flexibility in different temperature environment, cleaner oil for extended life of equipment, better oxidation and thermal stability, extra long drain interval, etc. Since most of the properties in any hydraulic oil is dependent on the type of base oil being used, the customers are demanding oils which are manufactured from Group II and Group III type base oils. One more changes which has happened is the design of the pump leading to change in the viscosity of hydraulic oil from earlier 68 cst to the current 46 cst. This has also lead to improvement in the overall energy efficiency of the equipment. Even with increase in power out, the hydraulic systems are running hotter which introduces a threat of various contaminants, which has given birth to use of detergent type of hydraulic fluids (HLPD/ HVLPD). With the evolution of these kinds of hydraulic oils in the recent past, the oil drainage interval has also gone up from a mere 1,500/2,000 hours earlier to almost 5,000 hours at present. Since most of the equipment operate at a very harsh open environment, the oil also gets exposed to various conditions like hot air, ingress of moisture and dirt in most of the situation. With the ingress of these unwanted materials, the chances of oil getting deteriorated faster is very common. But if the product goes through stringent testing methods like good air release value, good demulscibility, good filterability, etc, then the oil remains in healthy condition for a longer period.
When it comes to customer expectations, they are looking for the three 'Es' - economy, efficiency and environment. Debdas elaborates, 'Hydraulic power is directly linked with the flow created by pump and further restrictions to convert that flow into pressure which actually does the hydraulic work. Hydraulic power variation, pressure, or resistance to flow, will vary greatly depending on the type of pump being used.
This will also require making necessary changes in other hydraulic system parts in line with the out pressure requirement.'
According to Debdas, as regulatory requirements increase and equipment design changes, hydraulic oil technology must continue to evolve to keep pace. Currently major focus is on less downtime and higher operation efficiency with energy savings, which is driving the new technology in hydraulic fluids. He adds, 'To improve overall efficiency of a hydraulic system, you will have to continuously increase system pressure, hydraulic pump power-to-weight ratio, which will lead to increase in oil temperature, reduction in hydraulic oil sump capacity, servo electric motors to stabilise high pressures. All these conditions will put stress on hydraulic fluid, thus increases rate of oxidation, thermal degradation, and varnish and sludge deposits to stick valves.'
Electronics for improved performance
The integration of electronics and hydraulic systems may have initially seemed challenging to adopt for traditional users, but the numerous benefits of electro-hydraulic (EH) integration have erased these doubts. Alam elaborates,'Improved reliability of hydraulic systems, along with more flexibility, efficiency, and diagnostic capabilities, has helped EH become a norm than an exception. Part of the increased acceptance of EH systems has come from the reliability of onboard electronics that provide more precise levels of control than earlier generation valves. Operations that used to be controlled by the machine's main controllers, such as closed loop control of an actuator, have been moved onto the valve itself. More integrated approach on the valve brings the hydraulics, electronics, axis loop closure and even the main controller together as one unit.' Another advantage is easier programming. With both onboard electronics and main controller-driven devices, modern hydraulic components have maintained a high degree of configurability. Some devices are even designed to allow users to develop custom applications specific to their equipment and operations. The combination of advanced electronics and programmability provides more flexibility for the end-users.
Nijhawan comments on the use of electronics, 'We are moving towards electronic controls on engine. The engine interacts with the hydraulics system during power demand fluctuations. We are the first in India to introduce telematics in backhoe loaders.'
Hydraulic products and solutions
Hydraulic system components and solution have come a long way with many a developments over the years. Today, leading hydraulic solution providers offer products with cutting-edge technology. For e.g., Eaton has a wide range of products and solutions suitable for hydraulic equipment. Be it open circuit or closed circuit applications, Eaton has portfolio of products starting from the fixed displacement vane and gear pumps, to variable displacement piston pumps and motors, the spool and disc type of GG motors, mobile valves from the mechanically operated to the state-of-the-art CMA valves, SiCV and hydraulic integrated circuits. Eaton also has its range of electronic controllers and displays, the HFX range. Along with this, Eaton has the entire range of fluid conveyance offerings suitable for varied applications, pressures and fluid types.
Alam elaborates, 'Eaton's Life sense hose is an example of smart innovation offering superior value to OEMs and end-users. Eaton's Airflex range of clutches and brakes are prevalent in heavy duty applications including the mining segment. So be it backhoe loaders, excavators, skid steer loaders, compactors, scrapers dozers, concrete mixers boom pumps, wheel loaders, commercial vehicles, cranes, or mining equipment, Eaton has products and solutions suitable for all.'
Debdas explains on the products and solutions offered by Apar Industries for hydraulic systems, 'We have various products to offer for various kinds of equipment ranging from HL type to HVLP/HVLPD type. All the products confirm to stringent DIN 51524 specifications across the grades along with various pump and filterability specifications. All the products are manufactured from hydro-cracked base oil, which gives extra mileage over the competition. For example, Apar offers HLP grade hydraulic oil with minimum VI of 110 against the standard of 95 with better oxidation stability (TOST 6,000+ hr) as well as excellent air release properties. Similarly, the HVLP oils are having minimum VI of 150 against the standard of 135. Apar also offers hydraulic oil with ash less technology for different construction equipment requirement and fully synthetic fire resistance hydraulic fluid (HFDU type) for underground mining equipment.
Smart machines enhance performance and increase productivity and efficiency by helping end-users gain greater intelligence into their equipment. Alam elaborates with example, 'Eaton's CMA mobile valve or AxisPro? industrial valves have sensors built-in so that they can monitor conditions from within the machine, offering greater insight into operations and helping end users improve performance. Smart equipment has greater intelligence into the overall power requirements of a machine and they helps optimise machine output with increased diagnostics. Smart equipment will continue to evolve. As technology advances, there will be greater combination of centralised and decentralised decision points, where equipment level decisions are made from a centralised controller but individual components can also decide how much energy is required and provide a control loop. This will only improve the benefits that end-users can receive from upgrading their equipment to smart technology. With increased premium on fuel costs, efficiency and greater productivity the benefits provided by hybrids and smart technologies are only a precursor of the road ahead.'
According to Nijhawan, the hybrid and smart technologies are going to influence hydraulic equipment grow smarter in terms of customising equipment to application-specific, in diagnostics of the hydraulic system and regenerative systems makes optimum use of hydraulic energy and reduce disposal of energy in terms of heat.
He adds, 'We are working jointly with hydraulic suppliers making our equipment highly reliable and efficient. Measurement of system level parameter helps to under-stand operator under different operations and upgrade and also the data can be used for developing driverless machines to work in harsh environment and reduce operator dependency.'
According to Alam, getting more done out of less continues to be the focus for most of our innovations. The industry is looking for products that can withstand higher pressures, work at higher speeds yet are compact and lighter. Increased efficiency through reduced losses; ensure greater reliability, predictable execution, higher precision controls; and come with integrated electronics that are flexible, open platform communication so OEMs and users can configure them as required. 'Dynamic machine control, hydraulics providing inputs through sensors enabling necessary system adjustments in real time, prognostics and diagnostics, contamination control, advanced manufacturing and sustainable design are some of the areas in which one will continue to see the bar getting higher and the limits pushed harder,' explains Alam.
Debdas elaborates, 'Today's hydraulic systems are more robust and sophisticated. Most of the parts like pump, valves, hoses and reservoirs have gone for a dramatic change in the past few years. Tomorrow, mobile hydraulic systems will incorporate even more sophisticated capabilities to achieve integrated control solutions, including prognostics, speed control, and anti-cavitations and dry-motor prevention. The trend toward integrating valves into pumps and motors will continue, as will the trend toward the use of dense, compact manifolds and new hose and fitting technology, all of which reduce system part count, minimise the possibility for leaks, and further improve on the already high reliability of the systems. Full system integration to bring functions like power steering, alternator, and air-conditioning compressor functions under a single central control is an emerging trend that is sure to accelerate.'
With a lot of activities happening in infrastructure development, construction and mining, hydraulic equipment have a greater role to play in the coming years and upgradation of hydraulic components and integrated electronics in hydraulics is going to augment the growth of hydraulics in future.
- Sudheer Vathiyath