All hydraulic systems require a means of supplying a hydraulic energy. This is provided by a hydraulic power pack, which is essentially a machine that converts one source of energy to hydraulic energy. The input power can be fossil fuel (petrol or diesel), electricity or pneumatic supply this is used to produce a hydraulic fluid flow, which can be maintained at a pressure.
Thus we have the definition of hydraulics, the generation of forces and motion by means of a fluid (in our case hydraulic oil).
This content and other articles on our website aims to provide a resource that explains the how and why a hydraulic system is designed and constructed, giving you confidence that your hydraulic power pack is the right choice for your application.
How does a hydraulic power pack work?
Conversion of energy, that sounds grand! Actually what is meant here is that normally a rotating machine (engine or motor) is coupled together with a hydraulic pump to produce oil flow. This pump/motor combination is the prime element, but around that are many other essential items in a hydraulic power pack.
Where does the oil come from? The pump will draw oil from a Hydraulic reservoir, a storage vessel, and pump it into a connected system of valves and filters. This combination of functions means hydraulic fluid is provided to the motive elements of a machine, so it can perform force and motion safely and efficiently.
So the hydraulic powerpack is the beating heart of any hydraulic machine, circulating its oil around the body.
Why should I use a hydraulic power pack?
Hydraulics quite simply provides a very flexible and dense means of transmitting energy around a machine or installation. By use of a system of often small pipework energy can be pumped around and used for a variety of functions. Conversion of this energy into rotary or linear motion can be done neatly and efficiently at the point of use. If we look at what an electric motor and gearbox looks like compared to a similar hydraulic motor
we think this supports the need for hydraulics in modern machine design. Advances in electric actuator design for linear motion have been huge, but yet to outperform that of, centuries old hydraulic actuator designs. Hydraulic advances are ensuring that this technology can be the only sensible solution is many machine design scenarios.
Which type of hydraulic power pack do I need?
There are a huge variety of hydraulic power unit types and designs. What pump type is best?, what drive motor will I need? How big should my oil reservoir be? What valve technology is best? Narrowing this down to what is right for you, well that’s what we do best, ask the important questions.
So what should we consider together to get to the best solution?
1 - What will the power pack need to do?
So is the power pack driving a printing machine of operating a submarine hatch door? This sets the scene for a discussion about what kind of motive forces are going to be needed. The technical elements such as pressure requirements and flow rates can be analysed from there. This collaboration is core to a hydraulic power pack design, and works best when both parties have a shared understanding of how the machine is to operate and what you, the customer is expecting. All this analysis leads us closer to a solution.
2 - Where will the hydraulic power unit be installed?
Every environment is different and this is normally a big factor in selecting the type of hydraulic power pack that is best suited. Will it be getting wet?, will it be getting hot or cold extremes?, this is data that is crucial. Which country will it be in and what is the local electrical supply like? Power units can often emit undesirable noise levels particularly in the home or office building environment, so we they may installed a long distance from people, this must be considered.
3 - How long will it need to operate for?
Hydraulic power packs can be in operation 24/7 365 days of the year, but others only for a few seconds a year or less. So why over-engineer a design when it’s not appropriate. Or don’t cut corners when a full study of life-cycle wear and a full maintenance programme are essential to the package.
4 - What energy source do you have available?
Location and application generally lead to the answer here. Is there Electrical power available?, this is normally the most efficient and lowest cost solution. If not then can an Internal combustion engine operate in your environment? Or if the power required is low and intermittent often a battery supply is a good option. Others might be pneumatics, via an air motor or from a wind or water turbine.
5 - Can the power pack be serviced and maintained?
All hydraulic systems benefit from being well maintained, just like your car engine. But if this is not possible, then we need to acknowledge this and design accordingly. With sealed for life products, super high cleanliness levels and a clear brief as to what its life expectancy will be.
Why are hydraulics more cost effective than Pneumatics??
Having a discussion about Pneumatics versus Hydraulics is like comparing a bicycle to a car, one is cleaner and cheaper the other is more expensive, dirtier but more powerful.
But when the obvious advantages of both are acknowledged they both have their place in machine design.
Hydraulics is without doubt able to transmit more power by the use of an incompressible oil. It does however have a higher installation cost and can be dirtier than pneumatics.
Pneumatics will bring clean low energy to factory installations, but the operating costs are 5-10 times more expensive than the equivalent hydraulic power.
How do I fit a hydraulic power pack?
When fitting or installing a hydraulic power pack a great deal of preparation can be needed.
Firstly on most people’s agenda should be, will I be safe, and, will others be safe, installing this power unit, and of course will others be safe when it has been installed.
Secondly, will the power pack operate properly where it is fitted. Site conditions can be everything here, can it be kept dry and cool. Hydraulic power packs always prefer these conditions..
Also can you access the power source properly and can the hydraulic pipework be safely and neatly installed where it is needed.
When should I service my hydraulic power pack?
In keeping with all good equipment suppliers a good service manual will tell you how and when the hydraulic equipment should be maintained. Perhaps a discussion about the service conditions will alter the normal recommendations, so these details, as above are key to lifespan of a hydraulic power unit. In our experience an early service after commissioning is a really good idea for all systems, as many of the hydraulic contaminants are generated during installation, and a good systems flush cannot always be guaranteed. If a service log is kept this is useful and running hours can be often translated into service recommendations for your maintenance team. Prevention is better (and cheaper) than cure! The cost of a filter change can be £10 the cost of a replacement pump could be £1000’s.
What is the lifespan of a hydraulic power pack?
So many factors are at play here, that is difficult to give a clear answer. I am sure you won’t be surprised if we tell you a well maintained system will last a lot longer. A key list of factors effecting lifespan are:-
Pressure, higher pressures bring higher loads in the bearings, increasing the wear.
Temperatures, as this increases the oil performance often drops and its ability to lubricate and protect component’s from wear drops significantly.
Cleanliness, contamination simply leads to wear as particles rub together. Heavy contamination can clog filters and decrease the thermal efficiency of a cooling system.
Oil type, Grade composition and additives are key here and a vast range of options are available. Oils most suited to your market place will no doubt be available.
Are hydraulic power packs energy efficient?
Great improvements on pump efficiency have been made over the last few decades. Efficiency of a pump is comprised Mechanical and Volumetric, combined these vary from 85% to 92%. As a whole a typical hydraulic system comprised on Electric motor, hydraulic pump and hydraulic valves and actuators have an efficiency in the order of 85%. So this is not too bad compared to linear actuators, but does come under threat compared to a simple chain and sprocket. Of course to achieve this level a holistic approach must be taken when designing a machine with hydraulic actuation.
Can I upgrade my hydraulic power pack?
Fundamentally does the power pack you have do the job you require? If the answer is YES then, what improvements can be made. Energy efficiency, might be one area we all care about, is it running at its peak efficiency and if not why not. This is something a good hydraulic engineer can check for you, and make recommendations accordingly. One other area might be cleanliness, often if this is improved by introducing better filtration the life of the power unit can be extended.
If the answer is “No it is not working well for my application” then we can explore why not. Have your needs changed and does the system need to be re-designed to accommodate more functions or you simply need things to happen a little faster. These types of changes can be implemented, but of course they can’t always be done without significant re-working of the hydraulic power pack.
Where can I learn more about hydraulic systems and power packs?
If you are in Europe then we are lucky to have some of the best resources for Fluid power training in the world.
Technology centres such as the National fluid Power Centre, Worksop and the University of Bath specialise in training engineers in Hydraulics and pneumatics.
Hydraproducts do run training course for customers, your service engineers and technicians can be instructed in the installation and maintenance of our equipment. Run by our experienced team an in-depth understanding of our product is essential to offering customers an overall service package.
How safe is hydraulic energy?
A hydraulic power pack is a machine or part machine, as defined in the Machinery Directive 2006/42/EC and as such it must be demonstrable that it can comply with the ESR within this and other applicable directives.
So always ensure that the manufacturer or importer can provide such evidence, this will give you confidence that the hydraulic power unit has been designed and manufactured to be safe.
There are risk involved with all machinery, but those that pertain specifically to hydraulic machinery are centred around the use and transmission of oil under pressure. Oil escaping under pressure can cause high pressure injection injuries from as low as 7bar. These can be a crippling injury if oil is allowed to break the skin and enter the blood stream.
So what must be done, comprehensive preventative maintenance programmes, as well as appropriate training provisions. These mitigate the risk of hydraulic injuries within your environment.
What design and safety standards apply to hydraulics?
Here are a summary of some of the standards you can expect to be applied by Hydraulic equipment suppliers:-
ISO 4413:2010 applies to the design, construction and modification of systems and their components, also taking into account the following aspects: assembly, installation, adjustment, uninterrupted system operation, ease and economy of maintenance and cleaning, reliable operation in all intended uses, energy efficiency and environment.
ISO 1219-1:2012 establishes basic elements for symbols. It specifies rules for devising fluid power symbols for use on components and in circuit diagrams.
Pressure Equipment Directive (PED) 97/23/EC – This European Directive covers pressure equipment and assemblies with a maximum allowable pressure >0.5bar.
Pressure Equipment Regulations (PER) SI 1999/2001 – This regulation applies to design, manufacture and conformity of pressure equipment and assemblies of pressure equipment with a maximum allowable pressure of >0.5bar.
What’s new in hydraulic power pack technology?
Hydraulics is nothing new, considered as a motive force since the 17th century, but it is still improving, as it must, to keep track of todays digital environment.
The latest developments are focused around digitization and how hydraulic systems and components can interface with concepts such as IoT. These will bring hydraulically driven machinery into the modern age of Internet connectivity and “smart technology”. Notably in industrial technology the control and monitoring of wholes plant can take place remotely by many users over the internet.
Energy efficiency has been are area of great advancement across the hydraulic industry. When you consider the overall life-cycle cost of a medium size hydraulic system it is normal that the energy consumed can be 40% of the total cost.
Improvements in Electric motor design and manufacture have allowed the humble AC motor to bring 2-3 % more efficiency, which is the largest energy cost of a system. Other areas such as lower power rating solenoid designs and pump energy optimisation valves all contribute.
Of course a big area where efficiency can be optimised is at the very start of the design. Advances in CAD and CFD design tools are leading to more efficient and more effective designs. Lower weight systems means less fuel in mobile systems and less material resources used.