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This article focuses on the common problems associated with hydraulic systems and how these issues can affect individual components as well as the systems themselves. It gives an in-depth insight into how problems initially develop, any knock on effects and how failures can happen if the issue isn’t diagnosed correctly.
Abnormally high fluid temperatures
High fluid temperatures are usually caused when the system struggles to correctly dissipate heat and can lead to increased heat load. When fluid temperatures exceed 180°F (82°C), this can lead to damage to the seals and in turn start to degrade the fluid itself.
When viscosity levels drop below optimal values for the system components, the fluid temperature is judged to be too high and the reservoir should be checked for any obstructions or blockages.
The heat exchanger is another component that should be checked making sure the core is not blocked. In order for the heat exchanger to successfully dissipate heat, the flow rate of both the hydraulic fluid and cooling air/water should be at the correct levels.
When fluid circulates to areas of differing pressures without correct pressure correction, excess heat can be generated and any areas that show signs of internal leakage can increase the heat load on the system. This includes anything from a leaking cylinder to an incorrectly adjusted relief valve.
High fluid temperatures can also have an effect of components as they go through a thinning process which affects the oil film, otherwise known as a low viscosity which leads to inadequate lubrication. This issue can be tackled by setting up a fluid temperature alarm to warn of dangerously high temperatures.
When a machine starts to show signs of reduced performance and functionality this points to a problem with the hydraulic system. A loss of speed in the system is usually caused by a poor flow rate and can be noted when the system takes longer to cycle or is slow in its general operation.
Leakage is a common cause of slow operating speeds as flow can escape from hydraulic circuits. This leakage can be either internal or external with typical candidates being burst or degraded hoses or leakage from pumps, valves and actuators.
A useful tool to measure leakages and pressure drops is an infrared thermometer which can identify components with internal leakage. So going by the manufacturers limits for correct temperatures, the thermometer can pinpoint potential problems. Incorrect hydraulic oil out of manufacturer specification can also lead to pressure changes and a decrease in system performance. A successful infrared test will also pick this issue up.
Sometimes, under extreme operation, overworked machines start to overheat. Using the correct oil viscosity will help to alleviate this issue from occurring in the first place and avoid costly failures by lubricating the system effectively. It is also important to let the system prime itself before use thus ensuring all important components are lubricated correctly and to manufacturer standards.
Abnormal and irregular operative noise
Abnormal or irregular sounds while the system is operating are good warning signs of a potential problem either currently occurring or about to occur.
There are two main candidates that attribute to this problem – aeration and cavitation. Aeration is a condition where too much air enters the system and contaminates the hydraulic fluid within. This commonly leads to a loud banging or knocking noise from the system when it compresses and decompresses whilst the fluid circulates through the system. Actuator movement can also become erratic and the fluid degradation can eventually lead to damage to seals through overheating.
Cavitation commonly occurs when a hydraulic circuit demands too high a level of fluid than is being supplied at any given time. This in turn causes circuit pressure to fall below the level of vapour in the hydraulic fluid. The knocking sound that comes from this is caused as the vapour cavities implode during compression.
Both these issues can cause component or system damage with extreme cases of cavitation being known to cause metal erosion and failure of system components.
Hydraulics has been around for a very long time. But are you aware of how far it has actually come? You wouldn’t be alone if you responded with no. It is a very technical subject that can be quite difficult to understand, but in this article we want to tell you the story of hydraulics! We want to share with you who discovered hydraulics, what it was originally used for and how hydraulic power got to where it is today.
So why don’t we start at the beginning! Where does the word hydraulic come from?
The word hydraulic originates from the Greek word ‘Hydros’ which means water. Why water? Well, this is because water was the first liquid to be used in the hydraulic system. Today, hydraulics includes the physical behaviour of all liquids, not just water.
In this article we want to explain the ins and outs of hydraulic powerpacks. A vital piece of equipment that is used with so many machines we see every day.
In a nutshell, hydraulic powerpacks are self contained units that are used instead of a built in power supply for hydraulic machinery. Hydraulic power uses fluid to transmit power from one location to another in order to run a machine. It really is as simple as that.
So what do they look like?
In order to recognise and better understand hydraulic powerpacks, it is a good idea to get to know the key components. Hydraulic powerpacks come in many different shapes and sizes, some are very large and stationary whereas others are much smaller and more compact. In fact, some hydraulic powerpacks are so compact that they can easily be transported in a small van or even an estate car.
The only real way to identify hydraulic powerpacks is through its main components. No matter the size of the unit, all power packs will have the following; a hydraulic reservoir, regulators, a pump, motor, pressure supply lines and relief lines.
What do these components do?
It may be obvious to some but in this post we wanted to explain every hydraulic power pack component as simply as possible. So here goes.
First up is the hydraulic reservoir which quite simply holds the fluid. Reservoirs will come in different sizes.
Then we have the regulators. Regulators are vital as they control and maintain the amount of pressure that the hydraulic powerpack delivers.
Thirdly we have the pressure supply lines and relief lines. The supply line simply supplies fluid under pressure to the pump and the relief lines relieve pressure between the pump and the valves. The relief lines also control the direction of flow through the system.
Finally we have the pump and a motor. We will begin with the simpler component of the two, the motor. The motor is simply there to power the pump. Easy as that. Now the pump generally performs two actions. Firstly, it operates as a vacuum at the pump inlet and through atmospheric pressure forces fluid from the reservoir into the inlet line and then to the pump. It then delivers the fluid to the pump outlet and pumps it into the hydraulic system. We did warn you that the second part would be slightly more confusing.
So what is the function of hydraulic powerpacks?
Hydraulic powerpacks deliver power through a control valve which in turn runs the machine it is connected to. Hydraulic powerpacks come with a variety of valve connections. This means that you can power a variety of machines by using the appropriate valves.
Hydraulic powerpacks are relied upon by a range of different machines that use hydraulic power to do its work. If a machine is required to carry out heavy or systematic lifting then its likely it would need help from a hydraulic powerpack.
To make it easier for you to understand, we have included a list of trades that regularly rely on our powerpacks. On a building site you will see machines like bulldozers and excavators, which both need hydraulic powerpacks. But, it is not just on building sites that you will find these types of machines. Fishermen and mechanics both need hydraulic powerpacks too. If we did not have them then how would fishermen lift their nets or how would mechanics lift our cars?
When picking a hydraulic powerpack there are a variety of pumps and options to pick from and it is important to pick the right pack to meet your machines needs. It is also important to consider a pack that will help maximise productivity and minimise cost.
Many people will overlook the necessity of hydraulic powerpacks, but they really are vital to ensuring our society runs efficiently.
Do you need to maintain hydraulic powerpacks?
Yes you do and this is hugely important! Hydraulic powerpacks require regular maintenance to ensure they are working properly and safely and to help extend their life. Maintaining hydraulic powerpacks is relatively simple and includes checking the tubing, this can be for any noticeable problems such as dents or cracks. It is also vital to regularly change the hydraulic fluid and look at the reservoir to check for any corrosion or rust in hydraulic power packs.
What hydraulic powerpacks do we provide?
Generally we provide four different types of hydraulic powerpacks. You can pick from a standard powerpack, a mini powerpack, a micro powerpack or a bespoke powerpack.
The standard hydraulic powerpack uses a standard range of modular components and is ideal for the most demanding industrial applications. The mini powerpack is ideal for applications requiring up to 5.5kW. The micro hydraulic powerpacks were originally produced for mobility applications, so are great for when space is limited. Finally, if none of these seem to fit your needs then we offer bespoke hydraulic powerpacks ensuring your application gets the hydraulic powerpack it requires.
Finally, who is the genius behind hydraulic powerpacks?
The man behind hydraulics was Laissez Pascal. A French mathematician, physicist and religious philosopher who lived in the mid seventeenth century. Pascal made observations about fluid and pressure which led to Pascal’s law. Pascal's law states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container. Hydraulic powerpacks have been designed based on Pascal's law of physics, drawing their power from ratios of area and pressure.
So, interested in our Power Packs? Come on over to the main website and see what we can do for your Hydraulic Power Pack Needs .
After years of working in and supplying to the hydraulic power industry, we have accumulated extensive knowledge and experience of how hydraulic units work, what can go right and of course what can go wrong. In this post we are now going to share with you the 7 most common issues that we have seen when it comes to maintaining hydraulic power equipment.
Generally, premature hydraulic system failure can be traced to one of the following deficiencies:
1. Insufficient fluid level
Lack of oil in a system may not stop it from operating, but it may result in increased contamination, increased temperatures and poor oil lubrication.
2. The presence of air in the system
A sure sign of this is foam and air entrained in the oil. Air dissolved in the darkened oil will cause oxidation of the oil and foam will often be evident in the reservoir. Both of these cause failure of oil lubrication performance.
3. Oil Contamination
Hydraulic filters must be monitored in an effective manner so not to either waste money by changing them too early or risk contaminating the system by changing them too late. Filters that are clogged will stop holding any dirt particles; this allows dirt to circulate in the system. This will then decrease the life of each component in the hydraulic unit – resulting in more expense than necessary.
4. Incorrect system design and commissioning
Filters fitted in the wrong locations can be problematic. In fact two locations for hydraulic filters that will cause no end of problems are the pump inlet and the pump drain lines. Wrongly adjusted valves can cause excessive heat and noise, leading to valve wear and oil failure.
5. Fluid leakage
Where oil escapes from a system, air or other contamination can enter. As we have said contamination causes many early failures.
6. Wrong fluid type or viscosity
The quality of the oil is vital to the operation of the hydraulic system as it not only transfers the power; it also lubricates the entire system. The viscosity and therefore, effectiveness will depend upon whether the system is running at the correct parameters. Poor oil selection can result in premature degradation of oil properties and in turn excessive wear of the system components.
7. Excessive temperatures
Excessively high running temperatures can be easily detected in engines or electric motors, but not so in many hydraulic systems. Quite often there is no method of recognising overheating, but this is the single most effective way of damaging hydraulic oil and the system components. Constant high temperature lowers oil performance and diminishes lubrication. Premature wear is often a result of poor lubrication.
These are the issues that we’ve most commonly seen with operating hydraulic power units. You may want to share this with your less experienced colleagues and employees, so they may avoid them.
Subsea hydraulics is a very niche area in the world of hydraulics engineering. It’s an area that is mostly focused in the oil and gas industry (90%), 9% in military and 1% in other. It encompasses seafloor systems, surface control equipment and the control of oil wells amongst other tasks such as cable maintenance and seabed exploration.
The Role of the Subsea Hydraulics Engineer
Subsea hydraulics engineers have some seriously interesting challenges to solve. Not only are they faced with the day to day hydraulic challenges that most of us deal with, but they also have to handle the sea, its power and pressure. The pressure found on the seafloor is extreme. What’s even more extreme is the pressure found inside the wellbores for underwater energy extraction.
One of the biggest challenges for these engineers is the development of Blowout Preventers (BOPs) that are used to contain oil. It’s what prevents oil from emerging into the ocean and creating a giant spill that results in a wildlife emergency. This can prove to be very costly for oil companies.
BOPs have to be designed, tested and operated in addition to having procedures written and processes established. Subsea hydraulic engineers also handle other equipment such as the subsea robots that are also known as Remote Operated Vehicles (ROVs). ROVs need to be winched into and out of the water using hydraulic power at the winch. In fact, you may find some of our hydraulic power units in use at winches.
Developing a deep water oil field requires an astonishing amount of equipment. Although there are some electric systems used, the controls are typically managed with hydraulics. The field could be giant and cover miles from one side to the other.
Oil Fields can be miles across...
...and involve large amounts of subsea equipment. The job of the subsea hydraulics engineer is to ensure that all equipment is working the way it should be. There are calculations to do, designs to create in addition to plenty of operating procedure and process writing and revising. There’s also a requirement to develop a schematic of how each piece of equipment sourced from different vendors is going to operate and interface on the sea floor. This takes a lot of PowerPoint and Excel use to map this out for the other employees and management!
The Subsea Hydraulics Engineer Prevents Disasters
A major part of the role is to do the small day to day things that go a long way in preventing anything exciting from happening. We don’t want to have to get involved in issues such as needing to perform an oil spill recovery. In this industry, even the smallest mistakes can cause disasters that poison marine wildlife, sink expensive equipment or even kill people. It’s something that we take very seriously.
Some hydraulic engineers in other companies do tasks such as design remotely operated vehicles (ROVs) and launch and rescue systems (LARS) for use by the oil and gas industry, movie makers, the navy, explorers, scientists and even treasure hunters.
Hydraproducts has customers in a broad range of industries, including in the subsea fields. We supply hydraulic power units from micro size to bespoke size to suit whatever is required in all industries, including marine related.
How to read hydraulic circuits
Hydraulics symbols are an essential component of hydraulic circuit diagrams. Knowing some of the basic principles will help understand a wider range of symbols. Explaining the common ISO1219 symbols enables a complete hydraulic system to be followed:
1. Hydraulic Pump
Hydraulic pump produces flow. Oil is pumped from the hydraulic reservoir into the system. The basic symbol for a pump:
A fixed displacement pump is the simplest type and has a fixed output for each revolution of the input shaft. Modifications to this symbol describe the variable displacement pump. The types of control circuits show how the output is varied.
Filters clean oil entering the system, and are used in various places within a system. They protect hydraulic valves and pumps. Suction filters are placed at pump inlets to ensure only clean oil enters the system. Pressure filters can be placed throughout system. Return filters are common and filter oil returning to the reservoir.
3. Pressure Relief Valve
Pressure in a hydraulic system should be limited to control the force any motive devices produce and to ensure the safe/design limits are not exceeded. A pressure relief valve symbol is normally shown as:
A pressure relief valve or PRV passes fluid from an area of higher pressure to a lower pressure (typically the tank). Hydraulic pressure shown by the dotted line acts as a pilot to actuate the PRV by moving the arrow across the box. This happens when the pilot pressure produces an internal force equal to the spring load the valve begins to open and pass flow.
4. Check Valve
This valve is a one way valve that prevents flow in one direction. The addition of a spring ensures the valve will only open when this pressure is exceeded. Dotted pilot lines can be added so that pilot operating pressures can be used to open the valve and allow flow in the reverse direction. Commonly used to hold pressure in a hydraulic cylinder.
5. Hydraulic Reservoir (tank)
Hydraulic systems all have a means of storing hydraulic fluid. This is referred to as the hydraulic reservoir. Hydraulic reservoirs are shown as:
Vented hydraulic reservoirs are common place, but sealed systems can be found ion aerospace and marine applications. The return lines shown indicate the position above or below the oil level.
6. Directional Control Valve
Hydraulic fluid flow is controlled by a directional control valve. Commonly consists of four parts, valve body, spool, actuator, and springs. The spool is moved with respect to the valve body, this opens and closes internal flow galleries to control fluid flow. Various types of actuators provide power to shift the spool and springs are normally used to return the spool when the actuator is de-energised.
Look at the typical three position four way valve:
How to read directional control valve symbols:
a. Each box in the valve symbol represents a possible valve condition. In the three position valve above there are 3 possible conditions controlled by the actuators.
b. Number of ways tells you how many hydraulic connections could be connected to the valve.
c. Actuators always push and never pull the spool.
d. The box furthest away from the actuator is the normal or de-energized position, and is the position where the circuit connections are drawn. In the above valve this is the middle position.
7. Hydraulic Cylinder
Hydraulic cylinder or actuator uses hydraulic power to generate mechanical force. A hydraulic cylinder is shown as:
A double acting cylinder (above) has two ports and is therefore powered in and out. Single acting cylinders have one port and would typically be used for lifting applications.
We hope this gives you a useful introduction to hydraulic circuits. For a full list of hydraulic symbols can be found in ISO1219, or contact www.hydraproducts.co.uk for more help.
Hydraulic pumps, one of the more common mechanical applications of hydraulic technology, use fluid to push an arm a set distance forwards and backwards (or up and down). One example is the mechanical arms of a digger or other ground-working machinery. A hydraulic pump is perfect for this use, as the machinery works using the set distances between the components of the arms.
A hydraulic gear motor uses fluid to power movement for a much longer distance (or to put it another way, for an unspecified length of time). The motor works by running fluid through a chamber containing two cogs. One is linked to the drive shaft and transfers the power to the component that needs to move, and the other is idle, existing only to complete the mechanism. The same fluid is pumped through the motor chamber for as long as the power is needed, and it works in a similar fashion to an electric motor, but is much smaller and can be used in places where electricity is not safe or viable to use. It is a natural development of the waterwheel that was commonplace in the UK during the Industrial Revolution, powering cotton mills, woodworking and even bellows for blacksmiths forges.
A hydraulic gear motor is more appropriate than a pump for any piece of machinery that needs continuous power in a simple mechanism; a series of hydraulic pumps, arms and cogs can be used to create continuous power, but the resulting apparatus is bulky and made up of several components, which increases the likelihood of mechanical failure. A hydraulic motor, by comparison, can be very small and portable, meaning it is ideal for any application that is a long distance from traditional power sources and remote areas of the planet where other forms of energy are not viable. They are also reasonably simple in construction, so parts and maintenance are not an issue.
Hydraulic motors are ideal for use underwater and in dangerous places like mines and gas works, where the spark from an electric or petrol motor poses a serious fire risk. They are also good for any task where the motor is operated remotely, as the fluid can be pumped a long distance to the motor using comparatively little power and the only connection needed is piping, compared to more expensive electrical cable for running a remote electric motor. What is the most ingenious application of a hydraulic motor you have ever seen? Let us know in the comments below.
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