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What is the function of Hydraulic Power?
The function of Hydraulic Power is to simply convert a primary drive source into a hydraulic fluid flow.
The elements required to achieve this are :-
Primary source: AC or DC Motor or Internal combustion engine
Hydraulic Pump: Common types include gear, piston or vane
Oil tank or hydraulic reservoir: container for the hydraulic fluid
Filtration Pump inlet (suction), Pressure filter (pump outlet) and return filters (back into the reservoir) are the common types.
What are the Main Elements?
Primary drive sources could be direct current from a vehicle battery (DC),alternating current ( AC) from single or 3 phase motor, internal combustion engine or an air motor. These dictate the hydraulic power delivered to the oil and therefore control the flow and pressure limits.
Pumps produce flow and are designed to do this at a pressure that the system restrictions demand. Hydraulic pumps are usually selected based on their suitability to produce flow, pressure rating, economy and noise.
Hydraulics reservoirs are the storage vessel for the oil required to operate the hydraulic system components, such as hydraulic actuators or hydraulic motor, and ensure this oil is stored and maintained in the best possible condition. Common ancillary’s filler/breathers and drain ports, level gauge, level switches and inspection covers.
Filtration is a critical part of a hydraulic power pack, ensuring wear is minimised and efficiencies are maintained. Basic suction strainers ensure the very largest of contaminants do not enter the pump. Pressure filters are normally configured at the pump outlet ensuring highly filtered oil enters the hydraulic system. Contamination within the system is filtered out by the return filter before it enters the hydraulic reservoir.
What are Control Elements?
Pressure control valves, these limit or control the hydraulic pressure within the hydraulic system
Directional Control hydraulic valves: manual , electrical, pneumatic or hydraulic operated valves direct the oil flow around the system to operate actuators, motors or other functions.
Instrumentation, Oil level and temperature protection switch, Pressure switches and filter clogging switches are all common.
Cooling is another other key consideration, where efficiencies within a system or machine will produce heat in the oil, this must be cooled to ensure long life and high efficiency.
The simplest hydraulic power pack circuit is termed a “P&T pack” which is simply the provision of a Pressure outlet port and a Tank return port. Minimum hydraulic valves on this type of powerpack should be a maximum pressure relief valve and a check valve to protect the pump.
For detailed hydraulic system design guidance, you can refer to our FAQ pages or contact us at firstname.lastname@example.org
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 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.
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 .
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.
Many of our clients come to our engineers for advice on which hydraulic oil they should use in both our own bespoke mobile hydraulic systems and sometimes even hydraulic systems that we haven’t designed.
However, there is not just one simple answer for this. There are of course many different types of hydraulic machines that are located in different climates etc. However, there are three basic elements that need to be considered when making your selection.
Whether you need a mono-grade or a multi-grade can be determined by the climate and temperature conditions. If your machine operates in the same temperature every day of the year, then you could most likely get away with using a mono-grade. This will actually be a less expensive option too. If you have freezing conditions during winter and high temperatures in the summer, then multi-grade is your answer.
Oils with added detergent are able to help keep components deposit free. They are able to create an emulsion from added water, and also have some ability to handle sludge or varnish. However, these contaminants will still need to be filtered out in order to remove them.
When a detergent oil is in use, it’s important to keep a close eye on how much water there is in the oil. After all, its water that can age oil, reduce its lubricity and even how well it will filter in addition to creating more cavitation and corrosion. It can also be converted into steam. Overall, it’s best to keep any water below the 100ppm level.
If your hydraulic system is high-performance and high-pressure then you may want to look at adding an anti-wear element to your oil. This makes it possible for lubrication to be maintained. However, the downside is that there can be some negative effects. Take the additive known as ZDDP (Zine dialkyl dithiophosphate) for example. This can have undesirable effects as it begins to break down as soon as it comes across water and then can go onto corrode a variety of yellow metals.
Overall, making the right selection is very important for your machine. If you don’t get it right, it’s going to cost you and your machine dearly. Therefore, it’s worth investing the time and energy to get it right.
Hydraulic filtration is a vital component of keeping a system running smoothly.
For example, did you know that up to 75% of failures with fluid power can be attributed to contamination? With the use of hydraulic filters, contamination damage can be significantly lowered which can not only cut down on expense but lower that 75% drastically.
If you’re looking to save costs from less downtime then it’s also time you looked into what a difference hydraulics filtration can make for extending the life of your equipment. Running your system optimally is essential when it comes to cost saving, but protecting its longevity is also a critical element in running any business efficiently.
Muck and dust can destroy a hydraulic system, that’s why it’s essential to make the best use of hydraulic filters. You wouldn’t even be able to remove that dirt yourself, as it’s likely to be dust that is so fine that you won’t be able to see it without the use of a microscope. Dirt has the same detrimental effect as sandpaper or gravel and not only will generally deteriorate the system, but it could even destroy it.
However, through the use of a hydraulic filter system you will be able to maintain control over the level of contamination and by doing so reduce the failure of systems by as much as 75% just be removing that dirt.
Hydraulic parts are expensive. Combine that with down time and having to keep engineers on hand to fix worn components and that’s a lot of expense to deal with. Putting filters into place can even save costs by increasing how long the hydraulic fluid will last.
Degradation of fluid – hydraulic fluid that contains fine metallic particles can degrade rapidly through chemical breakdown. Without protecting against this, there could be issues such as slippage, internal leakage, corrosion or sticking parts.
Scoring of surfaces – this can occur when particles get trapped between surfaces of seals
There’s no doubt about it, but …
· System performance is affected by dirt levels
· Hydraulic filters can control levels of dirt. Without using this management method, the system will get dirtier and dirtier until it fails.
In fact, hydraulic filters are the only way to control how much dirt is in fluid. Without them you will be forced to change out the hydraulic fluid regularly, which can be a time consuming and costly event.
Hydraulic system dirt particles are incredibly small. In fact, they are so small that they cannot be seen by the human eye – and 98% of hydraulic fluid has some dirt in it.
Engineers have found that when it comes to size of particles in samples taken from operating systems, the smaller the particles, the more dirt there is in the system.
So where do these particles come from that we have to work so hard to deal with?
In order to have an idea of what goes on inside the closed system, let’s examine where these particles come from.
Instead of enjoying the typical 20 gpm that is the measurement of a pumped flow from a 2000 psi system, you can expect to see something in the region of just 10 gpm. Although your pump will still produce for you, you’ll discover that the degradation results in just 50% efficiency and you should als be prepared to experience extra heat and other unwanted issues.
As with any hydraulic system, there is an optimum level of cleanliness, but there is a point where you cannot get any better performance out of the system by improving the quality of the fluid. However, with the use of hydraulic filters you should be well set to extend the life of your machinery.
Electrostatic charge builds when there are two bodies moving and creating friction. The fact is that this also occurs in hydraulic systems from the friction caused by system components with moving fluid.
Although we haven’t had a lot of situations that have involved electrostatic discharge, it is still something that every engineer should be aware of.
When an electrostatic discharge occurs, there is a clicking noise as charge increases and is then released. This is something that will often occur in a filter – leaving burn marks and potentially other damage.
With the increasing preference of using non-metallic additives in hydraulic oils the electrostatic charge could be on the increase. Those hydraulic oils that contain anti-wear additives that are zinc-based have considerably high conductivity.
Conductivity in hydraulic oils helps when it comes to moving electrostatic charge around the system. Although zinc-based additives will rarely collect enough charge to cause a big problem, synthetic oils can. This is because they have less conductivity and therefore will potentially accumulate more charge before discharging it.
Another change that could lead to an increase in electrostatic discharge is that there has been a change made to the materials that filter elements are made of. In order to make them easier to dispose of them in an eco-friendly way, they have more non-metallic material in the design, which lowers conductivity and therefore increases the capacitance.
The manufacturers of hydraulic filters are aware of these issues, and are looking into how they can minimise or even eliminate these issues.
However, if you come across a situation where there is electrostatic discharge in the meantime, then consider this:
By adding larger filter elements you can reduce flow density and therefore the amount of charge that is being generated. You might also want to consider increasing the tank size so that the time between charge generations increases.
This is one of the reasons why you shouldn’t skimp on tank size or on filter capacity.
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Very informative. I shall most certainly be in contact next time I need a powerpack.
Hydraulic Power Pack
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