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When it comes to getting the best from hydraulic tools, their performance and longevity rely heavily on the quality of hydraulic fluid. Fluid that is both pure and of the right consistency will make the difference between a fully productive business and a sorry looking turnover.
In this blog post we look what will deliver best results from your choice of hydraulic oils.
It’s a fact that hydraulic systems work by transmitting force using an incompressible fluid. However, the type of application that is being used will have different needs for speed, pressure and in some cases electrical properties.
A key benefit of using fluid over the air used in pneumatics is the lubrication offered by it. A thicker oil may produce better results than perhaps a thinner oil that may develop a foaming behaviour when used under high pressure or speed.
Another key area to consider is the temperature that oil will used at. Fluids have the ability to dissipate heat whilst working as a deliverer of power. The negative of this is that when fluid builds up too much heat it can lead to the development of vapour in the hydraulics system. This can lead to system failure – not something that is wanted with a braking system for example. This is the reason that large trucks and other heavy vehicles use air braking.
Although water was used for the early hydraulic systems, most hydraulic fluid is now oil as it offers better lubricant properties in addition to being able to operate at higher temperatures. Other fluids in use include esters or glycols. More recently many manufacturers have been making fluids that are far more environmentally friendly and biodegradable. For example, vegetable oils. This is particularly popular in industries such as agriculture and around water tables that could threaten the safety of human consumption products.
A few blog posts ago we mentioned the “Jaws of Life” which are used by first response medical responders to cut away road crash vehicles to release victims. In this type of application, phosphate-ester fluid is used. Not only is it non-flammable but it has a high resistance to electricity.
If you work in an industry that needs a different solution than what’s available, it’s possible to mix fluids, however this is an area that needs experience and deep knowledge. Knowing how these mixtures will react and how they will perform under certain situations is essential.
Whatever your hydraulic system is, be careful about using the right fluid. It will make all the difference with the performance of your tool, but it could also affect health and safety considerations.
Some companies run a lot of different hydraulic equipment. Firefighters are one example of a workplace that uses a range of hydraulic equipment, each with its own specification of the type of hydraulic fluid that is indicated for use. Construction, healthcare and agriculture also use a range of different hydraulically powered equipment, from hospital beds to hay balers and everything in between. Being in charge of maintaining all this equipment is a large undertaking, and a common theme for those tasked with keeping everything running is staying on top of the sheer number of different types of hydraulic fluids that are stored and used routinely.
There may be very good reasons why a piece of equipment uses a certain type of hydraulic fluid, but sometimes the choice is determined by the past – “we've always used that type of oil so we will continue to do so” – is a common reason behind why different types of oil are used. That, coupled with the fact that some engineers have their own favourite types, can mean that after a few years the stock of hydraulic fluids is running into tens of bottles, all half empty (or full, depending on how you look at things) and taking up valuable storage space. There are some ways you can reduce the number of containers and types of oil you use.
Firstly, identify which bottle correlates to which piece of equipment. There may be more than one for very complex equipment. Mark the bottles so you know what hydraulic fluid goes with what. Anything that is unmarked can be discarded, as it is probably not in use anymore. Any bottles that are old or have been open for a long time may have degraded past the point at which they are still useable – the more contact there is between a hydraulic fluid and the air the more degradation will have occurred, so to avoid accidentally using hydraulic fluids that have gone off it is a good idea to regularly discard old containers.
The next stage is to identify where the same, or very similar fluids are being used on more than one type of hydraulic equipment. All hydraulic fluids have a viscosity rating, but these are a guideline of the viscosity under normal operating conditions. There is a 10 per cent variation on the viscosity grade, so where there are fluids of, say, 38, 40 and 42 grade then one grade should fulfil the requirements of the three varying grades. Consolidating the same types of fluid into one viscosity grade for all pieces of hydraulic equipment could reduce the number of bottles considerably, and make it much easier for anyone replacing or topping up the fluid levels.
It is important when consolidating fluid choices in this way that one refers to the specification of each piece of machinery, to ensure that there are no special reasons why a particular grade of hydraulic fluid is used. Pieces of machinery that experience a lot of fluctuation in operating temperature may require a certain type of hydraulic oil to ensure premium performance throughout operation.
When choosing new hydraulic equipment, it is worth considering whether the fluid types indicated by the manufacturer matches what you already have, and whether you are able to use one of the hydraulic fluids you already own if they are a close enough match. By keeping things very simple and reducing the number of hydraulic fluids kept on site you can save money, time and avoid unnecessary cross contamination of fluids within the machinery.
We have said it before and we will say it again: hydraulic power really is one of the most important technological advancements of all time! It frequently helps our society run and function far more smoothly and efficiently and most of us would not even realise. However, we are sure that nearly all of us would notice if the world suddenly stopped using hydraulic power because the world would be a very, VERY different place.
Hydraulic power is used in so many everyday applications from mechanical lifts to bulldozers and now even in our braking systems. In this article we are going to share with you, in our opinion some of the most interesting facts about hydraulic power out there.
All hydraulic power systems will contain four core components. These include the fluid reservoir, which quite simply houses the fluid, a pump to spread the fluid through the system, a cylinder to convert the fluid movement and the valves which control pressure and flow.
The word hydraulics originates from the Greek word ‘Hydros’ meaning water. This is because water was the first liquid to be used in hydraulic systems.
Hydraulic pumps are used by NASA’s in their space shuttle. These pumps operate at a whopping 3600 revolutions per minute and each one could supply hydraulic pressure of 3050 PSI.
For hydraulic power to work it must flow. If the flow encounters any block or opening, then the pressure will drop. For hydraulics to work, it is vital that the flow is unrestricted.
Hydraulics was discovered in the 17th and 18th century by two men Pascal and Bernoulli. Their principals led Joseph Bramah in the late 17th century to create the first hydraulic press. This press was used to pump beers from cellars to the taps in public bars.
Hydraulics are not the only way to transmit energy, many industries also used mechanical, electrical and pneumatic energy. Mechanical energy is from crank mechanisms, shafts and linkages, electrical is from electric motors. Pneumatics is the closest to hydraulics but instead of using fluid it used gas.
Without the pressure, you would not have hydraulic power. Hydraulic systems contain fluid that is under intense pressure. Pressurised fluid is what produces energy.
Did you know that not all hydraulic systems are the same? Generally you have two types of systems, firstly there is an open centre system and secondly there is the closed centre system. The open system has a varied pressure with constant flow and closed systems have constant pressure and varied flow.
Many people believe the common misconception that oil is pulled through the system, this is not the case. Hydraulic power is created by air pressure pushing the fluid through the system not pulling.
Finally, our last fact is that hydraulics can produce three different types of energy. You have kinetic energy which is caused by moving fluids, you have heat energy which is produced by resistance to the flow and lastly you have potential energy which is caused by the pressure.
There are so many other interesting facts about hydraulics but we really could be here all day.
Firefighters use hydraulic equipment on a daily basis when they put out blazes and rescue people from burning buildings or crashed vehicles. The ladder on top of a fire engine is raised and lowered by a hydraulic piston, that is controlled by the ground crew, with another set of hydraulic hoses controlling the extension of each section of the ladder independently, allowing the correct length of ladder to be deployed for each situation. The ladder position is also controlled by a hydraulic motor, that turns the ladder left and right, making it easy to get the ladder in exactly the right place by using all three hydraulic components.
It is not just the firefighters ladder that uses hydraulic power, but the rescue and cutting tools, as well. Fire crews are often called upon to rescue people from crushed vehicles and getting them free is often a time sensitive operation, so the large forces exerted by hydraulic cutters, rams and spreading equipment are vital in terms of getting people free as quickly as possible. These tools operate at 720 bar, which is a large enough force to cut through steel rods and easily bend the structure of a car or lorry cab. Often referred to as the Jaws of Life, some hydraulic rescue equipment combines cutting and spreading capabilities into one tool, as both these functions are usually needed in rescue situations. Hydraulic jacks are carried on some fire trucks that are called to the scene of a heavy vehicle crash, as lifting a crashed train carriage or petrol tanker requires some serious force to be applied quickly, especially if there are people trapped underneath or inside the vehicle.
The choice of hydraulic fluid is very important in fire engines, as by nature they are used in situations where high temperatures are present. The fluid used in hydraulic rescue equipment is usually a phosphate-ester fluid, that does not conduct electrical charge and is fire resistant. It is vital that the hydraulic fluid used is fire resistant and capable of operating at high temperatures. Hydraulic fluid does heat up under pressure, so adding this factor to the issues of prolonged exposure to high heat at fire scenes means that there are limited choices of hydraulic fluids for fire engines. If oil based hydraulic fluids are used there is a high risk of fire if a line breaks or there is a leak, so for safety reasons any fluids used on a fire truck must be non-flammable.
Regular checks and maintenance of hydraulic fluid levels should be performed with any equipment that uses hydraulic fluids, but in the case of fire trucks it can make the difference between life and death. Fluid reservoir levels should be checked under the same conditions each time, which is best done when the fluid is cold and the fire engine has not been recently used. Keeping the reservoir topped up reduces the risk of air entering the system through the pump, which can lead to faulty operation and lasting damage to the components. This is a job that firefighters can carry out at their station, but for testing the hydraulic fluid a professional service should be used. The hydraulic fluid should be replaced regularly to keep the equipment in good working order.
Each type of hydraulic equipment may use a different type of fluid, and it is important that these are not mixed up during routine maintenance. Most fire departments display the information clearly at the point of topping up on the inside of cap covers or nearby. It is also good practice to label the fluid containers so they are not accidentally used on the wrong engine or the wrong piece of equipment, as each fire department may favour a particular type of oil for each application, and when fire trucks are loaned out to other departments there is a serious risk of hydraulic fluid mix up.
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 .
The purpose of check valves within Hydraulic Power Packs and Systems is to allow fluid to pass in one direction but to prevent it from travelling the other direction, or doing what is known as a reverse flow. The device is usually added to a pipe to prevent oil from flowing backwards. When necessary the valve will close so that all backward movement of fluid is stopped.
The hydraulic check valve has two ports. One is the inlet for the hydraulic fluid to enter and the other is an outlet. They will both operate in combination with the motor, cylinders and hydraulic pump. The valve controls the flow of fluid for the correct operation of equipment.
Hydraulic valves are available in a number of different designs. They may look like a poppet, a disc or one of the ball or plunger types. This will depend on where and how they are being used as to what style and size is used.
Most often you’ll find hydraulic check valves used in application such as braking systems, construction tools, lifting systems and other hydraulic systems. They are installed in systems where the backup of fluid could cause serious issues.
For example, if oil flowed backwards through a pipe, it could empty a hydraulic system back into the equipment reservoir. Even when the machine is turned off the hydraulic valve can prevent fluid from flowing through the system, keeping it full ready for the next time it is operated.
Dual Pilot Operated Check valves (abbreviated P.O.C), are check valves that can be opened by an external pilot pressure. Flow is blocked in one direction as per a standard in line check valve, but it can be opened when sufficient pressure from a pilot line is applied to the third port. The pressure required at the pilot port is normally only 1/3 of the pressure locked within the cylinder. This is determined by the Pilot Ratio (3:1 and 4.5:1) are normally available. They are regularly used with double acting cylinders to lock the system when pressure is switched off, either intentionally or by accident or failure. They can be fitted directly between ports on a ram or incorporated into a power manifold block or module. It is preferable to mount them directly to a ram with “hard” pipework as this increases the integrity of the device. If the pilot check is only required or desired on one side of a cylinder then it can be on the A or B sides, referred to pilot check on A or B.
Regular applications for pilot check valves are rear loading ramps on commercial vehicles. Balers and compactors where the load needs to be held while baling occurs. Security access bollards and blockers to stop the creeping down when the system is at rest. It is important top note that POC are not best suited to applications that have a load that that will over run when they are reversed.
Flow control valves regulate the flow of a fluid and take many forms:
Fixed orifice: Basically a hole in a tube or an insert that fits into the hydraulic line, restricting the amount of fluid that can pass through it for a given pressure.
Adjustable orifice: The size of the effective orifice is adjustable. Common forms are inline and barrel type where the body of the valve is twisted, needle valves for fine adjustment on low flow systems. When set the adjustment can be locked. These are regularly used on lifts or tipper applications where the load is uniform.
Pressure compensating: When a load such as a cantilever passes through an arc the system pressure can vary. This causes the speed of the cylinder to change leading to potentially undesired results. To overcome this pressure compensating valve account for changes in pressure and delivers broadly uniform flow to the hydraulic actuator. In a scissor lift a high pressure is required at the initial raise and decreases as the mechanical advantage increases. The reverse is true when lowering under gravity so a compensating flow control is suited here.
Reverse flow check: On a single acting power pack the pump and motor combination are optimized to give the desired lift speed of the hydraulic cylinder. The flow control valve has an integral bypass line that allows full flow in the out direction, through a built-in check valve. When lowering the full flow oil path is checked and forced to go through the flow restriction allowing controlled descent of the cylinder.
This consists of two valves in one block. When operating a double acting ram the extend and retract speeds will differ, due to the different fluid volumes. From our control valve full flow is permitted through in one direction whereas the other side is flow controlled and/or vice versa, in this way the different valve settings will optimize the actuator speeds. A common example of this valve configuration would be a rear door on a horsebox where the door will need to close much more slowly to prevent shock and noise.
A relief valve is an important control device in virtually every hydraulic system. They protect the overall system from generating a pressure that could cause mechanical failure. It is a mechanical valve that requires no external input other the applied pressure. When this excess pressure is relieved it re-seats to allow normal operation to resume. The most common type comprises a spring and plunger pushing onto a seat. If the pressure exceeds that of the spring force the oil is spilled to a volume usually the oil reservoir. The springs have adjustment ranges for example 20-100 bar and the valves can be housed in cartridge, module or designed directly into an aluminum or steel hydraulic manifold.
A hydraulic circuit may have multiple relief valves, one at the power pack end to protect the pump, another may be fitted onto a control valve circuit to relieve an induced load caused by external mechanical forces. If a hydraulic cylinder requires different relief valve settings on it full bore or annulus side then a dual relief valve module can be set to handle these needs. On the annulus side the area the oil is acting upon is smaller requiring higher pressures to exert the same force as the full bore side hence two relief valve settings are needed. One example of this is a hydropower generation sluice gate operation where something jammed in the gate such as log stops it closing.
Some terms associated with relief valve operation:
Overshoot: The pressure reading when a relief valve operates to bypass fluid. (It can be two times the actual setting.)
Hysteresis: The difference in pressure when a relief valve starts spilling some flow (cracking pressure) and when full flow is passing.
Stability: pressure fluctuation as the relief valve is bypassing at its set pressure.
Reseat pressure: The pressure a relief valve closes at after it has been operating.
Counterbalance valves are fundamentally a relief valve that is fitted in an application to generate back pressure in a system. They are normally used for ‘counterbalancing’ a load to stop it from running away during lowering. The valve is usually set at 30 percent higher than the pressure induced by the load.
Figure 1 Counterbalance valve circuit.
A built in check valve allows flow in the reverse direction (i.e. to by-pass the counterbalance valve when lifting the load). It should be noted that both sides of the valve will be subjected to full pressure, this is not possible on all relief valve designs. In Figure 1 the counterbalance valve has an integral check valve. When counterbalancing the return path must have a low back pressure to tank, as this will be additive to the valve setting.
Hydraulic Power Pack
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