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In this blog we will be investigating hydraulic lifts; how they operate and why they are a cost effective, reliable alternative to other forms of lift power.
Along with traction lifts, hydraulic lifts are a popular choice for residential, corporate and construction applications and have a number of benefits over their traditional traction based counterparts.
As with any type of lift, hydraulic based lifts need to be maintained at regular intervals to ensure they operate reliably and effectively. Oil is a key part of the hydraulic set up as it is pumped from a purpose built oil reservoir through a hydraulic cylinder to operate the piston, which, in turn propels the lift. Oil cleanliness is paramount for this operation and is recommended to be checked at regular service intervals.
The key working components, i.e. the pump and oil reservoir are often situated in a machine room, commonly found in the near vicinity of the lift itself. This enables easy access for any maintenance engineer to check that things are working correctly with the lift and its components.
Operating the lift – In order for the lift to work correctly, the lift piston, which sits below the lift enclosure itself and controls its movement, must work in harmony with the oil that is pumped into the cylinder which controls the piston itself.
In order to get the lift to rise, the pump valve will need to be in the closed position, thus pushing the oil from the reservoir into the cylinder. The effects of gravity then come into play and the piston is pushed up, raising the lift in the process.
To lower the lift the opposite takes place, where the pump valve is opened and the oil is released back into the oil reservoir, thus allowing the piston, and the lift, in turn, to lower.
Advantages of using Hydraulic Lifts – Firstly, using a hydraulic lift will work out cheaper than its traction based equivalent, as it uses less components. There are no cables to set up along with other parts of machinery which are commonly situated above the lift shaft itself. This makes it a cost effective solution in general if a person is looking to meet a tight budget.
Speaking of cables, another advantage hydraulic lifts have is that they don’t rely on cables to operate making them a safer equivalent; if something were to go wrong with a hydraulic lift, it would lower at the same speed as the oil leaving the cylinder, thus reducing the likelihood of sudden drops.
If space is a key issue then hydraulic lifts are ideal as their main machinery is typically situated to the side of the lift in a machine room, as mentioned at the start of the blog. This leaves the lift shaft itself free from any space consuming machinery, which ultimately aids in the planning process.
At Hydraproducts, we specialise in a range of power packs and units that are suitable for lift applications and to support this, we have recently opened our Component Division, which offers a range of components from hydraulic pumps to cylinders to fit your bespoke unit. Feel free to browse the rest of our website to find out more about our products.
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 .
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.
Having spent over two decades developing a wide range of appropriate hydraulic power units, we have been told by our customers that our hydraulic power units are on point. Not only are they well thought out but they are maintenance friendly, efficient and leak proof. Each one is designed using the most advanced 3D modelling in combination with reliable fluid power analysis tools.
Our hydraulic power units range from micro sized to no-nonsense 375kW systems that are used offshore in the subsea oil and gas industry. Hydraulic power units are often used for serious hard core roles. After all, what else can perform such feats as pulling cars out of canyons, moving massive volumes of earth or lifting giant trees? The only machines that can are hydraulic power units that can convert the movement of liquid into mechanical force.
Power units are actually fairly simple. Their task is to pressurise fluid so that it can perform tasks such as those mentioned above. The fluid is then pushed along through a series of values as it cannot be compressed, so any pressure will cause it to move. At the end of the line, it will go into a piston which will extend as it fills and this is where the magic happens. A giant boulder is lifted up from a river bed or a disabled person’s wheelchair is lifted onto a bus. There are no end to the possible applications of hydraulic power.
Here’s an introduction to our range of hydraulic power units and examples of how they can be used in factories and out in the field:
Standard Hydraulic Power units
The most common requirements are satisfied by these workhorse power units. They offer AC motors up to 30kW and can produce flows up to 100 litres per minute. Holding up to 180 litres in the reservoir and producing hydraulic pressures of up to 250 bar, these machines are used across all manner of industries.
Easy to configure, assemble and maintain, these HPUs are often used for any application that needs a dependable source of power. Industrial machine applications include punching machines, niche areas such as charcoal drying drums and performing any lifting duties.
Mini Hydraulic Power Units
The little brother of the standard isn’t workshy either. Expect AC and DC hydraulic power units that product 30 litres per minute with reservoirs that can hold up to 100 litres and produce 250 bar pressure. These are the machines that can handle up to 5.5 kW.
Our customers find that our mini hydraulic power unit is perfect for a range of applications such as cardboard compacting machines, climbing walls, car park access control equipment and machine tool clamps. They have been designed for easy maintenance and deliver years of trouble free operation. Some of our customers use them on applications that have produced over 1 million operations.
Micro Hydraulic Power units
The smallest of our everyday offerings can still deliver serious power. Although it may have only an 89 mm wide footprint, this little beast is able to handle both reversible and uni-directional work, depending on what you need. DC motors range from 150 to 800 watts and the AC goes from 150 to 275 Watts with flow rates of 5 litres per minute. Hydraulic pressures of 200 bar are the norm.
Perfect for those applications where hydraulic power is needed but the space is limited. For example, our customers have fitted these to step lifts, wheelchair lifts and on through-floor lifts. Although they were originally designed for mobility applications, they have been found to be ideal for wider use including unmanned operations of pipeline control valves to tasks such as lifting glass into place on tall buildings.
Bespoke Hydraulic Products and Systems
Whatever you need, we can design it for you. We have already produced a broad array of hydraulic products that have been used for all manner or purposes across most industries.
Hydraulic power is still something that amazes us. When it comes to transmitting power, hydraulics offer the densest method of it. In the past, we’ve even developed a bespoke hydraulic power unit to flush out gearboxes in the pit garages of F1. You may not know it but next time you watch a movie and you see a full sized ship with rocking hulls on it, it could be one of our products that is creating that rock.
We enjoy solving hydraulic power challenges. If you have one and you don’t know quite how to solve it, contact us today and we’ll work with you to find a solution.
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.
If you’re curious about how hydraulic cylinders work, then you could find this post to be interesting. Let’s take a look at these powerful components that make it possible to move and lift the heaviest of items with ease.
You may not have ever considered this before, but what do you think deploys those huge wheels that aircraft need to land? They are put away tidily throughout a flight, and then when they’re approaching Heathrow, out they pop and all at the pilot’s press of a button.
Landing gear is operated through a hydraulic system. As with any hydraulic system, there are pipes, cylinders and of course hydraulic fluid. The fundamentals of this are the same as with any hydraulic system. When force is applied at one point, it is transmitted to another through the use of incompressible fluid.
Hydraulic cylinders mostly come in parallel pairs that are of differing diameters and are connected by a pipe. The cylinders will be at right angle to the pipe. This arrangement is then filled with a hydraulic fluid such as oil until the cylinders are partly filled.
The space that is left in the hydraulic cylinders will enable the pistons to operate. In one cylinder, the piston will be smaller than in the other. Fluid will be pushed into the chamber of the small piston and when force is applied, it will push the fluid into the chamber of the big piston as it will be incompressible fluid. This will then move the big piston. Due to the difference in size, the effect of the small piston’s movement will be multiplied. So for example if a small piston has a downward force applied to it of 100 lbs – the force on the big piston will be 900 lbs.
Hydraulic cylinders remove the need for a rigid structure when it comes to transferring force between two different points. This can be used to the hydraulic system’s designer’s benefit and a number of twists and turns can be added to the system. For example, there might be a space constraint. Using the different cylinders at different sizes, it’s possible to create a system that will pull, push or even lift heavy weights.
Although the hydraulic systems that are used in our everyday life are not built with cylinders quite as basic as what’s described above, they are fairly similar. Let’s look at the different components involved:
· Cylinder barrel
· Piston rod
· Cylinder bottom (Cap)
· Cylinder head
· Cylinder bottom connection
· Rod glands
There are two different main types of hydraulic cylinders used. The tie rod type of cylinders and the welded body type. The former are used when there is a need for heavy-duty industrial or commercial use. Some are small bore and others large bore. The welded body cylinder type has no steel rods in it. The top of the barrel of the cylinder is welded directly onto the object that is expected and designed to move. Although these cylinders are small in size, they are used in a surprisingly large number of different machines. In some cases it’s necessary to use a telescoping hydraulic cylinder where the piston rod will retract into the barrel of the cylinder.
Hydraulic power has really evolved over the last 50 years or so. Much of the progress has come from the aeronautical industry, surprisingly. Although hydraulics have been used since before the time of the first recorded history, it’s only now that they have really come of age and have made such a tremendous difference to us in so many fields.
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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