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As we have covered before, contamination of hydraulic fluid can cause a lot of different issues to the system. Therefore, removing this contamination can prevent damage and failure of the system. The approach we are covering here is the practice of flushing.
The damage that can be caused by contamination includes internal leakage, flow and pressure issues. This can lead to wasted power and an increase in heat to excessive levels. There is also the possibility of parts sticking due to there being silt or sludge in the system, which can even lead to seizures when there are large amounts of contaminants present.
Contamination can be caused by particles or by water or air. Moisture can cause many problems in the hydraulic system. When dealing with this issue, most engineers recommend that a lower viscosity ‘bog standard’ fluid is used to flush the system, one without any expensive additives in combination with a rig.
To get the best results, the flushing would take place in both directions with the fluid at a temperature of around 140°F with turbulent flow in effect. Usually turbulent flow is to be avoided, but when flushing is taking place, it’s important to do what’s possible to aid the dislodgement and removal of contamination.
This is also another reason why using low viscosity fluid helps. What rate of flow you’ll need to reach turbulent flow conditions will depend upon the diameter of the inside of the conductor.
The flushing rig must be able to generate a flow rate that is more than what the hydraulic system has been designed for.
How long you’ll need to do this for will depend upon what your particle rates are. They should be monitored and recorded regularly to avoid damage. Not doing so could become a costly mistake.
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.
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 the world of industrial, mobile and aerospace equipment, hydraulic power systems are very popular. They enjoy a high power-to-weight ratio in addition to being able to be stalled, operated intermittently and even reversed. They can also accelerate fast and are quick to respond. Another attractive feature of the fluid power system is that they can be very long lasting in addition to offer reliable operation rates.
Hydraulic systems are able to work as they contain incompressible liquid. In many situations, it’s much preferred to use hydraulics to move machinery. For one, fluid systems do not produce the same amount of wear as a dryer method would. It also does not require so many moving parts as a different type of system would.
The pressure of fluid in the hydraulic system is controlled by the valve. They also handle the flow rate and which way the flow is going. The funny thing about hydraulic valves is that they can change name depending on how they are being used and according to which system that are part of. Used in combination with cylinders and hydraulic pumps to control the flow of liquid, hydraulic valves are powerful.
The classification of hydraulic valves is determined by how much pressure they can handle. It is also related to the flow and how many directional control valves there are in them. They may also be classified on their looks and extra features such as needle valves, spools and poppets.
Apart from their ability at moving very heavy objects, one of the reasons that hydraulic systems are so popular is because they can operate at very low noise levels. In the manufacturing industry, a low noise level is sought after, in particular at less than 70dB. The hydraulic system and pump is able to accomplish this.
The hydraulic control valve is a clever piece of kit. Browse hydraulic valves here.
Although hydraulic systems must be lauded for the amazing technological innovation that it is, there are also some other points that you need to know.
When it comes to cars, there are a variety of ways that hydraulics brought benefits from their invention and use. For example, if you have a flat tyre you will reach for the jack to lift up your car to change the tyre. In more modern times the hand cranked device has evolved into the hydraulic jack. Not only does it save your own energy to use these devices, but it will also save time. (FYI here at HydraProducts we have experience in the automotive industry and design hydraulic drive shafts for Mondeo cars).
Another car related hydraulic use is that of hydraulic brakes. The power of the hydraulic system means that there is considerably greater stopping power than that delivered through other braking methods. Car designers are increasingly making use of hydraulics when it comes to back doors and closers. Doors on large vehicles used to difficult to open and close, but with an automatic closer vehicle owners that have their hands full of shopping or other items can conveniently operate this feature for easy access and use of their boot.
It’s not only with cars that hydraulics have entered into all areas of our lives. There are also other tools such as pulleys and levers.
However, for the lay person there are also some risks. For example, hydraulics can easily crush fingers and hands due to their power. A child’s hand in the wrong place at the wrong time can be hurt if a hydraulic powered door were to close on it.
It’s also important to know that the fluid in hydraulic systems can also be made up of very dangerous chemicals. They can cause burns if they touch human skin, although not every substance is harmful, it’s wise to pay attention to leaks and potential leaks.
Hydraulic systems that are not carefully designed and manufactured can cause injury if not handled safely.
All our designs take safety into mind as much as possible. We also make bespoke hydraulic systems for applications that can benefit from hydraulic power.
Humans are creatures of habit, we like routine and familiarity as it makes us feel safe. Change is a hard pill to swallow; although some people deal with it better than others it can take a lot for someone to proactively look at a different way of doing things. Change is usually something that is imposed upon a person out of necessity, so if there is no perceived reason to change a situation then we generally carry on as normal.
This thought pattern may be one reason why hydraulic systems designers tend to opt for high pressure systems and the familiar components that can cope with being under extreme pressure. It is far easier to take an existing basic idea and tailor it for a new application without even considering alternative approaches, which is why low pressure hydraulic systems are something of a rarity in the world of fluid power.
The basic equation of force = pressure x area, lends itself to working with a smaller area and a higher pressure to exact the same amount of force that a large area under lower pressure would exert. This is attractive to designers as it means systems can have sleek, narrow cylinders and in many cases, this is needed to ensure the assembly fits in the space available. That is not always the case, however, so hydraulic designers should consider low pressure systems as a possibility for some applications.
Low pressure hydraulic systems can be a lot more cost effective than high pressure ones, as there is a reduce possibility of leaks, and if they do occur they will take less time to clean up and fix. The materials used to build the components can also be a lot cheaper, as they will not have to withstand the high pressures normally associated with hydraulic systems. Plastic components, flexible nylon tubing and even thin extruded aluminium cylinders all work perfectly well at pressures under 50 or 60 bar, and are a lot more economical than the high pressure alternatives.
Sometimes a low-pressure system is really the only possible solution to a problem, especially when designing complex systems with many lengths of tubing, serving several small cylinders off a central motor. This is when the materials that need to be used dictate the operating pressure of the system, rather than the operating pressure dictating the materials. If the pipes need to fit through pre-defined holes in the machinery casing, or need to wind around parts of the machinery then flexible nylon is the best option. This low-pressure approach allows designers to consider every angle from which to solve the design problem, and can result in some great innovations that otherwise might have gone undiscovered.
The only drawback to low pressure hydraulic systems is the need for a larger reservoir to hold the extra fluid that is needed to fill the system when it is in operation. Size and space can be a stumbling block for low pressure systems, as the larger cylinder diameter means more space is needed. Sometimes this can be cleverly engineered in, by placing the reservoir further away from the operational components of the hydraulic system and making good use of the cheap nylon tubing to run the fluid up to the moving parts.
There will always be cases where high pressure systems are a must, due to the application, the forces needed and the space available to house the hydraulic system, but at the same time there will always be systems where low pressure is more effective in terms of performance and cost, so considering both angles before diving in to a design is a worthwhile task that could lead to the next big thing in hydraulics.
Global demand is not easing up when it comes to farming vital resources that are found in subsea environments. In fact, industries have now begun to expand their efforts and are putting more energy and effort into devising machines that are capable of delivering what is required.
With over 60% of the surface of the earth covered by water, it’s no secret that there are many resources that are awaiting exploration and development. This new frontier has a number of industries involved including oil and gas, natural science, mining, energy generation and infrastructure.
Hydraulic systems are incredibly useful to remote operated vehicles that are used underwater. They offer high power density and a reliability not found in other systems. It’s possible to use hydraulics in such a way that the vehicle is very compact and therefore it can be deployed and recovered easier.
Highly technical and complex systems need to be serviced and maintained by subsea remote operated vehicles. For example, equipment needs to be lowered and lifted to the seabed, emplaced systems need to be monitored, such as communication cables and petroleum wellheads.
Although some subsea hydraulic equipment is designed specifically for the task, in some cases, the equipment has been manufactured to a quality that can handle the high pressures and the corrosive conditions of the depths of the sea anyway and needs just a little customisation to perform at a reliable level. A major factor that is considered is the depth of the water and how that could impact the hydraulic system.
Here are other considerations that go into developing hydraulic systems for subsea operations:
Machines that operate at 1000ft below sea level are required to operate in salt water, but the water-pressure is not significantly high. Another factor that has to be catered for is that sunlight can reach up to 800ft into the water and could promote the growth of sea life over the surface of the equipment such as the cylinders and the rods.
Beyond 1000ft to as deep as 6,000ft, pressure becomes a major factor. Increasingly 14.5psi for every 10m of depth, it will be as high as 7250psi at 5000m. It’s at these depths that work is performed by subsea robots such as AUVs (autonomous underwater vehicles) and ROVs (remote operated vehicles).
Subsea vehicles aren’t typically in use for long periods of time. They will be used to accomplish tasks in electromechanically and electrohydraulic subsystems. Although they can operate beyond 100m of depth they typically won’t be submerged for long periods of time. However, they need to be ready when required and any downtime must be kept to a minimum.
Special design features may be required for components exposed to water pressures this high. For example, structural modifications may be required or pressure compensation.
These depths would normally be found a long way from shore, therefore would be operated by either ships, platforms or floating platforms. Water that is from 6000ft to 35,800ft is rarely entered unless it’s by subsea vehicles from the military or research. The conditions are so extreme, that every piece of equipment, including hoisting and tethering will need to be engineered to handle the weight and dimensions of systems at this water depth. In addition the size of the waves are larger, as are the forces brought on by maritime currents.
Ambient hydrostatic pressure is exposed to the hydraulic fluid using a pressure compensation system, with a flexible seal to prevent hydraulic fluid and seawater from making contact.
The benefits of hydraulic drives are brought into their own in these types of machines. Not only are they powerful and compact, rugged but precise, they are able to deliver power and be flexible for a wide range of tasks.
Engineers continue to work on how they can make the best of what hydraulic systems offer when it comes to subsea conditions.
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