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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.
If you’ve been in the hydraulic industry for some time, there’s no doubt that at some point you will have seen cloudy oil. This is what happens when there is contamination with water above the oil’s level of saturation. The definition of a saturation level is how much water can dissolve in oil – for mineral hydraulic oil this will typically be around the 200 to 300 ppm at 68 F or 20 C.
As an aside, something worth knowing is that bearing life can be increased by almost 150% if water concentration is reduced to just 25 ppm.
The more water in the oil, the more issues you’re going to face. One of our engineers recently witnessed oil that so was incredibly cloudy because it had over 10,000 ppm of water in it which actually made it more than 1% water!
Here’s what happens when there is water in hydraulic fluid:
· Either depletes or reacts with additives to form by-products that can corrode some metals
· Clogs filters by reducing filterability
· Increases ability of air entrainment
· The likelihood of cavitation increases
· Lubricating film-strength is reduced leading to corrosion and wear vulnerability
It’s also possible to spawn bacteria with water present in oil.
Measuring and Removing Water
How can you measure how much oil and how much water you have in your hydraulic fluid?
The test that is considered to be the standard laboratory method is the Karl Fischer Volumetric Regent Method which others may know simply as the Karl Fischer test. Another method sometimes used is the FTIR or Fourier transform infrared spectroscopy test. However, this is a test that can only really be considered effective with oil and water mixes that are greater than 1000 ppm of water. If you’re serious about measuring water contamination, we recommend that you go with the Karl Fischer.
Now that you know that there are some very unpleasant side effects when there is water in your oil, what are you options with regards to removing it? If you’ve got a system that has only a small volume of oil, then you may opt to change the oil. This option will most likely prove to be the most cost effective approach. For larger oil volumes, it’s best to use filters built for water removal when there is small amounts of water involved.
Water removal filters come in two types, polymeric and coalescing. The former works by using chemicals that attract water. They absorb water drops and retain them permanently. Whereas coalescing filters collect the water and put it into a collector which is drained once in a while. Water that has been dissolved will not be collected by either filter types.
Another approach to collect water is the headspace dehumidification approach. This uses the reservoir’s headspace to circulate and dehumidify the air. Water will then migrate to the headspace where it is removed by a dehumidifier.
Headspace flush is another approach that is similar to the previous method, except that it is collected by a small flow of dry compressed air that is flushed through the headspace. The dry air will pick up the water.
One more approach is to use a variation on the headspace flush by using a hygroscopic breather and then connecting a vacuum pump. This approach is reliant on a spare port located on the top of the reservoir, as distant from the breather as possible. This method does not need a source of dry compressed air.
We are in the business of supplying mobile power packs for hydraulic systems. If you want to know more about our products, browse through our hydraulic unit product pages or call us for a no obligation chat.
Businesses all over the world are now looking at how to move away from fossil fuels such as oil and our utter dependence upon them. A variety of experiments using alternative fuel are now being performed in many different areas of several industries. One of these experiments is to test whether water might be able to take the place of hydraulic oil.
Most hydraulic equipment uses oil to power the cylinders, pumps and valves that are at the core of the operations of industrial equipment such as hydraulic machines. Once the hydraulic oil is under pressure it can power the cylinders by exerting force. But is it possible that water can do the same job?
Although some hydraulic equipment has been used successfully with water, in particular for applications that require a high level of fire resistance, most hydraulics need the water to have an additive used. This then makes it possible for there to be lubrication in the machine, even if 95% of the fluid is water.
There are some exciting results coming from engineering company, Danfoss, who has been designing and manufacturing hydraulic equipment that can operate with just water. Working without any additives, this hydraulic equipment prototype is 100% green. It has made it possible for suitable components to be manufactured to support the hydraulic system.
Advantages of water hydraulics
Because water is not flammable, and it can be used for other purposes such as fire safety, it can work well. However, it operates at a much lower pressure as it’s not as viscous as oil. This means that it can transmit power far more efficiently than oil, and in a far smaller area. So it could actually be more powerful than oil when it comes to hydraulic powered activities.
As water transfers heat better, it will also mean a smaller heat exchanger than is necessary for oil.
However, because water is lower when it comes to viscosity, this could prevent an issue with greater leakage. Rubber seals would need to be used and there wouldn’t be such great lubrication, so finishes to components would need to be smooth to aid movement.
In addition, because water will easily turn to vapour, there will need to be pressurized lines into the pump. If temperatures are low, the machinery might not be able to operate as the water could freeze at a far lower temperature than oil.
Watch this space for latest news as more exploration is done in the area of replacing hydraulic oil with water.
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.
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.
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.
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