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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.
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.
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.
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.
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.
Although using high-pressure hydraulic systems is considered to be one of the safest methods of applying force, there are still some important factors to take into account. They are powerful tools and can take on any bending, lifting, pushing or pulling work that you need performed, but there are some important safety factors that need to be observed.
Surprisingly, one of the weak points of the hydraulic system when it comes to safety is that it is very easy to use. This can lead to complacency and in some cases abuse. As with any type of equipment use, there are rules to be followed and disciplines to observe in order to get the best from these machines whilst keeping yourself and others in the vicinity of the equipment safe from harm. Following these guidelines can also often ensure longer lifespan and greater efficiency of the machinery.
In the following passages we look at the different areas of safety that will need to be taken into consideration when dealing with high pressure hydraulic tools.
Just as with any equipment, it’s necessary to observe standard safety rules. This means that gloves, safety glasses, boots or safety shoes and a hard hat all need to be worn. As in any environment that can be hazardous, these should be considered fundamental necessities.
Although most engineers will take the most obvious precautions to avoid accidents whilst taking the longevity of the equipment life into consideration, most mishaps and issues will come from either not operating the equipment properly or not assembling it in the right way. It’s important to understand each function in addition to being clear how it works. Take time out to learn your machinery and how it works.
Lifting of loads that are over capacity is something that can result in trouble. Not only will the cylinders be at risk of damage but it can also result in bent plungers and blown seals.
Keep in mind the following points:
- Take an estimate of what you think the load will be, then apply a suitable safety factor.
- Keep in mind that some of your pumps will be equipped with relief valves whilst others won’t be.
- The use of a gauge will help to give an indication of which operating loads are safe.
- Your gauge should also be used to determine whether there is any pressure in the system before you make any changes or breaks in the hydraulic connection.
- Check your environment before you either advance or retract a cylinder.
Fundamentally, two types of cylinders are used in hydraulic systems. The single acting and the double acting.
Single acting cylinders may be any of these types:
· Spring return
· Load return
Double acting cylinders work with the use of hydraulics and advance and retract.
It’s important that you follow these safety guideline rules for cylinders:
- If you need to position the cylinder on the ground, ensure that the base is able to bear the weight of it. It wouldn’t be funny to watch your hydraulic cylinder disappear into soil. A jacking based should be used, or at least a steel or timber plate that will enable the load to be spread.
- The saddle should have the load spread across it, and not be point loaded.
- Stay clear of and be careful around any areas that are directly below a load that the hydraulic cylinder is supporting.
- Situate your cylinders in order to give enough clearance space for extension of them.
- Excessive heat is any heat that is above and beyond 65°C. This needs to be avoided otherwise packing will be softened and hoses weakened. If there is heat that is not avoidable, use either a piece of metal or a heat-resistant blanket to protect the cylinder.
- Keep oil connectors clean and wipe any couplers before they are connected. Dust caps are provided for a reason and that’s to keep dust and dirt out. If you choose not to use them, be aware that you’re likely to experience scoring of the cylinder walls and this can lead to the eventual failure of seals.
- Over-extending cylinders should be avoided as not all of them have safety stop-rings installed.
- If you need to add oil to the pump, check whether the cylinder is already extended, if it is be sure not to disconnect them. The trouble with having too much oil in the system is that your reservoir could become pressurised and blow. If it doesn’t blow it will rupture.
Hydraulic Hand pumps
Depending upon the speed and oil capacity of your system, there is likely to be a pump available for each cylinder. These may be power-assisted or they could be manual in nature. Those applications that are lower speed and where it’s necessary to have that added human ‘touch’ will usually have a hand pump. If the application needs faster movement, or the cylinder is particularly large, then it will use a power pump.
It’s essential that the pump valve is suitable for the cylinder. For example, with single acting cylinders, there is usually a pump that has a 2 way or a 3 way valve. This equates to one outlet. When it comes to double acting cylinders you’re likely to find a 4 way valve which means it has 2 outlets. It’s dangerous to use a 2 way valves in combination with a double acting cylinder.
Check the pump reservoir level before using. Fill using the correct procedures if necessary. Remember that pump hoses will shorten when they are filled with pressure, so ensure there is enough slack to handle this.
With regards to power pumps, you can expect to come across one of these types:
· Petrol / Diesel
It’s fairly obvious that hose failure can occur after heavy objects being dropped on the hose cause damage, but it’s surprising how this escapes the thoughts of many engineers. We often hear stories of how something was dropped but then it was a forgotten memory and the next thing the engineer knows, the hose has failed and there has been a hydraulics disaster.
Another strongly recommended tip is that hydraulic equipment should not be carried by the hose. Most of us are well aware of this, but you will need to keep an eye on any young apprentices who are as yet unfamiliar with the norms of operating hydraulic systems. There should also be an eye kept out for any sharp bends in the hose. The internal wire braids can be damaged from this type of event and this will weaken the set up and could result in leaks and at worst a lethal situation.
An essential fundamental when it comes to hydraulic system safety is to check all fittings, hoses and connections to ensure that they are tightened as they should be and that they comply with the amount of pressure that they will need to be able to handle with your specific system.
We generally recommend that hydraulic systems use oil that is suggested by the manufacturer. The system will usually have been manufactured around that oil and the creators know that it will perform best with that particular one. You will need to change the oil periodically. This will ensure that the system does not get damaged by dirty oil. Ensure that hydraulic oils do not touch your skin.
After you have finished using your hydraulic machinery, it’s time to get it ready for the next job. You will need to clean it before storing it. You can do this by wiping it down. You will also need to lubricate any parts that are exposed.
In conclusion, operating hydraulic systems safely entails using the right cylinder with the right pump and the right oil. Although these rules may seem obvious and safe, it’s surprising how many people fail to adhere to them and put themselves and others in danger. Hydraulic equipment is very powerful but it can also be very dangerous.
In this week’s blog we look at how water contamination can affect hydraulic fluid, especially with the winter months approaching, where freezing temperatures can interact with system operation causing potential system damage.
If you see a cloudy build up appearing within the oil in your hydraulic power unit, this could point to water contamination and must be investigated immediately, as it shows that water has risen above the typical saturation level when mixed with oil giving a cloudy-like appearance. This saturation level comes at approximately 200 - 300 ppm at 20°C (68°F) for mineral based hydraulic oil.
Ideally, preventative measures should be taken from the outset to remove the chances of water ingress contaminating oil and this is where desiccant breathers come in to the equation. We have covered these in a recent blog and highlighted their benefits in reducing moisture entering a hydraulic power unit. The silicone gel contained within the desiccate breather soaks up any moisture present, thus helping the system to run at optimal efficiency.
Passing dry desiccant air directly through the system to dry the oil is another effective method of filtering out water and this is best carried out at approximately -40°F dew point temperature. Water ingress and moisture is most commonly found entering the system through the reservoir breather cap, so replacing the standard cap with a purpose built breather will help to alleviate this problem.
When monitoring the colour of the hydraulic oil itself to identify any potential water contamination, it is not always a warning sign if the fluid had some discolouration as this could be attributed to such things as thermal stress and oxidation, which can be commonly found in systems but still need to be monitored to rule out any other issues that may arise. This may include increased heat generated through pressure loss and component failure within the system.
It is always best to take a sample of oil and check it fully for contaminant traces so the exact cause of discolouration can be identified, as speculating and guesswork at this stage could prove to be costly.
The environment around the hydraulic power unit can play a big part in the contamination process. For example, cold temperatures and lack of proper ventilation will contribute to moisture building around the system and increase the possibility of it seeping in, so locating the hydraulic system correctly is crucial. Freezing is another big issue because if the liquid is exposed to extremely low temperatures it could cause catastrophic damage to a system, rendering it in-operational as components could seize up and cause the system to malfunction.
At Hydraproducts, we have the facilities to test if contaminants are present in hydraulic fluid; these samples are then sent off to the lab for further analysis where required to pinpoint exactly what is causing the contamination so it can be effectively dealt with. We always test our hydraulic power units fully before they reach our end customer, to ensure that they are in optimal running condition prior to their first use in an application.
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