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Which machine would you point to as the best example of the use of hydraulics? Judging on raw power, you might point to a shredder. They can suck things in, chew them up and spit them out within seconds.
Alternatively, you might be under the impression that the bucket wheel excavator is the most outstanding example of hydraulics at work. It’s got serious power as it excavates at a rate of 10,000 yards of earth each hour. Unsurprisingly, your neighbours wouldn’t be happy with the 20ft wide swath at 8 ft deep if you drove one of these down your street though.
Something that many consider to be one of the most awesome machines is the tunnel borer. It can bore through rock at a rate of 22ft in diameter wherever it’s headed – through mountains or under the sea, lakes or rivers: Think Channel Tunnel.
However, I wouldn’t choose any of these; I’d go for the conveyor. Although you may not associate that with a hydraulic, the conveyor can be very powerful. Although the majority of conveyors have an electric motor to power them with either a chain or a belt drive, it’s not the case for all of them.
The hydraulic motor is far smaller and lighter than an electric motor that can deliver the same amount of power. They can also operate at lower speed and aren’t dependent on a belt, chain or gear drives to assist. This is what puts hydraulic motors in front, as this means that they need very little space.
These types of conveyors would be used in a fishing boat. In fact, one that we are aware of can process over 50,000 fish per hour in an environment that has a lot of wash-down. Not a great place for an electric motor to operate.
With hydraulic motors it’s possible to locate them inside the head pulleys of conveyors. There are no external drives, although they are really around the same size as the idler pulleys of the conveyors. If you weren’t aware of the hydraulic hoses that are connected to the pulleys, you’d be puzzled as to how the conveyors are powered. Impressive stuff!
Which hydraulic powered machine most awes you?
Are you interested in what can cut costs when it comes to Hydraulic Power in your business?
We can only imagine that the answer is ‘yes’ as most of us are. Well, we’ve got some good news for you. Today, we’re going to look at what the most common reasons are that hydraulic components fail, even those that have not been in service for long.
These points are worth making a note of:
1. Oil changes. It’s not necessary to keep changing the oil unless you have one of thes2 following conditions occurring.
The oil has degraded so far that the original additives have changed its makeup. Changing oil just because you feel it’s about time it’s changed is going to cost you a lot of outlay as oil is expensive. The larger your reservoir, the worse off you’ll be. However, if you keep operating your system with degraded oil, then that could cost you even more. Even changing the oil based on how long it’s been in service isn’t going to help. Oil needs to be analysed to fully understand its condition.
If you discover that your oil is contaminated with particles, the more economical manner to deal with this is to remove the particles through filtration.
So in summary, only change the oil when the additives have been depleted and the base oil is useless. You will have to perform oil analysis to make your decision.
2. Filter changes. It’s the same story with hydraulic filters. Changing them based on hours in service could mean that you’re too early or even too late. Early brings about waste as their capacity is not reached and you’ll be throwing away an unused amount of filter time. Changing them late is also an error as the particles will not be removed from the oil and therefore, it could lower the lifespan of each component in the entire hydraulic system.
The most effective approach is to only change filters once they have become full of dirt, but prior to the bypass valve opening. This may require a mechanism to be added that will monitor the pressure and deliver an alert when a point is reached. A clogging indicator is one of the most basic methods of handling this. However, continuous monitoring of pressure drop through the use of a differential pressure gauge or a transducer is the optimal solution. In summary, changing filters on hours is not maintenance effective, or cost effective.
3. Heat. If you’re driving along and you notice that your car engine is overheating, you would most likely stop. Most equipment owners won’t run an engine that is overheating. They know it’s going to cause problems. However, the same cannot be said about operators of hydraulic system.
Just as with a car, running an overheated engine is the quickest way to destroy hydraulic seals, hoses and other components. How hot is too hot? The answer depends on the viscosity of the oil in addition to the hydraulic components. Viscosity lessens with increasing temperature, so the answer is when the temperature is high enough to stop the oil lubricating as it should.
When it comes to hydraulic components, it’s worth noting that a vane pump needs more viscosity than a piston pump would. If you have a vane pump in your hydraulic system, then you’ll want at least 25 centistokes to be maintained.
Temperatures over 82°C will cause damage to seals and hoses in addition to accelerating the oil’s degradation. Never allow your hydraulic system to operate above 82°C with a viscosity lower than 10 centistokes.
4. The wrong oil. The most important element of any hydraulic system is always the oil. It’s what keeps everything lubricated and it is also what transfers the power. With these two major tasks to handle, keeping an eye on viscosity is a must.
The viscosity of the oil is what will determine the temperature at which the system should be run. You may have heard this referred to as temperature operating window or TOW. A temperature that is too high will prevent the oil from flowing or lubricating as it should. Oil that has a viscosity that is too low will not deliver adequate lubrication either. Keeping an eye on this will also ensure that you power isn’t lost due to either internal leakage or mechanical friction.
You don’t want increased power consumption as it will cost you more. The best way to handle this is to check what your machines temperature operating window is and to ensure that your machine operates within that window at all times. We won’t go into how to do this here, as it’s rather complex, but it’s something that does need to be addressed.
5. Filter locations. There are two locations for filters that cause the most problems – the piston pump and motor case line and the pump inlet. You may have a strainer attached to the pump inlet to collect any ‘garbage’ in your oil, but this oil is being drawn from a reservoir, not somewhere where there should be any garbage.
The pump inlet is also positioned off the bottom, so there should not be a lot of dirt passing through. By placing filters here, it can affect whether you get maximum pump life. If there is any form of restricted intake, it can reduce the lifespan of the gear pump by as much as half. Hydraulic pumps are not built with ‘sucking’ in mind! The way to handle this is to remove any suction strainers or depth filters on either the pump inlet or the piston pump.
Applying these points should be helpful to any hydraulic system operators and should deliver methods to save yourself and your business great expense.
Until next time..
When you work with hydraulics every day it is easy to take the technology for granted, especially when you know how it works and for what purposes. However, most hydraulic engineers focus on a specific application of the mechanisms and may not realise that there are other uses for the technology that we use every day. For example, petrol pumps use hydraulics to draw the fuel up from the reservoir and deliver it into your vehicle. When you draw up to the pump you make use of hydraulics to stop the car; most vehicle braking systems use hydraulic action to exert force on the brake discs. Hydraulics then allow you to fill the car up, and drive away, using your brakes several times on the journey home.
If you go to any large shopping centre or office there are lifts, which can make use of hydraulics to raise and lower the elevator car. Some older lifts still use a pulley system, but many newer systems use hydraulics. The sandwiches you have for lunch also rely on hydraulics to exist; the mechanisms in large bakeries use this technology to move conveyor belts and other large scale mixing machines to keep the dough moving along the production line. If you sit at an office chair while eating lunch you are also making use of hydraulics, as the mechanism that allows you to lower and raise the seat is usually a hydraulic one.
Visiting the dentist also involves hydraulics at least once, more if you drive there and fill the car up on the way! Dentist chairs use hydraulic pumps to lower and raise the body of the chair as well as to adjust the angle of the foot rest and head rest. Hospital beds and barbers chairs work on the same principle. Vehicle mechanics use hydraulic lifts to raise vehicles up for inspection and repair work in much the same way.
Hydraulics also make an appearance in entertainment; theatre stages that can be raised and lowered use hydraulic systems to make this happen, and similarly, theme parks rides use them to create and control motion. On arriving home from a day out at the theatre or a theme park you may drive your car into a garage with a hydraulically operated opening mechanism, or through a gate that employs the same technology to open and close at the touch of a button. Once in the house you may have to load the dishwasher and set it to run; even here there are hydraulics at work to improve water pressure for better cleaning. Hydraulics are found in many aspects of everyday life that it is possible to make use of six or seven different applications in a single day.
Keeping overheads low is a fundamental of good money management in business. When your supervisor tells you that the company are pulling in its purse strings and he wants you and your department to help, it’s might not always obvious as to how you can cut back on costs, in particular in this day and age of expensive parts and fuel.
One approach is to save on fluid. Although your hydraulic system may not even be leaking, if you could keep your oil in service longer than usual, whilst not putting your machine at risk of damage, then you know you’re going to be his favourite employee this month.
Here’s how to do it:
Keep it inside
The most important thing is not to waste it. Although you may have a couple of slow leaks that are on your list to be fixed at some point, they are costing you more as every day goes by. The price of oil might be lower than it was, but it’s still pricey. Solving leaks comes complete with a cost reduction. If you don’t attend to them, then you’re affecting your department’s economy.
Keep it responsive
Keeping your oil within optimal operating temperatures offers many advantages. For one, it’s going to have a longer life. By allowing it to get just 10 degrees warmer, it will not have an extended life according to Arrhenius's Law. There will be negative reactions including oxidation. This is caused by air entering the system and hydrolysis – the presence of water. The warmer the oil, the more you’ll suffer from these.
In order to illustrate this – consider what happens when you have cooking oil at home. You could pour it into a cup and leave it on the side. It will take a long time to change colour. However, if you put it into a frying pan and heat it as hot as you can, you’re soon going to have a pan of darkened oil.
Some oils have anti-oxidant additives added. In addition you may want to consider installing a heat exchanger, increasing the number of filters and magnetic plugs and even going so far as replacing any copper or brass tubings under circumstances where the pressure rating is more than 10 bar.
If you do opt to use magnetic plugs, then ensure that there is regular cleaning of them. Otherwise the particles may be dislodged by any oil surge and then they will be back circulating around your system and causing damage. In addition, using the magnetic plugs will help to reduce the work of the filter.
Keep the water out
Water can damage oil. It can also compromise any additives in it. Take ZDDP which is an anti-wear additive, add water to it and you’ll find that it’s completely unstable.
Keep it clean
It’s difficult to keep hydraulic oil clean. Every time you access the system there is a chance that it will collect dust particles. It’s also likely that particles are building up from wear inside the machine. Certain metals are worse than others when it comes to increasing how fast hydrolysis and oxidation happen. These metals include iron, copper, lead and zinc in addition to water. It’s also likely that particles will attach themselves to any additives in the oil, which will lead to depletion of the additives.
In summary, gaining extended longevity from your hydraulic oil comes from good maintenance; keeping your machine leak-free, keeping oil at optimal temperature and clean. Don’t change it until the oil has degraded or your additives have extensively depleted.
Performing maintenance often and well will keep you in the good books of your boss. There’s nothing better than good filtration and the prevention of impurities to keep the fluid clean. You may also want to look at your oil storage system prior to oil being entered into the system. For example, keeping oil barrels horizontal can protect them from water collecting near the bungs. It will also mean that the bung is kept wet and therefore will be more effective as an airtight seal.
Let us know how you get on and if you have tips to share on improving hydraulic system economy, do tell.
We’ve always been a fan of predictive maintenance for hydraulic systems. It can save time, system damage, expense and downtime. If it’s not already embedded into your workshop processes, then we recommend that predictive maintenance is put right in there along with your inspection processes.
In this post we look at the categories that John Moubray uses in his Reliability Centred Maintenance II book to understand how predictive reasoning should be approached. This is then followed by an example of how it could be used to understand what’s happening with your hydraulic system by using your powers of reasoning.
Broken into these 6 major categories, these maintenance actions can save you expense, time and of course loss of productivity through downtime. What any engineer who works with hydraulic systems should focus on are:
1. Dynamic effects including the monitoring of vibration, pulses and acoustic emissions.
2. Particle effects including the monitoring of particles in the operating environments of the component – ie the condition of the lubricant.
3. Chemical effects: monitoring of the chemical elements in the components operating
4. Physical effects such as cracks, wear, fatigue
5. Effect of temperature
6. Effects of electrical
Although Moubray’s list does cover most of the hydraulic systems maintenance needs, it does not cover all and there are new techniques being discovered and devised continually that should be researched. The visual inspection is one of the most basic and necessary of all predictive maintenance techniques.
Putting this to the forefront, it’s important to look for the following during a hydraulic system inspection:
· Both the quantity and the quality of the hydraulic oil in the tank needs to be checked. The appearance should be bright and clear.
· Check for any leaks or weeps around the seals, connectors and component bodies.
· The surface condition of the tubes, pipes and hoses external.
· The cylinder rod-wiper seal condition needs to be checked.
· The cylinder rod surface. Look for scores, nicks and dents.
· The filter clogging indicator position.
· The readings of the operating pressure (test-points and gauges that have been permanently installed should be used)
· The operating temperature of oil (use either an installed thermocouple or a heat gun)
· Listen out for abnormal noises such as knocking and clicking
The success of predictive maintenance tasks depends on whether data is recorded and then how it is analysed, whether it’s collected through human senses or by using sophisticated measuring tools. It is then necessary to take actions that will either remedy the situation or avoid damage from occurring. The process for predictive maintenance is this:
· Data collection
· Analysis of data
· Predictive reasoning to ascertain possible future issues if maintenance is not addressed
As an example, you may prefer to perform an inspection of your system as part of your regular maintenance routine. You may discover that there is a noise that has increased in volume and that there is no longer a smooth cylinder movement with your actuator. There could be an interpretation of this even as there being issues with reliability and performance of the system up ahead including issues with lubricity. These are all issues to record and take note of for future analysis.
In addition it’s necessary to ensure that the interpretation of the data is in the right context. Perhaps your visual inspection reveals an issue with the filter being clogged. You may identify this from the clogging indicator. Although this would not normally be an issue, it is if the last time the filter element was cleaned or changed was just the day before. Although the data is the same, used through the filter of a different context, then your reasoning will be entirely different.
Summary. It’s important to identify issues in hydraulic systems so that action can be taken whilst the issue is still small. Predictive engineering offers this solution. It also makes it possible to refine your system so that you can avoid issues and enable your machine to have less downtime and expense. It’s truly worth getting into the routine of looking for issues early on.
Our engineers are focused on producing mobile hydraulic power packs. We provide insights into hydraulic system maintenance for those who have an interest. If you’re looking for a custom solution to your hydraulic system application needs, contact us today.
Is your hydraulic system stuck in a breakdown and repair cycle? In today’s blog post we share with you 3 simple ground rules that will provide you with the opportunity to stop being terrorised and exhausted by this.
As with anything in life – the more you put in, the more you get out. This fact also applies to the results that you can gain from hydraulic equipment. You do the maintenance, and you can expect an increased level of reliability. Keep maintaining your system for best results.
Any machinery should be an asset to your business. You shouldn’t be in a position that you are beset by issues that are both time and profit consuming. Continually replacing oil, seals, pumps, cylinders, filters and valves can be costly, let alone the down time caused by an unreliable machine that can stop work at the most disadvantageous of times.
Even if your troubling fault has gone away in the short term, you know that it will soon be back, helping itself to your finances and sending your employees to spend the afternoon playing cards whilst they wait for the engineer to fix things up. Even if your company can afford to support such times, it certainly isn’t doing it any good.
If your machine is becoming more of a drain than an asset, then it could well be time to look for what the core problem is so that you can fix it, once and for all.
Before you get started, know that you are capable of fixing this issue and if you follow these 3 ground rules then you’ll be working your way to a satisfying ending:
Your first mission is to identify the temperature operating window (TOW) of the machine. The TOW is vital for the machine to run at optimal output with minimal downtime. Even if you tune up the machine with all the latest components, if it’s run outside of the TOW, then you will experience ongoing issues.
We’ve seen that many people don’t spend the time that is necessary to truly understand what the TOW is of their machine. However, it’s something that is essential knowledge for the wellbeing and reliable operation of your machine.
Something that will directly connect to the TOW of your hydraulic machine is the viscosity of the oil. This will determine what the minimum and maximum temperatures are that your machine will operate in safely.
Exxon Mobile Industrial produced data that specified that the initial viscosity is what the TOW depends upon. You should also be checking whether the machine’s actual temperature operating window is within the optimum temperature operating window. If it isn’t, then there is a need to change something.
The next point that you need to consider in your quest to keep your machine running well, is that each machine has an efficiency that will depend upon both its design and the components that are in use. However efficient the machine is at converting input power into work, will be closely tied to the level of heat that is being produced.
If the temperature is not within the safe TOW then it could get heat damaged and this in itself will make it unreliable.
Of course, clean oil is essential for hydraulic machines to be reliable and blessed with a long life. There are many aspects of this including the contamination caused by particulates and water. You’ll need to check whether you have optimal operating pressure, whether the components are suitable and of course, what type of system you’re running.
It’s not always easy to control how much contamination you have. However, it’s key to remember that contamination plus temperature work well to create oil failures. You can experience sludge build up and varnish as a result of not keeping on top of filter changes, prevention of water contamination and failing to test oil samples.
According to our own engineers in addition to our contacts in the hydraulic industry, most of the major failure causes (up to 90% of them) can be avoided by following these three rules. Wouldn’t you rather have a machine that is reliable?
If you’re in charge of the hydraulic machines for your company, one way of really annoying the company’s budget holder is to run your machines too hot. It’s going to cost you far more than either you or the financial director had bargained for. Another way that you won’t be a favoured employee is if you don’t get leaks fixed up, but we’re going to look at that at another time.
Here’s how an overheating hydraulic machine can cost so much money:
O-rings are going to fail. Running a machine outside and above the manufacturer’s or designer’s recommended temperature limit is going to cause issues, in particular with the o-rings and seals. The fluid will degenerate them and in turn, degrade the oil faster.
Your hydraulic fluid will need to be replaced more regularly. It will also affect how the hydraulic fluid performs and could cause it to deteriorate in terms of quality and cleanliness as viscosity will fall below optimal value.
Check your fire resistant hydraulic fluid. If you are using this, which is quite likely if your hydraulic machines are run underground or in any other very enclosed area, then you will need to check that it’s compatible with the rubber compound used in your o-rings and seals.
Running a hydraulic machine too hot is probably one of the most costly mistakes that any engineer can make. It needs to be brought down to under 82°C to operate in a way that isn’t going to be using up all spare company cash in repairs and replacements.
We recommend that you take these actions to ensure that your machine is not affected negatively;
· Bring the temperature below 85 degrees – knowing that even at 82 there could be some damage
· Check the condition of your seals and o-rings
· Check whether the fluid is fire-resistant
If you don’t check these then you could find yourself on the ‘naughty list’ of your finance director.
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