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If every hydraulics engineer had a crystal ball, there would be a huge decrease in unplanned downtime due to system failures because every single little problem would be addressed before it turned into a serious one. Most of us don't have the power to see in to the future, so how can we predict problems in hydraulic equipment?
One very easy way to stay on top of potential problems is to regularly monitor the temperature of the machinery and therefore the hydraulic fluid within. Heat is naturally generated by any machinery as it works, but too much heat is indicative of a larger problem and a warning of damage to come. Excess heat in a hydraulic system usually indicates air in the system or the fluid itself, which heats up under pressure. This in turn degrades the oil, leading to poor lubrication and the subsequent damage of moving parts, which presents as noise. By recording heat baselines, it is possible to see when a problem starts and allows operators and engineers to identify and rectify issues before they cause damage.
Temperature recordings of the hydraulic fluid should be done at the same time each day and at the same location, to ensure an accurate dataset is created. Although there may be some seasonal changes in temperature, for example the first reading of the day may be a lot lower in the winter than in the summer, regularly recording this data shows these seasonal patterns and what to expect, and may even be used to inform the choice of a change in hydraulic fluid to function more effectively in different seasonal temperatures.
Comparing the most recent hydraulic fluid temperature recordings to those of the previous days will show when the machinery is operating at a temperature that can cause problems further down the line. Excess heat causes hydraulic fluid to lose its viscosity, causing a lack of lubrication in the machinery and leading to unnecessary wear and tear. Hot hydraulic fluid can also degrade seals and hoses, causing leaks, which further exacerbate the problems of heat in the oil by allowing air in and fluid out.
Measuring and recording the temperature of hydraulic fluid may not pinpoint the site of the problem, but it does provide a reliable indicator that something is wrong, long before the effects of heated hydraulic fluid present with loud noises from within the chambers or a noticeable leak is discovered. Being able to act on this information and organise an inspection of the hydraulic machinery means that problems can be addressed before they become costly, and lead to longer downtimes and reduced productivity.
Laser thermometers are the most reliable piece of equipment for measuring temperature. They are inexpensive and easy to use, and the use of the laser means that a measurement can be taken in exactly the same position day in - day out, whether that spot is a label on the machinery or a sticker placed on it to create that location. Temperature checks are not onerous to carry out and can be done by untrained staff, as long as the data is being read by an engineer. A few minutes a day could save hours of repair work.
There are many factors involved in how much subsea hydraulic related applications are able to grow and increase in usefulness in the marine related industries. For example, key considerations are how long they can be kept in use without there needing to be maintenance performed or costly repairs and engineering undertaken. How safe are they for both the ocean and for people? How can the harsh environment be overcome for industries to achieve their goals?
Some maintenance for subsea work is of course something that cannot be avoided. For example, the high external water pressure, corrosion, powerful currents and operating machinery by remote control all come at a price. With clever design and careful planning, it’s possible to keep costs to a minimum.
Pressure compensation and seals
Something that can affect performance of any system is external pressure. Pressure compensation can be used to enable better underwater operation. Used as a means to keep pressure constant between the reservoir and the seawater, it helps to ensure that seals can still operate as they are usually designed to operate for flow travelling in just one direction, and to handle pressure drop for just one way.
The majority of components that are designed for hydraulic systems are land or surface based. They will have been built to cater for the environment without any specific issues such as high pressure. These components therefore cannot withstand the pressure found in deep water or even pressure drops that are severe.
One of the solutions to handling and supporting pressure-sensitive components in their operation is to seal them inside a protective chamber. However this can be difficult and costly to implement. The chamber would need to be of rigid construction with heavy-duty rugged seals installed that could handle the high external pressure. Pressure compensation is another method that is often seen as being more effective. It’s used by applying a pressure that is equal and opposite to that of the pressure found outside the component.
Piston rods and reservoirs
Plasma arc welding is used to apply high velocity oxygen fuel (HVOF) gun and cobalt-alloy coatings to piston rods that will be used in subsea deep water conditions as part of a hydraulic cylinder.
When it comes to reservoirs, they will often be replaced by sealed reservoirs. They will contain a flexible medium separator to ensure that the pressure of the external environment will also be in the reservoir, just as can be found in normal surface systems. However, the difference being that the oil and the seawater do not mix as they are prevented from doing so.
This ingenious system then makes it possible to use any component that is used on the land, underwater, as long as any areas are filled with fluid as opposed to the air that would normally be in them if they were operating on the surface. They will then need to be connected to the reservoir to maintain the balance of pressure.
Corrosion is a subsea challenge
Another area of challenge is that of corrosion. The study of keeping seals and seawater working together is known as tribology. It’s essential for subsea hydraulic system designers to be familiar with the concepts involved – keeping seawater out and hydraulic fluid inside a system. For large hydraulic cylinders, keeping the integrity of the piston rod in full operation, even after being exposed to extreme environmental conditions is critical for securing a long-term operation of the system.
Another area of concern is ensuring that all subsea application machinery is designed to a level that does not hurt the ocean environment or people.
Overall, the challenges of designing subsea equipment are multiple due to the harsh environment of the ocean, the reliability required for operators in addition to safety. As industries opt to travel deeper into the ocean, we can only see the challenges increasing.
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.
When designing hydraulic mobile equipment, it’s a necessity to position the reservoir in a suitable location. Unfortunately, this isn’t something that happens with every designer. They can be difficult to position in a compact area and can often be irregular in shape and then be situated in awkward and hard to reach locations.
Keep in mind that the mobile hydraulic equipment is usually operating under more extreme conditions than the static hydraulic machine. In addition to the limitations of needing to be smaller to retain the mobility, the limitations means that they are usually custom designed so that they can fit the exact space and requirements for optimal performance. It is possible to minimize size, cost and weight of the reservoir whilst ensuring that performance and efficiency do not suffer by taking time to consider what’s possible.
Quite often designers will use 3D modelling to produce the best designs for use and from a manufacturing point of view, designs that are complicated can be difficult and expensive to make. Here’s what is taken into consideration:
Balancing drawdown: the reservoir must provide enough fluid for the cylinder rods to operate effectively. There also needs to be enough time for the fluid to rest in the tank for contaminants to settle out and for air bubbles to coalesce. Here at HydraProducts we often use the rule of thumb to provide 1/3 of maximum pump output.
Thermal expansion: the reservoir needs to be large enough to be able to house fluid that has expanded from heat. This is why it’s important to not overfill the reservoir with cold fluid without considering what happens when that same fluid reaches maximum operating temperature.
Vented or pressurized: whether a reservoir is vented or pressurised depends on its location and what the inlet requirements of the pumps are. We usually recommend pressurisation otherwise there can be issues with cavitation which results in surface fatigue of metal.
Even humid air can get into the system if the oil level drops. Water can also get in by condensing on the interior walls when the ambient temperature drops. This condensate can lead to rust deposits and all manner of issues. Mobile reservoirs will usually be made of aluminium or stainless steel or steel to cut down on such issues.
Our mobile hydraulic solutions are designed carefully and to make the best of the limitations of size and weight. Call us today if you would like to discuss your requirements and we’ll see what we can do to help.
It’s no secret that every engineer wants their hydraulic system to run well forever.
During a recent chat with one of our clients we discovered that although they were using our mobile hydraulic power packs quite happily out in the field, back at base they had another hydraulic system that there were considering improving. They wanted to add a highly effective filtration system to it so that the fluid would be as clean as a whistle – or in this case, more like as clean as a fresh coat of paint - excuse the simile! (Even our editor couldn’t come up with anything else!)
Of course, as experienced engineers we are well aware that the cleaner the hydraulic fluid, the longer the service life will be of any component – in the case of all things being equal anyway. Whether taking action would deliver a worthwhile return on investment will also rest on a number of other variables that we won’t cover here. But this situation got us cogitating about something else.
We are fully supportive of the maintenance approach for hydraulic systems, rather than informing somebody of what they should have done a day too late when everything has jammed up and there is a huge repair bill hanging in the future. Although maintenance and design are seen as separate matters, in reality they are closely tied as the design of a hydraulic machine will impact both its reliability and its operating cost.
Taking this into consideration, it becomes clear that the best time to think about what your objectives are with regards to hydraulic system maintenance is before you purchase a machine.
Keeping operating costs in mind, before you order your system, you need to consider what you want when it comes to both reliability and maintenance. You need to avoid buying a flop that will cause more issues than output.
You will also need to consider what targets you have when it comes to contamination control. Ask for a machine that can reach your objectives on reliability because it has been equipped and designed to deliver on them.
Take the hydraulic oil that you plan to use and work out the ultimate running temperature for that oil. Then give directions to the manufacturer that you need your machine to have the right cooling capacity = using the temperature stats that you’ve given to him.
If you’re one to think that the temperature or viscosity of the oil is not all that important, then we’re afraid to inform you that you’re wrong. Based on our experience in hydraulic system repair, we know that failure of lubrication is one of the worst perpetrators when it comes to hydraulic component failure. There are of course other specifics that need to be considered when looking for reliability such as how much oil is in the tank, whether there is a flooded inlet for each of the pumps and what suction strainers are in place for the pump intake lines.
To clearly demonstrate this point, let’s go back to the viscosity and oil temperature connection. Let’s say you’ve got plans to buy a hydraulic excavator in the 25 ton range. According to directions from the manufacturer, you can expect optimum performance, reliability and longevity from keeping the oil in the range of 25 to 36 cSt with a viscosity index of 100.
The manufacturer has informed you that if you run the excavator at a temperature that is hotter than 70°C then you won’t be able to expect a lot from the machine. The oil won’t last long, the seals will fail and each component will struggle to last a long time.
So you ask the manufacturer to ensure that you cannot even run that machine hotter than 70°C, even on a day that is at 45°C (your local weather). If they do mess up and deliver something that does, then tell them that they will have to fix it at cost to themselves.
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.
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.
Hydraulic Power Pack
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