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Many subsea engineers align themselves with a product lifecycle management system that prevents costly waste and needless disposal of subsea equipment. The success of the use of product lifecycle management systems (sometimes referred to as PLM) depends on keeping records of products and relevant documentation such as drawings and maintenance records. When all records have been collected and well maintained then it’s possible to consider re-using components and refurbishing machines.
If it’s not possible to collect all documentation from suppliers and vendors, then it’s necessary to measure, calculate and take material samples to produce the documentation. Once the documents have been gathered and recorded, then it’s possible to look at how parts can be reused and aligned with new regulations, standards and field data.
With used subsea systems, there are occasions when components are no longer fully up to scratch. Perhaps a reservoir has lost some of its pressure or it allows water in to contaminate the product. Or it could just be that the product is no longer in alignment with local or regional regulations or standards that may have changed recently.
Once the engineers have communicated with the owners about what is involved both technically and financially in refurbishing a piece of subsea equipment, and agreement has been made, then it’s possible to start the project.
With so many different solutions available, it’s possible to arrange for a project to be implemented in a yard that is more local to the location of the equipment rather than towing it half way around the world.
However, if your equipment uses hydraulic power units, you may prefer to have one shipped to you to save time and money. We manufacture bespoke solutions for operators in the oil and gas industry. Call us today for more information.
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.
Hydraproducts provides subsea hydraulics to a number of businesses in the oil and gas industries. Our marine related products are designed to resist water ingress, water pressure of deep sea and corrosion caused by salt water.
Here’s what we have learnt about the oil industry on our travels:
Oil is key to the world’s economy. In fact, it’s what has been the lifeblood for the developing world over the last century and accounts for as much as 2.5% of the GDP of the world. It also provides at least 1/3rd of the energy required for humanity. It’s oil and gas that powers all of the transportation that we have on this planet, apart from a small number of vehicles that are electric powered. However, without oil it’s hard to move any vehicle at more than 25mph. It’s not possible to operate a modern economy without it. If oil stopped flowing, then modern civilisation would not run as it does currently, it would most likely collapse. Oil has become so important to modern life that it could be compared against agriculture.
Oil and gas have their own transport infrastructure that comprises of millions of miles of pipelines and shipping routes. The pipelines that distribute gas in the United States alone, could reach as far as to the moon and back between 7 and 8 times. Natural gas, crude oil and refined products are moved around in all of these pipes. Consider how you most likely have gas pipes in your home, these pipes connect to thousands of wells in rock that laid down millions of years ago. That is quite an amazing fact. Your home has a direct connection to the Pliocene era - thanks to the distribution infrastructure of the oil and gas industry. Also, thanks nowadays to subsea hydraulic power units!
Almost half of sea going cargo is oil. Surprisingly there is more cargo on the sea than there are fish in the sea. Although cargo that is oil is generally being transported for a much shorter period of time than most fish is alive for. So this makes the amount of oil that travels each year far greater than the fish biomass. Consider that for a moment. The sea isn’t full of fish…it’s actually full of oil cargo.
It’s very disturbing for some people to know this, but the scale at which oil and gas is currently being used is going to make it practically impossible to replace it with another solution during our lifetime. Renewables aren’t likely to replace oil any time soon. Oil is a huge commodity that is highly depended upon by industries and individuals all over the planet. Although both wind and solar power are renewable powers that are expanding, they are so small that they aren’t even making a dent.
Oil is the major wealth of this planet
It’s not just wealth for producers, but it’s wealth for all users of it. It’s a tool for productivity and is notably a cause of economic growth. The human condition can be greatly improved by the use of it. The Mayans discovered that it was energy that secures success for nations just a little bit too late, whilst China grasped that fact and used it to boost their economy. Whenever a cheaper and cleaner more concentrated energy source is used, there are dramatic results in global wealth. When electricity was used, it created serious growth between 1900 and 1950. Then oil helped with the boom from 1950 to 1970 and gas from 1970 to 1995. Due to coal consumption in Asia since 2000, the growth has been smaller and taken over by the digital revolution and impacted by the Great Recession.
Surprisingly oil companies don’t make as much money as you might imagine. They have a lot of bad years (for example the 1990s) and have to make a lot of layoffs. However, discovery and exploration costs are huge.
As you can see, the world of oil and gas is fascinating and it’s an industry that we’re proud to be involved in. We create subsea hydraulic power units that are used by a variety of marine related energy companies. Call us today for a no obligation chat if you’re looking for reliable subsea hydraulic power units.
When it comes to actuators, there are a few differences that you should know about if you’re in the engineering field. If you haven’t had a whole lot of experience, then here’s the lowdown.
Every mechanical movement system has a linear actuator in operation. It operates in a straight line but might be in the form of components, an assembly or a finished product. Used to perform the job of converting energy into movement or a force, an actuator might be powered by electricity, pressurised air or fluid.
Here’s what you need to know about the most common linear actuators, and what their pros and cons are.
How Actuators Work
Pneumatic line actuators. Consisting of a hollow cylinder with a piston inside, either a manual pump or an external compressor will move the piston. As pressure builds, a linear force is developed and the cylinder moves along the axis of the piston. It will then return to its original position using either fluid from the other side of it, or by a spring-back force.
Pneumatic actuators are really quite simple. They have bore sizes between ½ and 8 inches with a maximum pressure rating of 150 psi. So between 30 to 7,500lbs of force can be delivered. Steel versions can deliver forces between 50 to around 38,500 lb.
Because they don’t have any motors, and therefore produce no magnetic interference, they are often used in situations with extreme temperatures. You’ll find that they are very cost effective in addition to being lightweight and not needing of much when it comes to maintenance. Their components are durable as they aren’t under a lot of strain.
When it comes to disadvantages, they can suffer from pressure losses and therefore can be less efficient. Lower pressures equal slower speeds and lower forces. In addition, pressure must be made even if nothing is moving, so it’s necessary to continually run a compressor for them. For them to work most efficiently, they need to be sized for the job at hand and that makes them inflexible when it comes to other applications.
Hydraulic linear actuators. Working in a similar way to pneumatic actuators, this type of actuator is moved by incompressible liquid from a pump.
Being able to produce forces that are up to 25 times that of the pneumatic cylinder, they are considered to be rugged and well suited to high-force applications. The hydraulic actuator is able to hold force and torque without needing extra fluid or pressure sent through from the pump. Fluid is incompressible. This also makes it possible for hydraulic actuators to have both their motors and their pumps situated a distance away without suffering from loss of power.
The downside of the hydraulic actuator is that they can leak fluid and this can lead to them being inefficient. These leaks of hydraulic fluid can potentially damage components such as motors, fluid reservoir, heat exchanger etc…
Electric linear actuator. Powered by a torque converted from electrical energy connected to by a lead screw. As the screw rotates, either a ball or threaded lead nut will be driven along matching threads.
With the best precision control possible, the electrical actuator operates in a smooth and quiet fashion. They can also be reprogrammed and networked in a considerably short period of time. Without any fluid leaks, they are also less of an environmental hazard.
On the negative, each electrical actuator costs far more than that of either a pneumatic or a hydraulic actuator of similar power. They are also not suited to all areas either such as hazardous or flammable areas. There is also a danger that they can overheat due to having a continuously running motor.
Whichever motor is used is going to be reflected in terms of how much thrust, force and speed limits are required. If any of these need to be changed, then it will be necessary to acquire another motor.
As you can see for yourself, actuators come in 3 flavours, and it will depend upon your individual circumstances with regards to which one will give you what you need with the least disadvantages.
What do you need to know to keep yourself and other people safe in the workplace?
Keeping a load safe is dependent upon ensuring that the pressure of fluid is correct. If the pressure of it becomes too high, then it will want to give that energy to other surroundings, and it’s only the soundness of the components that will prevent it from doing so. It will try to escape any way possible and this includes through weak seals, valves or other points of plumbing failure.
The metering devices such as valves, flow controls and counterbalances prevent the fluid from running away. To demonstrate this, a cylinder that is installed with rod down, and tension under load will often have a meter-out configuration to stop the load from taking control of the cylinder
Although this is safe, there is still a risk of the pressure on the rod-side intensifying. If the piston seals get blown by this, then the load will drop.
Some engineers will use a counterbalance to avoid metering out errors from occurring. Although a counterbalance valve is considered to be the same a pressure valve, it is what controls the speed of an actuator. It will control how fast the cylinder moves, even if there is a pressure intensification.
Another situation that can cause a catastrophic failure and even personal injury is a leak in the cylinder hose or tube. If fluid in the actuator exits through a broken conduit, it is no longer able to hold up a load. In the event of a conduit failure, the counterbalance valve will prevent the load from dropping. Another safety function that will hold a load is a pilot-operated check valve. Although it will hold a load indefinitely, it will not be as smooth with control of load induced movement.
The essence of a hydraulic system is pressure. It’s something that is required to make the system as powerful and effective as it is. However, there are many reasons why pressure can easily rise including load spikes, ‘water hammer’, intensification and even thermal expansion. If there isn’t enough control over pressure, then components can fail and seals can give way – leaving the machine to be unsafe. It’s for this reason that the hydraulic system has so many different types of pressure control valves.
Damage can be prevented by limiting pressure with relief valves. They can control the pressure in the main system or in isolated sub-circuits. In some systems, it’s necessary for sub-circuits to operate at different pressure to others. This can be achieved through the use of the pressure reducing valve which is able to limit pressure downstream of itself. It is also able to reduce pressure in situations where the fluid has become too heated and therefore has increased its pressure. In some systems there are a number of valves that will work to ensure that pressure is limited to a safe level in every part of the machine.
In summary, it’s important to control both the pressure and the flow in hydraulic systems. It enables safe operation of the system and movement of loads. Safe employees are everybody’s concern.
Do you know how long any hydraulic pump should last? In this industry, using past experience might not always deliver the answers you were hoping for, and are likely to give you answers that are actually no better than guessing.
Disappointingly, there is no dependable approach to determine how long your hydraulic pump will last. Using historical data is perhaps something that will give you the best indicator, but if it’s a new pump and you have no data – that’s where the guessing game beings. Fortunately, there are a number of factors that determine how long any pump will last and using these can give you an estimate that is more informed.
For example, let’s consider your hydraulic system. The type of application it is will make a different to the pump life and so will the temperature. Using pumps that are graded as ‘industrial grade’ will deliver a better lifespan than those that are not. Using auxiliary information can also help. For example, an axial piston design pump has less heavily loaded shaft bearings and therefore are not at a great risk of premature failure.
Of course, roller type bearings in this type of piston design can fail prematurely due to brinelling. That’s why it’s better to use shell-type bearings as they are more like a bushing than a bearing.
Another major consideration is the type and grade of oil being used. If it’s ‘special purpose’ and is fire resistant then it won’t always have a positive influence on the service life. However, it will run cool which could help with its lifespan as there will be less temperature related lubrication issues.
Keeping a high level of oil cleanliness will also work well in extending the life of any hydraulic component.
Another point to ponder is how hard the pump is working. This is about how fast it’s spinning and under what pressure –how much of each hour is the pump under load? If they are under load for 55 minutes of every hour, then that’s going to be a 90% duty cycle, which is a lot to maintain compared to being under load for say 42 minutes of every hour. Under ideal conditions such as a duty cycle of 70% or less, 1200 rpm spinning with clean oil, you can hope an industrial grade hydraulic pump would last 20,000 hours or more. However, if you’ve got a 90% load with special purpose oil and 1800 rpm then you are more likely to get something in the arena of 10,000 hours of service life.
Running To Failure
There’s no doubt that these are only informed estimates using the information that we have about the pump and how it’s being used. Of course, if there are any hidden design flaws then the lifespan of the pump could be drastically compromised. For example, if there are pressure spikes that are caused by rapid valve shifts, then over time this could lead to a pump failure.
To continue to run a hydraulic pump until it fails is not a good idea. Its failure could cause consequential damage to other components. The cost of the rebuild of the pump will increase. Changing a pump before its life expires should be managed, whilst historical data is collected.
So if it’s looking like 20,000 hours is a strong lifespan possibility for any pump, then it’s wise to pull it out at 12,000 hours. It can be inspected and put back into service until say 15,000 hours. Then run to 17,500 hours and if all is well, then run until 20,000 hours. Getting too greedy will put the pump into the correct timeframe for a failure, so it’s not wise to push it too far.
Using this approach can provide information to make informed decisions on realistic expectations for component lifespan without putting the hydraulic system at great risk.
In a Hydraulic System, you are most likely aware that the main system pressure is maintained by the system relief valve or even another type of pressure setting device.
The purpose of pressure reducing values is to keep the secondary pressures correct in branches of hydraulic systems.
Most pressure reducing valves are open and 2 way, this allows the pressure to flow freely until they reach further downstream where there is a set pressure. They then shift to throttle the flow in the branch.
Forces from pressure downstream are what actuates pressure reducing valves. This is what will deliver the correct working pressure by enabling a pressure drop to occur in the main spool of the valve. The way that a press-reducing valve works is that it is not a device that is either on or off. In contrast, it delivers a continual adjustment to the pressure. Keep in mind that these types of valves are the most conducive to suffering from contamination when it comes to malfunctioning.
Pressure-reducing valves can go wrong in a number of ways. Again, pressure gauges will need to be installed in order to understand what’s going wrong with one. Once this has been done, you can look for:
· A low pressure at outlet port. If this drops below what it should be, the first action to take is to check the pilot head spool and seat. Check for wear and tear which may be affecting the drain flow. Too much drain flow through this area of the valve will result in reduced pressure and therefore affect performance.
· If you find that the valve will not retain a reduced pressure setting, and the pressure is exceeding it, then check whether the pilot drain line is blocked or affected by contaminants. This will increase pressure which will result in flow to the branch circuit. It’s also possible that the main spool is stuck open due to contaminants blocking it. Again, there could be scoring of either the main spool or bore.
· If you find that you cannot adjust the value to the low pressure setting, even after turning the adjustment knob, then check whether there is wear of the spool or bore. There may even be a broken spring in the pilot head, which will mean not enough force between spool to seat in the control head.
· If there is not enough pressure at the output port, check whether the main spool is stuck in the closed position. This will result in no pressure fluid being unable to flow to the branch. Contaminants could be to blame.
Come on over to our main site for detailed engineering knowledge and info on Hydraulic Systems, we're at www.hydraproducts.co.uk.
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