This is confirmed by Mattias Nord, Sales Manager High Pressure at Hydroscand. He further explains that one of the most common causes of leakage in a hydraulic system is incorrect hose routing, which drastically reduces hose service life.
– There are several different aspects of routing, ranging from going below the recommended bend radius to twisting the hose. If the hose is twisted by 7 degrees, its service life is reduced by 90 percent. So if you want durable systems, you need to understand how hoses should be routed.
Do not go below the bend radius
The bend radius specified in product data sheets for different hoses is the minimum bend radius the hose can have if it is to achieve its stated service life. If you go below the bend radius, service life is significantly reduced for every 10 percent that the radius is decreased.
– You must also not bend a hose too close to the coupling sleeve; if you do, service life is reduced. Another aspect of routing a hose correctly is that a hose should preferably not be bent in more than one plane. If it is bent in multiple planes, that also shortens its service life. He further explains that it is important for hoses to move as little as possible during use, since movement wears the hose and results in a shorter service life.
– You should therefore clamp the hose to the machine and use the right type of clamp for the hose in question, otherwise wear may occur on the hose. Even if the hose is fixed in place, it still moves because the fluid pressure in the hose varies and pulsates. If you then have a sharp clamp on a soft hose, damage will occur to the outer layer of the hose.
External damage significantly reduces service life
One of the most common reasons for different types of leakage in a hydraulic system is precisely that the hose is damaged by external wear or impact. Even a minor scratch in the outer layer can significantly affect service life.
– That is why it is so important to include hose selection and routing already at the design stage. You need to know what external, and also internal, conditions it will be used under in order to choose the right hose. If it is in an environment where there is a high risk of external damage, you need to choose a durable hose and perhaps also install extra external protection to ensure that it lasts as long as possible. Given that external damage is the biggest problem, you should also not bundle together hoses with different pressure cycles, because they will wear against each other and eventually fail.
– If you still need to bundle different hoses together, you should try to protect them in different ways. If that is not possible, you should choose a hose with an extra wear-resistant outer cover, Mattias Nord explains.
Take the surroundings into account
External impact does not only occur through mechanical wear; the surrounding environment also affects hoses.
– You need to think through the environment in which the hose will be used. If, for example, there is UV light, you need to choose an outer cover that is resistant to it. Other external conditions that need to be considered are whether the hose is mounted on, for example, an excavator arm where it needs to flex a lot. In that case, it is better to use a spiral-wound hose than a braided one, even if the braided hose can handle the pressure class.
Internal wear also has an effect
Although external damage is one of the main reasons for leakage from hoses and couplings, the hose also wears internally.
– There are several reasons why hoses wear on the inside; one of the more common is contamination in the oil. Most often, it is mechanical wear caused by particles collecting in the oil and wearing on the hose during flow. In addition, a hose is affected internally depending on how it has been dimensioned. If it is incorrectly dimensioned, wear occurs due to excessively high flow in the hose, which in turn reduces service life. Mattias Nord notes, however, that it is never possible to completely avoid wear on hoses in a hydraulic system. Rather, it is a matter of minimizing the risks of wear, both externally and internally.
– By optimizing hoses and couplings according to the conditions under which the hydraulic system is to operate, you minimize the risks of leakage occurring. Minimizing those risks is not only about designing a system for long durability; it is also about minimizing risks for personnel working with the hydraulic systems.
Leakage is a workplace safety risk
Pressurized hoses are a workplace safety risk if they are not handled correctly. If a hydraulic hose breaks, it can cause major damage because the pressure in the hose is very high. A fine pressurized jet, a so-called pinhole, which can occur if a hose develops a hole, has a speed of about 200 m/s, corresponding to the speed of a bullet from a pistol.
– To avoid that, there are different types of protective equipment that can be mounted on the hose, for example a textile hose protection sleeve that can easily be mounted on the hose. If the hose develops a hole, the protection captures the jet and the oil diffuses out through the textile protection as an oil mist instead. It also reduces the risk of oil leaking onto the floor or the ground, since smaller amounts of oil remain in the protection.
Awareness of the importance of hoses is increasing
As mentioned initially, awareness of the performance of different hoses and how they are installed has increased.
– We notice a change toward more people including the choice and execution of hoses and couplings already at the design stage. People have started to understand that this is of great importance in achieving an efficient and durable hydraulic system and thereby reducing, for example, major downtime costs that can otherwise arise in the event of an acute hose failure. The more information customers absorb about the relationship between a hose’s service life and how it is routed, the more understanding grows that hose selection and routing need to be considered early on.
– Understanding is also increasing regarding the importance of preventive maintenance of hoses and couplings. There are major economic gains in keeping an eye on hoses, for example by checking whether there is external damage and, if so, replacing the hose in time. By avoiding acute failures, you also reduce the risk of oil spills and potential injuries to personnel. To facilitate maintenance and service, it is also good if system designers think about placing, for example, hose couplings so that they are easily accessible.
Modern bio-oils are no problem
When bio-oils entered the market a number of years ago, they caused somewhat increased wear and other problems that hose suppliers had to adapt to.
– But today, high-quality biodegradable hydraulic oils often perform better than mineral oils. If you also choose a high-quality hose, problems arise very rarely. If you are unsure, you can contact an expert. In addition to the importance of a hydraulic hose being routed correctly, staying within the specified bend radius, avoiding routing in multiple planes and avoiding twisting, the installation itself also affects service life.
– It is important to do it correctly when the hose is inserted into the fitting and then apply the correct crimp dimension and check the crimp pressure on the sleeve. The internal collapse must be optimal for the coupling to achieve its intended service life.
On-site hose service
To help customers with both preventive maintenance, service and acute failures, Hydroscand SlangExpress has 99 service vans located in different parts of Sweden.
– These are well-equipped vans that are ready to respond and handle both acute hose replacements and maintenance. Our service technicians offer customers everything from preventive maintenance and inspections to remedying acute problems and providing advice during design and installation. Acute problems most often arise in mobile applications, such as forestry machines.
