What is Hydraulic Hose? How to Repair? Parts, Design, Types, Damages

Hydraulic hose is usually made of multiple materials with elastomers, silicone, thermoplastics, metal, and composite or laminated structures being the most common. It is common to choose elastomeric or rubber hydraulic hoses due to their flexibility.

The flex life of hydraulic hoses is good, and they are chemical and corrosion resistant as well as being able to withstand high temperatures. In addition to a tight minimum bed radius, thermoplastic hydraulic hoses are excellent at resisting kinks. High-temperature flow materials and high pressures can be handled by metal hoses. There are two types of stiffness: rigid and flexible.

Design of Hydraulic Hose

It is specifically designed to convey hydraulic fluid from hydraulic components, valves, actuators, and tools to other hydraulic components. Due to hydraulic systems frequently operating at high pressures, it is typically flexible, reinforced, and constructed with several layers of reinforcement.

• Various industrial hydraulic systems use hydraulic hoses. If you are looking for a hydraulic hose, you should consider dimensions, performance specifications, construction options, and features.
• It is important to consider the inside diameter, outside diameter, and minimum bend radius when selecting hydraulic hoses. The inside diameter and outside diameter of hydraulic hoses are used to determine their size.
• Hoses or liners have an inside diameter that refers to their interior. Hoses with corrugated or pleated construction are often specified by their outside diameter. It is based on a combination of acceptable deformation of the hose cross-section and mechanical bending limits of any reinforcement.

Construction of Hydraulic Hose

Nowadays, hydraulic hoses consist of three different parts: an inner tube, a reinforcement layer, and an outer layer that provides protection. A flexible inner tube must be compatible with the specific type of fluid passing through it.

• Hydraulic hoses usually have this part made of synthetic rubber or thermoplastic. A reinforcement layer may be made from braided wire, textile yarn, or spiral-wound wire in multiple layers.
• Last but not least, the protective covering is made to resist oil, abrasion, and corrosion. Depending on the environment in which the hose will be used, you will need to select the right type of protection.

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The SAE Standards of Hydraulic Hose

As a result, SAE has developed a standard called J517 which answers those questions. In the world of industrial hydraulics, this hose standard is one of the most widely accepted benchmarks on which to base your work. It is more precisely understood that J517 is a set of guidelines that are applicable to the current SAE 100R series of hoses.

Currently, there are 16 types of hoses that fall into this category, and they are designated as 100R1 through 100R16 (see descriptions on pages A105 and 106). It is pertinent to note that each of the styles must meet a set of dimensional and performance characteristics as described by SAE.

It should be noted, however, that SAE does not issue approval source lists, certifications, or letters of approval. This is because compliance with these standards is strictly voluntary on the part of manufacturers. Simply put, the purpose of the standards is to ensure that products from different manufacturers are similar.

Parts of Hydraulic Hose

There are hydraulic hoses specifically designed for hydraulic systems. Oils or water are conveyed between the fluid ports of the pumps and actuators so that mechanical motion can be created. A core or inner tube, reinforcement layers or inlays, and an outer cover make up the structure.

It is directly in contact with the fluid on the inner layer. Chemical compatibility is therefore required. In addition to steel, copper, or textiles of high tensile strength, reinforcement layers can be made out of wood, rubber, or plastic. High-pressure applications are made possible by this layer, which provides the necessary strength to the inner tube. 

In addition to helical, spiral, or braided reinforcements, there are others as well. Hose covers serve as protective layers and should be compatible with the environment in which they will be used.

Few of them are illustrated based on the highest rating as well as feedback:

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Requirement of Hydraulic Hose

Size

The hose size required depends on the volume and velocity of the fluid flow. The flow will be turbulent if the fluid velocity is too high.

Various sizes are available for fluid-power applications, ranging from 3 by 16 inches to 3 by 3 inches. Dashes are used to represent the numerator of fractions when designing sizes in 16ths of an inch. The hose is marked with these dash sizes.

Reinforcement Type

Reinforcements may be natural or synthetic yarns or fibers, metal wires, or combinations. There are two types of reinforcement: braided and spiral wound. In hydraulic applications, wire-braid reinforcement provides good service life at a moderate price. A braided wire with two plaits over two is usually economical, reliable, and dimensionally stable.

High-pressure systems often use spiral wire-wound hoses for high-frequency surge applications. Wire crossover points in braided reinforced hoses tend to fail as pressure surges. Wires that are already highly stressed can be bent and sheared by these points. By eliminating touchy crossover points, spiral wire reinforcement can theoretically cover up to 97 percent of the total area.

Temperature

Hydraulic and pneumatic hoses must be capable of withstanding both external ambient temperatures and internal fluid temperatures. The hose should be able to operate in a wide range of temperatures. Most operating conditions can be accommodated between -40°F and 200°F, for example. The elastomer of some hoses can withstand pressures and temperatures of up to 300°F. Others can withstand temperatures as low as -65 degrees Fahrenheit.

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Length

To allow for bending and flexing of the machinery parts, the hose length should be sufficient.

Material

Hydraulic hoses should be made of materials that are chemically compatible with hydraulic fluid. The hoses are typically made of synthetic rubber, such as NBR or nitrile, EPDM or ethylene propylene diene monomer, and SBR styrene-butadiene rubber. Thermoplastics, Teflon, and silicone can also be used.  Hydraulic oils can be used with synthetic rubber hoses.

Radius & Diameter

The bending radius of a looped hose is the minimum radius it can reach without being damaged. The hose end fitting should not be bent at the beginning, as this may cause leaks. Hydraulic fluid can be damaged by turbulence caused by tight bends in the hose.

Hoses should have an inside diameter compatible with the fluid flow rate. Higher velocity is associated with smaller diameters. Excess heat, friction, and turbulence will occur in the system because of the high velocity.

Accessories

For the hoses to fit properly on the pumps or actuators, they need to be equipped with specialized hydraulic accessories. In order to ensure that the hydraulic hose is properly connected to the fittings and crimped to the exact diameter, hydraulic hose clamps and hydraulic hose crimpers are used. 

High-pressure fittings should be used to suit hydraulic applications. You can cut the hose to the perfect length using a hydraulic hose cutter.  

Connection End

For easy customization, hydraulic hoses can be offered with or without pre-made fittings, depending on your application requirements. Fittings should be the correct size for compatibility with your system if they are pre-made.

Pressure

For transient pressures, hoses are impulse tested between 100 and 133 percent of rated pressure. The proof pressure is 50 percent of the burst pressure. According to SAE, the operating pressure should not exceed 25 percent of the minimum burst pressure. It is an acceptable safety margin for industrial applications, and it also allows the hose to handle some surge pressure.

Types of Hydraulic Hose

Hydraulic hoses of this type are lighter than metal counterparts, so they are easier to move. The mesh can also be added to make it more durable, preventing bending, bulging, and scratching. 

This hose fitting also has the ability to tolerate high temperatures, as well as linking with a variety of hose fittings. 

Steel Reinforced Teflon

It is sometimes difficult to use hydraulic hoses made of steel. The advantages of steel hoses can be found in Teflon hydraulic hoses with steel reinforcement. Unlike rubber, this type of material is more heat resistant. You should choose this type if your system involves a boiler or blast furnace. In addition, it is very lightweight, which is important if you are on the field.

Coiled

It is best to keep your hose in a place that is easy to store and maintain. Coil tubes are ideal for businesses that value efficiency and space, such as auto repair shops and welding shops. It is easy to pull, use, and snap back into place after use, making it a favorite among mechanics and engineers. 

Return Lines

Return lines are not designed specifically, but they are still an important part of any system. Fluids are returned to the pump via return lines when their pressure decreases. It is usually possible to get by with less expensive hoses. It can be quite a hassle to deal with breakdowns of return lines if they are not properly maintained.

Corrugated & Articulated

Hydraulic corrugated hoses work similarly to expansion joints, but are designed for hydraulic systems. Temperature fluctuations or sudden pressure surges can be accommodated. Conversely, articulated hoses can be twisted or maneuvered around corners freely, unlike corrugated hoses.

Types of Hydraulic Hose Damage

External Damage

Hydraulic hoses are covered with heavy-duty rubber on the outside. There is a network of crisscrossed metal wires below this that reinforces the structure. A separate rubber tube runs inside the hose, through which hydraulic fluid flows.

Rubbing against nearby hydraulic system parts causes the outer cover of a hose to rupture or tear. Friction caused by nearby machinery, brackets, and even other hoses can rupture a cover. There are a variety of external damages, such as scratching, denting, or impacting. It is necessary to replace hoses that have suffered such damage. A protective sleeve should be applied to the new hose to ensure that the problem does not recur.

Overheating

High temperatures are routinely encountered by hydraulic hoses. As a result of heat carried by the hydraulic fluid, these high temperatures may come from inside the tube. It is also possible that they are caused by the external environment of the hose. When heavy machinery is operating, hoses that run alongside it absorb a lot of heat.

Hydraulic hoses have temperature ratings that indicate how much heat they can withstand without causing problems. The plasticizers in hose walls become less flexible when overheated, causing them to harden and become brittle. Brittle hoses are more likely to develop cracks and other forms of damage that can cause leaks.

Choosing hoses that meet your hydraulic system’s general operating temperature can reduce the chances of overheating. It is inevitable that even a well-selected hose will become brittle over time. Thus, you should inspect your hoses regularly and replace any aging ones when necessary.

Life Span

When your hose fails due to wear and tear, you know it has reached its maximum lifespan.

However, a common cause of problems occurs when installers fail to tighten hoses. If the hydraulic fluid pressure is too high, the hose end can become detached from the fitting. It is common for both the hose and fitting to suffer damage during this process, necessitating the installation of a new assembly.

Fitting Issue

A fitting that has not been tightened enough to the machine’s port may also leak or blow. When installing fittings and hoses, technicians can avoid both of these problems by using a torque wrench. Using a torque wrench, you can determine how much force is being applied to a fitting.

In addition to preventing blown fittings caused by under-torque, torque wrenches also prevent leaks and damage caused by over-torque. There are different torque specifications for different components, so you should always check the specs for the component you’re working on before applying torque.

Dragging Cause

This may happen in cleaning applications where the hose must be frequently moved around and dragged over the ground. In high-pressure applications, constant vibration of the hose is another cause of external abrasion. It rubs on the ground and wears away the outer coating because of the vibrations from the pump. The nature of this type of application makes it difficult to prevent this kind of damage.

Hose End Damage

Whenever there is motion on a hose, any connection with a crimp or band is subject to more stress.

Hose fittings connect your machinery to hoses. Fittings attach to threaded ports on machinery by screwing on the outer portion. Hydraulic hoses can be threaded into the fitting’s threaded shell by threading them into the fitting. It is important to install hose assemblies properly to ensure they will form a leak-proof seal.

Methods of Hydraulic Hose Repair

Crimp Replacement

There are two caveats to swapping out a hose-end, though. Because of that, it can only be used in installment payments when a slightly shorter hose is feasible.

When attaching hydraulic hoses, the crimp specifications need to be followed. An SAE-compliant compression fitting is required to ensure that the hose can withstand the high pressures. 

The performance of the hose can be degraded or even compromised by slight deviations from the end.

It is not uncommon for our shop to see customers who want us to crimp a different tube type, but it does not work. If they don’t have the right pair, any decent repair tech will turn you away. Before you go, make sure the workshop stocks the manufacturer you need.

Cut & Repair Method

There are many ways for hoses to be damaged, such as when a tractor drives over them, when they encounter a rockfall, or when they are damaged by other types of impacts. If the hose has this type of damage, you can easily repair it by cutting and repairing it. A hydraulic or high-pressure hose can be cut and repaired in two ways.

• Firstly, you can use a mender to stick a physical piece into the tubing and crimp both ends. If you want to fix a hose, you can put two threaded pieces either side of splices and two pieces in the middle. The duct tape method is sometimes used to fix hoses. Although the tape may reduce splashing, it is obviously not a safe solution when you have 3000 PSI of pressurized fluid in your hose.
• Secondly, if the damage in a particular area becomes too great, a splice and repair can be done. Splicing multiple times is possible, but not ideal. The hose is slightly affected each time you splice and attach a hydraulic hose, both in terms of length and pressure drop.

This may work for simple cleaning applications. For hygiene reasons, you should not do high-pressure splicing more than once. Water pressure decreases and cleaning time increases when the hose’s function is reduced. If you are doing any serious work, you probably don’t need as many splice and repair connections as you might think.

Always check for Exposed Wires & Abrasion

If you catch the problem early enough, you can repair a hose with a cover repair. If you act immediately, you can protect a scratch on the cover of a hydraulic or high-pressure hose. The internal reinforcement wire of all hoses is protected by a protective sleeve.

You will need to replace, splice, or repair scratches or dents if you ignore them. You can protect damaged areas with plastic coil protectors, metal coil protectors, or plastic abrasion-resistant sleeves if you see abrasions or exposed wires. Abrasion and corrosion of the rebar wires should be prevented.

Long Hose Benefits

You may need to repair your hose immediately in many situations. It is not possible to wait for a new part because your equipment has stopped in the middle of production or during harvest. 

There are times when a hose and fitting are not the same sizes, for example. We can adjust the size if the jump is small, like from 1 inch to 1.5 inches, but if it’s a big jump, like from 2 inches to half an inch, there is a huge difference.

In cases of emergency, we jump from large to small or from small to large. If you are really in a pinch, this is a fix that will work, at least temporarily, until you are able to reconfigure your system.

Step by Step Process of Repairing Hydraulic Hose

If you can’t reach a professional right away, you may need to do the repair on-site. You don’t have to be a professional to temporarily attach a hydraulic hose. Repairing it can be pretty straightforward once you break it down into six steps.

Identification of Right Hose

There may be differing minimum pressure tolerances required for different functions by heavy equipment. Therefore, different hydraulic hoses can also have different minimum pressures for one device.

Before repairing a hose, you should determine which specifications it must meet. During the repair, there will be cuts that need to be compensated for with a shorter assembly. It is common to make tubing to a specific length.

When you replace the wrong hose even for the temporary purposes it can be very dangerous for user. Hydraulic hoses must be marked at the top with their minimum operating pressure and their maximum burst pressure. If you are unsure, speak with a trained professional.

Damage Area Removal

Tubing that has been damaged must be cut out once. It is also necessary to cut off the broken end of the hose if the only problem is leaking couplings. You must clean thoroughly the area surrounding the cut end of the hose. The hydraulic fluid may become contaminated if dust, dirt, or other contaminants are present.

A tiny smudge of dirt can damage internal components and cause costly failures. Prior to continuing with the remainder of the repair, it is important to clean both the fittings and the cut hose ends.

Adapter Using for Completing Installation

The installation of a repaired hose may require a hydraulic adapter. There are not always enough hydraulic couplings to carry, so having a kit with a variety of adapters is a good solution. The adapters should be installed in the appropriate ports and a secure connection should be made if necessary.

As part of the repair process, adapters and couplings must be tightened properly. There can be adverse effects on the hydraulic system if the torque is over or under-torque. You should consult the manufacturer or a trained professional if you are unsure how much torque to apply.

Right Length Confirmation

Make sure the hose assembly is long enough before installing it. Having an overstretched or poorly routed hose will result in additional pressure and fatigue. There is no such thing as too much tubing; it’s better to have too much than not enough.

Manufacturer guidelines specify that the length should be just right for proper laying. Short hoses are more prone to dangerous and costly failures in hydraulic systems due to the constant pressure they are under.

Once the hose is the correct length, make sure it is routed properly. As a result, the rest of the hydraulic system can function as normal. Hydraulic oil can flow more freely through angled fittings in many devices.

For correct positioning, install angled adapters or couplings first. Screwing the hose assembly onto the adapter or connector is easy once the angled adapter is in place.

Proper Seal Checking

Thread the tubing into the opposite opening or onto the opposite end so that it is properly sealed. A hydraulic system can fail even if there are small gaps or imperfections in the seal. 

It may be a good idea to check the seal for leaks before continuing. Keep seals snug, but not too tight; they should be secure, but not too tight. The hose should be attached without twisting or tightening. With a wrench, tighten the fitting without over-tightening the gasket.

Check for Any Leaks

Lubricating the hydraulic system with low-pressure oil or hydraulic fluid is recommended. This method can be used to identify leaks or damaged connections. Fluid and air are flushed out under low pressure. Pumps and other sensitive components can be damaged by air in the system.

• Before checking for leaks again, let the hydraulic system run for a few minutes. Hands could be injured while checking for leaks. It is possible to substitute paper for cardboard. It may take several minutes for a leak to become apparent. It is therefore always a good idea to check the system before operating a vehicle or using a piece of equipment.
• Keeping hydraulic hoses in good shape is not as difficult as you might think. If you would like to be sure your work is accurate, it is recommends that you have it checked by a professional. In this way, future problems can be prevented and mistakes will be minimized.
• You can repair or replace damaged hydraulic hoses immediately if you suspect they are leaking. An unattended leak can seriously damage the entire system and leave you out of pocket.
• A hydraulic system’s integrity depends on the quality of the hose, regardless of whether it is on a farm tractor, delivery truck, or industrial machine.

Application of Hydraulic Hose

Hoses are commonly used in applications requiring bending and flexing. When using hydraulic hoses, factors such as system pressure, pressure pulses, fluid velocity, temperature, fluid, and environmental conditions are critical.

Hydraulic hoses are used in many vehicles, equipment, and industrial machines. Although these hoses are generally durable and reliable, they will eventually fail if kept working or driving for a long enough time. An experienced professional who specializes in hydraulic hose testing and repair should be contacted in this case.

• Heavy construction equipment, such as excavators, dump trucks, loaders, bulldozers, and paves.
• A variety of agricultural equipment, such as different types of trucks, harvesters, fertilizer spreaders, manure spreaders, etc.
• Equipment for removing snow and ice.
• Equipment used in mining, such as excavators, miners, drills, etc.
• An assembly line, a press, a robot, hydraulic power units, etc., are examples of factory equipment.

Wrapping it UP

The hydraulic hoses are used to move hydraulic fluid between components in hydraulic systems. There are usually several reinforcement layers on these hoses, which make them relatively stiff. A hydraulic hose includes a variety of components, how to select the right hydraulic hose, and typical applications. 

FAQs on Hydraulic Hose Repair

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