Hydraulic Tube

Special Metal Alloys is a leading supplier of hydraulic tubes. In the modern world, we would hardly survive without hydraulics and much of our technology would be meaningless.

Hydraulic systems are used in every industry and household to harness the power of pressurised liquids by converting that energy into mechanical power, to efficiently and easily move, lift, and control objects.

For further information about hydraulic tubes, please contact one of our sales representatives on +44 [0]161 278 2386.

Alternatively, contact us via our contact form or email your enquiry via sales@specialmetalalloys.co.uk


Examples of hydraulics in everyday life

Construction:

Machines and equipment such as cranes, forklifts, elevators, jacks, and pumps.

Automotive:

Braking systems, power steering, shock absorbers, transmission systems, jacks, fuel and oil pumps.

Equipment to install engines, and for pumping fuel at the filling station.

Aeronautical:

Virtually all moving parts and components on an aeroplane, including landing gear and wing flaps, are controlled by hydraulic pumps and valves.

In space, hydraulic systems operate robotic arms, docking gear, landing gear, etc.

Domestic:

Shock absorbers and hydraulic pumps increase the water pressure on washing machines, dishwashers, and pressure washers.

Operating snow ploughs, dental chairs, office chairs, and door closers.

Entertainment:

Equipment at amusement park rides.

Ferris wheels.

Mechanisms in theatres to raise and lower the stage and stage props,

and much more.


What are the main components and functions of a hydraulic system?

The main function of a hydraulic system is to increase energy transmission with precision to the point where mechanical force is required.

A typical hydraulic system consists of:

Reservoir.

A hydraulic reservoir stores the fluid used in the hydraulic system to be drawn from as needed.

Pump.

The hydraulic pump pressurises the fluid using a mechanical or electrical motor or mechanism to generate fluid power.

Control valves.

Valves or levers are used to start, stop, and direct the direction and pressure flow of compressed fluids to the various parts of the system.

They prevent the fluid from flowing back, prevent over-pressurisation, and relieve the pressure when the part needs to move back.

Pressure regulator.

Together with the valves, it is a control mechanism that regulates how hydraulic fluid pressure is maintained throughout the system.

Actuating Cylinder.

Actuators are like pumps with cylinders, pistons, rods and seals that work in reverse.

Accumulator.

Accumulators can be compared to batteries that store energy for later consumption, in this case, compressed fluid.

Hydraulic fluid.

A huge range of specialist mediums, mostly oil, synthetic oil, or petroleum-based fluid, is used to transfer energy from the pump to the operating parts.

Heat Exchanger.

By removing heat from the hydraulic fluid and moving parts, the heat exchanger keeps the fluid at a safe and optimal, working temperature.

Hydraulic tubes and pipes.

The hydraulic fluid is carried to the varying parts of the hydraulic system by special tubes, pipes, or hoses that can withstand the pressure and chemical assault.


What makes hydraulic tubes special?

Ability to handle high internal pressure

Both seamless and welded hydraulic tubes can handle high internal pressure to transport compressed hydraulic fluid among the various components of a hydraulic system.

The energy exerted on the hydraulic fluid is converted into mechanical power. That power is transferred with precision to the mechanical parts of the machinery used for lifting, moving or controlling objects.

Hydraulic tubes made of diverse materials, of different standards and dimensions, are required for individual applications in various industries.


What type of tube is used for hydraulics and what are the differences?

Hydraulic tubes, pipes, and hoses are used for very different reasons and are typically not interchangeable, although they are often used in combination with a hydraulic system.

Hydraulic tube and pipe

Seamless carbon steel piping is used in basic hydraulic systems in grades ST37, S235JR, Q235, and ASTM A36.

E355 (ST 52.4 grade) is used for high-pressure and E235 (ST37.4 grade) for standard-pressure steel hydraulic tubes. They have different chemical compositions for conveying hydraulic fluids at different working pressures.

Seamless and welded stainless steel hydraulic tubes are incredibly versatile choices in both static and mobile hydraulic systems where high strength and corrosion resistance are important.

Zinc dichromate-coated steel tube.

Advantages of hydraulic tube:

An important advantage of hydraulic tubes is their ability to handle high heat without expansion or weakening.

More heat is dissipated, especially when painted or taped, keeping the temperature of the hydraulic fluid down.

Can handle very high pressure.

High strength.

High corrosion resistance.

Hydraulic tubes can be manufactured in a large variety of shapes and profiles, making them more versatile.

Tube fittings have metal-to-metal seals designed not to leak even under rugged operating conditions, making them tighter and faster to install than pipe.

Hydraulic tubing is generally easier to weld than pipes.

Tubing can usually handle higher pressure and on average has a higher strength-to-weight ratio than pipe.

Smooth internal surfaces reduce flow losses and friction.

Disadvantages of hydraulic tube:

In parts with high vibration, metal tubes may become brittle, work loose, or become damaged.

They also transfer vibrations to other parts of the system.

Tubing is generally more expensive than pipes and hoses.

Usually limited in length.


Hydraulic pipe

Toughened cold-drawn steel seamless precision hydraulic pipes are manufactured in three different grades:  37.4, 44.4, and 52.4.

Seamless carbon steel pipes.

Advantages of hydraulic pipe

Most of the advantages of hydraulic tubes apply to hydraulic pipes, with these additional distinctions.

Pipes are measured by their inside diameter, making pressure calculations easier.

Pipe is generally cheaper than steel tube too.

Disadvantages of hydraulic pipe

While the differences between hydraulic tubes and pipes are relatively small, these are some of the main additional disadvantages:

Whereas tubes can be manufactured in virtually any shape or profile, a pipe is always round, limiting its application, especially in tight spaces.

They are generally less flexible than tubing.


Hydraulic hose

Nitrile rubber hoses with textile braid for low-pressure applications up to 1000 psi, or tensile steel wire reinforcement for pressures up to 7000 psi.

Advantages of hydraulic hose

Rubber hoses are more flexible than tubes and pipes.

A hydraulic hose is more suitable in vibrating parts, where rigid metal tubes can be damaged or may come loose.

It can be used in areas with limited space and hard-to-reach places, particularly mobile hydraulics.

Hydraulic hoses are generally available in longer lengths than tubes and pipes.

Disadvantages of hydraulic hoses

They cannot handle very high operating temperatures.

At high heat, the hydraulic fluid heats up and the hoses themselves expand, leading to a loss of pressure in the system’s pressure.

Their service life is much lower than tubes or pipes, adding to cost and environmental contamination.

They expand and stretch under pressure, reducing pressure and requiring extra volume, which adds to machine cycle time.

Hydraulic hoses are heavier than tubes in most instances.


What is the difference between hydraulic tubes and normal steel pipes?

Hydraulic tubes and pipes are made with greater precision and have to be able to handle high internal pressure and corrosion.

Normal steel pipes are mostly used in machinery or systems that do not require special accuracy and pressure resistance.


What are the applications and uses of hydraulic tubes?

For control and power transfer in hydraulic systems.

For conveying liquid fluids among hydraulic components, fittings, valves, and flanges

Used in industries requiring high strength and corrosion resistance (e.g. marine, chemical processing)


How to choose the right hydraulic tube and size

General considerations

Consider the specific application, conditions, and requirements.

Determine the material specifications and dimensions for compatibility with each other and different parts of the hydraulic system.

Compare the priorities, benefits and compromises when choosing. Factors include cost, strength, flexibility, ease of installation, durability, and resistance to corrosion and internal pressure.

Determine working pressure and burst pressure values. Add safety parameters when calculating working pressure and burst pressure.

Check their compatibility with existing hydraulic systems, fittings, and components.

Measure the taper angle, thread pitch and size, and internal and external diameters.

To replace existing tubes, screw in a known fitting to ensure it fits, confirming whether the thread is BSP, metric, or JSC flare.

The pressure and forces change when the velocity, flow direction, or elevation is altered, making it necessary to measure pipe pressure and flow at various points in the hydraulic tube when selecting the hydraulic tube, size and fittings.

Consult with specialist suppliers or engineers for guidance on sizing, selecting the type, and fittings.

Measuring hydraulic tubing

Measure the inside diameter in mm, outside diameter and wall thickness.

Measure the overall length from the sealing surface of straight fittings and to the centreline of elbow fittings.

Tube length (up to 6 meters) and quantity for ordering

Determine and match fittings and connections (e.g. compression fittings, DIN 2353 pipe fittings, etc.)


What is hydraulic pressure?

Hydraulic pressure is exerted equally in all directions, with the force of the hydraulic fluid’s pressure acting at right angles to any surface with which it comes into contact.

First defined by Blaise Pascal, a French scientist, pressure equals the force exerted, divided by the area on which it acts.

Different units of pressure are used worldwide, such as Pascal (Pa), psi (pounds per square inch), and bar.

Pascal denotes the pressure in Newton per square metre. (1 Pa = 1 N/m²) and a bar is a metric unit of pressure equal to 100 kPa.

The force is expressed in Newtons, which measures the energy required to accelerate one kilogram of mass at one metre per second squared ( Force = mass x seconds2).

To help understand the relationship between force and pressure, as a rule of thumb, an object weighing 100 grams pushes down on a surface with the force of one Newton.


Does using a smaller tube increase pressure?

Yes. However, consider the following results of using a smaller pipe to ensure you have the correct tube size.

Scientifically, bigger tubes and lines do not always move the fluid faster or stronger. Smaller diameter tubes will increase the pressure and velocity.

If the thickness of the diameter is too small, it creates resistance and impedes the flow, thereby increasing the internal pressure.

Get in touch

Contact us online, or give us a quick call at +44 [0]161 278 2386 to find out more.

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