How is Non-Welded Piping used in mobile equipment?

Non-welded piping systems employ mechanical connections, such as flared, flareless, or flared press-fit fittings, to join tubing of hydraulics without heat and are the most preferred option for mobile equipment since they are resistant to vibration fatigue; permit field serviceability without welding equipment; and reduce the possibility of weld-induced contamination as well as thermally affected zones that could cause pressure instability in excavators, loaders, cranes, and agricultural equipment.

Mobile hydraulic equipment is used under conditions that stationary industrial systems do not encounter: constant vibrations and flexing of the chassis and temperature fluctuations and remote work sites where a damaged welding connection can cause long periods of inactivity. This is the reason why piping that is not welded is now the most common joining technique across construction, agriculture, and machinery for handling. Knowing how the systems operate and how they perform better than welded alternatives aids the fleet manager, technicians in hydraulics, as well as OEM engineers to make more informed decisions regarding specifications.

What is non-welded pipe?

"Non-welded piping" is a term used to describe any pipe or hydraulic tube connection that is made using mechanical methods instead of fusion welding. Instead of melting base metal in order to join two ends of a tube Non-welded systems rely on flaring, compression, or crimping for the seal. Some common methods of joining that are not welded are the following:

• Flared fittings (37-degree JIC and 45-degree SAE flares) that are fitted with flares, in which the tube's ends are mechanically shaped into a cone-shaped form, which connects with a fitting seat
• Flareless (bite-type) fittings, in which ferrules bite into the tube's diameter while the nut is driven down
• Swage and press-fit fittings, which make use of mechanical or hydraulic presses to permanently change the shape of the tube's sleeve
• Face seal O-ring (ORFS) fittings, that make use of a flat face as well as an O-ring instead of a metal-to-metal flare seat

Each method ensures a leak-free seal without introducing heat into the tube's wall. This is the primary benefit over pipe assemblies that are welded.

Why mobile equipment prefers non-welded systems

Resistance to fatigue and vibration

Mobile equipment chassis flex continuously when under stress, and the engine and travel motor vibrations are transmitted directly to the hydraulic pipework. Welded joints form a heat-affected zone (HAZ) near the weld's bead. This is where the structure of the metal's grain changes, and fatigue strength decreases. When a cyclic vibration load is applied, cracks are more likely to begin near the HAZ boundary instead of in the tube's material of origin. Non-welded joints that are mechanically formed do not introduce this weakness in metallurgical processes and therefore last longer over the lifetime of a machine that experiences thousands of cycles of vibro-force.

No heat-affected contamination

Welding hydraulic tubes causes weld scale as well as oxidation on the surface of the pipe, unless the joint is cleared with an inert gas before welding—an action that is frequently skipped or executed poorly in the field. A loose, oxidized scale that breaks off at the time of system start-up is the main cause of servo as well as proportional valve sticking, something we've covered in detail in our latest article on stiction and sticking of valves. Fittings that are not welded do not pose this internal risk of contamination because there is no melting.

Field serviceability

It is the most useful benefit of mobile equipment. A pipe that is welded does not work on a job site without portable welding equipment or transporting the machine back to a workshop. A flareless or flared pipe can be disassembled and put back together using hand tools in just a few minutes. For fleets of skid steers, excavators, or agricultural equipment that are spread across work locations, this difference in serviceability will result in a reduction in time to repair and lower cost of ownership.

Relative motion can be accommodated

The mobile equipment parts move in relation to one another. For instance, booms can articulate, axles rotate, and the chassis sections pivot. Non-welded pipes are usually installed with a little routing flexibility and are able to incorporate fittings that swivel (see our discussion on swivel and fixed fittings). fitted fittings fixed) in places where rotational freedom is required. Welded assemblies that are rigid are less tolerant of dynamic movement.

Common mobile applications

Construction equipment

Wheel loaders, excavators, and dozers utilize massive non-welded tubes and networks to transport high-pressure fluids to the bucket, boom, and arm as well as travel circuits. Fittings with flares and flared fittings are the most common tubes of steel that connect the valve bank, the pump, and the cylinders, whereas fittings for hoses with fitted fittings that are crimped or reusable are used to handle sections that bend in response to boom movement.

Machinery for agriculture

Tractors as well as sprayers use a lot of non-welded connections due to the variety of equipment they connect to. Quick-disconnect couplings, banjo fittings, and flared connections allow operators to swap implements in the field without specialized tooling—a requirement we've explored previously regarding agricultural-specific fitting standards.

Material handling and cranes

The crawler and mobile cranes employ non-welded piping extensively for the outrigger and boom extensions as well as winch and outrigger circuits. A combination of pressures that are high as well as the requirement to disassemble the pipe regularly during transportation or for maintenance makes mechanical fittings the ideal option over permanently joined joints that are welded.

Equipment for mining and forestry

These systems combine extreme vibration and abrasive, filthy environments. Non-welded systems that use ORFS and flareless fittings offer secure sealing while also being serviceable even when the equipment is located far from repair facilities.

Considerations for design and installation

Wall thickness and tube material compatibility

There are different fitting types that work with all tube materials. Flareless bite fittings, for instance, need adequate wall thickness to allow for the ferrule to properly bite without bursting the tube. Thin-wall tubing is typically suitable for flared and ORFS connections. Making sure that the fitting is compatible with the tube specifications during the design phase helps prevent premature failures.

Correct torque and assembly procedure

Non-welded fittings are as secure as the fittings they are joined to. When a flareless fitting is under-torqued, it leaves the ferrule unseated, which could lead to leakage when pressure cycling. Over-torquing could fracture the ferrule or deform the tube. Manufacturers provide specific torque values and usually recommend a predetermined number of turns beyond finger-tight instead of using torque wrenches only because friction variation affects the precision of tightening torques based on torque.

Support and clamping of vibrations

Even fittings that are vibration-resistant are benefited by proper tube support. Industry guidelines typically recommend the clamping of tube runs at intervals that correspond to tube diameter to avoid resonance from concentrating stress on the fitting's connection instead of spreading it across a supported run.

Cleanliness in assembly

Since non-welded systems are unable to avoid welding scale as they do, they shift the primary contamination risk to the assembly stage -machine chips thread sealant fragments or dirt formed in the field during connection. In line with ISO cleanliness standards during assembly, which we've previously discussed with regard to the control of contamination in hydraulic fluids, is still vital even without welding involved.

Non-welded in contrast. weldable When welding makes sense

Non-welded pipe isn't always the best choice. Industrial systems that are stationary and have low vibration, large-diameter pipe runs, and extremely high-pressure applications often still opt for welding for its long-lasting leak-free joint for less cost per connection when disassembly doesn't have to be a requirement in the design. For mobile equipment, that is, where accessibility to the field and ease of servicing top the list of design criteria, non-welded systems for piping remain the most common choice across every category of equipment.

What's the main difference between flared and unflareless plumbing fittings for hydraulics?

The flared end of the fitting must be formed mechanically into a cone-shaped shape that sits against a similar angle inside the fitting, forming the metal-to-metal sealing. Flareless fittings utilize a distinct ferrule that is inserted into the tube's outside surface as the fitting's nut is tightened, thus eliminating the flaring process.

Are fittings that are not welded as sturdy as joints made by welding?

If properly designed and assembled, non-welded fittings are able to meet or surpass the strength and performance in fatigue and pressure of joints that are welded for mobile applications in large part because they are able to avoid the weakness caused by heat, which welding creates near to the joint.

Are fittings made of non-welded materials reused following removal?

Flared fittings are typically reused as long as the flare's surface is not damaged. Flareless fittings are more prone to reuse since the ferrule has been shaped to bite into the tube. Many manufacturers suggest replacing the ferrule at the time of the first assembly to ensure the integrity of the seal.

What is the reason mobile equipment manufacturers prefer not to use welded hydraulic pipes?

Welded pipes are susceptible to vibration fatigue in the temperature-sensitive zone and are hard to repair in the field and are more at chance of internal weld scales contaminating the hydraulic system. All of these are not suitable for the working conditions mobile equipment faces.

What is the reason for leaks from non-welded fittings in time?

The most frequently cited reasons are improper torque at the beginning or ferrules reused that do not fit properly, the vibration of tubes caused by insufficient clamping, and the degeneration of seals or O-rings due to thermal cycling or incompatibility with the fluid.