How is Non-Welded Piping used in mobile equipment?

Non-welded piping is a term used to describe hydraulic tube connections and hose connections constructed using mechanical fittings—such as flare compression, O-ring face seals (ORFS), and flange joints—instead of brazed or welded joints. For mobile equipment such as excavators, cranes, loaders, or agricultural machines, the non-welded pipe is utilized in the entire hydraulic circuit since it is able to withstand continuous movement, flexing, and thermal cycling much superior to the rigid connections made by welded joints, while providing faster field repair and replacement of components without the need for hot work.

Why does mobile equipment rely on connections that aren't welded?

Mobile hydraulic machines work in environments that stationary industrial systems do not have to deal with. Wheel loaders articulating on rough terrain, an excavator swaying an arm under load, and a harvester for combines that is swaying during a total shift put their hydraulic lines under repeatedly flexing shock load along with mechanical stresses. Welded joints, although durable and long-lasting in a fixed location, are weak and brittle when subjected to these kinds of cyclical movements. A joint that is flawlessly formed in a stationary press may become fatigued and crack after a few months on equipment that is never stopped moving.

Non-welded pipes solve this problem through the use of mechanical joints that are made to allow for some amount of motion and misalignment without causing failure. The connections are based on compression, deformation, or elastomeric seals, rather than an elastomeric metallurgical fusion bond that allows them to tolerate the expansion and vibration that are the basis of the mobile equipment's duty cycle.

Common non-welded fitting types used in mobile applications.

The fittings of a flare (37 deg. JIC and 45 deg. SAE)

JIC (Joint Industry Council) 37-degree flare fittings are among the most frequently employed non-welded connections within mobile hydraulics. The tube's end is flared to be in line with the angle of the fitter's seat, and a nut is used to compress the flare to the body of the fitting to form a metal-to-metal seal. The fittings can be reused and relatively simple to check in case of damage. They are also tolerant of the slight vibrations that are common in a majority of off-highway vehicles.

O-ring face seal (ORFS) fittings

ORFS fittings are now the most popular choice for high-pressure mobile circuits, especially for skid steers, excavators, and forest equipment. Instead of a metal-to-metal flare seal, ORFS makes use of an elastomeric O-ring that is compressed against a flat surface. This eliminates leak pathways that may develop in flare fittings during the force of vibration and also provides a more durable seal at pressures that exceed 3000 psi. ORFS will also not be as vulnerable to damage from over-torquing. This is crucial when field technicians need to make repairs using a limited set of tools.

Fittings for compression and bite

Compression fittings, like ferrule-style bite fittings, grip around the outer diameter tubes by using a ferrule, which will deform slightly as it is tightened. They are commonly used in smaller diameter lines that are carrying signals for control or pilot rather than the main working pressure and where the ease of assembly and disassembly is more important than pressure ratings.

Connectors for flanges (code 61 as well as code)

For high-pressure lines with larger diameters, such as the ones that feed main hydraulic motors or pumps for large excavators as well as mining equipment, four-bolt flange connections are a standard. Code 61 (standard pressure) and Code 62 (high pressure) Flanges are fitted with split-flange clamps with an O-ring seal. This distributes the clamping force equally around the connection. This design is able to handle tension spikes and pulsation that occur in high-flow circuits and does not rely on thread engagement by itself.

The piping that is not welded appears on mobile machines

Boom arm, bucket, and boom circuits

For loaders and excavators, the hydraulic lines connecting the arm and boom to the cylinders are nearly always not welded. They flex indefinitely as the linkage changes, and hose assemblies that have fittings that are crimped or field-attachable at both ends allow the replacing of a damaged part without disrupting the remainder of the circuit.

Implementation and hitch lines for steering

Motor graders and articulated dump trucks steer by flexing hydraulically at the center pivot. The lines that cross the pivot point undergo continuous angular motion, which makes flexible, non-welded hose connections more of a necessity for functionality than a style preference.

Circuits for remote and auxiliary circuits

Attachments such as hydraulic hammers, grapples, and augers connect to the machine's hydraulic auxiliary circuit by means of quick-disconnect couplings that are paired with hose assemblies that are not welded. This enables operators to switch attachments on the go within a matter of moments.

The chassis-routed and cab-mounted lines are available.

Lines that run from the valve bank to the cab-mounted controls or through the frame to distant cylinders make use of rigid tubes with flares or ORFS fittings at connections. This helps keep the majority of the line rigid and secure while allowing joint repair at each connection point.

The advantages of non-welded pipes in mobile equipment

Field serviceability. A fitting or hose that is damaged could be replaced on the roadside or on a job site with no welding equipment or hot work permits or a trip back to an establishment.

Vibration and resistance to fatigue. Mechanical joints made of elastomeric and compressive sealing elements can withstand more cyclical stress than welded joints that are rigid and extend the life of their service in extreme vibration environments.

Modularity. Components are able to be added, removed, or reconfigured, which is useful in machines that experience frequent changes in attachments or retrofits.

A reduced installation cost and time. The process of assembling or replacing the fitting that is not welded takes less time than needed for welding and does not require certified welders as well as post-weld examination.

Easier leak diagnosis. Mechanical joints can be visually inspected A leak that is developing typically manifests as a weep at the fitting prior to a catastrophic failure, providing maintenance teams an opportunity to warn that a concealed weld defect will not.

Limitations and considerations

Non-welded pipes aren't necessarily superior to connections made with welded wires, but it is an alternative that's appropriate to particular circumstances. Mechanical fittings create more problems than uninterrupted welding, and inadequate torque during installation is among the leading causes of leaks in fields in portable hydraulic systems. Over-torquing could deform seals and fracture fitting bodies, while the wrong torque can lead a joint to leak during pressure cycling. This is why manufacturers require exact torque specifications and, more often, markings for torque verification in ORFS or flare fittings.

The fitting selection is also important to ensure thermal and chemical compatibility. Elastomeric seals that are used for ORFS or compression fittings need to be compatible with the hydraulic fluid being used. Standard O-rings made from nitrile, for example, are not suitable for certain high-temperature or high-temperature liquids that are fire resistant and may require FKM or PTFE substitutes.

Non-welded piping is the foundation of the way the hydraulics of mobile machines are constructed and assembled as well as maintained. Beginning with the flare and ORFS fittings that connect excavators' main lines to the connection of a flange that feeds the main pump of a mining shovel, mechanical joints provide mobility, tolerance to vibration, and field reliability that welded connections cannot meet in a fast-moving and load-cycling setting. For maintenance and fleet operator teams, gaining a better understanding of the proper fitting type and techniques for torque is among the best ways to cut down on infrequent downtime and increase the life of hydraulic systems.

What's the distinction between non-welded and welded hydraulic pipes?

Welded piping is a fused joint, which is typically used within stationary systems for industrial use, and non-welded pipes use mechanical fittings, such as flare, ORFS, compression, or flange connections. These fittings are able to be disassembled, assembled, and reinstalled without any hot work.

Why can't mobile hydraulic machines make use of pipes that are joined by welding?

Welded joints are incredibly rigid and susceptible to cracking from the constant flexing, vibrating, and shock loads that mobile equipment is subjected to, while mechanical fittings can withstand motion and are much more easy to maintain on the job.

Which is the more commonly used non-welded fitting that is used on excavators?

ORFS (O-ring sealing the face) fittings are commonly utilized on excavators and other high-pressure mobile equipment due to their O-ring seal with a flat face that resists leaks caused by vibrations better than metal-to-flare seals.

Hydraulic fittings made of non-welded materials take on high pressure?

Yes. The correctly evaluated ORFS as well as Code 61/62 fittings for flanges are specifically designed to be used in high-pressure mobile applications that include motor and main pump connections on big excavators as well as mining equipment, which can often exceed 3000 PSI.

What can cause leaks in hydraulic fittings that are not welded?

Most often, the cause is insufficient torque when assembly is being performed (both over- and under-torquing) and seal material incompatible with hydraulic fluid, as well as physical damage to the surface of the seal caused by vibrations or improper handling during the installation.