A spiral pipe mill submerged arc welding system consists of two weld heads — one for the internal pass and one for the external pass — each containing several interdependent consumable and semi-permanent components. Understanding the function of each component is essential for maintenance planning, troubleshooting, and procurement.
The Contact Tip
Function: Transfers welding current from the weld head to the wire electrode. The wire passes through the contact tip bore, making continuous electrical contact as it feeds toward the workpiece.
Critical parameters: Bore diameter (matched to wire diameter), material grade (CuCrZr or CuCo2Be), thread form, and overall length. The contact tip is the highest-consumption component in the system and the primary determinant of arc stability.
The Contact Tip Nozzle
Function: Houses and positions the contact tip. The nozzle provides the mechanical interface between the contact tip and the torch body, and protects the tip from spatter and mechanical damage.
Critical parameters: Thread form (must match contact tip), nozzle bore geometry, and face design. Nozzle geometry affects tip protrusion and shielding flux distribution.
Wire Feed Liner
Function: Guides the wire electrode from the wire straightener to the contact tip entry point, maintaining consistent wire positioning and minimising feeding friction.
Two variants in spiral pipe mills:
- External SAW liner: Guides the wire to the external weld head. Typically a straight or gently curved conduit.
- Internal SAW liner: Routes the wire through the internal weld head boom into the pipe interior. Subject to more complex routing geometry and higher wear at bend points.
The Spindlebox
Function: Drives wire electrode from the coil through the liner to the weld head. Contains the drive rolls, motor, and wire feed speed control interface.
Critical parameters: Drive roll groove profile (matched to wire diameter), roll pressure setting, and motor speed calibration. Incorrect drive roll pressure is a common cause of wire feeding inconsistency and contact tip bore wear.
Wire Straightener (5-Roll System)
Function: Removes the cast (residual curvature) from the wire electrode before it enters the wire feed liner. Unstraightened wire causes arc wander, inconsistent bore wear in contact tips, and variable bead profile.
Configuration: Five-roll straighteners are standard in spiral pipe mill applications. Three fixed rolls and two adjustable rolls apply opposing pressure in two planes, removing both vertical and horizontal cast components.
Torch Holder
Function: Provides the structural interface between the weld head carriage and the consumable assembly. Maintains the correct angular position of the contact tip relative to the pipe surface and weld seam.
Internal Conduit Adjustment Bracket
Function: On internal weld heads, positions the wire feed liner exit relative to the torch holder and contact tip entry. Allows fine adjustment of wire approach angle after weld head setup changes.
Component Interactions — Why Upstream Wear Matters
The performance of each component depends on the condition of the components upstream and downstream:
- A worn wire straightener → increased wire cast → oval bore wear in contact tip
- A kinked wire feed liner → inconsistent wire feeding → arc instability → increased tip wear
- A misaligned torch holder → incorrect tip-to-workpiece angle → off-centre bead profile
Consumable troubleshooting should always start at the wire source (spindlebox and straightener) and work downstream to the contact tip.
Procurement
All components listed in this guide are available as standard catalogue items or as custom-manufactured parts to drawing. Ersan Industrial supplies all weld head components from stock in Kocaeli, Turkey, with worldwide delivery in 48 hours.
Contact us with your weld head details for a compatibility check and quote.