Oil, Gas & Energy
Field retrofits and instrumentation lines.
K76 / K114 / K168 / K219 / K273 / K325 for Sch.40 carbon, stainless, and duplex pipeline tie-ins. AVC compensates for field pipe out-of-roundness across positions.
Read the methodologySystem family 02 / Open-frame
The head that handles production runs and field welds.
Modular open-head clamps with AVC arc-length control and integrated wire feeder. Six K-series heads (K76, K114, K168, K219, K273, K325) cover OD 20mm through OD 325mm pipe OD on the FXT40 Pro industrial power source. For pipes >=219 mm, the K600 track-type head extends the platform.
OD 20-325 mmOD range across 6 modular heads
AVCPer-quadrant arc-length control
FXT40 ProIndustrial-grade power source
ASME Sec IX / API 1104Code-fit standards
01 / Why the family exists
When the joint can't fit a chamber, the chamber can't be the answer.
Closed-chamber heads are the right choice when the inner bead needs to be reviewed against SEMI F20-type or ASME BPE-type requirements. They are not the right choice when the pipe is 6" or bigger, when the wall is 5 mm thick, or when the joint sits in a field trench where there's no clean way to clamp a chamber around it.
The K-series is the open-frame answer. A mechanical ring snaps to the pipe, the torch tracks the exterior, shielding gas flows through the cup. AVC (Arc Voltage Control) reads arc length 50 times per second and adjusts torch height in real time, so wall variation across the rotation doesn't change the weld profile.
K-series heads (K76, K114, K168, K219, K273, K325) cover the full pipe range from 2" instrumentation tubing to 24"+ process and pipeline piping. Paired with the FXT40 Pro industrial-grade power source, the K-series is engineered for open-frame production work where wall thickness, current capacity, and field durability matter more than the compact form factor of the FXT20 that drives C-series and PT-series.
02 / Six heads, one digital interface
The K-series head matrix.
K76
OD 20-76 mm
V groove. Small-bore instrumentation tubing, hydraulic lines, skid-mounted piping. 2-10 mm wall.
K114
OD 25-114 mm
V or U groove. Process piping on chemical and refinery skids, instrumentation manifolds. 2-12 mm wall.
K168
OD 60-168 mm
V or U groove. Mid-diameter process piping, refinery unit headers, shipboard pipe. 2-12 mm wall.
K219
OD 89-219 mm
V or U groove. Large process headers, refinery main lines, naval auxiliary piping. 2-12 mm wall.
K273
OD 133-273 mm
V or U groove. Heavy process piping, transmission lines, large refinery service. 2-12 mm wall.
K325
OD 159-325 mm
V or U groove. Largest K-series, heavy industrial mains and refinery transfer piping. 2-12 mm wall.
K600
>=OD 219 mm / >=8.62"
Track-type. Long-distance pipeline, large boilers, nuclear main steam. 1-100 mm wall (with cold wire option).
+ FXT40 Pro power source
Three-phase 380V / 21.5 kVA / 5-400A / Siemens S7-200 SMART V3.0 PLC
All six K-series modular heads (K76 - K325) plus K600 track-type share one FXT40 Pro power source. Integrated wire feeder (0.8 / 1.0 / 1.2 mm wire), water-cooled host and head, 50-group recipe library. Industrial-grade for production process pipe and field welds.
03 / Engineering specifications
The K-series spec sheet.
Pipe OD range
OD 20-325 mm (3/4" - 12.8") K-series; >=OD 219 mm with K600 track-type
Wall thickness
2-13 mm (K-series); 1-100 mm (K600 with cold wire fill)
Materials
Sch.40 carbon / 316L / 304L / duplex 2205 / 22Cr / chrome-moly
Arc control
AVC arc-length control, programmable per-quadrant
Position
1G / 2G / 5G / 6G across all heads
Field setup
Single-operator deployable, no chamber assembly required
Power source
FXT40 Pro industrial-grade digital pulse, K-series heads
Data log
Per-joint current / voltage / speed / wire-feed speed / travel-angle / welding-time fields per FXT40 Pro KB
Code fit
ASME Section IX / API 1104 / AWS D1.1 / ISO 13847
04 / The shared power source
FXT40 Pro - industrial-grade pulse control for open-frame work.
FXT40 Pro is the industrial-class digital power source FYID-Feiyide engineered specifically for K-series open-frame heads. Higher peak current, AVC arc-length feedback at production duty cycles, and a field-durable enclosure built for trench, refinery, and outdoor pipeline work.
For high-purity tube-to-tube work (C-series closed-chamber) and tube-to-tubesheet work (PT-series), the FXT20 is the compact power source. For open-frame production scale, FXT40 Pro is. Two power sources, two clearly different jobs.
Power source
FXT40 Pro
Industrial-grade digital pulse TIG power source. Purpose-built for K-series open-frame heads and production-scale field welding.
Class Industrial open-frame
Programs on-board 50 groups per FXT40 Pro KB
Duty cycle full-shift duty per rated current
Head compatibility K76 / K114 / K168 / K219 / K273 / K325
Arc control AVC per-quadrant programmable
Safety CE EN 60974-1:2012 / M.2025.206.C125225
Programs on-board 50 groups per FXT40 Pro KB
Duty cycle full-shift duty per rated current
Head compatibility K76 / K114 / K168 / K219 / K273 / K325
Arc control AVC per-quadrant programmable
Safety CE EN 60974-1:2012 / M.2025.206.C125225
05 / Industry fit
Where the K-series is the right answer.
Heat Exchangers / Shell
Large-diameter shell-side welds.
For heat exchanger shell-side pipe-to-flange and pipe-to-pipe welds, K-series open-frame complements the PT-series tube-to-tubesheet head. Two separate power sources - FXT40 Pro for K, FXT20 for PT - covering both sides of the exchanger build.
Read the methodologyProcess Piping
Production-scale shop fabrication.
For batch production runs on 4" - 6" piping where throughput matters and closed-chamber inner-bead requirements don't, K-series with FXT40 Pro gives orbital repeatability at production scale.
All industries06 / Common questions
What buyers ask about K-series before the quote.
What is the K-series open-frame orbital welder?
The FYID-Feiyide K-series is a family of six modular open-head orbital TIG weld heads (K76, K114, K168, K219, K273, K325) covering pipe OD from OD 20 mm to OD 325 mm. All six are paired with the FXT40 Pro industrial-grade digital power source (three-phase 380V, 21.5 kVA, 5-400A, Siemens S7-200 SMART V3.0 PLC). For pipes >=219 mm requiring track-type assembly, the K600 head extends the platform on the same FXT40 Pro power source.
Which industries does the K-series serve?
FYID-Feiyide K-series heads are deployed in oil and gas field installations (ASME Sec IX, API 1104), large-diameter process piping, pipeline tie-ins, and refinery retrofits. Customers also use K-series for the shell-side welds of shell-and-tube heat exchangers, complementing the PT-series tube-to-tubesheet head.
When should I choose K-series over C-series?
Choose K-series for pipe OD over 6", for field welds where chamber assembly isn't practical, and for production runs where the inner-bead doesn't have to meet SEMI F20 or ASME BPE color level criteria. Choose C-series when high-purity inner-bead quality is the deciding factor - semiconductor UHP, biopharma WFI, sanitary food.
How does the K-series handle pipe out-of-roundness in field conditions?
K-series heads include AVC (Arc Voltage Control) that tracks arc length 50 times per second and adjusts torch height in real time. When the pipe wall is thinner on one side of the rotation, the arc length stays the same. Parameters are programmable per quadrant for cases where wall variation is severe.
Can a single welder set up a K-series head in the field?
Yes. K-series open-frame heads are designed for single-operator field deployment; the mechanical ring clamps to the pipe without chamber assembly. Delivery for K-series + FXT40 Pro is confirmed by configuration, production schedule, inspection requirements, and logistics.
Send us the pipe specs. We'll spec head + AVC profile + position-fit programs.
Engineering review timing is confirmed by project and timezone. Include OD, wall, material grade, position, and standard.
Talk to an engineer