Split Frame Pipe Cutting & Beveling Machines
COHOG® clamshell split frame machines cold-cut and bevel large-diameter pipe from 2.375″ to 24″ OD in a single pass — no bore access required, no heat-affected zone, no sparks.
What Is a Split Frame Pipe Cutting Machine?
A split frame pipe cutting machine (also called a clamshell cutter or clamshell lathe) is a portable machine that mounts around the outside of a pipe using a hinged, two-piece frame. The frame clamps onto the pipe OD, and a cutting tool rotates around the full circumference to sever the pipe wall and machine a weld-prep bevel — all in a single continuous operation.
Split frame machines are essential for large-diameter pipe work where internal clamping is impossible: closed systems under pressure, subsea and offshore pipe, heavy-wall process piping, and any application where the pipe bore is inaccessible. They are the standard tool for refinery turnarounds, pipeline maintenance, power plant outages, and offshore platform pipe repairs.
The Esco Tool COHOG® split frame machine covers pipe from 2.375″ to 24″ OD (60.3mm to 609.6mm) across 8 interchangeable frame sizes. The clamshell design opens to fit around an in-service pipe, locks closed, and the pneumatic or electric drive unit rotates the cutting head through the pipe wall using a cold cutting process that produces zero heat-affected zone and zero sparks.
Cold Cutting vs. Torch Cutting — Why It Matters
Cold cutting is a mechanical metal-removal process that generates no significant heat at the cut point. For large-diameter pipe, the choice between cold cutting and thermal cutting affects safety, metallurgy, and code compliance.
| Factor | Cold Cutting (COHOG®) | Torch / Plasma | Abrasive (Grinder) |
|---|---|---|---|
| Heat-Affected Zone | ✓ None | ✗ Significant HAZ | ⚠ Localized heat |
| Sparks / Open Flame | ✓ None | ✗ Open flame | ✗ Sparks |
| Safe in Hazardous Areas | ✓ Refinery, offshore, gas | ✗ Hot work permit required | ✗ Hot work permit required |
| Weld-Ready Bevel | ✓ Cut + bevel in one pass | ✗ Requires grinding after | ✗ No bevel capability |
| Alloy Pipe Integrity | ✓ No metallurgical damage | ✗ Carbide precipitation, HAZ | ⚠ Contamination risk |
| Cut Surface Finish | ✓ Machine-quality | ✗ Rough, requires grinding | ⚠ Acceptable with skill |
| Operator Skill Required | Setup + monitoring | Certified flame cutter | Experienced fitter |
Why the COHOG® Split Frame
Purpose-built for the most demanding pipe cutting and beveling applications in refinery, pipeline, power, and marine environments.
Cut + Bevel in One Pass
Sever the pipe and machine the weld-prep bevel in a single continuous operation. Eliminates the need for a separate beveling machine, cutting setup time in half.
No Bore Access Required
The clamshell design opens and wraps around the pipe from the outside. Mount on in-service piping, closed systems, subsea pipe, and any application where internal access is impossible.
Zero Heat-Affected Zone
Cold cutting process — no sparks, no flame, no metallurgical damage. Safe for refineries, offshore platforms, gas processing, and confined spaces without a hot work permit.
Pendant Remote Control
The COHOG® features an optional pendant control that lets the operator stand back and run the cutting operation from a safe distance — critical on elevated pipe racks and overhead work.
8 Interchangeable Frames
One drive unit, eight frame sizes covering 2.375″ to 24″ OD. Swap frames to match the pipe — no need to purchase separate machines for different pipe sizes.
Single-Operator Setup
Lightweight clamshell frame mounts without cranes or rigging. One operator can install, align, and run the machine — reducing crew size requirements on turnaround work.
8 Sizes — 2.375″ to 24″ OD
The COHOG® split frame series uses interchangeable clamshell frames paired with a common drive unit. Select the frame that matches your pipe OD, mount it around the pipe, and the machine handles cutting, beveling, or both.
All sizes are available in pneumatic drive (for offshore, refinery, and marine environments) and electric drive (for shop and plant applications). The cutting tooling accepts standard V-bevel, compound bevel, and custom bevel profiles.
View Full COHOG® Specs →| Frame Size | Pipe OD Range | Metric (mm) |
|---|---|---|
| COHOG 1 | 2.375″ – 3.500″ | 60.3 – 88.9 |
| COHOG 2 | 3.500″ – 4.500″ | 88.9 – 114.3 |
| COHOG 3 | 4.500″ – 6.625″ | 114.3 – 168.3 |
| COHOG 4 | 6.625″ – 8.625″ | 168.3 – 219.1 |
| COHOG 5 | 8.625″ – 10.750″ | 219.1 – 273.1 |
| COHOG 6 | 10.750″ – 14.000″ | 273.1 – 355.6 |
| COHOG 7 | 14.000″ – 18.000″ | 355.6 – 457.2 |
| COHOG 8 | 18.000″ – 24.000″ | 457.2 – 609.6 |
Four Steps to a Finished Cut & Bevel
Open & Mount
Open the clamshell frame and position it around the pipe at the cut location. Close and lock the frame halves together.
Align & Clamp
Tighten the OD clamping mechanism to center the frame on the pipe. Verify alignment with the built-in indicators.
Cut & Bevel
Engage the drive unit. The cutting tool rotates 360° around the pipe, severing the wall and machining the bevel in one pass.
Inspect & Weld
Remove the cut section. The remaining pipe end has a machine-quality, weld-ready bevel — no grinding required. Ready for fit-up and welding.
Industry Applications for Split Frame Cutting
Split frame pipe cutting and beveling is the standard method across every industry that works with large-diameter process piping.
Refinery Turnarounds
Remove and replace corroded process piping during scheduled turnarounds. Cold cutting eliminates hot work permits in hydrocarbon environments, reducing safety overhead and accelerating the work schedule.
Pipeline Maintenance & Tie-Ins
Cut and bevel pipeline sections for tie-in welds, valve replacements, and repair sleeves. The COHOG® handles carbon steel, chrome-moly, and high-strength pipeline grades up to 24″ OD.
Power Plant Outages
Main steam lines, HRSG headers, and feedwater piping. Split frame cutting on P91, P22, and other chrome-moly alloys without heat — preserving the metallurgy that post-weld heat treatment is designed to maintain.
Offshore & Marine
Platform pipe repairs, riser work, and subsea tie-ins. Pneumatic drive is standard — no electrical power needed. Cold cutting is mandatory on offshore platforms where hot work restrictions apply.
Shipyard Fabrication
New construction and repair work on naval vessels, cargo ships, and LNG carriers. Split frame machines handle the large-bore pipe systems common in marine engine rooms and ballast systems.
Water & Wastewater
Municipal water mains, treatment plant piping, and force mains. Cold cutting on HDPE-lined steel pipe and cement-lined pipe without damaging the internal lining — a critical advantage over thermal methods.
Split Frame & Cold Cutting FAQ
Need to Cut & Bevel Large-Diameter Pipe?
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