Clamshell Machines

What Is a Clamshell Machine?

A clamshell machine is a split-frame pipe machining system that mounts around the outside diameter of an installed pipe or tube.

Unlike conventional machining equipment that requires the workpiece to be removed and positioned inside a machine shop, a clamshell machine travels to the workpiece. The split frame opens around the pipe, is aligned and secured, and uses rotating tooling to perform the required machining operation.
Depending on the machine configuration and tooling, a single setup can support:

• Cold cutting — cuts pipe without flame or thermal cutting methods
• Beveling — prepares the pipe end for welding
• Facing — produces a controlled, flat pipe or component face
• Counterboring — machines the internal bore for specified fit-up requirements

This makes split frame machining particularly useful when access, downtime, or pipe removal presents a challenge.

How a Split Frame Pipe Cutting Machine Works

A clamshell machine consists of a split frame that opens around the pipe and is secured to the pipe's outside diameter. The machine's fixed ring provides the mounting and alignment structure, while a rotating ring carries the tool slides and cutting tools around the circumference of the pipe.

The basic machining process includes:

1. Open the split frame and position the machine around the pipe.
2. Secure and align the machine to establish the required machining position.
3. Install the appropriate tooling for cutting, beveling, facing, or counterboring.
4. Set the tool slides according to the required machining dimensions.
5. Engage the drive system to rotate the tooling around the stationary pipe.
6. Complete the machining operation using controlled tooling movement.

Because the pipe itself does not need to rotate, split frame machines can be used on large-diameter piping and installed systems where conventional machining methods are difficult to implement.

Key Advantages of Clamshell Machines

Inline & On-Site Machining

The primary advantage of a clamshell machine is its ability to machine pipe in place.

The OD-mounted design allows technicians to perform precision pipe machining without transporting the workpiece to a conventional machine shop. This can be particularly valuable during plant maintenance, field repair, and turnaround operations.

Cold Cutting Capability

Clamshell machines use mechanical cutting rather than torch, plasma, or other thermal cutting methods. Cold cutting can eliminate the heat and sparks associated with conventional flame cutting methods, making it an important consideration for applications with strict hot-work requirements.

Site-specific procedures, permits, isolation requirements, and safety protocols should always determine whether cold cutting is appropriate for a particular application.

Portable Field Machining

Split frame machines are designed for field deployment and can be transported directly to the job site. Their portability makes them useful for:

• Plant maintenance
• Pipeline work
• Shutdowns and turnarounds
• Field fabrication
• Pipe repair
• Weld preparation
• Large-diameter pipe machining

Precision & Repeatability

A properly aligned split frame provides a controlled tooling path around the pipe circumference. This allows operators to produce consistent cuts, bevels, and machined faces according to the application's dimensional and weld-preparation requirements.

Multiple Machining Operations

With the appropriate tool slides, cutters, and accessories, one clamshell machine can perform multiple machining operations. A single setup may be configured for cutting, beveling, facing, and counterboring, reducing the need to move the workpiece between different machines or machining processes.
 

---

Clamshell Machine Specifications

Selecting a split frame pipe cutting machine requires matching the machine configuration to the pipe, machining operation, available access, and site conditions. Key specifications include:

Pipe Outside Diameter Range

The machine must accommodate the pipe's actual outside diameter. Standard split frame machines are available across a wide range of pipe sizes, with KRAIS configurations covering applications from approximately 1" through 48" OD.

Wall Thickness

Pipe wall thickness affects the required cutting capacity, tooling configuration, and drive requirements. Heavy-wall pipe applications may require higher torque and a machine configuration capable of maintaining the required cutting performance.

Machining Operations

The required machining operation determines the appropriate tool slides, cutters, and accessories. Depending on configuration, clamshell machines can support:

• Pipe cutting
• Beveling
• Facing
• Counterboring
• Weld-end preparation

Machine Profile & Access

Available clearance around the pipe is an important consideration when selecting a split frame. Low-profile clamshell machines can provide an advantage when machining must be performed in confined areas or where radial access is restricted.

Drive Type

Clamshell machines are available with different drive configurations depending on the machine size and application.

• Pneumatic drives are commonly selected for applications where compressed air is preferred or electrical equipment is restricted.
• Hydraulic drives provide high torque output for demanding, heavy-wall machining applications.
• Electric drives provide a versatile option for many general industrial machining environments.

Drive selection should be based on the machine model, available utilities, required torque, site requirements, and application conditions.
 

---

Industrial Applications for Split Frame Pipe Machining

Clamshell machines are used where installed pipe requires precision cutting or machining without conventional machine-shop processing. Common applications include:

• Pipeline maintenance and repair
• Oil & gas facilities
• Petrochemical plants
• Refineries
• Power generation facilities
• Heat exchanger piping
• Boiler piping
• Industrial process piping
• Shutdown and turnaround operations
• Field weld preparation
• Pipe modification and replacement

For critical piping systems, machining requirements should be established from the applicable engineering specifications, drawings, weld procedures, and site requirements. 

KRAIS Clamshell Machines at EGI

EGI is the exclusive North American distributor of Krais tube tools and machining equipment providing access to KRAIS split frame machining systems for industrial and field applications. The KRAIS SFSF Slim Fit Split Frame Series is designed for precision pipe machining where access, portability, and machining capability are critical.

KRAIS SFSF Slim Fit Split Frame Features

• Slim-fit design: The low-profile configuration is designed for applications where radial clearance is limited. Machines up to 24" measure approximately 3.248" in height, while machines up to 48" measure approximately 4.47" in height, with a consistent 2.5" width.
• Wide pipe size coverage: The SFSF series includes 15 standard models covering approximately 1" through 48" OD, with pneumatic, hydraulic, and electric drive configurations available across the range.
• Keyway-mounted motors: Keyway motor attachment helps resist motor rotation under load and protects the gear ring during operation.
• Multiple motor configurations: Available drive options include electric, hydraulic, K70 inline, and K70 right-angle motor configurations, depending on the machine model.
• Integrated squaring system: Steel squaring plates and a lever-type tripper module help operators establish the required machine position before beginning the machining operation.
• Expandable tooling capability: Bridge cross slides and additional tool holders can expand the machining capabilities of the base machine.
• BCS cross-slide compatibility: The BCS bolt-on cross slide provides an additional machining configuration that can be installed without replacing the base split frame.

Explore KRAIS Tube Tools & Machining Equipment

---

Choosing the Right Clamshell Machine

The correct clamshell machine depends on more than pipe diameter alone.
Before selecting a split frame machining system, consider:

• Pipe outside diameter
• Pipe wall thickness
• Required cutting depth
• Required bevel geometry
• Facing requirements
• Counterbore requirements
• Available radial and axial clearance
• Required machining tolerances
• Available pneumatic, hydraulic, or electrical power
• Required torque
• Tooling and accessory requirements
• Job-site conditions
• Production, maintenance, or turnaround schedule

Providing these application details allows EGI to help identify the appropriate machine, drive configuration, tooling, and accessories.

Tube & Pipe Machining Equipment for Heat Exchanger and Boiler Applications

Clamshell machines are one component of a broader range of equipment used for industrial tube and pipe maintenance.
EGI supplies tooling for heat exchanger, boiler, condenser, and process piping applications, including tube expanders for tube-to-tubesheet installation and tube plugging and testing equipment for tube isolation and pressure testing.

• Explore Tube Expanders
• Explore Tube Plugging & Testing Equipment

For a broader overview of the industries and applications supported by EGI, visit our Industries Served page.

Why Choose EGI for Clamshell Machines?

EGI combines access to KRAIS machining equipment with industrial tooling expertise and application support.

KRAIS Distribution & Product Access

As the exclusive North American distributor for KRAIS Tube Tools, EGI provides access to KRAIS split frame machining equipment and associated tooling.

Application Support

Selecting a clamshell machine requires evaluating pipe dimensions, machining requirements, access limitations, drive requirements, and tooling configuration. EGI can help identify a machine configuration suited to the specific application.

Complete Industrial Tooling Solutions

Clamshell machining is part of EGI's broader portfolio of tube and pipe tooling for industrial maintenance, repair, fabrication, and outage applications.
From split frame machines and tube machining equipment to tube expanders, plugging systems, testing equipment, rental tooling, and service support, EGI can help consolidate tooling requirements through a single industrial equipment source.

Explore EGI Tube & Machining Equipment

Contact EGI for Clamshell Machine Specifications & Pricing

The right split frame machine depends on the pipe dimensions, machining requirements, available access, drive requirements, and job-site conditions.
Contact EGI to discuss your application and determine the appropriate KRAIS clamshell machine, drive configuration, tooling, and accessories. Contact EGI or request a quote for KRAIS clamshell machines.

With technical expertise, industrial tooling solutions, and 24/7/365 emergency support, EGI is positioned to support your pipe and tube machining requirements from equipment selection through field application.