Caldwell Model AST Non-Locking Structural Shape Lifting Clamp

Non-Locking Structural Shape Lifting Clamp — Precision Control for Beam Lifting, Turning & Stacking

The Renfroe Model AST Non-Locking Structural Shape Lifting Clamp (AST-01.50-A) is engineered for lifting, turning, and stacking lightweight beams and structural shapes with a 1.5-ton capacity. Designed for use in steel erection, fabrication, and structural staging operations, it is built for contractors and trades professionals who need reliable, controlled handling of I-beams, channels, and other structural profiles. A constant tension must be maintained on the lifting shackle during all lifting operations.

The Model AST's horizontal shackle design sets it apart from standard vertical plate clamps by enabling the clamp to be positioned with the shackle over the web and between the flanges of a beam, allowing the load to be lifted in a near-horizontal position. This geometry also permits the beam to be lifted from a horizontal position, turned 90°, and raised to a vertical position — a capability that general-purpose plate clamps do not provide.

Key Features & Benefits

Horizontal Shackle Design for Beam Web Positioning

The horizontal shackle allows the clamp to be placed with the shackle positioned over the web and between the flanges of a beam or structural shape. This configuration gives operators direct load control when lifting beams in a near-horizontal orientation, reducing the risk of load shift during pick-and-carry operations.

90-Degree Turn and Vertical Raise Capability

With the clamp placed so the shackle overhangs the flange, a horizontally positioned beam can be lifted, rotated 90°, and raised to a vertical position in a single rigging setup. This eliminates the need to re-rig the load mid-operation, saving time and reducing handling risk on the job site.

Constant Tension Operation

The Model AST requires constant tension to be applied to the lifting shackle whenever a load is being lifted. This design characteristic ensures the cam gripping mechanism remains engaged throughout the lift, maintaining a secure hold on the structural member.

Purpose-Built for Lightweight Structural Shapes

Developed specifically for lightweight beams and structural shapes, the AST-01.50-A is rated at 1.5 tons and weighs 20 lbs — making it practical for field use without being cumbersome. Its compact clamp dimensions (8.5 in. height, 7 in. length, 2.56 in. width) suit standard structural profiles encountered in commercial and industrial construction.

Cam Gripping Mechanism

The clamp features a gripping cam and swivel jaw assembly that engages the structural shape securely during lifting. The cam pin and shackle pin bushing are discrete, replaceable components, supporting long service life and field-level maintenance using manufacturer repair kits.

Common Applications

Lifting Structural Beams in a Near-Horizontal Position

The clamp is placed with the shackle over the web and between the flanges, allowing I-beams and similar shapes to be hoisted while lying nearly flat — useful for placing beams into position on a structure without excessive vertical swing.

Turning Beams from Horizontal to Vertical

When a beam is lying flat on a surface and the clamp is positioned with the shackle overhanging the flange, the beam can be lifted, turned 90°, and raised to a vertical position in a controlled sequence.

Stacking Lightweight Structural Shapes

The AST is designed for stacking operations where lightweight beams and shapes need to be placed precisely in storage or staging areas, with the clamp providing controlled positioning throughout.

Steel Fabrication and Staging Operations

Fabrication shops and structural staging yards use this clamp to handle beams and shapes during processing, transport between workstations, and pre-assembly staging.

Compatible Materials

• Lightweight steel I-beams
• Structural channels
• Structural angles and other rolled steel shapes
• Steel members with plate thickness up to 0.75 in.

Product Documents

• Download Catalog
• Download Manual
• Lifting Clamp Survey Report
• Lifting Tool Inventory and Maintenance Form
• Minimum Recommended Clamp Inspections
• Renfroe Repair Kits Catalog

Application Instructions

Lifting a Beam in a Near-Horizontal Position

1. Read and understand the Operator's Manual (OM 211-AST/L) before putting the clamp into service.
2. Inspect the clamp before each lift per the pre-lift inspection instructions in the Operator's Manual.
3. Place the clamp on the beam with the shackle positioned over the web and between the flanges.
4. Connect rigging from the crane to the lifting shackle using a flexible connection — do not attach the clamp directly to the crane hook.
5. Apply constant tension to the lifting shackle before and throughout the lift to keep the cam mechanism engaged.
6. Lift the beam to the desired position.

Turning a Beam from Horizontal to Vertical

1. With the beam lying in a horizontal position, place the clamp with the shackle overhanging the flange.
2. Connect rigging to the lifting shackle using a flexible connection.
3. Apply constant tension to the shackle and begin the lift.
4. Lift and turn the beam 90° until it is raised to a vertical position.
5. Ensure the load is balanced and within the 1.5-ton rated capacity throughout the operation.

Technical Specifications

Safety Data Summary

Safe Handling

• Read and understand the Operator's Manual before putting the clamp into service; take the tool to your immediate supervisor before first use.
• Constant tension must be applied to the lifting shackle at all times when lifting a load.
• Do not lift over workmen or personnel.
• Do not attach the clamp directly to the crane hook; always use a flexible connection between the crane and the clamp shackle.
• Do not use a heavy flexible connection.
• Use the correct clamp for the job; do not use large-capacity clamps to lift light loads.
• Use an adequate number of clamps to balance the load; do not lift unbalanced loads.
• Do not overload the clamp beyond its rated 1.5-ton capacity.
• Inspect the clamp before each lift and follow all inspection and maintenance instructions in the Operator's Manual.
• Do not use a clamp that has been overloaded.
• Do not side-load with this clamp.
• Do not alter, grind, weld, or modify the clamp in any manner.
• Use only RENFROE replacement parts to ensure proper operation.
• Do not misuse: do not lift plate from the bottom of a plate stack.
• Do not improvise; always use the correct clamp for the job.

Frequently Asked Questions

Q: What is the difference between the Model AST and the Model ASTL?
A: Both the Model AST (non-locking) and Model ASTL were developed for the same primary purpose — lifting, turning, and stacking lightweight beams and structural shapes while constant tension is applied to the lifting shackle. The ASTL designation indicates a locking-type variant; the AST-01.50-A covered here is the non-locking version.

Q: Must tension always be applied to the shackle during lifting?
A: Yes. The Model AST requires constant tension to be applied to the lifting shackle whenever a load is being lifted. Releasing tension can disengage the cam gripping mechanism and result in an unsafe condition.

Q: Can this clamp be attached directly to the crane hook?
A: No. The Operator's Manual specifies that a flexible connection must always be used between the crane and the clamp shackle. Direct attachment to the crane hook is not permitted.

Q: What is the maximum plate thickness this clamp will accept?
A: The AST-01.50-A accepts material up to 0.75 in. plate thickness.

Q: Can replacement parts be sourced for this clamp?
A: Yes. The clamp consists of discrete replaceable components including the gripping cam, cam pin, swivel jaw, lifting shackle, shackle pin, and shackle pin bushing. Refer to the Renfroe Repair Kits Catalog for compatible repair kits.