6.4 Plate Clamps, Beam Clamps & Below-the-Hook Lifters

Plate Clamps, Beam Clamps and Below-the-hook Lifters

These devices connect a crane or hoist to a load or supporting structure through geometry, friction, teeth, screws or engineered attachment points. Their capacity depends on more than mass: material, thickness, hardness, surface, direction and minimum load can all matter.

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Vertical Plate Clamps

A vertical plate clamp commonly uses a cam and pad or jaw that increases grip as load is applied. A locking mechanism may keep the cam in contact during attachment and when load briefly reduces. The lock does not make an unsuitable plate acceptable and is not a substitute for maintaining the load direction.

Before use, match the exact clamp to:

• plate mass and any published minimum load;
• plate thickness range;
• material and maximum or minimum hardness;
• surface condition, coating and contamination;
• vertical, horizontal or turning orientation; and
• number of clamps and any required lifting beam.

Some clamps need a minimum fraction of WLL to develop reliable grip, but the value is model-specific. Likewise, HB 300 appears in some product data but is not a universal hardness ceiling. Very hard plate may prevent teeth from biting; very soft plate may deform; paint, scale, oil or ice can reduce contact.

Do not use a vertical clamp for horizontal handling, stainless steel, polished plate, stacked sheets or plate turning unless the instructions expressly cover it. Avoid shock and side pull. Make a controlled trial lift just clear and check that the plate remains seated.

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Horizontal and Special Clamps

Horizontal plate clamps are often used in matched pairs or sets, sometimes with a lifting beam, so force and orientation are controlled. Some designs grip an edge; others support beneath it. Use the specified number, sling angle and plate-size range. Unequal sling lengths or an off-centre centre of gravity can overload one clamp.

Non-marking clamps, screw clamps, rail grabs and specialised clamps use different gripping principles. Do not transfer a serrated-cam rule or minimum load from one design to another.

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Beam Clamps and Trolleys

A beam clamp provides a temporary suspension point on a suitable beam flange. Confirm beam capacity and local flange resistance as part of the supporting structure; a 5 t clamp does not prove that the building can carry 5 t.

Match flange width, thickness, slope and profile. Centre the clamp and tighten or lock it as instructed. Side loading can twist the clamp or beam flange and is prohibited unless the exact product provides an angular rating. Manufacturer angle charts, where supplied, are product-specific.

A trolley differs because it is intended to travel along the beam. Wheel profile, flange clearance, end stops and anti-drop features must match the runway. A stationary beam clamp must not be dragged along the flange as a substitute for a trolley.

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Lifting Beams and Spreaders

A lifting beam commonly has a top connection near its centre and lower lifting points. It resists substantial bending and can provide low headroom. A spreader commonly uses an upper sling at its ends and keeps lower slings apart; its main member often acts primarily in compression. Real designs also include bending, connection and stability effects, so “pure bending” and “pure compression” are teaching simplifications, not design calculations.

Use the marked configuration: lifting points, span, sling angle, centre-of-gravity range and any adjustable-hole position. Include the lifter's self-weight in crane gross load. Never add holes, weld attachments or change an adjustable spread without design approval and re-verification.

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Inspection

For clamps, inspect WLL and identity, body, suspension eye, cam or pad, teeth, pins, springs, locks, screws and threads. Look for cracks, spreading, worn teeth, contamination, seized movement and unauthorised repair. A clamp that will not close or lock smoothly is withdrawn, not lubricated indiscriminately where lubricant could reach gripping surfaces.

For beams and spreaders, inspect lifting points, pins, bolts, welds, main member, adjustable joints and markings. Look for cracking, permanent bow, local buckling, corrosion and loose or substituted parts. Numerical deflection or wear limits come from design and manufacturer records; L/500 and ten-percent wear are not universal discard limits.

As lifting accessories, these devices normally use LOLER's six-month default thorough-examination interval unless an examination scheme sets another. Equipment whose safety depends on installation may also require examination after installation.

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Selection Example

A 1.5 t plate with a 10 t clamp gives a 15% load fraction. That fact alone says neither safe nor unsafe. Verify the clamp's minimum load, thickness, hardness, surface and orientation. If its instructions require at least 20%, select another clamp; if they expressly permit 10% and all other conditions match, 15% may be within scope.

The rule is match the device to the material, geometry and direction—not only the tonnes.