Crane Load Cells

Specialist Load/Tension Monitoring Buying Guide

What a crane load cell reads, and how well. A crane load cell is a strain-gauged element you put in the load path so it reads the force running through that path, not an estimate off a drawing. Put it between the hook and the load and it weighs the pick; put it in a line and it reads that line's tension. The Straightpoint cells here read to plus or minus 0.1 percent of full scale and ship with a calibration certificate, so the number on the display is a measurement you can defend. Because the housings carry high IP and NEMA ratings, the cell can stay rigged in weather through a whole job like any other piece of hardware. One habit worth building: a load cell tells you the force, so use it to confirm a load before the crane commits, not to discover a problem after the pick has left the ground.

Tension links: the standard under-hook cell. The LoadLink Plus is the shape most people picture for a crane load cell, a shackle-to-shackle link you hang between the crane hook and the sling with a Crosby shackle at each end. It covers 1 to 300 tonnes, reads on a built-in LCD, and its resolution runs past 5,000 divisions, which is why it works as both a weigh point and a dynamic load monitor. The thing to keep straight is that this link is a structural member in your rig, not an instrument bolted to the side of one. It carries a working load limit, it takes the full force of the lift, and it gets shackled, rated, and inspected like the rest of your rigging hardware, with the shackle connections following ASME B30.26. Size the link to the load, not to the reading you want.

Load pins: measure force where a link will not fit. When the pick has no spare height for a link, or the joint you want to measure is already built, a load pin is the answer. It is a shear pin machined to drop straight into a pinned joint you already run, a sheave axle, a shackle jaw, a clevis, or a winch anchor, with strain gauges set in a bore down its center that read the force across it. Straightpoint builds them from 500 kg up past 1,000 tonnes, cabled or wireless, so the cell disappears into the machine instead of adding length to the rig. This is the route for cranes, davits, and winches that need permanent monitoring, and for any pick where two shackles plus a link would eat headroom you do not have. Match the pin diameter and grip length to the joint before anything else.

Compression cells and dynamometers. Not every force is a pull. Compression cells like the LoadBlock Plus and the wireless LoadSafe read a squeeze instead, sitting under a hydraulic jack, a structural support, or a proof-test bed from 250 kg to 150 tonnes, which is how you weigh a structure by its supports or confirm its center of gravity. On the tension side, when you want a fast readout rather than a full monitoring rig, the self-indicating dynamometer gives a mechanical dial that needs no power and rigs on a Crosby G2130 shackle with only about 156 mm eye to eye, and the Bluelink sends the same reading to a phone over Bluetooth. The ChainSafe is the specialist here, a Bluetooth tension cell up to 4 tonnes built to sit in a run of Crosby chain fittings so you can read the tension in a chain sling or tie-down.

The COLT: read a line you cannot take apart. Sometimes the line is already under load and you cannot open it to insert a link. The Straightpoint COLT, a clamp-on line tensionmeter, solves that by clamping onto a standing wire rope and reading its tension through a calibrated shunt, up to 11,000 lb or 5,000 kg on rope up to 1 inch or 25 mm in diameter. That makes it the tool for tuning guy wires on a mast, checking a stay or a standing rigging line, or verifying a line on a structure that is already holding load. Because the reading depends on the rope, calibrate the COLT to the diameter and construction you are actually measuring. It is the one instrument in this group that reads a line you never disconnect, which is a large part of why it costs more than a link of similar capacity.

Wireless, displays, and monitoring several cells. Most of these cells come in a wireless build, and the radio matters as much as the sensor. Straightpoint's wireless range reaches up to about 1,000 m or 3,280 ft on the standard system, dropping to 700 m or 2,300 ft on ATEX units for hazardous areas, so an operator can stand well clear of the load and still read it. For a single cell, a handheld or a large scoreboard display does the job; when you are running an array, INSIGHT software connects up to 126 cells at once on a Windows laptop or tablet, logs them at timed intervals, and averages several weighings into a center-of-gravity report. Whatever the display, hold to two disciplines: recalibrate on a documented schedule so the accuracy figure stays true, and inspect any cell in the load path before every lift.