Weighing equipment, containers, tooling, or bulk product may not always involve setting the object on a scale. Maybe the product is too large or oddly shaped, or it’s too difficult to stop it from moving. A crane scale allows operators across several industries to weigh on the fly.
If you’re looking for a weighing solution involving suspended objects in motion, a crane scale can be a safe, efficient, and accurate solution. Applications, capabilities, and capacities vary by scale type, so it’s worth taking the time to learn a little more about these industrial tools.
What Is a Crane Scale?
A crane scale is an industrial tool used to determine weights of loads in suspension. In other words, crane scales weigh things that are hanging. Weighing suspended items is a common practice for any of the following situations:
- No floor scales or load cells are present.
- An object can’t be set down safely.
- An object needs to be weighed while in motion.
Crane scales are precision instruments built to withstand regular and heavy use and still provide accurate measurements for the items they’re tasked with weighing. Crucially, these devices need to be mechanically safe, as a failure in the mechanical components of the crane scale could result in a load dropping from suspension.
What Goes Into a Crane Scale?
Generally, the components of a crane scale are as follows:
- Fastening equipment: The fastening equipment by application might vary, but fundamentally, all crane scales must have a way to fasten to the crane or hoist itself and a way to hold the load that you’re seeking to weigh. Hooks, shackles, and eyebolts are commonly used as fasteners. These hardware components need to be highly robust — high-strength steel or composites that are resistant to corrosion or other environmental factors are an absolute must (components in red outline above).
- Load cell: The load cell is the component determining the weight of the load in suspension through a subcomponent called a strain gauge. Load cells measure the mechanical force exerted by the suspended object and translate that mechanical force into a more semantic variable for people to understand — weight in pounds, kilograms, tons, and so on (component in orange outline above).
- Display: With a crane scale holding a load in suspense, and the force of the weight of that load being captured by the load cell, operators need a mechanism for understanding the weight. Through either a wired or wireless transmission, the weight can be displayed for operators (component in green outline above).
Where Are Crane Scales Used?
With crane scale capacities ranging from 0 to well over 100 tons (220,462 pounds / 100,000 kilograms), multiple industries can benefit from these devices. In the greater Louisville area, we see a spectrum of industries such as logistics, food and beverage manufacturing, small and heavy-duty industrial equipment manufacturing, and construction. All these industries have applicable activities for which a crane scale could be an appropriate solution.
It’s important to note that a crane scale needn’t only be used on cranes — it’s equally useful across any of these material handling equipment types:
- Forklifts and booms: Warehouse activities (inbound and outbound transportation and weight verification activities), small and medium construction projects (bulk material weighing and load testing)
- Overhead hoists: Equipment maintenance and manufacturing, commodity production activities, bulk material production
- Indoor factory overhead equipment: Heavy-duty and specialty industrial equipment manufacturing and maintenance
- Intermodal terminals: Cross-docking, railcar load and unload, container transfer
How Does a Crane Scale Work?
A crane scale serves two roles simultaneously: to support the load in suspense and measure the weight of the suspended load. With the load suspended, the load cell component within the crane scale measures the downward force exerted by the object in suspense.
Advanced scales can account for item movement, be sized or shaped in a way to reduce headspace, provide wireless capabilities, and integrate with preexisting material handling or broader Manufacturing Execution System solutions.
Given that objects could be lethal if dropped, certain safety measures are also built into a crane scale and form an integral part of how the scale functions. Such features may include:
- Intrinsically safe construction: This can aid in reducing the risk of an electrical explosion hazard.
- Overload mechanisms: An overload of the crane scale can result in irreparable damage to the scale, so certain protections are often built into the equipment to register an overload and protect itself from the force of the load. Overload protection — ranging from 150% to 500% of capacity — can often far exceed the capacity of the scale, as investments in these pieces of equipment are often thousands of dollars.
- Alerting systems: In integrated scenarios, a scale registering an excessive weight can provide a signal to an alerting system that might stop the handling equipment from continued movement, provide visual or audible alarms, or force a safe emergency stop.
How Accurate Are Crane Scales?
Crane scales should be accurate to well within a 1% threshold, often targeted closer to 0.1%. As a rule of thumb, as the capacity of a crane scale rises, the increments of weight a scale measures become less discrete. For example, the CNS Crane Scale by B-TEK has a capacity and weight increment scale as detailed below:
|Incremental Weight (pounds)
It’s worth noting that regular weight checks and calibration activities are integral to ensuring that scale systems of any kind retain their accuracy.
What Is the Load Capacity and Size of a Crane Scale?
Load capacities vary from as little as a couple pounds to over 100 tons. As a scale’s capacity grows, so does its size, weight, construction, and cost. Small-capacity scales can weigh as little as 3 pounds and measure only a matter of inches, while large-capacity scales will weigh well over 100 pounds and might measure well over a foot in length.
As such a range in size and capacity exists, you should be able to clearly articulate your use case before buying a crane scale. American Scale can assist in extracting the right user requirements to ensure you select an appropriate model.
With an array of crane scale sizes, the design will vary as the duty type moves from light to heavy. Light-duty crane scales are built to be easily moved and used, and are often associated with an integrated display as shown below on the B-Tek Tension Link Scale:
A heavy-duty crane scale will need to focus on holding massive weights safely, and an integrated display may not be as important because of the distance you’ll maintain from the suspended object.
What Are Things to Look for When Choosing a Crane Scale?
Many options can be found within the crane scale product category beyond just “total capacity.” Other specifications to consider include:
- Adjustable units of measure — toggling between metric and imperial (kilograms and pounds)
- Power supply (battery types)
- Load stabilization/settling adjustment
- Remote operation and display
- Wi-Fi capability
- Overload thresholds
- Safety certifications
- Display size
- Fastening system
Because so many options exist for crane scales, it’s important to evaluate the working conditions of the scale once it’s in application. Questions one should consider when looking for a crane scale include:
How frequently will the scale be used each day? If it’s frequently or near-constantly used, it’ll be important to choose an option with robust parts availability — and perhaps with protective cages or cases around the load cell.
To what degree of accuracy does the weight need to be measured? Paying attention to accuracy and weighing increments will be crucial, as manufacturers’ tolerances will vary.
Will weighing operators be in close proximity to the suspended materials or in a remote control room? If operators are in close proximity, a bright, backlit, large integrated display will be crucial. If operators are in a control room, wireless connectivity to an external display is critical.
Will the scale be subjected to extreme temperatures, direct sunlight, regular dust, or vapors? If yes, choosing a scale that’s safety rated with IECEx / ATEX , FM, or HazLoc approvals will be an absolute necessity for the safety and integrity of the operation.
Will the scale be integrated with other operating systems? If yes, choosing a reputable service to assist with integration activities and the selection of scales with wireless capabilities will be keys to success.
Does the scale need to retain industry-specific certifications or form part of a broader validation activity? Some scales can be provided with calibration certifications out of the box. If broader validation is required in highly regulated environments, American Scales can assist in providing services and consultation, as we are ISO/IEC 17025:2005 accredited and abide by traceability standards defined by the National Institute of Standards and Technology.
How Are Crane Scales Maintained?
Crane scales can be maintained on a periodic basis (for infrequent use cases) or on a cycle basis (for frequent use). Periodic basis maintenance means at specific time intervals (every three months, for example), whereas cycle basis maintenance is based on the number of uses (such as every 10,000 cycles). A robust, planned maintenance schedule will ensure not only accurate and long-lasting service from the equipment, but it will also support safe operations for the site.
Example maintenance activities can be simplistically divided into two types: hardware status and functionality analysis.
As the hooks, shackles, eyebolts, and other ancillary components of the scale undergo much strain in supporting loads, maintenance professionals should seek to evaluate the state of each piece of hardware on the scale.
You should measure the change in shape, size, and condition of each component and try to evaluate cracking or gaps in the components. Tools like magnetic powder and optic instruments will help give you a better picture of the components than what the naked eye can see. Critical in performing this activity is both understanding the degree of variation from when the component was new and establishing a tolerance for acceptable variation.
Paired with variation inspection, there should be regular lubrication of joints or any parts where any metal-on-metal contact is to be expected. Examination of rust, corrosion, or any other cosmetic imperfections should be documented and tracked to understand the rate of growth.
Lastly, the status of the electronic equipment should be evaluated. This will include checking wiring for frays, looking for breaks in the protective lining of wiring, evaluating the display modules, and checking for any signs of external environmental conditions — like moisture or debris — entering into parts of the system.
On a shift, daily, or perhaps weekly basis, standard operators should perform basic checks of the function of the equipment. This might include using some reference loads to confirm the weight, checking display readouts, and confirming the function of fastening equipment.
Maintenance professionals should assist on a broader interval basis to perform checks as well. These checks should include true calibration activities (and performing any recalibration tasks as stipulated by the calibration test), checking display functions, and any button or controller operations.
How Long Will a Crane Scale Last?
Service life on a crane scale can be up to 10 years or 500,000 cycles, according to one manufacturer. It’s worth clarifying that the key to meeting or exceeding a service life is contingent on timely, holistic, and appropriate maintenance activities.
Next Steps on Your Crane Scale Journey
American Scale has been servicing the greater Louisville region for nearly 40 years. With offices in Louisville and Bowling Green, Kentucky, and Evansville, Indiana, we service the following states: Kentucky, Indiana, Illinois, Ohio, and Tennessee. Contact us and leverage our industry knowledge and scale expertise to provide you with the optimal crane scale application.