GUEST COLUMN | THE CALDWELL GROUP


THE HEAVY MOB


Whether the marketplace refers to them as mill-duty or heavy-duty lifters, there are certain below-the-hook products that are designed for heavy- and severe-duty service. A coil lifter is a good example says Dan Brenneman, applications specialist at Caldwell.


helpful to think in terms of duty cycle. Generally, there are two ways of rating a lifter, either in capacity or duty cycle. Duty is related to the frequency with which a product is used at or near its capacity. As we know, some lifters are used on occasions, nowhere near capacity; and others are operated at or near capacity, in 24/7 applications. That, in simple terms, is low and high duty cycle. Note that a low-capacity product can be mill- or heavy- duty, and the opposite is also true. It is never advisable to try to


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employ a lifter, or any equipment, in an environment for which it isn’t designed. Even where the capacity of the crane, hoist, or attachment might be sufficient to lift the load in principle, there are many other factors that need to be considered.


LONG LIFE, MINIMUM MAINTENANCE In general terms, a mill-duty below-the- hook device is one that is used in direct production of an integrated mill, meaning material is taken from its raw or semi-raw form and converted directly into a finished or semi-finished product. The term mill- duty, especially, is frequently used as it relates to the production of ferrous and non-ferrous metals, but it can also be related to other material, such as paper.


ASME BTH-1 SERVICE CLASS ILLUSTRATION Desired Life (Years)


Cycles/ day


50


100 200


300 33 750


1000


33 4


510 20


30 3


33 4 4


3 444 3 444


Refer to ASME BTH-1 for detailed design considerations of lifting devices.


Mill-duty below-the-hook products, like this coil lifter, are designed for heavy- and severe-duty service


At Caldwell, we refer to mill-duty lifters as those designed for heavy- and severe- duty service per The American Society of Mechanical Engineers (ASME) B30.20, BTH-1 Design Category B, Service Class 3 or 4. Design Category B is when loads and conditions are not accurately defined (ASME BTH-1); Service Class 3 is 500,001 to 2,000,000 load cycles; and Service Class 4 is over 2,000,000 load cycles. Product features typically include


replaceable wear plates/hardened steel bushings in high-friction areas; suspensions designed for long-term life; as well as electrical and mechanical protection to help minimise an over-torque condition in the drive arrangements. These types of lifters will be registered, and metal identification tags, capacities, and safety warnings made clearly visible. They are nearly always custom made.


22 | September 2024 | www.hoistmagazine.com


hen we talk about mill- or heavy-duty equipment, it’s


Lifting equipment


manufacturers typically have separate lines of products designed for heavy- and severe- duty service utilising features that incorporate mechanical components to ensure long life with minimum maintenance. Also techniques such as interlocked, parent metal structural connections, to reduce weld stress and increase fatigue life.


COIL LIFTERS AND UPENDERS The type of products included in mill- or heavy-duty ranges is hugely varied. In fact, designs are only limited by an end user’s imagination and the laws of physics. However, a good example is our coil lifter. An enclosed drive protects the


lifter from impact, yet still provides easy access for maintenance. An alloy steel lifting pin keeps headroom to a minimum, which is often a prerequisite in an environment where coils need to be handled. Motorised bail rotation allows for independent


and precise positioning of the load or the lifter, while a lockout limit switch helps to prevent inadvertent leg opening during a lift. Other standard features include anti- clamp and toe rollers, which protect the sides of the coil from lifter damage. The range can be further customised with lifting beams, to perform other lifts without the need to remove the grab from the crane hook. We often supply lifters with urethane padding, which can be attached to the legs, feet, or both, for further coil protection. Another customisation is photo-electric sensors, which indicate lifter foot alignment with coil identification. Also popular are parking and maintenance stands and indicator lights. All things considered, it’s important to source mill- or heavy-duty below-the-hook products for heavy and severe duty service as its manufactured to guidelines to protect.


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