How to Design and Use Below-the-Hook Lifting Devices According to ASME Standards
Below-the-hook lifting devices are tools that attach a load to a hoist, crane, or other lifting equipment. They can come in various forms, such as hooks, clamps, magnets, slings, and beams, and they are used for lifting, moving, and positioning loads of different shapes, sizes, and weights.
However, designing and using below-the-hook lifting devices is not a simple task. There are many factors to consider, such as the load characteristics, the lifting device components, the environmental conditions, and the safety requirements. That’s why it is important to follow the ASME standards that provide guidance and best practices for below-the-hook lifting devices.
In this article, we will introduce two ASME standards that are relevant for below-the-hook lifting devices: ASME BTH-1 and ASME B30.20. We will explain what they are, what they cover, and how they can help you design and use below-the-hook lifting devices more efficiently and safely.
Table of Contents
What is ASME BTH-1?nbsp;
ASME BTH-1 is a standard that provides minimum structural, mechanical, and electrical design criteria for below-the-hook lifting devices. It applies to the design or modification of any device that is used for attaching a load to a hoist, such as structural and mechanical lifting devices, vacuum lifting devices, operated close proximity lifting magnets, remotely operated lifting magnets, or scrap and material handling grapples.
ASME BTH-1 does not replace ASME B30.20, which is another standard that addresses the safety requirements for below-the-hook lifting devices. ASME BTH-1 only covers the design aspects, while ASME B30.20 covers the marking, construction, installation, inspection, testing, maintenance, and operation of below-the-hook lifting devices.
ASME BTH-1 requires that lifting devices be designed by, or under the direct supervision of, a qualified person. It also specifies the rated load, load geometry, design category, and service class that must be considered during the design process. It provides formulas and methods for calculating the allowable stresses, materials, welding designs and procedures, and other design criteria.
The latest edition of ASME BTH-1 was published in 2023 and it includes some changes from the previous edition, such as:
Design Categories in Lifting Device Designnbsp;
Design Categories determine the level of risk associated with the lifter’s operating environment and loading conditions. These categories are also tied to specific Nominal Design Factors Nd, which ensure the structural integrity of the device under varying conditions.
Why Design Categories Matter
Each category is tailored to specific conditions:
Service Classes
Service Classes classify lifting devices based on the expected number of load cycles during their operational life. They primarily address fatigue life criteria, ensuring the lifter can withstand repeated loading and unloading over time. The five Service Classes are outlined below:
Why Service Classes Matter
Service Classes focus on fatigue life, which is distinct from static strength. They establish:
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While Service Classes do not directly impact the Nominal Design Factor (Nd), they ensure the lifter is durable enough for its intended usage over time.
How Design Categories and Service Classes Work Together
Although Design Categories and Service Classes address different aspects of lifting device design, they are used together to tailor a lifter to its specific application:
For instance:
What is ASME B30.20?
ASME B30.20 is a standard that provides safety requirements for below-the-hook lifting devices. It applies to the marking, construction, installation, inspection, testing, maintenance, and operation of any device that is used for attaching a load to a hoist, such as structural and mechanical lifting devices, vacuum lifting devices, operated close proximity lifting magnets, remotely operated lifting magnets, or scrap and material handling grapples. It also applies to clamps used for positioning and anchoring.
ASME B30.20 is part of the ASME B30 series, which is a collection of standards that cover various aspects of cableways, cranes, derricks, hoists, hooks, jacks, and slings. ASME B30.20 is intended to complement ASME BTH-1, which is another standard that covers the design criteria for below-the-hook lifting devices. ASME B30.20 focuses on the safety aspects, while ASME BTH-1 focuses on the design aspects.
ASME B30.20 requires that lifting devices be operated by a qualified person.
It also specifies the marking, inspection, testing, and maintenance procedures that must be followed to ensure the safe performance of the lifting devices. It provides guidelines and precautions for the proper use and handling of the lifting devices, such as the load rating, the load balance, the load control, and the environmental factors.
The latest edition of ASME B30.20 was published in 2021 and it includes some changes from the previous edition, such as:
Safety Requirements of ASME B30.20
One of the important aspects of ASME B30.20 is the safety requirements, which are used to ensure the safe performance and operation of the lifting devices. ASME B30.20 defines four types of safety requirements: marking, inspection, testing, and maintenance.
How Can SDC Verifier Help You Comply with Various Standards?
SDC Verifier is a software and consultancy firm that provides advanced simulation and standard verification solutions for structural engineering. Our software, SDC Verifier, is a powerful tool that can help you design and verify according to various standards.
Currently, in SDC Verifier, it is possible to perform code checking according to two ASME standards:
SDC Verifier can help you save time and money by automating and streamlining the design and verification process. You can also benefit from our expertise and experience in structural engineering and standard verification.