ASME BTH-1:2008 pdf download

ASME BTH-1:2008 pdf download.Design of Below-the-Hook Lifting Devices
1-1 PURPOSE
This Standard sets forth design criteria for ASME B30.20 below-the-hook lifting devices. This Standard serves as a guide to designers, manufacturers, purchasers, and users of below-the-hook lifting devices. Commentary: This Standard has been developed in response to the need to provide clarification of the intent of ASME B30.20 with respect to the structural design of below-the-hook lifting devices. Since the origi- nal publication of ASME B30.20 in 1986, users have requested interpretations of the construction (structural design) requirements stated therein. The level of detail required to provide adequate answers to the questions submitted extends beyond that which can be covered by interpretations of a B30 safety standard.
1-2 SCOPE
This Standard provides minimum structural and mechanical design and electrical component selection criteria for ASME B30.20 below-the-hook lifting devices. The provisions in this Standard apply to the design or modification of below-the-hook lifting devices. Com- pliance with requirements and criteria that may be unique to specialized industries and environments is outside of the scope of this Standard. Lifting devices designed to this Standard shall comply with ASME B30.20, Below-the-Hook Lifting Devices. ASME B30.20 includes provisions that apply to the marking, construction, installation, inspection, testing, maintenance, and operation of below-the-hook lifting devices. Commentary: ASME BTH-1 addresses only design requirements. As such, this Standard should be used in conjunction with ASME B30.20, which addresses safety requirements. ASME BTH-1 does not replace ASME B30.20. The design criteria set forth are minimum requirements that may be increased at the discretion of the lifting device manufacturer or a qualified person.
1-4 GENERAL REQUIREMENTS
1-4.1 Design Responsibility Lifting devices shall be designed by, or under the direct supervision of, a qualified person. Commentary: Although always implied, this provi- sion now explicitly states that the design of below-the- hook lifting devices is the responsibility of a qualified person. This requirement has been established in recog- nition of the impact that the performance of a lifting device has on workplace safety, the complexity of the design process, and the level of knowledge and training required to competently design lifting devices. 1-4.2 Units of Measure A dual unit format is used. Values are given in U.S. Customary units as the primary units followed by the International System of Units (SI) in parentheses as the secondary units. The values stated in U.S. Customary units are to be regarded as the standard. The SI units in the text have been directly (softly) converted from U.S. Customary units. Commentary: The requirements of this Standard are presented wherever possible in a manner that is dimensionally independent, thus allowing application of these requirements using either U.S. Customary units (USCU) or International System of Units (SI). U.S. Customary units are the primary units used in this Standard. 1-4.3 Design Criteria All below-the-hook lifting devices shall be designed for specified rated loads, load geometry, Design Category (see section 2-2), and Service Class (see section 2-3). Resolution of loads into forces and stress values affecting structural members, mechanical compo- nents, and connections shall be performed by an accepted analysis method. Commentary: The original ASME B30.20 structural design requirements defined a lifting device only in terms of its rated load. Later editions established fatigue life requirements by reference to ANSI/AWS D1 4.1. ASME BTH-1 now defines the design requirements of a lifter in terms of the rated load, the Design Category, and the Service Class to better match the design of the lifter to its intended service. An extended discussion of the basis of the Design Categories and Service Classes can be found in Chapters 2 and 3 Commentaries.