What is ASME BTH-1?

ASME BTH-1 is the American Society of Mechanical Engineers’ standard for “Design of Below-the-Hook Lifting Devices.” It establishes the design requirements — structural, mechanical, electrical, and fatigue-life — for devices that attach between a crane’s load hook and the load being lifted. That includes lifting beams, spreader beams, plate clamps, coil grabs, magnets, vacuum lifters, C-hooks, and custom attachments.

BTH-1 is the companion to ASME B30.20, which covers the operation, inspection, and maintenance of below-the-hook devices. BTH-1 tells the manufacturer how to design the device; B30.20 tells the end user how to use it safely.

For portable industrial lifting equipment — including eme’s Eagle Beam aluminum lifting beams, spreader beams, and accessory attachments — BTH-1 Category B with a 3:1 design factor is the applicable requirement.

What BTH-1 covers

The standard is comprehensive. Its scope includes:

  • Structural design. Load-bearing components must be designed to handle the rated load, with a specified design factor on yield stress and ultimate stress.
  • Mechanical components. Pins, bolts, fasteners, bearings, and similar parts must meet strength and fatigue requirements for the service class.
  • Electrical systems (where powered). Magnets, motors, hydraulic components — each carries its own design requirements.
  • Fatigue life. The device must be designed for a specified number of load cycles based on its service class.
  • Inspection access. The design must allow the periodic inspections required by ASME B30.20.
  • Markings. Rated capacity, manufacturer identification, and serial number must be clearly marked on the device.
  • Documentation. Design calculations, assembly drawings, and user manuals are required.

BTH-1 does not cover: the crane itself (see ASME B30.17 for cranes with underhung trolley or bridge), slings (see ASME B30.9), wire rope (see ASME B30.7), or the hook on the crane (see ASME B30.10).

Category A vs. Category B

BTH-1 defines two design categories based on the severity of service:

Category A

Design factor: 2:1 on the yield stress of load-bearing members.

Category A applies to below-the-hook devices used in controlled environments with predictable loading — typically fixed-facility equipment with consistent load patterns, skilled dedicated operators, minimal shock loading, and limited frequency of use.

Category B

Design factor: 3:1 on the yield stress of load-bearing members.

Category B applies to devices used in more severe service — higher frequency, more variable loading, multiple operators, potential for shock loading, or use in less controlled environments. Portable industrial lifting equipment almost always falls under Category B.

For portable aluminum lifting beams — including eme’s Eagle Beam — Category B with a 3:1 design factor is the applicable category. This means the load-bearing members are designed to handle three times the rated load before reaching yield stress, with additional margin beyond yield before ultimate failure.

Service classes

Independent of category, BTH-1 defines service classes based on expected fatigue life:

  • Service Class 0: fewer than 20,000 load cycles — occasional or dedicated light use
  • Service Class 1: 20,000 to 100,000 cycles — regular use
  • Service Class 2: 100,000 to 500,000 cycles — frequent use
  • Service Class 3: 500,000 to 2,000,000 cycles — continuous heavy use
  • Service Class 4: over 2,000,000 cycles — very high-intensity use

The service class determines the fatigue analysis and the inspection and maintenance intervals. Most portable below-the-hook devices are rated for Service Class 1 or 2, appropriate to contractor and maintenance-shop use patterns.

How BTH-1 applies to eme products

The Eagle Beam aluminum lifting beam is the only below-the-hook lifting device eme manufactures. It is designed to ASME BTH-1 Category B with a 3:1 design factor on yield stress — the conservative end of the BTH-1 framework, appropriate to the portable, variable-operator, multi-jobsite service pattern typical of the product. Eagle Beam uses all-bolted construction with Grade L9 fasteners; because it has no welded joints in the load-bearing structure, CSA W47.2 aluminum welding certification does not apply to the beam itself.

The standard gantry crane main beam is part of the crane itself — covered by the crane standard (ASME B30.17) rather than BTH-1, since BTH-1 applies only to below-the-hook attachments. Every eme gantry is load-tested to 125% of rated capacity before shipment, with a Certificate of Test.

eme’s other accessories (spreader beams, Split Beam, Cantilever Option, Grip Eye, cable holder, pneumatic casters, transport frames) serve specific roles in the lifting system — spreader, beam extension, reach, pump attachment, storage, mobility, transport — but are not classified as ASME BTH-1 below-the-hook lifting devices under eme’s product architecture.

The gantry crane itself is not a below-the-hook device either (the gantry is the crane, not the attachment). The crane standard — ASME B30.17 — applies to the gantry. BTH-1 applies to anything attached between the gantry’s hook and the load — and in the eme catalog, that is the Eagle Beam.

”Designed to” vs. “certified to” — the distinction matters

ASME BTH-1 is a design standard, not a third-party certification. There is no independent body that inspects a lifting beam and issues a BTH-1 certification stamp. Instead, manufacturers:

  • Design the device to meet BTH-1 requirements
  • Document the design with engineering calculations and drawings
  • Mark the rated capacity and identify the device
  • Ship the device with manual and documentation that reflect the BTH-1-compliant design

Accurate language uses “designed to ASME BTH-1, Category B” — not “BTH-1 certified.” The only genuine third-party certification commonly in play on aluminum lifting equipment is CSA W47.2, issued by the Canadian Welding Bureau for companies performing aluminum fusion welding. For products with no welded joints — like the Eagle Beam, which uses all-bolted construction with Grade L9 fasteners — W47.2 does not apply because the product has no structural welds to certify.

How to verify BTH-1 compliance on a specific product

Request the documentation. A manufacturer designing to BTH-1 will provide:

  1. Engineering drawings showing load-bearing members with the BTH-1 design factor applied
  2. The category and service class (e.g., “Category B, Service Class 1”)
  3. The rated capacity marking on the device matching the design documentation
  4. A user manual with inspection, maintenance, and operation procedures consistent with ASME B30.20

If a manufacturer claims BTH-1 compliance but cannot produce engineering drawings or refuses to specify the category, the compliance claim is not verifiable. Treat this as a red flag — below-the-hook devices are often used in life-safety applications, and unverifiable design claims are the specific thing BTH-1 exists to prevent.

Every eme below-the-hook device ships with an engineer-stamped drawing, a Certificate of Test (125% of rated load, verified with a load cell), and a user manual aligned to ASME B30.20.

Frequently asked questions

Is ASME BTH-1 the same as ASME B30.20?

No — they are companion standards that address different lifecycle phases. BTH-1 is the design standard for below-the-hook devices. B30.20 is the operation, inspection, and maintenance standard. A below-the-hook device should be designed to BTH-1 and operated per B30.20. Both are voluntary consensus standards under the ASME B30 series framework.

What does “below-the-hook” mean?

A below-the-hook lifting device is anything that attaches between a crane’s load hook and the load being lifted. Spreader beams, lifting beams, plate clamps, magnets, vacuum lifters, coil grabs, C-hooks, and custom attachments are all below-the-hook devices. The crane, hook, and sling are not below-the-hook devices — they have their own standards (B30.17, B30.10, B30.9 respectively).

What is the design factor on a BTH-1 Category B device?

3:1 on the yield stress of load-bearing members. This means a Category B device with a 5,000 lb rated capacity is engineered to handle 15,000 lb of applied load before the load-bearing members reach yield stress, with additional margin before ultimate failure.

Why Category B instead of Category A?

Category A (2:1 design factor) applies to controlled environments with predictable loading — fixed facilities with dedicated equipment and trained operators. Category B (3:1 design factor) applies to more severe service with variable loading, multiple operators, and potential for shock loads. Portable industrial lifting equipment almost always uses Category B because the service pattern (multiple jobsites, different operators, occasional shock loading) matches the Category B profile.

What BTH-1 category and design factor does Eagle Beam use?

Eagle Beam is designed to ASME BTH-1 Category B with a 3:1 design factor on yield stress — the more conservative of the two BTH-1 categories, appropriate to portable, variable-operator, multi-jobsite service.

What standard applies to the eme gantry crane itself?

The gantry crane is covered by the crane standards, not BTH-1 (BTH-1 applies to below-the-hook lifting devices like spreaders and lifting beams, not the crane itself). eme’s gantries are top-running single-girder box-beam cranes, designed to ASME B30.17. Every eme gantry is load-tested to 125% of rated capacity before shipment, with a Certificate of Test.

What eme product is a below-the-hook lifting device?

The Eagle Beam aluminum lifting beam is eme’s only below-the-hook lifting device. It is designed to ASME BTH-1 Category B with a 3:1 design factor. Other eme accessories (spreader beams, Split Beam, Cantilever Option, Grip Eye, cable holder, pneumatic casters, transport frames) are not classified as below-the-hook lifting devices under eme’s product architecture — they serve other roles in the lifting system.

Is BTH-1 legally required?

BTH-1 is a voluntary consensus standard, not a law. However, OSHA regulations in the United States (and provincial regulations in Canada) frequently reference ASME standards as the accepted engineering practice for lifting equipment. A jurisdiction, employer, insurer, or jobsite compliance officer may require BTH-1 compliance as a condition of use.

Does BTH-1 apply to gantry cranes?

BTH-1 applies to below-the-hook devices — the attachments between a crane’s hook and the load. The gantry crane itself is covered by the crane standard: eme’s top-running single-girder box-beam gantries are designed to ASME B30.17. The hook is covered by B30.10. The slings are covered by B30.9. A lifting beam or spreader beam hung from the gantry’s hook is the device BTH-1 applies to.

What’s the difference between BTH-1 Category A and Category B design factors?

Category A uses a 2:1 design factor on yield stress; Category B uses 3:1. The higher factor for Category B reflects the more severe service pattern — higher frequency, multiple operators, variable loading, potential for shock. The practical effect is that a Category B device is more conservatively sized than a Category A device of the same rated capacity.

  • Eagle Beam Aluminum Lifting Beams (up to 10,000 lb) — eme’s only below-the-hook lifting device; ASME BTH-1 Category B, 3:1 design factor, all-bolted construction with Grade L9 fasteners
  • Aluminum Gantry Cranes — top-running single-girder box-beam cranes designed to ASME B30.17 (not BTH-1); load-tested to 125% of rated capacity with a Certificate of Test
  • Aluminum Davit Cranes — jib-type cranes designed to a design factor on yield stress well in excess of the proof-test load (not BTH-1)

Last reviewed April 2026. Content reviewed by eme engineering for technical accuracy. ASME BTH-1 is published and maintained by the American Society of Mechanical Engineers; the authoritative source is asme.org.