11.1 Rigging Hardware: Slings, Shackles, Eye Bolts & Inspection Criteria
Key Takeaways
- Rigging hardware and slings operate under strict design safety factors: 5:1 for general hardware, wire rope, and synthetic slings; 4:1 for alloy steel chain slings; and 10:1 for personnel lifting platforms.
- Only Grade 80 and Grade 100 alloy steel chain slings equipped with legible manufacturer identification tags are certified for overhead lifting; carbon steel chains (Grade 30, 43, 70) are strictly prohibited.
- Shoulder eye bolts must be derated down to 25% to 30% of rated capacity when loaded at a 45-degree angle (and non-shoulder eye bolts must never be loaded angularly), whereas swivel hoist rings maintain 100% rated capacity throughout a 360-degree rotation and 180-degree pivot.
- Under ASME B30.9 and OSHA 1926.251, wire rope slings must be immediately removed from service upon detecting 6 randomly distributed broken wires in one rope lay, 3 broken wires in one strand in one lay, or 1 broken wire at an end fitting.
- Rigging hooks must be permanently retired if the throat opening stretches more than 5% (or 1/4 inch max) beyond nominal dimensions or if the hook tip twists more than 10 degrees out of plane.
Last updated: August 2026
Rigging Hardware: Slings, Shackles, Eye Bolts & Inspection Criteria
Core Concept: Industrial boilermakers routinely hoist multi-ton pressure vessels, steam drums, tube bundles, boiler casings, and heavy structural modules. Selecting the correct rigging assembly, verifying design safety factors, and rigorously inspecting every sling, shackle, eye bolt, clamp, and beam prior to hoisting under ASME B30.9, ASME B30.26, and OSHA 29 CFR 1926.251 is critical to preventing catastrophic rigging failures and workplace fatalities.
1. Slings: Types, Construction & Material Properties
Slings serve as the direct mechanical link between the crane hook and the load. Industrial boilermakers select slings based on material characteristics, load geometry, surface finish, environmental exposure, and chemical compatibility.
+-------------------------------------------+
| INDUSTRIAL RIGGING SLINGS |
+-------------------------------------------+
|
+----------------------------------+----------------------------------+
| | |
v v v
+-------------------------------------+ +--------------------------+ +-------------------------------------+
| SYNTHETIC SLINGS | | WIRE ROPE SLINGS | | ALLOY CHAIN SLINGS |
+-------------------------------------+ +--------------------------+ +-------------------------------------+
| * Flat Synthetic Webbing (Nylon/Poly)| | * 6x19 / 6x37 Class EIPS | | * Grade 80 & Grade 100 Alloy Only |
| * Endless Roundslings (Poly Yarn) | | * IWRC vs. Fiber Core | | * 4:1 Design Safety Factor |
| * 5:1 Design Safety Factor | | * Flemish Eye Swaged | | * High Heat & Abrasion Resistance |
+-------------------------------------+ +--------------------------+ +-------------------------------------+
Synthetic Web Slings and Endless Round Slings
Synthetic slings protect polished or machined surfaces (such as tube sheet gasket faces, machined boiler nozzles, and clad alloy vessels) from marring and scratching. They are lightweight, highly flexible, and non-sparking.
- Synthetic Flat Web Slings (Nylon vs. Polyester):
- Nylon (Polyamide): Exhibits high elasticity, stretching approximately $6%$ to $10%$ at rated Working Load Limit (WLL), which absorbs dynamic shock loads. Chemical Limitation: Severely degraded by acids (e.g., boiler chemical wash hydrochloric acid), but resistant to caustic alkalis and hydrocarbons.
- Polyester (Dacron): Low stretch (approximately $3%$ at WLL), providing greater control during precision setting of heavy components. Chemical Limitation: Resists mineral acids, but is rapidly destroyed by concentrated caustics and alkalis (e.g., sodium hydroxide solutions).
- Synthetic Round Slings (Endless Loop): Consist of multiple continuous loops of polyester core yarn encased within a seamless, double-wall tubular polyester protective jacket. The load-bearing internal yarns never contact the load directly. If the outer jacket suffers abrasion, the internal load-bearing fibers remain protected. Round slings conform tightly around cylindrical shapes in choker and basket hitches.
Wire Rope Slings: Metallurgy, Core Construction & Splices
Wire rope is the standard heavy-duty rigging medium for boilermakers, offering high tensile strength, predictable bending fatigue, and robust abrasion resistance.
+--------------------------------------------------+
| WIRE ROPE CROSS-SECTION (6x19) |
+--------------------------------------------------+
Strand (19 Wires)
/ \
( o o o o o o )
( o o o o o o o o o )
( o o o (c) o o )
( o o o o o o )
|
v
IWRC (Independent Wire Rope Core) at Center
- Steel Grades:
- IPS (Improved Plow Steel): Baseline carbon steel alloy.
- EIPS (Extra Improved Plow Steel): Approximately $15%$ higher tensile strength than IPS; the modern industrial standard.
- EEIPS (Extra Extra Improved Plow Steel): Approximately $10%$ higher tensile strength than EIPS, used for ultra-heavy critical lifts.
- Strand Classifications:
- $6 \times 19$ Classification (6 Strands, 19 to 26 Wires per Strand): Features larger individual outer wires. Delivers superior resistance to exterior abrasion, scrubbing, and dragging across boiler steel, but possesses moderate flexibility.
- $6 \times 37$ Classification (6 Strands, 27 to 49 Wires per Strand): Features smaller individual wires. Delivers superior flexibility and bending fatigue resistance around small-diameter boiler lugs and tight sheaves, but has lower resistance to abrasive scrubbing.
- Core Types:
- IWRC (Independent Wire Rope Core): A miniature steel wire rope functioning as the central core. Prevents rope flattening and crushing when wound under tension on crane drums or rigged over small-radius shackles. Operating temperature limit: up to $400^\circ\text{F}$ ($204^\circ\text{C}$).
- Fiber Core (FC): Synthetic or sisal natural fiber core impregnated with lubricant. Highly flexible, but easily crushes under heavy multi-part loading and degrades above $180^\circ\text{F}$ ($82^\circ\text{C}$). Fiber cores must never be used in heavy boiler construction rigging.
- End Terminations:
- Flemish Eye Mechanical Splice: The wire rope strands are unlaid, looped into an interlocking eye, and secured with a swaged carbon steel or aluminum sleeve. Delivers $95%$ to $100%$ of catalog wire rope breaking strength. This is the only acceptable field eye termination for overhead boiler rigging.
- Hand-Tucked Eye Splice: Strands are woven manually back into the body; develops only $80%$ to $90%$ efficiency.
- U-Bolt Wire Rope Clips (Crosby Clips): Strictly prohibited for fabricating overhead lifting slings under OSHA 1926.251. When used for non-lifting winching or temporary guy lines, the U-bolt must sit on the dead (short) end of the rope ("Never saddle a dead horse"), reducing termination efficiency to $80%$.
Alloy Steel Chain Slings (Grade 80 and Grade 100)
Chain slings resist cutting, high ambient temperatures, and rough industrial surfaces. Under ASME B30.9, only two grades of alloy steel chain are certified for overhead lifting:
- Grade 80 (T8): High-strength alloy steel with an energy-absorbing elongation capacity of at least $20%$ prior to fracture. Operating temperature up to $400^\circ\text{F}$ without derating ($400^\circ\text{F}-600^\circ\text{F} \rightarrow 10%$ derate; $>1000^\circ\text{F} \rightarrow$ permanently condemned).
- Grade 100 (V10): Premium alloy steel providing roughly $25%$ higher WLL than Grade 80 for the same nominal wire diameter, reducing rigging tare weight.
- Prohibited Chains for Overhead Lifting: Carbon steel chains—including Grade 30 Proof Coil, Grade 43 High Test, and Grade 70 Transport (Tie-Down) chain—lack the alloy microstructure, shock-load toughness, and elongation characteristics required for overhead lifting and are strictly prohibited.
- Mandatory Chain Sling Identification Tag: Every chain sling must feature a permanently affixed, stamped metal identification tag detailing: (1) Manufacturer name, (2) Grade, (3) Nominal chain size, (4) Number of legs, (5) Rated capacity at specified sling angles, and (6) Reach length. If the tag is missing or illegible, the sling must be removed from service immediately.
2. Rigging Hardware: Shackles, Eye Bolts, Rings & Clamps
All rigging hardware must be forged from high-grade alloy steel and permanently embossed with the manufacturer's trademark, nominal size, and Working Load Limit (WLL).
+-----------------------------------------------------------------------------------------+
| RIGGING HARDWARE SELECTION MATRIX |
+-----------------------------------------------------------------------------------------+
| Hardware Type | Design Safety Factor | Primary Application & Operational Limits|
+-----------------------+----------------------+------------------------------------------+
| Rigging Hardware | 5:1 (ASME B30.26) | Shackles, turnbuckles, master links, |
| (General) | | swivel hoist rings, eye bolts. |
+-----------------------+----------------------+------------------------------------------+
| Alloy Chain Slings | 4:1 (ASME B30.9) | Grade 80 and Grade 100 overhead slings. |
+-----------------------+----------------------+------------------------------------------+
| Personnel Baskets | 10:1 (ASME B30.23) | Crane-suspended work platforms. |
+-----------------------+----------------------+------------------------------------------+
Forged Alloy Steel Shackles
Shackles are the universal connecting component in rigging assemblies:
- Bow (Anchor) Shackles vs. D (Chain) Shackles:
- Bow Shackles: Feature an enlarged, rounded bow profile that accommodates multiple sling legs at angles up to $45^\circ$ from the centerline without pinching the sling or generating severe side-loading bending stresses.
- D (Chain) Shackles: Feature straight, parallel sides designed strictly for single-leg, inline $0^\circ$ axial tension. Applying angular or side loads to a D-shackle induces destructive bending moments on the ears.
- Pin Configurations:
- Screw Pin Shackles: Threaded pin screws directly into the tapped shackle ear. Quick to install for temporary picks. Operational Rules: The pin must be fully seated and then backed off $1/4$ turn ($90^\circ$) to prevent mechanical binding under load. If used in vibrating or dynamic settings, the pin must be "moused" (secured with stainless steel safety wire). Moving lines (chokers) must never run across a screw pin, as line friction can unscrew the pin during hoisting.
- Bolt-Type Safety Shackles: Feature an unthreaded bolt shank secured by an external hex nut and stainless steel cotter pin. Mandatory for permanent rigging, heavy critical lifts, multi-crane tandem lifts, and lifts where rotation could back out a screw pin.
SCREW PIN SHACKLE BOLT-TYPE SAFETY SHACKLE
+-------+ +-------+
/ \ / \
| BOW | | BOW |
| BODY | | BODY |
\ / \ /
(O) (O) (O) (O)
===|=====|=== ===|=====|==[Nut]-[Cotter]
Threaded Pin Bolt Shank
Eye Bolts vs. Swivel Hoist Rings
Rigging into threaded vessel bosses requires strict hardware selection based on the angle of pull:
- Non-Shoulder Eye Bolts: Designed strictly for $100%$ inline, axial pulls ($0^\circ$). Non-shoulder eye bolts have zero angular capacity. Any angular load introduces extreme cantilever bending stress across the root threads, causing sudden shear failure.
- Shoulder Eye Bolts: Feature a forged, machined shoulder that seats flush against the equipment mounting surface. While permitted for angular rigging, shoulder eye bolts suffer severe load deratings under ASME B30.26:
- $0^\circ$ (Inline Axial Pull): $100%$ of rated WLL.
- $75^\circ$ to $89^\circ$ Pull Angle: Derated to $55%$ of rated WLL.
- $45^\circ$ to $74^\circ$ Pull Angle: Derated to $25%$ to $30%$ of rated WLL.
- $< 30^\circ$ Pull Angle: Strictly Prohibited.
- Installation Rule: The shoulder must seat $100%$ flush against the machined surface. If necessary, hardened steel shims/washers are used under the shoulder, ensuring full thread engagement of at least $1.5 \times$ bolt diameter in steel.
- Swivel Hoist Rings: Engineered lifting devices featuring a forged alloy bail that pivots $180^\circ$ vertically and swivels $360^\circ$ horizontally on an internal bushing. Swivel hoist rings maintain $100%$ full rated capacity at any angle from $0^\circ$ to $90^\circ$, provided the mounting bolt is torqued to manufacturer specifications with a calibrated torque wrench.
SHOULDER EYE BOLT SWIVEL HOIST RING
(Severe Derating!) (100% WLL at ANY Angle)
/---\ /---\ <- 180 deg Pivot Bail
| | | |
\---/ \---/
+-----+ <- Shoulder Seats Flush +=====+ <- 360 deg Swivel Base
| |
| <- Full Thread Engaged | <- Torqued Cap Screw
Lifting Beams, Plate Clamps & Beam Clamps
- Spreader Beams vs. Equalizer Beams:
- Spreader Beam: A rigid horizontal tubular or wide-flange strut suspended between two top sling legs. The spreader beam converts the angled tension of the top rigging into pure vertical drops to the load, subjecting the beam itself to pure axial compression. This protects thin-walled boiler ducts, steam drums, and tube bundles from inward crushing forces.
- Equalizer Beam: A structural beam designed to operate in bending, equipped with multiple lower connection points or center pivot pins/sheaves. Equalizer beams equalize load sharing between two cranes in a tandem lift or distribute unequal loads across asymmetrical pick points.
- Plate Clamps:
- Vertical Locking Plate Clamps: Feature a spring-loaded, hardened serrated cam that bites into steel plate. The manual lock lever must be fully engaged before hoisting. Crucial Limits: Minimum load requirement is typically $20%$ of WLL (to prevent cam disengagement); plate surface hardness must not exceed $300\text{ to }400\text{ HB}$ ($32\text{ HRC}$); lifts are restricted strictly to one single plate at a time.
- Horizontal Plate Clamps: Used in matched pairs connected to a two-leg sling bridle to transport flat steel sheets in a horizontal orientation.
- Beam Clamps: Mechanical jaw clamps engineered to grip structural I-beam flanges for hoisting or rigging anchorages. Must be loaded strictly perpendicular ($90^\circ$) to the beam flange unless specifically rated by the manufacturer for angular loading.
3. Rigging Inspection & Rejection Criteria (ASME & OSHA)
Rigging failure in boiler construction often results from unspotted hardware fatigue or wear. ASME B30.9, ASME B30.26, and OSHA 1926.251 mandate daily pre-use visual inspections by a Competent Person.
+-----------------------------------------------------------------------------------------+
| COMPREHENSIVE RIGGING REJECTION CRITERIA REFERENCE |
+-----------------------------------------------------------------------------------------+
| Rigging Component | Mandatory Rejection Criteria (Immediate Removal from Service) |
+-----------------------+-----------------------------------------------------------------+
| **Wire Rope Slings** | * 10 randomly distributed broken wires in one rope lay. |
| (ASME B30.9 / OSHA) | * 5 broken wires in one strand in one rope lay. |
| | * 1 broken wire at an end fitting, sleeve, or termination. |
| | * Severe localized wear (> 10% nominal diameter reduction). |
| | * Kinking, birdcaging, doglegs, core protrusion, heat/arc burns.|
+-----------------------+-----------------------------------------------------------------+
| **Synthetic Slings** | * Acid burns (nylon) or caustic chemical burns (polyester). |
| (ASME B30.9) | * Melting, charring, or weld spatter burns. |
| | * Snags, tears, punctures, cuts, or broken load-bearing stitches.|
| | * Exposed red core warning yarns visible through outer jacket. |
| | * Missing, illegible, or detached manufacturer capacity tag. |
+-----------------------+-----------------------------------------------------------------+
| **Chain Slings** | * Missing or illegible metal identification tag. |
| (ASME B30.9) | * Cracks, breaks, or severe gouges in any link or fitting. |
| | * Wear exceeding 10% of original link stock diameter. |
| | * Stretch or link elongation exceeding 5% of total reach. |
| | * Heat exposure exceeding 400 deg F (Gr 100) or 600 deg F (Gr 80)|
+-----------------------+-----------------------------------------------------------------+
| **Shackles & Rings** | * Pin or body wear exceeding 10% of original dimension. |
| (ASME B30.26) | * Bent, twisted, or distorted shackle body or pin. |
| | * Missing cotter pins or damaged pin threads. |
+-----------------------+-----------------------------------------------------------------+
| **Rigging Hooks** | * Throat opening stretch exceeding 5% (or 1/4 inch max). |
| (ASME B30.10) | * Hook tip twist exceeding 10 degrees from plane of unbent body.|
| | * Bowl or saddle wear exceeding 10% of nominal dimension. |
| | * Missing or inoperable spring-loaded safety latch. |
+-----------------------+-----------------------------------------------------------------+
WIRE ROPE DEFECTS REQUIRING IMMEDIATE CONDEMNATION
BIRDCAGING: KINKING: BROKEN WIRES:
,---. /\ --x-------x--
/ \ / \ <- Permanent ----x---x----
| ( ) ( ) | <- Strands / \ Deformation --x----------
\ / Opened Out / \ 6 in 1 Lay OR
`---' / \ 3 in 1 Strand
4. Realistic Trade Scenario: Boiler Header Rigging Pre-Check
+-----------------------------------------------------------------------------------------+
| FIELD TRADE SCENARIO |
+-----------------------------------------------------------------------------------------+
| Scenario: A boilermaker rigging crew is tasked with lifting an 18,000-pound economizer |
| inlet header inside a utility boiler penthouse using a 2-leg wire rope bridle and |
| screw-pin shackles rigged into welded lifting lugs. |
| |
| Pre-Lift Inspection & Rigging Protocol: |
| 1. Wire Rope Sling Check: |
| - Inspect 1-inch EIPS 6x19 IWRC slings. Verify Flemish eye swaged sleeves are intact.|
| - Examine rope body: Zero birdcaging, zero kinking, and broken wire count is 0. |
| - Confirm manufacturer capacity tag reads WLL >= 18,000 lbs at 60 deg sling angle. |
| 2. Shackle Verification: |
| - Inspect 1-1/4 inch alloy bow shackles (WLL = 12 Tons each). Check pin wear (< 10%).|
| - Thread shackle pin into lug, fully bottom the pin, and back off 1/4 turn (90 deg). |
| - Mouse the screw pins with stainless steel wire to prevent dynamic loosening. |
| 3. Rigging Geometry & Hook Safety: |
| - Verify the crane hook safety latch closes completely over the master link. |
| - Check hook throat opening against caliper baseline (zero stretch detected). |
| - Ensure sling legs maintain a minimum 60-degree horizontal angle during pick. |
+-----------------------------------------------------------------------------------------+
Test Your Knowledge
When inspecting a 6x19 wire rope sling under ASME B30.9 and OSHA 1926.251, what is the maximum number of randomly distributed broken wires permitted in one rope lay before the sling must be immediately removed from service?
A
B
C
D
Test Your Knowledge
When rigging a heavy boiler component using forged shoulder eye bolts loaded at a 45-degree horizontal angle, what is the allowable working load limit derating compared to an inline vertical pull?
A
B
C
D
Test Your Knowledge
What is the ASME B30.10 and OSHA removal criterion regarding the maximum allowable increase in the throat opening dimension of a forged rigging hook?
A
B
C
D
Test Your Knowledge
A boilermaker needs to select an alloy steel chain sling for an overhead boiler header lift. Which chain grade and marking configuration is legally certified for overhead lifting under ASME B30.9?
A
B
C
D