Screw Pin Anchor Shackles
Table of Contents
Engineering Reference for Multi-Directional Load Control in EPC, Offshore & Capital Projects
Manufacturer & Global Exporter: Super Industries
Website: https://superindustriesindia.in
1️⃣ Industry Context: Why Screw Pin Anchor Shackles Are Critical Safety Components
In EPC, offshore, marine, and infrastructure projects, lifting operations are governed by engineered load paths, not by individual components in isolation. Within these load paths, screw pin anchor shackles are often the most highly stressed connectors because they sit at convergence points—between slings, chains, pad eyes, and lifting lugs—where forces are rarely perfectly aligned.
Anchor shackles are therefore classified as safety-critical load-bearing hardware. Failure or deformation at this point compromises the entire lifting system, regardless of crane capacity or sling rating.
They are specified when:
- Loads are applied at angles or through multi-leg slings
- Connection geometry requires increased internal clearance
- Temporary rigging must accommodate misalignment and articulation
- EPC and third-party inspectors require recognized standard compliance
In Oil & Gas modules, LNG skids, offshore structures, power plant components, and heavy infrastructure elements, screw pin anchor shackles are chosen deliberately for their geometry-driven load distribution advantages, not convenience.
2️⃣ Technical Definition: What Screw Pin Anchor Shackles Are and How They Function
A screw pin anchor shackle is a forged steel shackle with a wide, rounded bow and a removable threaded pin, designed to connect lifting elements under multi-directional loading conditions.
Geometry and Construction
- Anchor (bow) profile: Wider internal radius compared to chain shackles
- Forged body: Continuous grain flow aligned with load paths
- Screw pin: Precision-machined, removable, and reusable
- Shoulder interface: Ensures correct pin seating and load transfer
Functional Role in Lifting Systems
Screw pin anchor shackles function by:
- Allowing angular load entry without inducing side loading
- Distributing forces evenly across the shackle body
- Maintaining predictable stress behavior under combined loading
They are commonly installed between slings and lifting points where geometry cannot be constrained to a single plane.
3️⃣ Engineering Relevance: Multi-Directional Load Behavior & Deformation Control
Load Distribution in Angled Lifts
In multi-leg sling configurations, forces are resolved into vectors that act at angles to the shackle axis. The anchor shackle’s wide bow:
- Reduces stress concentration at the pin
- Minimizes bending moments
- Prevents localized yielding
Pin-to-Body Interaction
Under correct use:
- The pin is primarily loaded in double shear
- Threads do not carry tensile load
- Bearing pressure is shared across the bow radius
Improper alignment or undersized shackles can shift load into bending or tensile modes, which is why anchor shackles are preferred over chain shackles in angled applications.
Deformation and Rejection Criteria
Anchor shackles are designed to exhibit elastic deformation up to proof load. Permanent deformation, thread damage, or pin bending are rejection conditions and are easily detectable during inspection—an important safety feature in EPC environments.
4️⃣ Load Rating & Design Logic
Anchor Shackle Shape
The bow geometry increases internal clearance, allowing:
- Multiple sling legs to seat correctly
- Reduced bearing stress
- Improved articulation during lifting
Pin Diameter and Thread Engagement
- Pin diameter governs shear capacity
- Thread engagement is designed for strength and repeated use
- Full shoulder seating is mandatory for rated performance
Load Ratings
- Working Load Limit (WLL): Maximum allowable load in service
- Proof Load: Typically 2× WLL to verify elastic behavior
- Minimum Breaking Load (MBL): Ultimate capacity with defined safety margin
Safety Factors
Depending on governing standard, anchor shackles are typically designed with 5:1 or 6:1 safety factors, with higher margins applied for offshore and critical lifts.
5️⃣ Anchor Shackle vs Chain Shackle: Engineering Selection Logic
Screw Pin Anchor Shackles
- Best for angled, multi-leg, or rotating loads
- Reduced risk of side loading
- Preferred for general EPC lifting
Screw Pin Chain Shackles
- Narrow jaw profile
- Optimized for in-line chain loading
- Not ideal for angular sling configurations
For EPC lifting studies, anchor shackles are generally specified unless geometry is strictly controlled and in-line.
6️⃣ Material & Standard Alignment
Material Selection
Screw pin anchor shackles are manufactured from:
- High-strength carbon steel
- Alloy steel for higher WLL and offshore duty
Material chemistry and mechanical properties are controlled to ensure toughness, ductility, and resistance to brittle fracture.
Applicable Standards
- ASME B30.26 – Rigging hardware requirements
- EN 13889 – European shackle standard
- ISO 2415 – International reference
- ASTM A148 / A668 – Forged steel material specifications
- DIN & IACS rules – Dimensional and offshore acceptance
Compliance with recognized standards is mandatory for consultant approval and third-party inspection.
7️⃣ Manufacturing & Quality Discipline
Forging Integrity
Anchor shackles are hot-forged to achieve continuous grain flow following the bow profile, maximizing fatigue and impact resistance.
Heat Treatment
Controlled heat treatment achieves:
- Required tensile strength
- Adequate elongation
- Consistent hardness across body and pin
Threading Accuracy
Pins are precision-threaded and gauged to ensure:
- Full engagement
- Smooth assembly and disassembly
- Predictable load behavior
Inspection & Traceability
- Dimensional verification of bow width and pin fit
- Visual inspection for laps, cracks, or surface defects
- Proof load testing
- Heat and batch traceability
This discipline ensures repeatable compliance in EPC procurement cycles.
8️⃣ Procurement, Installation & Inspection View
During Technical Evaluation
EPC engineers and rigging specialists verify:
- Correct shackle type and WLL
- Compliance with project standards
- Manufacturer test certificates
- Suitability for angled loading
During Incoming Inspection
Third-party inspectors check:
- Markings (WLL, size, manufacturer ID)
- Thread condition and pin seating
- Absence of deformation or damage
During Installation and Use
Best practice requires:
- Full pin engagement with shoulder seated
- Correct orientation relative to load direction
- Secondary retention (mousing) where vibration or rotation is possible
9️⃣ Application Mapping Across Industries
Oil & Gas
Module lifting, equipment installation, shutdown maintenance.
Offshore & Marine
Deck lifts, mooring accessories, temporary rigging.
Power & Energy
Turbine components, boiler erection, balance-of-plant handling.
LNG
Skid lifting, prefabricated module handling.
Infrastructure & Construction
Bridge segments, precast elements, heavy civil works.
Heavy Engineering
Fabrication yards, transport and erection operations.
🔟 Professional Technical Tables
Nominal Sizes & Pin Diameters (Indicative)
| Shackle Size | Pin Diameter (mm) |
|---|---|
| 1/2″ | ~16 |
| 3/4″ | ~22 |
| 1″ | ~28 |
| 1 1/4″ | ~35 |
| 1 1/2″ | ~38 |
Load Ratings (Indicative)
| Size | WLL (t) | Proof Load (t) | Min. Breaking Load (t) |
|---|---|---|---|
| 1/2″ | 2 | 4 | 12 |
| 3/4″ | 4.75 | 9.5 | 28 |
| 1″ | 8.5 | 17 | 51 |
| 1 1/4″ | 12 | 24 | 72 |
Actual values depend on governing standard.
Weight per Piece (Approximate)
| Size | Weight (kg) |
|---|---|
| 1/2″ | ~1.0 |
| 3/4″ | ~2.7 |
| 1″ | ~5.0 |
| 1 1/4″ | ~9.0 |
Material Grades & Surface Finishes
| Material | Finish |
|---|---|
| Carbon steel | Hot-dip galvanized |
| Alloy steel | Painted / galvanized |
| Offshore grade | Project-specified coating |
Standards vs Application Mapping
| Standard | Typical Application |
|---|---|
| ASME B30.26 | EPC & industrial lifting |
| EN 13889 | European projects |
| ISO 2415 | Global reference |
| IACS | Offshore & marine |
Project-Specific Customization Options
| Parameter | Options |
|---|---|
| Size & WLL | Project-defined |
| Pin type | Standard / secured |
| Coating | Galvanized, painted |
| Marking | EPC-specific |
| Certification | EN 10204 3.1 / 3.2 |
1️⃣1️⃣ Manufacturer-Focused Conclusion
In EPC, offshore, and infrastructure lifting operations, Screw Pin Anchor Shackles are critical connectors designed for multi-directional load behavior. Their performance depends on forged geometry, controlled material properties, precise threading, and disciplined inspection.
Super Industries manufactures screw pin anchor shackles under controlled forging, heat treatment, and inspection systems aligned with international lifting standards and EPC acceptance requirements. Our engineering-driven manufacturing discipline, traceability control, and inspection readiness support safe load transfer, predictable behavior, and third-party approval in demanding lifting and rigging applications.
Unrivaled Versatility: High-Strength Screw Pin Anchor Shackles
For rigging applications demanding both safety and flexibility, the Screw Pin Anchor Shackle is the go-to solution. Distinguished by its wide, curved bow, this shackle provides superior capacity for handling multi-leg slings, angular loading, and bulky rigging components where a standard chain shackle simply won’t suffice.
Super Industries India is a trusted manufacturer and supplier of certified, forged Screw Pin Anchor Shackles. Built from high-tensile alloy steel and finished with corrosion-resistant galvanization, our shackles are rigorously proof-tested to ensure maximum safety and reliability across construction, marine, offshore, and heavy industry projects in India.
What is a Screw Pin Anchor Shackle?
The Anchor Shackle (also known as a Bow Shackle or Wide Body Shackle) is the most versatile type of shackle available. It features:
- The Body (Bow): A wide, rounded, or O-shaped body that allows it to accommodate wider slings, multiple rigging legs, and bulky connection points. This wider bow is the key difference from the narrow Chain (D) Shackle.
- The Screw Pin: A removable, threaded pin that screws into the body’s ear. This design enables quick and easy connection and disconnection, making it perfect for applications where the shackle is frequently used and removed.
Key Features of Super Industries India Shackles
- Forged Alloy Steel Construction: Each shackle is drop-forged, creating a continuous grain flow that maximizes strength, fatigue resistance, and shock-load capacity, far surpassing the integrity of cast alternatives.
- Hot-Dip Galvanized (HDG) Finish: We apply a durable, thick coating of zinc to the shackle body and pin to provide superior corrosion resistance, which is vital for marine, coastal, and outdoor industrial environments.
- Design Factor and WLL: Manufactured with a certified Safety Factor (typically 6:1 or 5:1), ensuring the Ultimate Breaking Load far exceeds the marked Working Load Limit (WLL).
Anchor Shackle vs. Chain Shackle: The Key Difference
Choosing between an Anchor Shackle and a Chain Shackle hinges on the loading requirements:
| Feature | Screw Pin Anchor (Bow) Shackle | Screw Pin Chain (D) Shackle |
| Body Shape | Wide, rounded bow (O-Shape) | Narrow, straight body (D-Shape) |
| Loading Suitability | Excellent for Angular Loading (side pull) and Multi-Leg Slings | Best only for In-Line Loading (straight pull) |
| Versatility | High; accommodates more components. | Lower; limited to single-point connections. |
The wider bow of the Anchor Shackle significantly reduces the stress on the shackle body when the load is applied at an angle, making it the safer choice for complex rigging assemblies.
Applications and Versatility of the Anchor Shackle
The Screw Pin Anchor Shackle is indispensable in situations requiring flexibility and high safety margins, especially when angular forces are unavoidable.
- Multi-Leg Sling Attachment: Used to gather the terminal fittings of two, three, or four-leg bridle slings, connecting them safely to the single hook of a crane or hoist.
- Angular Lifting: Essential for any lift where the rigging lines will pull at an angle greater than 5 degrees from the shackle centerline. The wide bow minimizes the reduction in WLL caused by side loading.
- Anchor Points and Mooring: Historically and currently used for connecting anchors (hence the name), mooring lines, and heavy-duty towing applications.
- Temporary Connections: The screw pin allows for quick setup and removal, making it perfect for construction sites where rigging points change frequently.
Safety and Traceability: Your Guarantee of Quality
At Super Industries India, every Screw Pin Anchor Shackle is manufactured under strict quality control to guarantee maximum safety and compliance.
- Permanent Marking: All shackles are permanently stamped with the clear Working Load Limit (WLL), the size/diameter, and the manufacturer’s mark for easy inspection and traceability.
- Pin Safety: The screw pin must be fully seated and tightened before lifting. For permanent or long-term installations, a Safety Pin Shackle (using a bolt, nut, and cotter pin) is recommended, but the Screw Pin is ideal for frequent changes.
- Certification: We provide full Material Test Certificates and traceability documentation, meeting or exceeding standards like ASME B30.26 and EN 13889.
For the safest, most flexible, and most durable connection point in your rigging system, choose the versatility of the Screw Pin Anchor Shackle.
Contact Super Industries India today to secure certified Anchor Shackles designed for your most challenging angular and multi-leg lifts.