Guide to Turnbuckle Selection Installation and Maintenance

Wire Rope Turnbuckles: The Core Component of Tensioning Systems

In various engineering and industrial applications, the reliability of tensioning systems using wire ropes and cables is paramount. The wire rope turnbuckle, a crucial rigging hardware component, serves as the key element for achieving precise tension and eliminating slack. However, with numerous turnbuckle products available in the market, how does one select the appropriate type? What are the correct installation procedures to ensure safety? And what maintenance practices can extend their service life? This comprehensive guide examines all aspects of wire rope turnbuckles to provide engineers, technicians, and professionals with practical operational knowledge.

Wire Rope Turnbuckles: The Core Component of Tensioning Systems

Wire rope turnbuckles, also known as rigging screws or stretching screws, are adjustable devices used to regulate the tension in wire ropes, cables, or other tensioning systems. According to the American Society of Mechanical Engineers (ASME) B30.26 standard, a turnbuckle consists of three primary components: a body, a right-hand threaded end fitting, and a left-hand threaded end fitting. By rotating the body, both end fittings simultaneously extend or retract, thereby adjusting the tension in connected wire ropes or cables.

The applications of turnbuckles are remarkably diverse, ranging from simple fence tensioning to complex suspension bridge construction. Like other rigging hardware, turnbuckles come in various sizes, configurations, and types to accommodate different application requirements. Proper selection and use of turnbuckles are essential for maintaining safe and effective rigging systems.

Components of a Turnbuckle

Understanding the components of turnbuckles helps in comprehending their operation and proper usage:

Body

The central metal frame connecting two threaded end fittings. Rotation of the body adjusts tension by extending or retracting the end fittings. Two body types exist:

• Open Body: Traditional type with visible threads in the frame.
• Closed Body: Also called pipe body, with threads enclosed within the frame for compactness in space-constrained applications.

Locking Nut

Also known as a jam nut, installed on the threaded end fitting against the body to prevent loosening or unscrewing.

End Fittings

Connection points at both ends of the turnbuckle body, featuring opposite thread directions (right-hand and left-hand). Common types include:

• Hook End: For quick temporary connections, unsuitable where tension might accidentally release.
• Jaw End: Consists of a jaw with a bolt secured by nuts or pins, connecting to non-opening components like shackles.
• Eye End: A closed loop connecting to shackles or quick links.

Thread Diameter

The diameter of threaded portions on end fittings, directly correlating with load capacity.

Take-up Length

The total length end fittings can screw in/out of the body to adjust tension, measured when fully extended or retracted.

Types of Turnbuckles

Turnbuckles are classified by their end fitting combinations:

• Jaw-Jaw
• Eye-Jaw
• Eye-Eye
• Hook-Hook
• Hook-Eye

The combination depends on connection requirements and whether the connection is permanent or temporary. Hooks suit temporary connections needing frequent attachment/detachment, jaws connect to non-opening points like shackles, and eyes attach to openable connections like quick links.

Common Applications

Turnbuckles serve various tensioning purposes across industries:

• Sports & Recreation: Tensioning ropes around wrestling/boxing rings (often covered with soft materials for safety).
• Marine Transport: Securing ship lashing and rigging assemblies.
• Construction: Supporting tension in suspension bridges, large buildings, and highway guardrail cables.
• Aviation: Adjusting tension in aircraft structural cables (wings, flight control systems).

Installation Procedure

Proper installation is critical for safety and effectiveness:

1. Unscrew end fittings from the body until fully extended to maximum take-up length.
2. Connect both end fittings to anchor points:
   • For eye ends: Pass through connection points (shackles, quick links).
   • For hook ends: Loop around temporary connection points.
   • For jaw ends: Remove bolt, position connection point between jaws, reinsert and tighten bolt.
3. Rotate the turnbuckle to bring end fittings closer until desired tension is achieved.
4. Tighten locking nuts (if used) against the body.

Note: Always observe the Working Load Limit (WLL) during installation.

Material Selection: Galvanized Steel vs. Stainless Steel

The two most common turnbuckle materials each have distinct advantages:

Stainless Steel: Ideal for outdoor and saltwater environments due to superior rust and corrosion resistance. The preferred choice when corrosion is a concern.

Galvanized Steel: More economical than stainless steel and suitable for outdoor use, though with comparatively lower corrosion resistance.

Identification Markings

Per ASME B30.26 standards, turnbuckles must display:

• Manufacturer's name or trademark
• Size or rated load capacity

Inspection and Retirement Criteria

Turnbuckles should be retired if exhibiting any of these conditions per ASME B30.26:

• Missing or illegible identification markings
• Evidence of heat damage (welding spatter, arc strikes)
• Excessive pitting or corrosion
• Bent, twisted, deformed, stretched, elongated, cracked, or broken load-bearing components
• Significant nicks or gouges
• 10% reduction in original dimensions at any point
• Excessive thread damage or wear
• Evidence of unauthorized welding or modification
• Any visible damage raising doubts about continued use

Conclusion

This guide has examined turnbuckle fundamentals, operation principles, and application considerations. While mechanically simple, turnbuckles effectively manage tension in virtually any system. Key selection factors include:

• Three main end fitting types can combine in various configurations for different connection requirements.
• Material choice (galvanized or stainless steel) depends on environmental conditions and budget.
• Installation follows straightforward procedures while observing load limits.