GB/T 5974.2-2006 Wire Rope Clamp Plate Standard Guide
GB/T 5974.2-2006 "Wire Rope Clamp Plates – Part 2: Grooved Clamping Plates" is the product standard for grooved clamping plates. It specifies the type dimensions, technical requirements, and inspection rules for grooved clamping plates used to fasten wire rope ends on crane drums. The key difference from standard clamping plates is the longitudinal locating groove machined on the bottom face, which prevents lateral slippage of the wire rope.
Scope of Application and Standard Positioning
The core difference between the grooved clamping plates specified in GB/T 5974.2-2006 and standard clamping plates (GB/T 5974.1) lies in the longitudinal locating groove machined on the bottom face. Once the wire rope is seated in the groove, lateral movement is prevented, giving the grooved plate higher fixing reliability when subjected to side forces on the rope. Grooved clamping plates are available in three types: Type A (single-bolt fixing, for wire rope diameters 6–14 mm), Type B (two-bolt fixing, 16–28 mm), and Type C (four-bolt fixing, 32–60 mm), covering more than 30 specifications from 6 mm to 60 mm.
Compared with standard clamping plates, the groove depth of grooved plates is slightly deeper — R = (0.55–0.60)d (standard plates: R = 0.53–0.55d) — to accommodate the locating groove. The locating groove width is W ≈ 0.8d and depth h ≈ 0.3d, ensuring the wire rope sits snugly without being over-compressed. The plate width B ≥ 3d, wider than the 2.5d of standard plates, due to the added locating groove structure. Kelude supplies grooved clamping plates in all specifications as a supporting supply.
Material and Manufacturing Technical Requirements
Grooved clamping plates are manufactured from Q345B steel (≈S355J2) — chosen for its better toughness required for machining the locating groove — or from ZG310-570 cast steel (cast type). Cast plates must undergo normalizing to relieve casting stress. Manufacturing precision requirements: groove radius tolerance H12, locating groove width tolerance Js12, locating groove depth tolerance +0.2 mm, and bolt hole center distance tolerance ±0.2 mm. Surface roughness: Ra ≤ 12.5 μm on groove and locating groove surfaces. Surface treatment shall be galvanizing (hot-dip galvanizing with zinc layer thickness ≥ 15 μm) or phosphating.
Bolt holes are typically countersunk (bolt heads recessed below the plate surface to avoid interfering with wire rope layering). Per batch, 3% (minimum 3 pieces) are sampled for breaking force testing — with the plate installed, 1.5 times the wire rope minimum breaking force is applied and held for 5 minutes; the plate must show no cracks or failure. Locating groove inspection: a steel rod with a diameter equal to the wire rope nominal diameter must slide freely in the groove without noticeable play (clearance ≤ 0.3 mm).
Installation, Inspection, and Scrapping Criteria
The installation method recommended by the standard: at least two grooved clamping plates per wire rope end (spacing between plates ≥ 50 mm). Before tightening bolts, confirm that the wire rope has at least 2 safety wraps around the drum — safety wraps use the friction force generated by the rope wrapping around the drum to reduce the tensile load at the end fastening point. Bolts must be tightened with a torque wrench in 2–3 passes, alternating diagonally, to the specified torque (M16 ≈ 150 N·m, M20 ≈ 250 N·m, M24 ≈ 400 N·m). After installation, draw an alignment line across the bolt head and plate surface to facilitate visual inspection for bolt loosening during routine maintenance.
Grooved clamping plates are particularly suitable for the following applications: operating conditions with a large fleet angle of the wire rope on the drum (≥ 3°), such as the open/close rope drums of two-rope grab cranes, and cranes subject to high vibration, such as grab cranes and metallurgical cranes. Scrapping criteria: any crack, groove or locating groove wear depth exceeding 2 mm, plate thickness reduced by more than 20% due to corrosion, damaged bolt hole threads, or bending deformation — the plate must be scrapped. The standard specifically notes that grooved and standard clamping plates must not be mixed on the same wire rope end.
Standard Comparison and Application Recommendations
GB/T 5974.2-2006 (grooved clamping plates) and GB/T 5974.1-2006 "Wire Rope Clamp Plates – Part 1: Standard Clamping Plates" are companion sister standards. The locating groove design of grooved plates provides higher fixing reliability under large fleet angles and vibration conditions, but requires greater alignment accuracy during installation. When selecting, choose the appropriate clamping plate type based on the fleet angle of the wire rope on the drum and the vibration level of the crane.
In maintenance management, special attention should be paid to the alignment line marking on the clamping plate bolts — this is the most direct and effective method for detecting bolt loosening. Whenever replacing the wire rope, the clamping plates and bolts should also be replaced simultaneously to ensure the integrity of the fixing system.
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| clamping platetype test | Bolt Quantity | wire rope diameter | Groove Radius R | clamping platewidth B |
|---|---|---|---|---|
| A Type | Single Bolt | 6~14mm | 0.55~0.60d | ≥3d |
| B Type | Double Bolt | 16~28mm | 0.55~0.60d | ≥3d |
| C Type | Quadruple Bolt | 32~60mm | 0.55~0.60d | ≥3d |
| Comparison Item | grooved clamping plate(5974.2) | Standardclamping plate(5974.1) | Difference Description |
|---|---|---|---|
| Groove Radius | R=0.55~0.60d | R=0.53~0.55d | Slightly Deeper Groove |
| locating groove | Yes(W≈0.8d) | No | core difference |
| clamping platewidth | B≥3d | B≥2.5d | Wider Groove |
| Applicable Fleet Angle | >2° | ≤2° | Broader Groove Coverage |
| Price | Approx.1.3Times | Baseline | Slightly Higher Groove |
Related Standards
• GB/T 22437.2 — Couplings for Cranes, Part 2
• GB/T 6974.2 — Crane Terminology, Part 2
FAQ: Wire Rope Clamping Plate Selection & Maintenance
Q: When should a grooved clamping plate be used instead of a standard one?
A: A standard clamping plate is sufficient when the wire rope fleet angle on the drum is ≤2°. For fleet angles exceeding 2° — such as on grab crane open/close drums — or in applications with significant crane vibration, a grooved clamping plate is recommended. The locating groove in a grooved plate restricts lateral wire rope movement, improving fixing reliability, though at a cost premium of roughly 30%.
Q: What is the purpose of the scribe mark on clamping plate bolts?
A: After torquing the bolts, the installer draws a continuous straight line across the bolt head and the clamping plate surface using a scribe. If a bolt loosens due to vibration-induced rotation, the line becomes misaligned. A simple visual inspection of the scribe line alignment reveals loosening — no torque wrench re-check is needed for each bolt.
Q: Why must two safety wraps of wire rope remain on the drum?
A: The friction generated as the wire rope wraps around the drum reduces the tensile load transferred to the end fastening point at the clamping plate. After one wrap, tension attenuates by approximately 40–50%. With two safety wraps, the load at the end fastening point drops to roughly 20–25% of the maximum rope tension. If fewer than two safety wraps are maintained, the clamping plate bears the full rope tension directly, which can easily lead to fixing failure.
Q: Can clamping plates be reused?
A: Reuse is not recommended by the standard. During initial use, the rope grooves and locating groove in the plate develop permanent indentations from the wire rope, and the bolts undergo slight plastic tensile deformation during preloading. On reuse, the bolt preload may not reach design requirements. Safe operating code recommends replacing all clamping plates and bolts whenever the wire rope is replaced.
