Introduction:
Ropes are essential to ship mooring. Appropriate rope selection and proper use are critical to mooring safety. Rope selection should take full account of the vessel’s design requirements and operating conditions. For example, creep is a key design consideration for deepwater mooring ropes used under long-term loading, such as those serving offshore drilling platforms. For applications exposed to typhoons or other severe weather, key considerations include sudden high shock loads and sustained severe abrasion.
Ropes under a static load may experience forces above the working load limit (WLL) when suddenly subjected to a high shock load. In extreme cases, a rope may fail if the instantaneous shock load exceeds its residual strength. For ropes that may have experienced dynamic loads above WLL, we recommend prompt inspection and documentation to support rope replacement decisions or service-life assessments.
Drawing on its research and development capabilities and extensive application experience, Four Brothers Rope (FBR) has introduced three generations of POWERNEEMA® ROPE HMPE ropes over the past 20 years to address the operating requirements of ship mooring. All three generations have received broad recognition from users.
In the third-generation POWERNEEMA® ROPE III, each strand is individually protected before the 12 protected strands are braided into a 12-strand rope. The jackets are integrated with the strands. This non-separable jacket construction prevents the outer-cover peeling associated with conventional double-braided ropes, even when the outer strand surfaces become worn. If a strand jacket becomes worn, it can be repaired quickly, helping to slow the loss of rope strength and improve mooring safety. Wear on this rope is also easy to describe and record, providing a basis for rope inspection and maintenance.
Performance Comparison of HMPE Ropes
| Property | POWERNEEMA® ROPE I | POWERNEEMA® ROPE III |
|---|---|---|
| Breaking force (kN) | 1327 | 1327 |
| Construction | 12-strand | 12-strand |
| Jacket (Yes/No) | No | Yes |
| Jacket material | – | HMPE |
| Material density (g/cm³) | 0.97 | 0.97 |
| Diameter (mm) | 42 | 48 |
| Linear density (kg/m) | 0.979 | 1.264 |
| Maximum tenacity (t/kg/m) | 135.91 | 105 |
| Creep resistance* | 3–4 | 3–4 |
| Abrasion resistance* | 4 | 5 |
| Resistance to particle ingress* | 3 | 5 |
| Tensile fatigue (TCLL)* | 82.5% | 90% |
| Chemical resistance | Resistant to acids, alkalis, and seawater | Resistant to acids, alkalis, and seawater |
| UV resistance* | 4–5 | 5 |
* Creep resistance, abrasion resistance, resistance to particle ingress, and UV resistance are rated on a scale of 1–5: 1—Poor; 2—Fair; 3—Good; 4—Very Good; 5—Excellent.
* Tensile fatigue (TCLL, Tension Cycling Load Limit ) refers to the residual strength retention after cyclic tensile loading. The percentage indicates the ratio of the breaking strength after fatigue testing to the original breaking strength of the new rope. A higher percentage indicates better fatigue resistance.
Note: The data above are based on HMPE ropes with a breaking force of 1327 kN. The results were obtained under laboratory conditions, are not intended as an assessment of actual field performance, and are provided for customer reference only.
Lifecycle Cost Control and Safety Assurance
POWERNEEMA® ROPE III is designed to improve abrasion protection, inspectability and maintainability, with the objective of improving service durability under appropriate operating and maintenance conditions. To help users manage lifecycle costs and maintain safety, FBR’s application engineers assist with the development of Line Management Plans (LMP) and provide ongoing guidance and services for on-site inspection, care, and maintenance.
FBR | MARITIME