Elliott Digger Derrick, Operation & Maintenance Manual, Page: 159 / 376

Synthetic Rope Usage EEC-0060 V1.2
Synthetic Rope Usage,
Inspection, and Retirement

Elastic Hysteresis: Elastic Hysteresis refers to a recoverable portion of stretch
or extension over a period of time after a load is released. In measuring elastic
recovery, it is the portion that occurs immediately when a load is removed.
However, a remaining small percentage of elastic recovery occurs gradually over
a period of hours or days. Elastic hysteresis is measured in a length/time scale.

Permanent Extension (PE) After Relaxation: Permanent extension while
working is the amount of extension that exists when stress is removed but no
time is given for hysteretic recovery. It includes the non-recoverable and
hysteretic extension as one value, and represents any increase in the length of ta
rope in a constant working situation, such as during repeated surges in towing,
or other similar cyclical operations. The percentage of PE over the working load
range is generally in order of 4-6 percent for braided ropes, and 2-3 times as
much for plaited. However, it varies slightly with different fibers and rope
constructions. In some applications, such a s subsurface mooring or devices that
demand precise depth location and measurement, allowances must be made for
this factor.

Creep: A material’s slow deformation that occurs while under load over a long
period of time. Creep is mostly non-reversible. For some synthetic ropes,
permanent elongation and creep are mistaken for the same property and used
interchangeably when, in fact, creep is only one of the mechanisms that can
cause permanent elongation.

Constructional Elongation: The elongation of a loaded rope that results from
compaction as the fibers and strands align and adjust.

Slice Setting: The elongation of a spliced rope caused by the adjustment and
setting of the strands in the splice.