Application Notes - Pfeifer Messschieber 40 Manual

Note: Varying between light and strong pressure and
depending on the measurement displayed, a medium
pressure point can be determined.
5. Note the minimum and maximum diameter displayed,
observed when rotating the measuring jaws around
the rope axis, whilst maintaining the "right angle"
position.
6. Repeat steps 3 to 5 in accordance with the instruc-
tions in the measuring prerequisites chapter. At regular
intervals or if unrealistic measurements appear, check
the correct zeroing according to Step 2.

11. Application notes

Accuracy of the measuring instrument.
According to DIN EN 12385-1, a maximum measuring
accuracy of the measuring instrument of ± 0.02 mm
for rope diameters up to and including 25 mm, ± 0.05
mm for rope diameters over 25 mm up to 100 mm and
± 0.1 mm for rope diameters over 100 mm is required.
The requirement from this standard is primarily aimed
at the inspection and compliance of accurate diameters
(tolerances), which are to be ensured and inspected
during production and when new.
The PFEIFER calliper gauge 60 complies with the requi-
rements according to EN 12385-1 and thus meets the
highest accuracy requirements. The PFEIFER calliper
gauges 45, 75 and 125, due to their geometry, can't
meet this requirement, but are suitable without restric-
tions for inspecting ropes in operation (regarding
discarding time according to DIN ISO 4309).
NOTICE: The (theoretical) accuracy of the measuring
instrument in relation to the other influencing factors
(see following sections) can be ignored.
Factors influencing measuring accuracy
In an internal PFEIFER study, possible influencing factors
were examined more closely and quantified. The individual
result and influences from this study are described below.
In this study, two measuring points were defined on
a section of rope with a nominal diameter of 16 mm. At
these two measuring points, the diameters were measured
and documented by various qualified persons and experts
under exact specification of the measuring method.
This produced the following results and deviations:
• Person-dependent measurement difference:
± 0.03 mm (± 0.19 % of nominal rope diameter)
• Orientation of the measuring jaws "at right angles"
vs. "lengthways": ± 0.05 mm (± 0.31 % of nominal
rope diameter)
PFEIFER rope calliper gauge 01/2022 / Subject to change!
8
• Force exerted: ± 0.05 mm (± 0.31 % of nominal
rope diameter)
• "Measuring jaws" vs. "Calliper" pressure point:
no significant deviation
• Strand tension/load condition "unloaded" vs.
"maximum working load limit": up to ± 0.5 mm
(–3.13 % of nominal rope diameter)
Conclusion:
Even with exact compliance to the measurement me-
thod, measuring errors of up to ± 0.05 mm can hardly
be avoided. The assessment of the measured rope
diameter is therefore only meaningful in the 0.1 mm
range (rounded to the closest 0.1 mm increment). The
actual measurements can nevertheless be specified
with 0.01 mm accuracy to represent the measurement
tendencies.
Diameter over rope life cycle depending on condition
Settling in operation
Ropes experience a settling of their structure and hence
a reduction in diameter when first loaded. The definition
of the diameter tolerance/specification for the new rope
therefore only applies to the completely unloaded and
unsettled new condition and must be checked before
the rope is laid/assembled on the installation.
Strand tension
Ropes experience a reduction in diameter under tensile
force. In this respect, the diameter reduction rate is
highest at low strand tensions, i. e. the relative diameter
reduction from the unloaded state to a strand tension
of 5 % of the rope's minimum breaking force is much
higher than the relative diameter reduction between
5 % and 10 % of the rope's minimum breaking force.
1,4%
1,2%
1,0%
0,8%
0,6%
0,4%
0,2%
0,0%
10%
0% 5%
Strand tension [%
Strangzug [%
Fig. 4: Example progress of diameter across strand tension (not generally applicable)
15% 20% 25% 30%
]
]
Fmin
Fmin