Dynamic Elongation of Rescue Rope

1
Dynamic Elongationof Rescue Rope

• 2005
• International Technical Rescue Symposium

2
Overview

• Impetus of testing
• Assuming a mainline failure resulting in a 0.33
  fall factor, what is the elongation of the belay
  (safety) rope supporting the load?
• And, should there be a second dynamic event on
  the same rope, how will it perform?

3
Overview

• Additionally
• What are the consequences of this dynamic
  elongation to a rescue operation?

Is this dynamic elongation consistent and
predictable?
Will this dynamic elongation differ between
manufacturers and between new and used ropes?
4
Disclaimer

• While every effort was made to represent the
  testing methodologies, conditions and results
  accurately, errors may have occurred. The
  investigators limited the testing to two
  manufactures (PMI and Sterling) and to a total of
  three models of rope. The investigators make no
  claim to know or be able to predict rope dynamics
  or behavior. The real life applications and
  conditions will differ from those during testing.
  The investigators or their employers are not
  responsible for use or misuse of the information
  presented or conclusions drawn from the testing
  results. The National Park Service and West
  Valley College has not endorse the testing and
  test results.

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Rescue Ropes Explained

• Cordage Institute defines
• Static rope may have an elongation of up to 6
  with a static force equal to 10 of the ropes
  minimum breaking strength (MBS)
• Low Stretch rope may have an elongation of
  between 6 and 10 with a static force equal to
  10 of the ropes MBS

6
Rescue Ropes Explained

• Ropes of the same size manufactured by two
  different companies are not the same!
• Actual size varies 7/16 11, 11.1, 11.5, 11.8mm
  (etc)
• Minimum Breaking Strengths (MBS) vary
• Advertised static elongations vary
• Methods for testing static elongation vary
• - 10 MBS, 300lbs, 600lbs.

7
Ropes Used in Tests

• PMI Classic EZBend
• Diameter Advertised 7/16 True 11.2-11.5mm
• MBS 6550lbs/29.1kN
• Elongation 4.8 at 10 MBS
• Construction 100 Nylon multifilament
• virgin fiber
• Ropes Tested
• Two new ropes, manufactured in 2001 and 2003
• Four used ropes, manufactured date unknown for
  three and the other pre 1993.
• Information provided by PMI, except rope
  diameter true measurement

8
Ropes Used in Tests

• Sterling Superstatic
• Diameter Advertised 7/16- True11.5mm
• MBS - 8182lbs/36.4kN
• Elongation - 9.8 at 10 MBS
• Construction Nylon
• Ropes Tested
• Two new ropes, manufactured in 1999 and 2005
• Information Provided by Sterling

9
Ropes Used in Tests

• Sterling HTP
• Diameter Advertised 7/16 pre 8/05 - True
  12.0 mm
• post 8/05 - True 11.1 mm
• MBS - pre 8/05 - 7791lbs/34.7kN
• post 8/05 - 7520lbs/33.5kN
• Elongation pre 8/05 - 2.1 at 10 MBS
• post 8/05 - 2.8 at 10 MBS
• Construction 100 Polyester
• Ropes Tested
• Two new ropes, manufactured in 4/05 and 8/05
• One used rope, manufactured in 2002
• Information Provided by Sterling

10

• Warnings as noted in Sterling and PMI literature
• Sterling
• HTP has very low elongation (less than 1 at
  300lbs). It should not be used in situations
  where any potential for shock-loading (fall) may
  occur. It will result in very high impact
  forces. In these situations, a nylon static or
  dynamic rope might be more appropriate. If you
  have questions always consult the rope
  manufacturers manual or contact a certified rope
  professional.
• PMI ISOSTATIC
• 100 Polyester ropes have significantly lower
  energy absorbing capability than conventional
  nylon ropes and are not suitable for every type
  of use. If the user is in doubt about what types
  of forces an all polyester rope could generate in
  a shock-load or fall situation the all polyester
  rope should not be used.

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Test Procedures
12
Test Procedures
13
Test Procedures
14
Test Procedures
15
Test Procedures
16
Test Procedures
17
Test Procedures

• Data collected
• Time
• Sample
• Temperature
• Stopping Distance (max elongation with knots)
• Resting Length
• Top Knot Extension
• Bottom Knot Extension
• Elongation with Top Knots
• Actual Elongation (subtracting out top knot
  extension)

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Results

• Total of Samples 47
• Total of Drops 94
• Note Due to data collection errors/problems and
  setup errors, actual data used to calculate
  results differs from total drops and samples.

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Results

• PMI Classic EZBend
• New Samples from ropes manufactured in 2001 and
  2003
• Total of Samples11
• Total of Drops22
• First Drop Data
• Min Elongation 15.57
• Max Elongation 18.33
• Median 16.31
• Second Drop Data
• Min Elongation 16.10
• Max Elongation 19.28
• Median 17.37

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Results

• PMI Classic EZBend
• Used Rope 1 Unknown manufacture date.
• Total of Samples 2
• Total of Drops 4
• First Drop Data
• Min Elongation 24.26
• Max Elongation 24.36
• Median 24.31
• Second Drop Data
• Both samples failed on second drop

21
Results

• PMI Classic EZBend
• Used Rope 2 Unknown manufacture date.
• Total of Samples 2
• Total of Drops 4
• First Drop Data
• Min Elongation 23.20
• Max Elongation 25.64
• Median 24.42
• Second Drop Data
• Both Sample failed on second drop

22
Used vs. New PMI
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Results

• PMI Classic EZBend
• Used Rope 3 Unknown manufacture date.
• Total of Samples 2
• Total of Drops 4
• First Drop Data
• Min Elongation 14.92
• Max Elongation 15.25
• Median 15.09
• Second Drop Data
• Min Elongation 15.89
• Max Elongation 15.89
• Median 15.89

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Results

• PMI Classic EZBend
• Used Rope 4 manufacture pre 1993
• Total of Samples 3
• Total of Drops 6
• First Drop Data
• Min Elongation 19.70
• Max Elongation 21.93
• Median 19.92
• Second Drop Data
• Min Elongation 20.55
• Max Elongation 21.61
• Median 21.40

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Results

• Sterling Superstatic
• New Samples from rope manufactured in 2005
• Total of Samples 10
• Total of Drops 20
• First Drop Data
• Min Elongation 18.43
• Max Elongation 24.47
• Median 21.29
• Second Drop Data
• Min Elongation 19.07
• Max Elongation 25.42
• Median 23.46

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Results

• Sterling Superstatic
• New Samples from rope manufactured in 1999
• Total of Samples 5
• Total of Drops 10
• First Drop Data
• Min Elongation 17.80
• Max Elongation 19.07
• Median 18.59
• Second Drop Data
• Min Elongation 18.64
• Max Elongation 21.61
• Median 20.13

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Results

• Sterling HTP
• New Samples from rope manufactured in 4/2005
• Total of Samples 3
• Total of Drops 6
• First Drop Data
• Min Elongation 9.85
• Max Elongation 11.23
• Median 10.81
• Second Drop Data
• Min Elongation 10.59
• Max Elongation 10.91
• Median 10.75
• Note One sample failed on second drop

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Results

• Sterling HTP
• New Samples from rope manufactured in 8/2005
• Total of Samples 3
• Total of Drops 6
• First Drop Data
• Min Elongation 12.08
• Max Elongation 12.82
• Median 12.57
• Second Drop Data
• All three samples failed on second drops

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Results

• Sterling HTP
• Used Samples from rope manufactured in 2002
• Total of Samples 5
• Total of Drops 10
• First Drop Data
• Min Elongation 17.16
• Max Elongation 19.92
• Median 18.01
• Second Drop Data
• Min Elongation 19.92
• Max Elongation 20.13
• Median 20.13
• Note Two sample failed on second drop

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Problems Encountered

• Knot extension Changes Peak Forces
• Problems with Data Collection
• Problems with Setups
• Carabiner Issues
• Mass Failures

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Problems Encountered
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Conclusions

• Testing was not intended to show that one type of
  rope was better than the other.
• When data for both Sterling SuperStatic and PMI
  were examined, with 33 1st drops and 26 2nd
  drops for a total of 59 drops, there was no
  dynamic elongation of less that 15.
• User should buy ropes based on intended use. No
  two ropes are the same and are often manufactured
  for specific purpose/application.
• No ropes, new or used, failed on the first drop.
  
• Failures during second drop raises questions?

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Conclusions

• More Questions Than Answers
• What is Used Rope?
• Can elongation data be applied to longer lengths
  of rope?
• What about the other manufacturers? How will
  their ropes behave?

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Acknowledgements

• Primary Investigators
• Scott Fischer, NPS Joshua Tree National Park
• Kim Aufhäuser, West Valley College Park
  Management Program
• Phil Spinelli, Joshua Tree Search and Rescue
• Dave Pylman, Joshua Tree Search and Rescue
• Thanks to the following for their assistance
• Loui McCurley of PMI and Sam Morton of Sterling
  Rope Company assisted us with advice on
  methodology and provided test cordage.
• Byron Cook, Karen Kokiba-Russell and Jim Russell
  of Joshua Tree Search and Rescue gave their time,
  energy and expertise to the process.

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Questions?
http//instruct.westvalley.edu/aufhauser/itrs2005.
html