Matthew Smith: An Assessment Of The Effects Of Environmental Conditions On The Performance Of Dynamic Climbing Ropes

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An Assessment of the Effects of Environmental Conditions on the Performance of Dynamic Climbing Ropes Matthew Smith of Mechanical Hons Mechanical Dr A J McLarenProject Number into the effects of environmental operating conditions on thebreaking strength of dynamic climbing ropes has been limited Studies havebeen carried out observing the effects of a small number of conditions Theaims of this study were to provide data for a number of other including salt water treatments high ambient temperatures sandand varying fresh water and freezing treatments This would then which are most degrading and require further research into themechanisms of the degradationIt was also intended to study two samples that had experienced real use andto compare their comparative used for the testing of high strength fabric belts were used to testthe ropes on a standard tensile testing machine This allowed the testing of alarge number of ropes such that a statistical analysis could be conducted Intotal 87 tests were carried out on 14 different rope conditionsIt was found that some treatments degraded a ropes strength and markedly Conclusions were also drawn as to the effect ofappearance treatment intensity area of rope and dependence on sample setsize Mechanisms of degradation were suggested and areas for further sample size1 first standard deviation2 second standard deviationX sample mean averageProject Number 2004056 Matthew Smith 2001157731 concerning the time at which a rope should be replaced is at best hazyIt is generally said to depend on the type length and intensity of use It hasbeen found that few studies have been carried out into the effects that operating conditions may have on the degradation of a These studies have been fairly narrow in their scope and havenot taken into account many obvious environmental hazards They havelooked mainly at the effects of UV degradation water treatments and 1 Must studies have been concerned with analysing a as it falls over a sharp edge the time at which failure is mostlikely to occur 23 It is possible that the environmental conditions to whichthe rope has been exposed will have a bearing on this sharp It is the intention of this study to produce data that will furtherthe knowledge of how the environment affects the performance of what is inmost cases a climbers only means of safetyIn order to produce a valid study it was necessary not only to on samples conditioned in the laboratory but also to examine ropesthat have been exposed to real environmental regimes To solve this shortfalla sample of ropes was subjected to a period of 13 weeks of a West coast ofScotland Winter Two samples were also procured from the Royal Air ForceOutdoor Activities Centre GrantownonSpey which had been used for theinstruction of novice climbers Both ropes were exactly the same save thattheir frequency of use and environmental operating conditions were different 1Project Number 2004056 Matthew Smith 200115773A study of these ropes would hopefully yield information as to how mucheffect the difference in operating conditions has had on the two ropesThe study aimed to produce twelve different conditions in the laboratory fromwhich it was hoped that the comparative level of degradation imposed byeach treatment could be measured and ranked by use of a control sample Intotal 87 tests were carried out It was desired to carry out more but meant that this would be impracticable A statistical approach wasemployed to produce the ranking and judge whether a treatment was deemedto be a treatment is known to be significant it is clearly desirable to know bywhat mechanisms the treatment is causing the degradation To this end it isendeavoured to suggest possible mechanisms for each degrading treatmentand to suggest how this study may be modified or another devised such thatthese conjectures can be confirmed Through the course of the study it wasfound that further studies had to be undertaken or that some studies had to bedropped therefore whilst a plan was devised from the outset it was found thatfollowing this plan to the letter proved almost impossible 2Project Number 2004056 Matthew Smith 2001157732 Procedure21 Sample preparationAll laboratory conditioned samples were produced from a 9mm Polyamide 6half rope manufactured by Edelrid for the ropes technical data seeappendix A further two sample sets were produced from ropes procuredfrom the RAF Outdoor Activities Centre Table 1 details all the samples thatwere tested It shows which rope each sample set was made from whatcondition they were subjected to the relative time dependency of thetreatment and the subsequent conditioning period Sample set Rope Condition Relative time Condition dependency period 0106 Old half 10yr service 0 0 life 1116 Rocky half None 0 0 21 24 Rocky half None 0 0 3138 Rocky half None 0 0 4146 Rocky half Dry frozen 2 7 days 5156 Rocky half Heat treated 5 14 days 6168 RAF CC5 1yr service 5 60 days life 7178 RAF CH8 1yr service 5 19 days life 8186 Rocky half Wet frozen 3 7 days 9196 Rocky half Wet dried 4 14 days 101106 Rocky half Roof samples 5 91 days 111116 Rocky half Wet salted 4 14 days 121126 Rocky half Dry salted 4 14 days 131136 Rocky half Sand treated 1 7 days 141146 Rocky half Core only 0 0 151156 Rocky half Aged 5 176 days samples 161166 Rocky half Fresh wet 4 7days Table 1 listings of all samples tested with rope condition time dependency and conditioning period 3Project Number 2004056 Matthew Smith 200115773The relative time dependency determined how long each sample should betreated for A low time dependency required little conditioning time to achieveits effect The total time available for testing also had an influence on period that could be used211 Old half ropeThe old half rope was obtained from Dr A J McLaren This rope 10 years old and contained many surface defects It was usedfor configuration tests which determined the best way with which to constrainand load the samples212 Baseline testsSamples 2124 and 3138 were tested in an as new condition Thisallowed the measurement of the baseline performance of the rope in terms ofload carrying capacity and Dry frozenSample set 4 was subjected to a 7 day freezing treatment The samples wereloaded into a chest freezer again in an as new condition which was set at atemperature of 25C After the conditioning period they were removed andimmediately tested such that the minimum level of thawing was incurred214 Heat treatedThe heat treated sample set was subjected to a temperature equivalent to themaximum ambient temperature that a rope would likely encounter A 4Project Number 2004056 Matthew Smith of 50C was set in a fan assisted oven This treatment wasdeemed to be highly temperature dependent so a conditioning period of 14days was applied215 Wet frozenThis set was subjected to the same freezing treatment detailed in section213 However before freezing the samples were soaked in a container offresh water for a period of 24 hours Again it was important that the timebetween removal from the freezer and testing was kept to a minimum Theambient laboratory temperature was also noted such that any effect from thismay be noted216 Fresh wet and wet driedBoth of these sample sets were subjected to a 7 day immersion in a containerof fresh water The only difference being that the fresh wet samples weretested immediately after removal from the water whereas the were left to dry in a cool dark environment for a further 7 days217 Wet and dry saltedThis treatment was carried out in exactly the same way as in 216 The onlydifference being that the water used for conditioning was salt water This saltwater was designed to replicate that which may be found around the shores ofthe UK As such an aquarium salt was used mixed to a specific gravity of1022 using a hydrometer 5Project Number 2004056 Matthew Smith 200115773218 Sand treated samplesThe sand conditioned samples were produced by firstly rubbing sand into therope by hand and then leaving for a period of seven days entirely coveredwith sand before testing The samples were removed from the 24 hours before testing and any excess sand on the sheath wasshaken off219 Core only samplesIn order to determine what proportion of load was carried by the core a setwas prepared where a portion of sheath was removed from the centre of thesample This left a section of sheath at either end so that the method could be used Care was taken not to damage anystrands of the core such that the result would be Aged samplesIn order to gauge any effects which ageing might have on the performance asample set was left untouched in a dark dry cupboard for the period of theproject The samples were removed at the last available opportunity andtested as normal2110 Roof samplesThis sample set was left on the roof of the James Weir building for a period of91 days The conditions for the period were recorded using the station The data deemed most relevant was that of the amount ofrainfall recorded and the amount of UV radiation experienced Ultra violet 6Project Number 2004056 Matthew Smith was found to have a detrimental effect on a ropes performance in astudy by Signoretti 1 The total rainfall recorded was 5054mm and a totalradiation of 311762 kJm22111 RAF rope samplesTwo rope samples were procured from the Royal Air Force Outdoor These ropes were used in the instruction of novice climbers using atop roping technique Both ropes were used for a period of exactly one yearwith rope cc5 being used a maximum of 63 times and ch8 a maximum of 19times Cc5 was used in a sea cliff environment and ch8 in an inshore cliffThese ropes were visually inspected and any defects noted with the use of aMacro Camera They were then split into the appropriate lengths with theposition of each rope in the original sample being noted These ropes wereboth 11mm single ropes 7Project Number 2004056 Matthew Smith 20011577322 Test apparatus and methodThe desired method for testing dynamic climbing ropes is detailed in EN 892 4 This involves the use of a dynamic testing machineknown as a DODERO It was deemed that due to the expense and timerequired for the construction of such a rig it would be more suitable to use aslow speed tensile testing machine a decision which is supported by a studyby Casavola and Zanantoni 5 In order to restrain the samples a pair ofshackles was obtained originally used for the testing of high strength fabricbelts Each shackle consisted of a solid steel drum of 110mm diameter Thedrums were held in a pair of a parallel plates and a locking plate was attachedto the plates The ropes were secured to each shackle by wrapping the ropetwo times round the drum and using a locking knot to prevent the sampleslipping through the locking plates as shown in figure 1 The drums raisedstresses in the ropes such that a true representation of the ropes strengthwas not obtained It was not possible for the ropes to be restrained stress but as this study aims to compare the relative strengths of theconditions it was decided that these stresses were not to the detriment of thestudyThe shackles were loaded into testing machine MOM35 and a distance of200mm was set between the two shackles and two marks made 100mm apartin the centre of the gauge length The sample was loaded to 1000Lbs and thedistance between the two marks remeasured This was used to compare therelative of the samples The samples were then loaded to 8Project Number 2004056 Matthew Smith The failure load was recorded from the both the analogue and from the apparatus Fig 1 testing rig set up and shackle detail 9Project Number 2004056 Matthew Smith 2001157733 Results and discussions31 Analysis methodThe breaking loads and extensions were recorded for each of the samplestested The values for the breaking load were taken from an analogue scaleas the digital readings were taken only once every 3 seconds such that it wasunlikely that a reading would be taken at the precise moment of failureThe mean breaking loads and extensions were calculated from the data Itwas decided that in order to determine whether a result returned wassignificant then the standard deviations in the sample sets should becompared Charts were then constructed using the standard deviations aserror bars this allowed the comparison of each result against the baselineThe standard deviation calculation was taken as the following 6 x x 2 1 1 n 1If there was no overlap between the first standard deviations of two samplesets then a confidence level of 68 could be applied If the second errors displayed no overlap then this confidence rose to a level of95 It was decided that a confidence level of 68 would be satisfactory32 Results 10Project Number 2004056 Matthew Smith 200115773The results returned from the analysis are described in the charts below Thedata from which these charts have been drawn are shown in the appendix Adata number was allocated to each treatment to allow for easier 20 19 baseline mean breaking load kN 18 dry frozen 17 heat treated 16 wet frozen 15 wet dried roof samples 14 wet salted 13 dry salted 12 sand treated 11 core only 10 aged samples 0 1 2 3 4 5 6 7 8 9 10 11 12 13 fresh wet data numberChart 1 mean breaking loads of laboratory conditioned samples witherror bars corresponding to 1 standard deviation 11Project Number 2004056 Matthew Smith 200115773 19 mean breaking load kN baseline 185 dry frozen heat treated 18 wet frozen wet dried 175 roof samples 17 wet salted dry salted 165 aged samples fresh wet 16 0 1 2 3 4 5 6 7 8 9 10 11 12 13 data numberChart 2 mean breaking loads with error bars corresponding to 1standard deviation not showing sand treated and core only samples 47 baseline dry frozen mean extension mm 42 heat treated wet frozen wet dried 37 roof samples wet salted 32 dry salted sand treated core only 27 aged samples 0 1 2 3 4 5 6 7 8 9 10 11 12 13 fresh wet data numberChart 3 mean extensions at 1000lbs with error bars corresponding to 1standard deviation 12Project Number 2004056 Matthew Smith 20011577333 Discussions331 Dryfrozen and heattreated samplesFrom charts 2 and 3 it can be seen that the error bars of the mean breakingloads and of both the heattreated and dryfrozen samplesoverlap with those of the baseline sample The difference in by the heattreated sample is on the verge of being significant and alarger sample set may have returned this result However from the datagathered it should be said that neither the dry freezing of the rope nor a highambient temperature produces a significant change in performance from abaseline sample332 Wetfrozen samplesFrom studies on wetfrozen ropes carried out on the DODERO 1 it wasfound that the thawing of the rope due to friction influenced the It was hoped that a slow speed test may improve the accuracy ofthese results However it was found that the use of a slow speed machineproved more problematic Due to the difficulties in working the rope it wasfound impossible to break within the travel of the testing machine It wasdecided that the ropes should be thawed entirely and dried so that anydifferences between this rope and the wetdried samples could then be said tobe due to the freezing process From charts 2 and 3 it can be seen that theperformance of the wetfrozen rope is significantly worse than the baselinebut not significantly different to that of the wetdried samples It can be seen 13Project Number 2004056 Matthew Smith 200115773that the mean values for the wetfrozen rope are closer to the mean baselineload than the wetdried this may be due to the freezing action inhibiting effect that water has on polyamide 6 structures 7333 Wetdried and freshwet samplesIt can be said with 95 confidence that the freshwet sample produces asignificantly worse load carrying performance than the baseline It can also besaid that the freshwet samples produce a significantly worse load than the wetdried 68 confidence This implies that effects of the water are to some extent reversible If it isassumed that the freshwet samples are to be 100 plasticized it can beinferred that the drying of a wet rope brings the polymers back to a level ofbeing only 56 plasticized This would then imply that if a rope becomesmore than 44 plasticized then this plasticization is then permanent and Wet and dry salted samplesIt was found that both these samples performed worse than the baseline inload carrying capacity 68 confidence but with no significant difference The freshwet sample had a significantly lower breaking loadthan the wetsalted set 68 confidence this may imply that there is somemechanism which prevents the water plasticizing the polymers The wetsalted and wetdried are not significantly different from each other This may 14Project Number 2004056 Matthew Smith 200115773imply that the plasticization which has occurred in the rope is still recoverableit has not gone above 44It is possible that there is an osmotic action in operation due to the high in the solvent The rope may act as a selectively hindering the passage of salt into the core This will mean that thesalt is at a lower concentration in the rope and as such the fresh water whichhas penetrated the rope will seek to dilute the salt in the solution therebyleaving the rope This could be confirmed by testing the rate of in fresh water and salt water solutions335 Sandtreated and coreonly samplesThe sandtreated and coreonly samples results were very similar with bothmean loads varying significantly from the baseline 95 confidence Thecore did not return a significantly different extension as may be expected butthe sand treated did This could be accounted for by the fact that moisturefrom the sand was absorbed and that some plasticization may have occurredThe difference in load can be accounted for in the coreonly sample as only62 of the rope proportion is carrying the load for the ropes technical datasee the appendix Manufacturers guide books 8 warn against the effects ofsand having a detrimental effect on the core of the rope However this studyfound that it was in fact the sheath that suffers most from sand all other tests it was found that the samples failed with 15Project Number 2004056 Matthew Smith 200115773sand however the sheath failed first and the core failed progressively afterThis implies that in all the other samples the core was reaching its limit loadbefore the sheath this would be expected from the way the sheath isconstructed however here it is the sheath that is determining the strength ofthe ropeThe cause for this may be due to the increased friction between the drum andthe rope caused by the sand This friction may restrict the movement of thesheath whilst allowing the core to slip There may also be a serration effect onthe polymers due to the sharp granular nature of the sand particles336 Roof and aged samplesNeither the roof nor aged samples returned significant differences in load orextension This was as expected for the aged samples as previous studies 9have shown age to have no effect However a treatment period of 91 days ofwinter conditions may be expected to cause some degradation This lack ofdegradation could be explained by the fact that the samples were held clear ofthe ground and so there was no prolonged exposure to water Thedegradation due to UV light would be minimal at this time of year due to skyconditions and the position of the sun This then may imply that it is not onlythe type of treatment that is applied to the rope but more the intensity of thistreatment which determines the amount of degradation in performance 16Project Number 2004056 Matthew Smith 200115773337 RAF rope samplesThe data returned for the RAF rope samples are shown in the appendix 23 21 19 load kN cc5 17 ch8 15 13 11 0 1 2 3 data numberChart 4 mean breaking loads of RAF rope samples with error to 2 standard deviations 17Project Number 2004056 Matthew Smith 200115773 41 39 extension mm 37 35 cc5 33 ch8 31 29 27 25 0 05 1 15 2 25 data numberChart 5 mean extensions of RAF rope samples with error to 1 standard deviation 19 45 18 40 breaking load kN 17 extension mm 35 16 15 30 load 14 25 extension 13 20 12 11 15 10 10 0 1 2 3 4 5 6 7 8 9 position on ropeChart 6 variance of load and extension through the length of rope cc5 18Project Number 2004056 Matthew Smith 2 comparison of sheath damage between area 3 top rope andarea 7bottom ropeIt is clear that there is a marked difference in both load carrying capacity between the ropes This difference is most likely due to cc5 beingused more than three times more often than ch8 The differing by both ropes sea and inland will also have an effect It wouldbe expected that the sand treatment that cc5 has experienced will havelowered the strength but to what extent is uncertain The significance of saltwater treatment can be discounted as it would be expected that the freshwater contacted by ch8 would produce more degradation than any salt in cc5The strength of the rope varies greatly through its length Chart 3 shows thatthere is a possible correlation between the strength and extensibility of therope A low strength seems to be associated with a high extension thiscompares well with the laboratory conditioned samples The difference in 19Project Number 2004056 Matthew Smith could be due to the different loading regimes each area most significant result returned comes from the comparison of figure 2with chart 6 It can be seen that the sample from area 7 has suffered greatlyfrom abrasion to the sheath and the sample from area 3 appears to be ingood order From chart 6 it is seen that area 3 is weaker than area 7 Whencompared with area 1 area 3 also appears less abraded but it is seen thatarea 1 is the strongest part of the rope This implies that a poor indicated a weak rope but the converse is not true a good lookingsheath does not necessarily indicate a strong rope 20Project Number 2004056 Matthew Smith 2001157734 ConclusionsThe project was limited in its scope mainly due to time constraints Givenmore time it is recommended that more samples be tested to decrease theeffect of scatter in the data It would also be beneficial to test more realworld ropes such as the Air Force ropes as these returned significant resultsWhilst it is probable that the conditions tested will not weaken the strength ofa rope by more than 10 it should be well noted that these factors whencombined with a fall situation could lead to rope failure This applies mainly tofresh water contamination and especially sand contamination where only 70of the strength of the rope was maintained Further studies may wish toinvestigate the mechanisms for these degradations including osmosis in saltwater treated ropes plasticization and rate of water absorption in fresh waterand salt water treatments and the failure of sheaths at low load due to most significant results returned were i That the degradation due to environmental conditions depends on type time and intensity ii Intense fresh water treatment produces up to a 10 loss of strength almost immediately iii Some of the degradation is recoverable by drying the rope although a portion will be permanently plasticized iv Water degradation is inhibited by the freezing of a rope 21Project Number 2004056 Matthew Smith 200115773 v Water degradation is inhibited by the presence of salt vi Dry freezing or high ambient operating temperatures have no discernible effect on a ropes performancevii The scatter in results is due largely to the variability of the treatment processviii Samples treated with water exhibit less scatter than other treatments ix Sand contamination produces the biggest loss in performance x It is more harmful for sand to be in the sheath than in the core which apparently contradict statements made in manufacturers guide books 8 xi Strength varies greatly through the length of a used ropexii Sheath damage may indicate low strength but perfect appearance does not indicate good performance 22Project Number 2004056 Matthew Smith Material Polyamide 6 Nylon Diameter 9mm Weight per meter 51gm Number of falls 12 Impact force 66Kn Sheath slippage 0mm Elongation in use 88 Proportion of sheath 38 Knotability 07 Table 1 Technical data for the Edelrid rocky half rope used for laboratory conditioning Data Mean Breaking Load Condition Number kN anlg 1 2Baseline 1 18159876 041436111 082872222Dry frozen 2 173691 060183963 120367926Heat treated 3 1773576 041770625 08354125Wet frozen 4 174069 0217144468 0434288936Wet dried 5 171612 034644272 6 178038 044404946 088809892Wet Salted 7 1709505 01701 03402Dry Salted 8 171234 039282912 9 129843 0726114289 1452228578Core Only 10 11718 069288545 11 171234 074361353 12 164808 017322136 034644272 Table 2 mean breaking load and standard deviation results returned for all laboratory conditions tested 23Project Number 2004056 Matthew Smith 200115773 Data Extension Condition Number mm 1 2 Baseline 1 353 287 574 Dry Frozen 2 308 232 464 Heat Treated 3 318 075 15 Wet Frozen 4 3825 2061553 4123106 Wet Dried 5 41 1 2 Roof Samples 6 3325 1892969 3785939 Wet Salted 7 3825 2629956 5259911 Dry Salted 8 4025 2629956 5259911 Sand Treated 9 445 2645751 5291503 Core Only 10 35 3 6 Aged Samples 11 37 1 2 Wet Ropes 12 42 3464102 6928203 Table 3 extensibility results returned for all laboratory conditioned samplesRope label CC5 CH8Start date 171103 211003End date 161104 201004Times used max 63 19 Table 4 RAF rope information mean breaking sample load kN 1 st dev s st dev cc5 1481382 174870987 349742 ch8 206577 075703879 1514078 mean extension sample mm 1 st dev 2 st dev cc5 3725 2810694 5621388 ch8 29625 2529822 5059644 Table 5 results returned for the mean breaking load and extension of RAF rope samples 24Project Number 2004056 Matthew Smith author would like to thank his supervisor Dr AJ McLaren for hiscontinual help and guidance over the course of the studyThanks are extended to Mr A Crockett who helped to run the throughout the whole of the studySgt P Gray of the Universities of Glasgow and Strathclyde Air Squadron andMr A Wells of the RAF Outdoor Activities Centre Grantown for their adviceand generosity in providing materials for the studyMr E Duncan Mr C Cameron and the technicians who provided advice andsupport with laboratory equipment and testing facilitiesMs S Mcvie student and Mr G Bartlett of the national and Archive for the environmental information they kindly provided 25Project Number 2004056 Matthew Smith SIGNORETTI G The Influence of Water Ice and Sunlight on the Dynamic Performance of Climbing Ropes La Rivista del Club Alpino Italiano 20012 ZANANTONI C SharpEdge Rope Testing Status and Prospects Commissione Centrale Materiali e Tecniche Torino March 20023 Henkel O Sharp Edge Testing of Rope Commissione Centrale Materiali e Tecniche Torino March 20024 BS EN 897 Mountaineering equipment Dynamic mountaineering ropes Safety requirements and test methods October 19965 CASAVOLA P ZANANTONI C Rope Testing and Wear Equipment of the CMT Commissione Centrale Materiali e Tecniche 20036 BOWKER AH and LIEBERMAN GJ Engineering Statistics Prentice Hall 1972 2nd Edition7 CALLISTER WD Fundamentals of Materials Science and Engineering John Wiley and Sons 2001 26Project Number 2004056 Matthew Smith 2001157738 MAMMUT ROPE MAMMUT Sports Group AG 20049 BRESSAN G Rope Wear in Climbing and in the Laboratory Commissione Centrale Materiali e Tecniche Torino March 2002 27

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