*** Hauling System Weak-Link Tests *** Subject: Hauling System Weak-Link Tests Date: Sat, 7 Dec 1996 21:14:16 +1100 (EST) From: Alan Sheehan To: SAR-L@islandnet.com, ses@gec.com.au Thought I'd share some of the test results from our last Vertical Rescue Instructor's Workshop: one of the syndicate sessions was doing some destructive testing on various methods of attaching a bolt-on haul system to the main-line. The following paragraph is copied from the newsletter following the workshop, the results are my interpretation of the graphs (unfortunately I don't have first hand access to the data) and a few comments from the particular session I was involved in. Harry Patz wrote: "The following results were received as a result of 5 syndicate sessions during the VRI wrkshop. As you all know, the weak link in any haul system is the point of attachment on the load line by the haul system. A variety of hard and soft ascenders used by Australian Emergency Services were used, along with the Queensland Emergency Service system which uses a fusible link (4mm cord attaching hauling system to a Shunt ascender which is attached to the load line). The test included three cordages, 11mm Blue Water II+, Kinnears 11mm (pre-Arapaline), and Smiths Safety Group 13mm (USA)." The tests were done as one of the syndicate sessions at the Vertical Rescue Instructors workshop. All instructors were divided into five groups who rotated around the 5 stands (which included, BTW, the ascender/rope tests, prusik rig tuning, edge management, belay devices and systems, and anti-fall systems for storm damage work). The rig was as follows: A-C-O=====================O-C< \_\_\_\_\_C-L-C=8----------------------- where \_\_\_\_\_ represents a pickets and picket plate anchor C represents a karabiner -L- represents a load cell with a needle to remember maximum load achieved =8-------- represents the "mainline" with fig. 8 loop A represents the ascender connecting the haul system to the mainline -O and O- represent the pulleys of the haul system < represents a tape sling (to the FBT anchor) represents a tree better than my ascii art can! :o) Each group conducted a series of tests. Not all the tests were the same, some groups tested different things. Each test simply involved setting up (especially resetting the max load needle!). The haul system used was a 5:1 MA hauling rig, and the haul team consisted of up to 4 or 5 people as required. The rig was loaded until something slipped, or failed. The load was released and the maximum load achieved read from the dial of the loadcell. I don't have details of the load cell, but it is a similar type to what can be bought from Enerpac or similar hydraulic suppliers for proof testing rigging gear (minimum full scale deflection of 5 tonnes, I suggest). Note that all the karabiners, ascenders and ropes used were either previously retired/condemned from life support use or were so after the tests! (And painted with red paint for indentification for future destructive testing). So, the measured loads were loads in the mainline when the ascender/rig slipped or otherwise failed. Different results are very likely if you are concerned about shock loads. We were specifically looking at an overloaded/jammed haul situation, especially what systems allow some sign of overloading without catastrophic failure. The type of load cell used we believe was entirely appropriate for the tests we performed, whether the same type of cell would be appropriate for the sudden transient loads of shock load testing would be subject to testing in itself! BTW maybe it wasn't clear in my original posting, so I'll explain the fusible link (4mm static cord). The fusible link is tied between the running block (pulley) and the ascender attached to the mainline. The intention is that the fusible link is supposed to fail before any damage is done to the system due to overloading. Tests on the 4mm fusible link show it failed at approximately 240kg, 180kg,and 240kg on 11mm Kinears, and 180, 180 and 190 kgs on 11mm BWII+. The link certainly protects the mainline from damage due to overloading, but with a load of a stretcher, casualty and an attendant there's not much allowance for friction. (Note that the fusible link strength is independent of interaction with the mainline, though these result may suggest otherwise). Testing the Petzl Shunt showed that on 11mm Kinnears it began to slip at about 410, 410, 400 and 360 kgs, while on 11mm BWII+ the results were approx. 370 and 310 kgs. On 13mm SSG the Shunt slipped at about 390 kg on the first test. On the 2nd and 3rd tests the Shunt slipped(?) at about 600 and 620 kgs, but in both these cases the sheath of the main line was damaged and the Shunt suffered some distortion of the body. On the 11mm tests that I witnessed, no damage was evident on the rope due to the Shunt slipping. A two wrap 6mm prusik loop slipped at about 400 and 450 kgs, while a two wrap 8mm loop slipped at about 250 and 240 kgs. On my session no evidence of mainline or loop damage was apparent following the slippage. A 3 wrap 8mm prusik loop was found to slip at about 1100, 1400 and 1250 kgs on 11mm Kinnears, and 1300, 1200 and 1700 on 13mm SSG. On the session I was involved with, once the loop started to slip fusion was evident between the mainline and the loop, and they would partially weld together when the load was released. Apart from the Shunt, two other hard ascenders were tested: a Jumar and a CMi 5004. The Jumar let go at about 920 kgs on 11mm Kinnears, and 950 kgs on 13mm SSG. During my session the Jumar completely stripped the sheath right round the mainline when the system failed. The CMi 5004 let go at about 900 kgs on 11mm BWII+ and 840 kgs on 11mm Kinnears. Though we expected the CMi to tear a patch out of the sheath (from previous tests) on my session it stripped the whole sheath, jammed the core up beside the cam and suffered some distortion of the body. In summary, on 11mm rope, rough average loads of failure were as follows: 4mm fusible link 250 kgs No damage to mainline 2 wrap 6mm prusik 400 kgs No damage to mainline Petzl Shunt 400 kgs No damage to mainline CMi 5004 850 kgs Sheath damage to mainline (tearing) Jumar 1050 kgs Sheath damage to mainline (tearing) 3 wrap 8mm prusik 1100 kgs Fusion damage to sheath ------- Alan Sheehan Oberon State Emergency Service, NSW, Australia Oberon Mole Patrol als@ix.net.au AlanS@obe.woodpanels.csr.com.au All opinions are my own so don't blame anyone else... Either lead, follow or get the hell out of the way! ______________________________________