Low Angle Rope Rescue Outline

Transcription

1 Low Angle Rope Rescue Outline Low angle rescue techniques differ from high angle skills in more rescue personnel at risk on the litter, more tension on the ropes, but less potential for free falls during a major system failure. These techniques are usually used by fire departments and mountain rescue teams for over an embankment, or mountain rescue situations. Litter operations using the aerial as a means to remove a victim from a elevated incident requires preplanned tactics to overcome the dynamics of the operation. Scenario Overview: A. Where do we need low angle rescue? Give examples B. Where do we need to use aerial pick-offs? Give examples Equipment: A. Personal equipment- seat harness, the proper level of PPE should be worn by all entry and back-up personal, helmet, gloves, proper boots. B. Software and Hardware 1. Rope: 200' and 300' ''/z " static kernmantle bs./44kn 2. Prusik Cord: 7mm and 8mm 22001bs./lOkn bs./12kn 3. Webbing: 1" flat 6000lbs.126kn 4. Carabiners: Steel and Aluminum locking bs./72kn 7000lbs./30kn 5. Rescue 8 with ears: Used for one person self lowers 8093+Ibs./36+kn 6. Pulleys: 2.5" prusik minded, 2" single pulley bs.136kn 7. Brake Rack 4000lbs./26kn 8. 4:1 Mechanical Advantage 'W' static kernmantle 99001bs./44kn 9. Litter Harness with 4 steel carabiners bs./44kn C. Knots Overhand Figure 8 Figure 8 on Bight Figure 8 follow through Directional Figure 8 Butterfly Bowline with Safety Double sheet Bend with Safety Webbing- Water bend, Overhand Hitches- Munter, Load release Prusik- Double fisherman ' s, 3 wrap D. Anchors: 1. What can be used for an anchor? a. Anything that is bomb proof b. Trees, vehicles, rocks, posts, guardrails, etc. c. Back up questionable anchors 2. Single Point Anchor (wrap 3 pull 2, basket hitch) 3. Tensionless Hitch 4. Load Sharing Anchor (multi anchors overhand knot to make load pull at certain point) 5. Critical Angles Page 1

2 E. Mechanical Advantage: 1. What is a mechanical advantage? Enables a rescuer to lift a load applying less force than the load itself, but over a longer distance. 2. What is the disadvantage or short fall of a mechanical advantage?(the bigger the MA the more rope used to move load a short distance) 3. Simple, Compound, Complex. a. Simple pulley systems are characterized by having one continuous rope flowing back and forth alternately between the pulleys on load and the anchor (or the anchor and the load), and all pulleys at the load side (referred to as traveling pulleys) travel towards the anchor at the same speed. All pulleys at the anchor side of the system remain stationary. The tension in the rope remains the same throughout the pulley system. b. Compound pulley systems are characterized as one simple pulley system pulling on another simple pulley system; the traveling pulleys travel towards the anchor at different speeds. Compound pulley systems are useful because they can provide greater MA than simple systems for the same number of pulleys, thereby reducing overall friction loss for the same MA. c. Complex pulley systems are characterized by being neither simple nor compound. There is no one definition that characterizes all complex systems due to their greater diversity. Complex pulley systems are not being seen in rescue work, similar objectives can be met using Simple or Compound pulley systems that are easier for rescuers to recognize and are more flexible for modifications as required. 4. Simple Systems- Demonstrate how to set up each one. a. 1:1 b. 2:1 c. 3:1 d. 4:1 e. 5:1 5. Compound Systems- Demonstrate how to set up each one. a. 6:1 b. 9:1 F. Litter: l. TieIns a. Patient tie in. b. Attendant attachment. 2. Number of attendants a. scree slope * 4 to 6 personal. b. scree slope 40-60* 3 personal. G. Lowering System: Scree 1. Brake rack 2. Rescue 8- one person self lowers.(used to get paramedic down to vehicle or patient) H. Raising System: 1. Counter balance/ change of direction a. Concern: doubles the load on the anchor with rope coming back 180*, b. Bombproof anchor. 2. Mechanical advantage Page 2

3 I. Belay System: I. Tandem Prusik Belay- What is it? Why we use it? When to use it? How to set it up? J. Aerial Operation: Look at photo's- We do not want to rely on ladder to move litter up or down. NO ATTENDANT 1. Litter setup 2. Belay line setup 3. Webbing with large carabiners setup 4. 4:1 setup 5. Tagline if needed setup Page 3

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5 10:1 safety factor Brake rack 26kn/4000# 1-person load 1 kn/200# PMP pulley 36kn/8093# 2-person load 2kn/440# Alum. Carabiner 30kn/7000# 3-person load 3kn/660# Steel Carabiner 72kn/16185# 7mm 1 0kn/2200# Brake tube 44kn/10000# 8mm 1 2kn/2875# Micro 4:1 31kn/7000# 7/16" rope 30kn/7000# CMI mini rack 62kn/14000# 1/2" rope 44kn/9900# Rigging plate 36kn/8093# 1/2" knotted 30kn/7000# 1" webbing 17kn/4000# 5/8" rope 53kn/1 1900# wrap 3 pull 2 35+kn/8090+# 5/8" knotted 36kn/8093# RRH 30+kn/7000+# Page 5

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16 VICTIM TIE-IN EXTERIOR LASHINGS Do interior lashings first (upper torso & lower torso). Start with Litter Strap #1 (foot stirrups). Finish with Strap #2 (exterior lashing). All straps start with a bowline and a safety. They are finished with a round turn with two half hitches. Do not wrap or tie knots around the large rail. This could catch on the rocks during rescue. Scraping against rocks will damage webbing. Placement of straps may be modified to accommodate specific injury sites. Tape or tie the patients hands together. Page 16

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19 Rescue Systems Testing (background summary) British Columbia Council of Technical Rescue Research Section Box 399, Invermere, B.C. Canada, VOA 1K0 August 2, 1990 The B.C. Council of Technical Rescue's first tests were done in conjunction with the Provincial Emergency Program's Third Annual Technical Rescue Seminar held in March of As more testing took place each succeeding year we had to hold the testing as a separate session outside of the annual week long seminar. These tests were expanded further during test sessions that took place in Denver, Colorado (fall' 87) and Sedona, Arizona (spring '89). The BCCTR has the following minimum standard: wi t h a 200 kg mass (two persons + equipment) tied to 3 metres of rope the belay system must be able to withstand a 1 metre drop of the load and stop it in less than 1 metre of additional travel and with less than 15 kilonewtons of force. It is of great concern that a number of systems in present use cannot manage this bare minimum! To date the only belay system tested successfully in accordance with the above standard is the Tandem Prusik Belay. Like any other belay technique it requires competent training and continued practice for safe operation, but it is also relatively easy to learn and does not rely on the strength of the belayer. The Tandem Prusiks are of unequal lengths and are clipped into the same carabiner, generally with an LR Hitch between the prusiks and the anchor. The prusiks are pushed together for ease of handling during most operations. During raises the Prusik Minding Pulley makes their use particularly easy. Two prusiks are needed where shock loading is a possibility, such as the belay line, and are also desirable in high load situations such as highlines. They do not share the work equally though and the primary purpose for having two is not to increase the tension at which slippage occurs to twice what it was with one prusik (for that does not hold true) but rather to have twice as much mass of nylon that must be melted before failure occurs. A single 8 mm 3-wrap prusik of nylon kernmantle low-stretch cord is suitable for ratchets and connecting the pulley system to the main line. On rigid towers tandem 8 mm 3-wrap nylon kernmantle prusiks gripping an 11.1 mm low-stretch belay line, would consistently hold a 175 cm fall in Denver and a 200 cm fall in Sedona (250 cm if only tests of nylon prusiks on a nylon belay line are considered), In Denver a Gibbs ascender would totally cut off the rope and the test block crash to the ground on a 75 cm fall. At 50 cm the Gibbs often does serious damage, if not cutting the rope, then tearing the sheath and bunching it up the rope or forcing the rope beside the cam. Even on a 25 cm drop the Gibbs often starts to display this condition where the rope is forced around the side of the cam and between the cam and the side plate of the U shell. Since the Gibbs was considered, until the recent introduction of the Rescucender, to be the most gentle ascender, one was not surprised to see that other ascenders damaged the rope on similar drops. To date no ascender tested has met the BCCTR 1 metre minimum. Most manufactures include (or should) a notice in their material that their ascenders are designed for a single person ascending a line. New slow pull tests applying constant tension have shown that many of them will totally cut off a 11.1 mm nylon kernmantle rope without warning at 1/3 of the its rated strength or less. Many safety minded rescue groups will not use ascenders in haul systems or as ratchets. Page 19

20 Failures during tests in the mid 1980's showed that belay devices such as slot type belay plates and descenders allowed transmission of forces to the belayer that could result in injury. Not desiring to hurt anyone, these tests were discontinued. More recent tests have shown that a rescue load cannot be held even statically (no fall Involved) by many slot type belay plates. Manufactures of these devices should be encouraged to document the units efficiency (output/input) with representative ropes so the purchaser can see if it is below the.05 efficiency level the BCCTR recommends as a ceiling for belay devices to be used with rescue loads. When tested in Denver with an LR Hitch between the tandem 8 mm prusiks and the anchor the combination once held a 300 cm fall (fell factor of 1). In Sedona this same combination held a 300 cm fall with some materials but not with others. Without an LR Hitch wet prusiks managed a 275 cm fall and wide spaced prusiks 300 cm. One may feel that a larger diameter prusik may be desirable since melting does occur within the prusiks when such severe falls are arrested, however this has not been confirmed. It appears (all else equal) that larger diameter prusiks do not grip quite as well and slip further, which generates more heat. There may be a case for using 9 mm prusiks (if suitable materiel can be found) on 12.7 mm belay lines but further testing is necessary. One must keep in mind that less stretch in a larger diameter rope will mean that more of the energy of the fall must be absorbed at the belay rather than in the rope itself. I will caution you that texture, stiffness, sheath thickness etc. of the prusik material can have some affect on its performance. Our supply for 8 mm nylon kernmantle accessory cord is the European manufactures such as Edelrid, Mammut etc. and this is our present standard. Our tests indicate that other materials such as Wellington-Puritan polyester Prusik Rope has a tendency to grip too well and often fails instead of sliding. Erratic results suggest that one should also stay away from ropes coated with Rhino-Kote if you intend to use prusiks for belaying. All our information indicates that prusiks of suitable materials perform better as a belay than mechanical rope clamps even when wet or muddy. Prusiks tighten in to the diameter of the rope (within reason) and grip it all around it's surface. When slippage occurs they generate an operating temperature that is suitable to the materials and energy absorption needs we are dealing with. The water seems to be driven off by the heat. This added energy outlet, for wet prusiks, may actually make the prusik stand up better. The behavior of prusiks on "icy" ropes has yet to be determined, however test results confirming that falling rescue loads can be successfully arrested by the use of mechanical rope clamps, descenders or slot type belay plates used on "icy" ropes are not available either. While it is true that different materials give different results, this must not be blown out of proportion. Assuming that the material is not too stiff to work well as a haul or ratchet prusik, is sufficiently large (a mm), and two 3-wrap prusiks are used in tandem, then it can be said that you have a better chance of catching a severe fall with prusiks (regardless of whether they are nylon, perlon, polyester, braid on braid, plaited, kernmantle, 3 strand twisted) than with mechanical rope clamps or slot type belay plates. And when using nylon kernmantle low-stretch prusiks on a nylon kernmantle low-stretch belay line the improvement is significant. Let me know if you have questions, concerns or corrections. Submitted by, Arnor Larson (copyright 1990) Note: (This sheet is a brief summary and does not give the details necessary to operate a Tandem Prusik belay safely.) Page 20

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23 Pulley Systems Terms & Definitions MECHANICAL ADVANTAGE (MA): The ratio of the load to the pull required to lift the load. For example if 1 kn of force is required to raise 2kN, the mechanical advantage said to be "2 to 1" or 2:1. Mechanical Advantage is gained at the expense of endurance. Even though, less force is required, it is required over a longer distance. IDEAL MECHANICAL ADVANTAGE (IMA): The MA of a pulley system without taking into account friction and other factors. ACTUAL MECHANICAL ADVANTAGE (AMA OR PMA): The actual observed and/or measured MA when the pulley system is being pulled on. THEORETICAL MECHANICAL ADVANTAGE (TMA): The estimated actual (or Practical) MA that is calculated when friction losses are taken into account. PULLEY SYSTEM: Combination of fixed and traveling pulleys and rope used to create MA. TRAVELLING (MOVING) PULLEYS: Those pulleys in a pulley system that move toward the anchor when the Pulley system is pulled on. STATIONARY (FIXED) PULLEYS: Those pulleys in a pulley systems that do not move when the pulley system is pulled on (usually those pulleys at the anchors). EFFICIENCY: Me measure of friction loss calculated as the input force over the output force, expressed as a percent. For example if 90 N is required on 1 side of a pulley to hold a 100 N load on the other side, the efficiency of the pulley is said to be 90% or 90/100. In pulley systems, this ' is typically the efficiency of pulleys and carabiners (if used). RESET: As a pulley system is pulled on, it collapses to the point where I or more of the traveling pulleys meet the stationary pulleys. At this point the load cannot be pulled up any further. The term reset describes the act of re-expanding the pulley system to its original dimensions so that pulling may continue. RESET OR THROW DISTANCE: the distance that a pulley system collapses between resets. HAUL PRUSIK: the Prusik in the pulley system that is closest to the load that attaches the pulley system to the mainline going load. RATCHET PRUSIK: A Prusik used to hold the mainline while the haulers reset the pulley system, so that progress is not lost. ' SELF-MINDING RATCHET': The use of a Prusik Minding Pulley to mind the ratchet Prusik and therefore eliminate the need for a rescuer to mind it. Page 23

24 The T-Method for Pulley Systems A pulley system's Ideal Mechanical Advantage 1 (IMA) is expressed as a ratio of the amount of output force to the amount input force (e.g. 6:1 or "6 to 1 "). The input force is the tension you apply to the system, and it is always expressed as one. One method of calculating the IMA of any pulley system in the world is often referred to as the Tension Method, or T-Method. Some basic physics principles need to be understood and applied to knowing how tension is distributed through a pulley system. Mechanical advantage in pulley systems is gained by increasing the number of times your initial one unit of tension is applied to the load. Recognize that there are many ways that this can be accomplished, or rigged, using simple, compound or complex pulley systems. By assigning one unit of tension (called "T" in subsequent diagrams) to where you pull on the pulley system, then following the path of the rope through the pulley system to the load itself, the 1MA can be determined by keeping track of how that initial unit of tension is distributed throughout the system. Simply compare the amount of tension the load receives to the initial input unit of tension. The key to understanding the T-method is in recognizing what happens to the tension in the rope as it flows through the pulley system. Whenever there is a 'junction' in the ropes of the pulley system where either more than one rope acts on another rope, or one rope acts on more than one rope, then the tension on one side of the junction must he equal to the tension on the other side of the junction, and for each side of the junction, the tension must be distributed appropriately (not always equally) to each rope. For example, if a rope having one unit of tension makes a 180 change of direction through a pulley (a junction), then whatever that pulley is connected to receives two units of tension (Fig 1). In essence, two ropes each having a tension of one (for a total of two units of tension) are acting on (and being opposed by) what the pulley is connected to. Below are some illustrations of tension distribution in ropes at junctions: 1 Ideal Mechanical Advantage assumes that there are no losses in pulley system mechanical advantage due to factors such as pulley friction. or ropes rubbing, bending or unbending. Pulley System Graphics created by Earl Fröm Page 24

25 The T-Method for Pulley Systems Summary of how to apply and use the T-Method to Calculate the I MA of any Pulley System: 1. Assign one unit of tension to where you pull on the pulley system. 2. Follow the rope through the pulley system and when you encounter a junction, apply the principles of tension distribution. Keep track of all units of tension through to the load. 3. Total all units of tension that reach the load; the Ideal Mechanical Advantage is the ratio between this total and the initial one unit of tension. Examples of using the T-Method to Calculate the IMA of pulley systems. Page 25

26 The T-Method for Pulley Systems Calculating the Theoretical Mechanical Advantage (TMA) The TMA is the estimated Actual Mechanical Advantage (AMA) calculated after taking into account factors that affect IMA; the largest component of which is friction. The greatest friction losses occur as the rope comes into contact with the pulleys. Sometimes carabiners are used in place of pulleys which results in an even greater friction loss. To calculate the losses due to friction, one must first know the efficiency of the pulleys and/or carabiners being used. Efficiency is the measure of friction loss calculated as the input force over the output force, expressed as a percent. For example if 90 N is required on 1 side of a pulley to hold a 100 N load on the other side, the efficiency of the pulley is said to be 90% or 90/100. With efficiency information, the friction loss through the system can he calculated. Figure 7 shows the calculations for a pulley system with pulleys that have an efficiency of Page 26

27 The T-Method for Pulley Systems Assuming that the pullers pull at the end of the pulley system with 1 unit of Tension (1T), only 0.90 T will be transferred past the first pulley. When that 0.9 T reaches the 2nd pulley, only 0.81T will be transferred on (0.9 * 0.9 = 0.81) as the friction loss is now compounded over two pulleys. Follow this process all the way through the pulley system. When you are finished, use the T-method to determine the final TMA, which in this example is 2.7 1:1. If higher efficiencies pulleys are used (i.e efficiency), the TMA is increased to 2.85:1, which is closer to the IMA of 3:1. Also important to note, is that if you are using pulleys of different efficiencies, less losses occur if the most efficient pulley is placed closest to the pullers. This is because the loss at the 1st pulley is compounded throughout the system. Page 27

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34 Rope Rescue for Aerial Operations Purpose: To evacuate an injured party from a roof or elevated platform using the aerial apparatus. Maximum ladder tip load is 500lbs. This applies to the main and fly section of the ladder and not the extension bolted to the end. (Orange section) No attempts should be made in utilizing the orange section for any load application. Set-up for Aerials with eyelets: Equipment needed flat webbing. 2 Large Steel Carabiners Tie an overhand bite on both ends of webbing and place carabiners into loops. Attach each carabiner into fixed eyelets at ladder tip. Create a focal point centered below the ladder by tying an overhand knot in the webbing. Mainline- Connect pre rigged 4:1 into centered webbing attached to ladder with upper pulley having progress capture on it, (release with cord). Bottom pulley and carabiner get attached into litter harness tri-link. This is the complete mainline set-up which enables you to raise or lower basket via the 4:1. Litter set-up: Junkin litter w/ CMC litter harness. The red straps go to the head, blue to feet. When lifted at the tri-link, the basket should have a slight head up aspect. Patient tie in procedures are shown in book and accompanying photos. Belay Line set-up: Equipment needed. 2-8mm prusik cords (1 short/1 long) for tandem prusik belay, /2 rope, 1-20 flat webbing, and 1-prusik minding pulley. Tie webbing in the center at base of ladder for anchor. Run ½ line up center of ladder, pass rope over the rung corresponding to eyelets, and down to litter. Tie a bowline with long tail and attach bowline to tri-link. Long tail gets a figure 8 on a bite with carabiner connected to patient seat or chest harness. Attach rope to anchor at base of ladder with the 2 8mm prusik cords and include the prusik minding pulley. Should attach in order from anchor. Carabiner, short prusik, long prusik, prusik minding pulley. Ensure that prusik s are on the spine of carabiner. On trucks without pin-able waterways to keep rope centered on ladder, use a 7mm prusik with carabiner. Should be attached opposite side to which rope descends next to nozzle/waterway. See photo. Most, if not all, elevation moves should be made by the 4:1 once the victim is in the system. While lifting, the belay needs to be kept tight and managed separately from aerial operation. If extension or retraction is needed on the aerial device, the belay person and D/O need to work in a coordinated effort to maintain proper belay tension and control as these movements will affect belay length. Corresponding photo s of all knots and applications accompany this directive. This is for fixed lifting only. No attempt of rescue rappels or belays shall be attempted from aerial devices for any reason. Page 34

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