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RAISING / TENSIONING SYSTEMS 


Rescue operations often require evacuations up cliffs or steep slopes. Since a "Load" (defined as the weight of the element that is being raised i.e. litter with tenders, equipment, etc.) can be as much as 600 lbs. (or higher), and a haul team could consist of only a few rescue members, mechanical advantage (T-System calculation) is needed to make a raising system possible. This chapter covers systems used by the rescue team for raising and tensioning (Tyrolean applications) systems.  

Mechanical Advantage systems employed by SAR include the following:  

          3:1 "Z" pulley system  (Read as "3 to 1" advantage)

          5:1 Pre-Rig Haul System

          Vehicle winches  

These systems may be augmented by:  

          2:1 Advantage systems

          Piggy Back systems (3:1 hauling on a 3:1 making a 9:1)

 The following is an attempt to answer, "Why does mechanical advantage systems work?"  Regardless of the type of system used to haul a load, the same amount of technical "WORK" is always done. Work is defined as:  

WORK = LOAD FORCE X LOAD DISTANCE

             = HAUL FORCE X LOAD DISTANCE

WHERE:

FORCE is equal to the weight of the load

DISTANCE is the distance that the load moves (In this case the length of the raise)

HAUL FORCE is the amount of force the hauling team applies

HAULING DISTANCE is the amount of rope hauled by the hauling team  

This ignores the effects of friction in the system. (The best systems minimize friction). Therefore 72,000 FT-LBS of work is required to raise a 600 LB load a distance of 120 ft. independent of the type of haul system that is employed. (3:1, 6:1, 5:1 etc.)   

With no mechanical advantage (1:1) the haul team must haul the least amount of rope (distance) but with the most amount of force. This is the case presented in figure -1. Assuming that each rescuer could haul 80 lbs, 7 to 8 haulers would be required to raise the load. From the definition of work it is apparent that if the distance that the hauling team moves is increased the amount of force that must be applied to raise the load will be decreased, therefore reducing the number of haulers that are required. The device that allows this capability is the pulley.  

Figure -2 is an example of the use of a pulley to generate a 2:1 advantage. In both systems the load will be raised from point A to point B. In system Y (Note the pulley used here is a change of direction only.), the hauling distance is the same as the load distance and therefore the system is a 1:1 system. In system X however, twice as much roped is used in the hauling distance as is used in the load distance and therefore 1/2 as much hauling force is needed in system X as is needed in system Y. This can be verified by using a small piece of string and a little weight.  

To determine the amount of mechanical advantage in a given system, the number of moving lines at the load is the mechanical advantage of the system. (This does not apply directly to piggy back systems that will be discussed later.)  
If the 2:1 system was applied  to the application shown in figure - 1 only half the haulers would be required as is shown in figure - 3.

 The drawback of the 2:1 is that it requires that the available rope be over twice the load distance. (Which for a 300 ft haul would be considerable.)

 3:1  THE "Z" PULLEY SYSTEM

The "Z" Pulley System is quite universal in the SAR community. It is easily constructed from standard rescue gear typically carried by field teams. This system provides sufficient mechanical advantage to suffice rescue requirements if the load is kept to a minimum and at least 4 haulers are available.  

Figure - 4 is a schematic diagram of the 3:1 system. Note that there are now three moving lines at the load.  

If the rescue system were connected exactly as shown in the schematic, even more rope would be required. A "RATCHET" system is employed to solve this problem. Figure - 5 shows the actual implementation of the "Z" pulley system. Two Gibbs Ascenders (prussik ascenders may replace the Gibbs if Gibbs ascenders are not available) are utilized. The ascender closest to the load is named the "Ratchet" ascender, and the ascender attached directly to the anchor is the "Lock-off" ascender. The haul team hauls on the free end on the rope until the ratchet ascender nears the lock-off ascender. The haul team then releases (slowly) some tension to allow the lock-off ascender to assume the load. After the complete load has been taken by the lock-off ascender the ratchet ascender is free to be moved back down toward the load after which the hauling process resumes. A runner or a length of 1"webbing, termed the "Reset Line," may be attached to the ratchet Gibbs to help facilitate the reset operation. This ratchet cycle continues until the load reaches the top or it becomes necessary to re-configure the system to a lowering system. The leader will call out "HAUL," "STOP,"  RESET." "HAUL," to coordinate the activity of the haulers. Note that the 3:1 system is typically comprised of the haul rope.  

It is not necessary to coordinate "RESET-HAUL" commands with tenders or over the radio. The ratchet effect is well known and expected by the tender. This minimizes unnecessary traffic and allows the system to flow more efficiently.  

            Note:  In all applications of the Gibbs Ascender the proper placement of the device requires that the "Fat End" of the ascender to be closest to the anchor. This should always be considered the rule when using Gibbs ascenders in mechanical advantage systems. As is always the case when using hard ascenders in rescue work, slack in the operational lines must be eliminated to minimize the possibility of a hard ascender catching a dynamic load.  

CONVERTING A 3:1 HAUL SYSTEM TO A LOWERING SYSTEM (FIGURE 8)  

The rescuer should be capable of converting haul systems to lowering systems and vice versa with little difficulty. A problem managing a difficult overhang by a litter team may justify a direction change.  

When a change is required the Site manager will command and control the various system level requirements. To convert a "Z" pulley system, follow the following steps:  

    

  1. Replace the pulley with a figure 8 (fig -6a)
       

  2. Remove all slack between the lock-off ascender and the
    figure 8 and lock off the figure 8 (See option note below)
       

  3. Place tension on the normal haul point. (to release tension on the lock off ascender.   

       

  4. When tension is released remove the lock-off ascender (6b)  
       

  5. Release tension on the haul (slowly) to allow the load to be taken by the figure 8. (6c)
      

  6. Remove the ratchet ascender and clip unused hardware in an accessible area (never place equipment in the dirt) (6d)
       
    Note: When converting from a raising to lowering or vice versa, it it critical that the belay line be as tight as possible.
       
    Option to step 2:  If the figure 8 is not locked off, a higher mechanical advantage will be present for step 3. It is important to control the lowering lines carefully and lock-off after step 5. Use this option only if personnel is limited and additional mechanical advantage is needed.

In general, whenever a haul system is to be implemented the necessary lowering station gear should also be readied and clipped into an accessible area. An extra ascender, several biners, and a length of webbing should also be handy in the event a problem arises. In the scenario above, the standard figure 8 brake was used. The system can be adapted to any valid brake. 

In an operation the rescuer assigned to assemble a given station may wear the systems rack of equipment or may mount the equipment in an area accessible to all. It is critical not to lose pieces of equipment or entire racks of equipment due to careless storage. It is even more damaging to drop a piece of system gear onto resources or subjects at a lower station.

PASSING KNOTS WITH THE 3:1 SYSTEM

At times it is necessary to pass knots through a haul system. The knot may exist to eliminate a damaged section of rope or to simply make a longer haul line. (Combining two 200 ft rope sections to create a 400 ft main haul line.) Passing a knot in this situation requires an extra ascender and two additional runners for attachment reasons. Knot passing appears more difficult than it actually is. It is essential to a potential rescue that the knot pass operation be as smooth and quick as is possible. The suggested manner for passing a knot through a 3:1 haul system is as follows:

  1. Be aware that a knot is present in the haul line. 
    Figure -7a
        

  2. Prepare an extra ascender that will function as a temporary  lock-off ascender and a runner that will allow the temporary ascender to be placed closer to the load than the normal lock-off ascender. (The extra ascender is commonly a prussik.)  
        

  3. As the knot approaches the ratchet ascender, continue hauling until the knot is as close to the lock-off ascender using the normal reset technique.

  1. With the load being completely assumed by the lock-off ascender, disconnect the ratchet ascender and replace it on the load side of the knot. (figure -7b)
        

  2. If necessary haul the knot up to a distance of 1/2 to 1 ft from the lock-off ascender. Connect the temporary ascender  on the load side of the knot. figure C13-7c

  1. Haul up slightly to release tension on the lock-off ascender and to bring the knot as close to the pulley as is possible. Release haul tension (slowly) and allow the load to be taken by the temporary ascender.
          

  2. Disconnect the lock-off ascender and clip it into the anchor  or an easily available location. Extend the length of the pulley runner so that the knot is on the haul side of the pulley. figure -7d  

  1. Haul to progress the knot along the haul line to a position indicated in figure -7e. This places the knot close to the ratchet assembly.
         

  2. With the load being held by the temporary ascender, disconnect the ratchet assembly to pass the knot through the pulley. This requires that the slack ratchet assembly be slid away from the load to have proper rope length.
          

  3. Replace the pulley to its original location and replace the original lock-off ascender. (Note:  If additional knot passing on the current haul line is not required, the rescuer may elect to complete the haul using the temporary ascender and the new pulley location. This is a judgment call.

 

THE 5:1 HAUL SYSTEM  

Adding another 2:1 advantage to figure -4 creates the system drawn in figure -8. There are now 5 moving lines at the load. This system may be created by simply adding two pulleys to the 3:1 system, however the 5:1 system is best implemented using special pulleys that have 2 independent wheels on a single axle. The pre-rigged 5:1 haul system, complete with a ratchet ascender (Gibbs) and 200 ft of haul line is kept ready to be used in a team pack called the "haul pack." Note this system is also utilized by Ventura Co. Fire. In this case the "Lock-off device" must be tended by a rescue member. 

The lock-off device may be a figure "8" descended, or an ascender (Gibbs or Prussik) as is shown in figure -9. The 5:1 is a stand alone haul system and is attached to the haul line using the ratchet Gibbs which is contained in the 5:1 haul pack. Since the haul pack is a unique piece of equipment suited for one task, its application to back country operations is limited to times when the personnel for transportation of gear to the rescue site is not limited.

 It is very important to note that the 5:1 hauling system must be connected in the manner shown in the diagram. If the system is connected backwards a mechanical advantage of only 4:1 will be created. (The reader is encouraged to prove on their own.)  

CONVERTING A 5:1 HAUL SYSTEM TO A LOWERING SYSTEM (FIGURE 8)

Since the 5:1 haul system is independent of the haul line, converting a 5:1 system is an easier operation than converting a 3:1 system. The principle remains the same:  Insert the lowering device, transfer tension momentarily to release the lock-off device and transfer the load to the lowering device. The following two options exist for the 5:1 conversion.  

CONVERTING WHEN THE LOCK-OFF DEVICE IS A FIGURE 8  

This represents the simplest conversion. The rescuer merely needs to remove the ratchet ascender and the system is a lowering systems.

 CONVERTING WHEN THE LOCK-OFF DEVICE IS AN ASCENDER

  1. On the slack side of the ascender insert a figure 8 and after removing all the slack between the lock-off ascender and the figure 8, lock off the figure 8.
        

  2. Apply tension with the haul system until the load is removed from the lock-off ascender.  
        

  3. Remove the lock-off ascender.  
       

  4. Release tension (slowly) on the 5:1 until the descending device assumes the load.  

PASSING KNOTS WITH THE 5:1 SYSTEM  

Passing knots with an independent haul system is more straightforward than the 3:1 application. The following technique provides a safe method independent of the type of lock-off device that is being employed. The rescuer should be aware that there is a knot in the haul line and should be ready for the event by preparing an ascender and a runner. The following technique should be followed:  

  1. As the knot approaches, haul the knot as close to the lock-off device as is practical for the given station set-up.
       

  2. Continue hauling until the knot is within 1/2 - 1 ft of the lock-off device. Connect the temporary ascender to the haul line on the load side of the knot.
        

  3. Continue hauling 1 or 2 ft of main haul line using the temporary ascender as the lock-off device. Transfer the load (slowly) onto the temporary ascender. Move the original lock-off device to the opposite side of the knot.
        

  4. Continue hauling and remove the temporary ascender at the next comfortable opportunity.  

USE OF A 3:1 OR 5:1 AS A TENSIONING SYSTEM  

In certain applications it is necessary for the lock-off device to be positioned to sustain the maximum tension of the hauling system. Tyrolean systems require this type of capability. In this case the lock-off ascender must be closer to the load than the ratchet ascender. To capture the maximum tension, the haul team hauls to exert the tension, while the lock-off device is positioned, then the haul team releases tension (slowly) and transfers the near complete load to the lock-off device. See figure -10.    

  WINCH HAULING SYSTEMS  

             Caution:   

This type of operation requires knowledge of the working strengths of the equipment being used. Advanced training and experience are needed to operate this type of system. Power winches are never used to tension rope systems.

In areas where a rescue truck is available the winch may be used as a raising system. For small evacuations the winch cable may be extended directly to the load. In the more typical case the winch cable is attached to the haul line using an ascender. (This forms the ratchet ascender.)  The winch cable, more specifically, should be attached to a runner or similar device which is then attached to the ascender. This provides the capability of cutting the haul system free of the haul line if a problem arises that requires such drastic action. Also, in the event of a stock system scenario, the runner should "snap" before the main line does. The haul line would then be fed directly through a lock-off device similar to the set- up for the 5:1 haul system. This hauling system is typically employed with a change of direction for a "vehicle over the side" operation as is shown in figure -11. Two winches from two different trucks can be used alternately to provide an almost continuous raising system. One winch is hauling while the other is being reset. When one winch reaches the end of its haul the other takes over and the cycle repeats until the raise is complete. This would be especially helpful on long hauls (>600 ft).  

USE OF THE MARINERS KNOT IN ANY HAULING STATION.

 The Mariners knot should be used to attach the lock off ascender to the anchor. This gives the capability of extending the "runner" length of the lock-off ascender to release tension on the ascender. This may prove useful when converting from a raising system to a lowering system when only a few rescuers are available. This would also prove useful if "by mistake" the litter becomes jammed or snagged and there is not enough slack in the haul system to convert to a lowering system by the conventional technique. Whenever possible, the mariners knot should be immediately re-tied and readied after extension. Figure -12 depicts the proper usage of a mariners knot in a 3:1 application.  

REVERSIONARY MODES  

The standard haul systems employed by SAR have been selected for their simplicity, ease of operation, and for reliability. Certain problems may arise in the field which require modifications to the existing standards. A solid working knowledge allows the rescuer to evaluate any situation. Lack of equipment is often a problem which excites a reversionary mode. Pulleys can be replaced by biners. Two biners used side by side create less friction due to a less hard turn radius. Prussiks can be used in place of mechanical ascenders. Various biner combinations can replace figure 8 descending devices. The objective of reversionary systems is to generate the same reliability and safety as the primary systems with the presence of less than optimum conditions. The reader is encouraged to try various implementations of the above haul systems under reversionary conditions before they are needed in actual applications.

  
Ventura County Sheriff's Volunteer Search & Rescue  |  Fillmore Mountain Rescue  |  Team 1
Mailing Address:  P.O. Box 296 |  Fillmore, CA  93016
 
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2005 Ventura County Sheriff's Volunteer Search & Rescue, Fillmore Mountain Rescue, Team 1

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