Thread: Haul prusik?

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    Default Haul prusik?

    How many prusiks do you use to attach a haul system to your mainline and why? Does it change if you use a higher MA?

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    I'll answer your questions in order.

    1. One haul Prusik.
    2. If properly rigged, it works well.
    3. The load doesn't change just because the MA does, so no it does not. Or another way to put it... The Prusik cord has no idea how many strands of rope are behind it in a pulley system.

    My answers are based on the assumption that you are talking about raising a person or two, or three. If the load you're trying to move is beyond the capacity of what a single Prusik can handle (such as lifting a large object off your patient, then you'll apply tension with whatever MA you've got until the Prusik simply slips while the load doesn't move. Upping to a higher MA in this situation will only mean that you'll expend less energy to make the Prusik slip.

    Best of rigging to you.

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    I'll add to Mr. Ulner's.

    When piggy backing your MA to your mainline you really have few options. A Gibbs/rescue accesnder (not a handle assender which would shread rope in this application) or a prusick. A Gibbs will begin to damage rope at around 3500# and a prusick will slip before that level of damage occurs. Either device works well as a haul cam.

    It basically comes down to efficency; if you want to carry a Gibbs with you or for the same weight carry a half dozen prusiks which can be used for multiple applications.
    ~Drew
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    We use a single prusik for the haul prusik (and for that matter, the ratchet or progress capture prusik too), this is regardless of the MA used.
    If the haul prusik is slipping, then something else is wrong, like the load is hung up on something.
    Dave

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    One prusik for both the rope grab and the ratchet, independent of the MA. No more is necessary.

    The dynamic safety factor of a single 8 mm three-wrap prusik exceeds 1.5 even up to when the haul system experiences its maximum possible forces, i.e. right before the prusik starts to slip and self-limits the system forces.
    Last edited by servantleader; 06-26-2012 at 02:16 PM. Reason: small correction

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    I get using a single haul prusik, but I don't get only using a single prusik for the rachet. Wouldn't you want to use 2 prusiks for the same reasons that you use tandem prusiks on a tandem prusik belay?

    And then just to clarify, when I asked about the MA before I was wondering if maybe on a 3:1 you used tandem prusiks and then if you were going to use say above a 6:1 then you only used a single prusik so you would have some slippage if the rescue package got hung up. It sounds like the single haul prusik is the way to go regardless of the MA

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    Quote Originally Posted by Dibbs12 View Post
    I get using a single haul prusik, but I don't get only using a single prusik for the rachet. Wouldn't you want to use 2 prusiks for the same reasons that you use tandem prusiks on a tandem prusik belay?

    And then just to clarify, when I asked about the MA before I was wondering if maybe on a 3:1 you used tandem prusiks and then if you were going to use say above a 6:1 then you only used a single prusik so you would have some slippage if the rescue package got hung up. It sounds like the single haul prusik is the way to go regardless of the MA
    Quote Originally Posted by Dibbs12 View Post
    I get using a single haul prusik, but I don't get only using a single prusik for the rachet. Wouldn't you want to use 2 prusiks for the same reasons that you use tandem prusiks on a tandem prusik belay?

    And then just to clarify, when I asked about the MA before I was wondering if maybe on a 3:1 you used tandem prusiks and then if you were going to use say above a 6:1 then you only used a single prusik so you would have some slippage if the rescue package got hung up. It sounds like the single haul prusik is the way to go regardless of the MA
    There is only a single ratchet prusik because it's only there to hold a static load. There should be no way to introduce a dynamic load onto the ratchet. There should only be an inch or two from the ratchet and the pulley. You will only be holding between 1-3ish KN static load. That's no problem for a single prusik. Tandem prusiks are needed to catch and hold a dynamic load in the 10-13KN range. A single haul prusik acts as a clutch and alerts the haul team to over tensioning when a slip occurs. If you rigged a double haul prusik, you decrease the prusiks ability to function as a clutch. A doubled ratchet at the anchor is not a safety issue, just rigging that's not necessary.

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    Quote Originally Posted by Dibbs12 View Post
    I get using a single haul prusik, but I don't get only using a single prusik for the rachet. Wouldn't you want to use 2 prusiks for the same reasons that you use tandem prusiks on a tandem prusik belay?
    TTRPB is intended to catch a falling load, tandum to offset the dynamic load or fall factor when the bite in the hands of the operator snaps out.

    A single triple rapped prusik used for a haul cam or progress capture will not (shouldn't) see a fall factor of any concern.

    edit; didn't see bottrigg's response, what he said.
    ~Drew
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    Hello everyone! New to the forum and rope rescue, but this topic brings up a question.

    I fully understand the concept of having a single triple wrapped prusik as the haul cam, to act as a clutch. In training we used a tandem TWP here, but I do like the idea of only using one an early warning system, but if we use a single TWP as the progress capture device, won't this lower the SSF to only about 5:1 for a single person 300lbs load given 1500lbs for the prusik grab strength if its a "hands off" system?

    B.Green

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    I might not of communicated clearly... a single TWP as a progress capture in low angle; used as a 1:1 or counter-balance CoD. But as a haul cam, yes.

    The SSF; The haul system is piggy backed onto the mainline. The mainline is where a progress capture (TTWPB, munter, MPD, etc...) is in the system. If you would blow out the MA or the haul cam the SSF goes back to the PCD on the main line.

    Also slipping and breaking are two very diffrent things in a piggy back haul system. If the prusik starts to slip, you have something terribly wrong (you've possibly hung your basket/patient up on something).
    ~Drew
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    Has anyone mentioned redundancy?

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    Quote Originally Posted by FiremanLyman View Post
    I might not of communicated clearly... a single TWP as a progress capture in low angle; used as a 1:1 or counter-balance CoD. But as a haul cam, yes.

    The SSF; The haul system is piggy backed onto the mainline. The mainline is where a progress capture (TTWPB, munter, MPD, etc...) is in the system. If you would blow out the MA or the haul cam the SSF goes back to the PCD on the main line.

    Also slipping and breaking are two very diffrent things in a piggy back haul system. If the prusik starts to slip, you have something terribly wrong (you've possibly hung your basket/patient up on something).
    So if your using a z rig that is made out of the mainline then you need 2 prusiks for the ratchet but you only need one haul prusik, if that correct?

    Also what is a counter balance CoD, not familiar with that term.

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    Quote Originally Posted by Dibbs12 View Post
    So if your using a z rig that is made out of the mainline then you need 2 prusiks for the ratchet but you only need one haul prusik, if that correct?

    Also what is a counter balance CoD, not familiar with that term.
    3:1 z-rig made out of the mainline is 1) not a piggyback, and 2) used in low angle environment. We use one prusik for the haul cam and one for the set/ratchet cam.

    If you would build any block and tackle as a mainline vertical MA system (like a raise/lower into a confined space off a tripod), still would only need one prusik inside the system for the set cam.

    Move to a 3:1 or a 4:1 pig-rig (piggy back rig), used to piggyback onto a mainline in a horizontal orientation between your anchor and an edge. A haul cam is all we use, others might add a set cam to pass the whistle drop test we don't play that game. The progress capture is on the mainline, not the MA.

    CoD is change of direction. Are you familiar with counter balance as a form of low angle haul system? It is basically having your haul team walk down the slope pulling your patient up the slope. 1:1 MA, use a pulley with a prusik as a PCD in case the haul team falls down or something.
    ~Drew
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    Quote Originally Posted by MichaelXYZ View Post
    Has anyone mentioned redundancy?
    Michael, great to hear from you.

    As in redundant prusiks? They are used in tandum when placed into a system that is expected to catch a falling load with a fall factor. Not needed as a haul or set cam though. Accessory cord rated at ~3000# tied into a prusik loop is rated ~4000#. Actual tests on 8mm cordage show a prusik failing at the prusik hitch near 2500#, which is still an 8:1 SSF on a 1 person load, and will start to slip at 1500# but that is OK.

    Rig for sucess and trust in your equipment, the single prusik will work fine as a haul or set cam. If you rig expecting failure, you will put so many redundancies into your system that it can become inefficent.
    ~Drew
    Firefighter/EMT/Technical Rescue
    USAR TF Rescue Specialist

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    Quote Originally Posted by FiremanLyman View Post
    I'll add to Mr. Ulner's.

    When piggy backing your MA to your mainline you really have few options. A Gibbs/rescue accesnder (not a handle assender which would shread rope in this application) or a prusick. A Gibbs will begin to damage rope at around 3500# and a prusick will slip before that level of damage occurs. Either device works well as a haul cam.
    The instructions from Gibbs on their latest ascender say the Gibbs will cut through 1/2" rope at 2,000 lbf. Haul testing we have performed had the Gibbs cutting through the rope at a maximum of 2,400 lbf while a single 8mm triple wrapped prusik began to slip at 2,600 lbf.

    Drop testing we did had a stainless steel Gibbs cutting through 1/2" rope when dropping a 500 lb load one meter (39"). An aluminum handled ascender (jumar) broke the frame in two. A munter hitch never slowed the load down on its rapid descent to the ground. Tandem triple wrapped prusiks were the only method that would catch the load. This was before the 540 rescue belay and MPD were invented.

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    Quote Originally Posted by rsqman View Post
    The instructions from Gibbs on their latest ascender say the Gibbs will cut through 1/2" rope at 2,000 lbf. Haul testing we have performed had the Gibbs cutting through the rope at a maximum of 2,400 lbf while a single 8mm triple wrapped prusik began to slip at 2,600 lbf.

    Drop testing we did had a stainless steel Gibbs cutting through 1/2" rope when dropping a 500 lb load one meter (39"). An aluminum handled ascender (jumar) broke the frame in two. A munter hitch never slowed the load down on its rapid descent to the ground. Tandem triple wrapped prusiks were the only method that would catch the load. This was before the 540 rescue belay and MPD were invented.
    Thanks for the data. I probably meant to say less for Gibbs, it was 11pm. I would like to do some testing ourselves, we just don't have much of a budget for it... got to get the HAZMAT team to bill a few more incidents to up the SPECOPS budget.

    There was rope work before the 540? We have taken that dinosaur out of service.

    Interesting that the munter would not catch it. Munter is rated for a Rescue (old NFPA Light) load (300#), bit we have practiced catching 420# and 600# with it. The 600# is tough, but if manning the munter right (keeping tension and maintaining hand over hand instead of letting it slide through the hands) you will catch the falling load. They demonstrated it in our Rope II class, I disagree with even showing it because I don't want students to put a General load on a munter.

    We train a lot with the munter, it is our team's and regionally the DCD most often used for Rescue loads.
    ~Drew
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    I'm curious why you would classify the 540 as a dinosaur, yet rally for the Munter Hitch? The Munter is good tool with certain uses, but catching a rescue sized load is not one of them.

    Have you tried replicating the BCCTR drop test with it?

    Here is an excerpt from some old talks that are relevant to Prussik's, Munter's, etc...:

    3) everyone has opinions on the different belay devices, especially the
    munter hitch and the Tandem Prusik Belay (TPB). there are safe
    applications for both in certain situations. a few years back a few
    people from the ROCO camp tried to prove that the munter hitch can catch
    a rescue load as a belay device. they did write an artice to prove that
    it could, but under careful and detailed questioning at NATRS 94, Mike
    Roop was unable to answer questions about the testing procedure that
    folks had. since no one in that room had ever been able to catch a
    rescue load with a munter hitch, it was agreed that the way the testing
    was set up (ie: angles, numerous areas the rope contacted providing
    added friction, etc) affected the results of the test in favor of
    proving what the authors already decided, that a munter hitch can catch
    a rescue load.


    And the link for the rest of it;

    http://www.sarinfo.bc.ca/Library/Skills/prussiks.skl

    If you are completely opposed to anything other than a Munter, maybe try a Super Munter:

    http://www.youtube.com/watch?v=rU9DUf5r4k4
    I used to be DCFDRescue 2. Forum changover locked me out.

    www.rescue2training.com

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    Sarcasum does not display well when typing, the 540 is not a dinasour, we just don't use it anymore.

    No opposition to using other devices. Like some of them alot, use them often. But we most commonly use a two tension rope system using dual munters for rescue loads with a MA ready to hook up to either line if needed to haul. Dosen't pass a whistle drop test, but why would our rescuers drop the DCD's? As someone said last year talking about this topic, the driver's ed teacher never blows a whistle to have a student take their hands off the steering wheel.

    We have caught loads with the munter. Often. No science to our method. A tower, a load, a change of direction at the top and a munter at the bottom. The load is raised using a MA with a quick release. Catch it every time.

    I'll read up on the links you sent. Thanks.
    ~Drew
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    Reread your post, the only time the munter is a belay for us is in a two tension rope system. Not catching anything with a significant fall factor. Hope that helps.
    ~Drew
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    Quote Originally Posted by FiremanLyman View Post
    Michael, great to hear from you.

    As in redundant prusiks? They are used in tandum when placed into a system that is expected to catch a falling load with a fall factor. Not needed as a haul or set cam though. Accessory cord rated at ~3000# tied into a prusik loop is rated ~4000#. Actual tests on 8mm cordage show a prusik failing at the prusik hitch near 2500#, which is still an 8:1 SSF on a 1 person load, and will start to slip at 1500# but that is OK.

    Rig for sucess and trust in your equipment, the single prusik will work fine as a haul or set cam. If you rig expecting failure, you will put so many redundancies into your system that it can become inefficent.
    Thanks Lyman, I think I was getting my prusiks confused, I was thinking of the ones at the anchor plate, not the pulley.

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    Quote Originally Posted by FiremanLyman View Post
    Reread your post, the only time the munter is a belay for us is in a two tension rope system. Not catching anything with a significant fall factor. Hope that helps.

    Don't munters easily flip? I was told this hitch was for use when lack of a better device is available. Not being a wiseguy, just seeking enlightenment.

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    Yes, the munter flips, and that is a good thing. The purpose of flipping the munter in the carabiener is to change direction with it. Lowering with it it proceeds in one direction, when you go to raise (either by adding a MA or in low angle having a litter carry team walk back towards you) you pull on the running end and the munter flips in the carabiener and changes direction.

    Back to the 540... funny we had the discussion, on our Task Force team we just talked about it in application. Evidently we will be using it more often on the US&R team.
    ~Drew
    Firefighter/EMT/Technical Rescue
    USAR TF Rescue Specialist

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