Thread: Redundancy In Rope Systems
04-28-2011, 03:01 PM #1
Redundancy In Rope Systems
I thought this topic would generate some great discussions being it's a popular topic amongst us rope guys. I don't think redundancy in a system is a bad thing, the safer the better right? I will admit however I have seen this thought process taking completely out of control. A knowledgeable rigger will build redundancy into a system and keep the two most vital traits....1. Organization and 2. Simplicity.
I'm a big fan of backing up your anchor systems even if it's a bombproof anchor. On BPA's I often create a separate attachment point on the anchor and connect a length of rope to the desired line via a butterfly. Some may say there's no need for this, however it only takes a min or so and increases my safety by 100%. I'm not concerned the anchor will, fail I'm backing my line up for the one in a million shot I have a hardware failure.
Let the posts fly....
Mike Donahue"Training Prepares You...For Moments That Define You
04-28-2011, 05:47 PM #2
- Join Date
- Jan 2004
I'll take the first shot at it:
I think having a belay line is the built in redundancy. Eric Ulner's response in this thread sums it up very nicely:
http://www.firehouse.com/forums/showthread.php?t=120460 (Rigging the Petzl ID'L for raise and lower)
At what point do you stop?
I guess this is the crux of the debate. I am clearly more comfortable stopping before you. I feel absolutely no need to back up a bombproof anchor. If I am backing it up, it ain't bombproof.
Where's the trail of bodies?
I would be curious to see properly used, hell even improperly used, equipment that has broken due to overloading. I'm betting that the evidence will be hard to come by. There's probably plenty of evidence of humans showing decidedly less than bombproof judgment and goofing up the mainline rigging; this is why we have a belay. No amount of backing up your BPA is going to fix this.
I agree, however, that this will be a fun topic to see discussed here>
04-28-2011, 05:58 PM #3
- Join Date
- Apr 2001
I guess I'll go first as I am some where on the other end of the spectrum.
1. The system is already backed up...In the US the use of a two rope system is commonplace. Why complicate the system and eat up resources to make something that is already safe, safer? This doesn't mean that you get slack on rigging your mainline!
2. Redundancy breeds inefficiency and is usually a result from a lack of expertice (of course a lack of redundancy when needed is also a result from a lack of expertice). Building multiple redundancies into a system requires more equipment (as mentioned earlier), more room to work, and more personnel. Not a very efficient operation.
I find that personnel that are not confident in thier skills, or use the answer "I don't know" build the most redundant systems. The more experience you gain the more confident you will become in the equipment and its capabilities. This is usually why personnel feel compelled to make a system redundant in the first place...They are not confident in the gear.
3. The failure of a rope system is 99% in the control of the rope technician. Worried about abrasion?..use edge pro; worried about a shock load...build the system using fall factor calculations to reduce force at points in the system(along with solid rigging practices and equipment operation); worried about your gear?...TAKE CARE OF IT!!! Most accidents happen due to operator error...not equipment error. Based on this the problem should be fixed with training, not by adding another level of redundancy.
There are two things analagies I use in my classes...1. If we want to be totally safe we would wear parachutes (Even a parachute only has 1 backup) 2. I don't drive two cars to the mall in case one breaks down. Your rope system is no different.
I think some municiple teams have to live with a certain amount of redundancy. It can be difficult to get a large number of people to a level of proficiency where they can be "free thinkers" vs using cookie cutter systems that work for many problems. I have been fortunate to teach in a lot of states and have found everyone has their local flavor. It can be difficult to break this mold. Many times the local flavor has been passed on generation after generation and either gets distorted through the years or was wrong to begin with. Some of them may not be best practices, but work. That is the true value of these forums as well as taking courses outside you local jurisdiction.
Mike - I would consider backing up a BPA as a redundant act. If you're worried about your hardware use two carabiners?? Or get new gear However, backing up an anchor is not redundancy...It is part of the anchor system and is a good rigging practice when needed.
Take Care and Stay Safe!
04-28-2011, 05:59 PM #4
- Join Date
- Apr 2001
Darn you DC...You got me by 10 minutes....
04-28-2011, 06:05 PM #5
Rig for success, not failure. You need to have a safety in your system, but backing up everything can add to much to your system, making it impractical and possible so many parts that it becomes unsafe. When you rig expecting things to break, then you need to re-think your approach to rigging. If you don't think your G-rated hardware will hold, then you need to place that piece of equipment out of service and purchase a new one.~Drew
USAR TF Rescue Specialist
04-28-2011, 06:09 PM #6
04-28-2011, 11:57 PM #7
Awesome points, everyone. One thing we make SURE to do everytime is to be redundant in CHECKING our system and rigging. If rigger A built it, rigger B checks it for him.
04-29-2011, 10:05 AM #8
- Join Date
- Oct 2010
I will agree with everything that has been said. I feel that we have too many redundacies at the cost of efficiency.
That being said, let me run something by you in regards to webbing and anchors. It has always been preached that for rescue work, we NEVER use a single loop webbing for an anchor ( flat mbs 6000#). Even though the strength of this loop should be about that of a 1/2 inch rope with a knot in it. Yet many times I see a short single loop connecting the PCD pulley of a z rig to the rigging ring in order to get it far enough away so that a rack can easily be inserted for a system change over. Does this not violate the "do not use single loop" rule? After all the entire haul system comes together at this point, where it all boils down to a single loop.
I actually prefer to use a mini haul to do my system changeovers. Thus eliminating the issue alltogether. sorry about redirecting the thread, but they kind of go together.
04-29-2011, 02:53 PM #9
Kudos to DC and Jeff. I concur.
I found Reed's article in TR Mag #59 excellent, The Dreaded Disease of Redundinitis. a must read.
-stickMy opinions posted here are my own and not representative of my employer or my IAFF local.
04-30-2011, 10:00 PM #10
Anyone have a link to the redundancy article from Reed online?John D. Calamia, BS, NREMTP, FP-C
05-01-2011, 10:01 AM #11
www.trescue.com you'll have to signup for sub though since it's in a members only section. $10/year for the electronic subscription... emag is free but not as many articles and not reed's redundancy article.My opinions posted here are my own and not representative of my employer or my IAFF local.
05-01-2011, 09:16 PM #12
- Join Date
- Apr 2001
Additionally, there are times when a single loop won't be adequate. It has become an easier practice to require a wrap-3 pull-2 for all anchors as they will meet the demand much of the time.
Personnally, I prefer to use rigging methods that take the knot out of the equation. This goes for webbing and the rope. I'll use a wrap-3 pull-2 as my first choice, and will rig a mainline locked into a rack, through a cheater system (tandem prusiks and a figure 8 on a bight), or a tensionless hitch. I really do make a conscious effort not to simply terminate the rope with a knot and attach a carabiner. Most hardware these days supports over 10,000 lbs...why shouldn't the connections? Additionally in a fall situation, while the rope will see some of the hit all of that force terminates in one place...the anchor. It should be a strong component of the system.
If you are using a single loop anchor (no matter what the use), you have an increased potential for abrasion (the loop can move relatively easy around the anchor) so ensure you use edge pro. Additionally, remember one of the downsides of flat webbing is that is doesn't maintain untensioned knots very well. Be sure to prestress the water bend and leave adequate length of tails to prevent the ends pulling through the bend when it is tensioned. (We teach a palms width or use overhand saftety's)
With your comment to mini-haul they are worth their weight in gold. There are many on the market, but we primarily use one with a build in cam. The prusik models work just as well, but I have a hard time manipulating the cord with my man hands!
05-02-2011, 05:36 PM #13
- Join Date
- Mar 2010
- eastern WA
I think TRT24 was referring to the jumper across the DCD when doing a hot changeover from lower to raise. This question has arisen with my team also.
For this particular application, I've attached calculations of SSSF for 1" flat and tubular webbing for both a BCCTR defined rescue load (2 kN) and an NFPA defined load (about 2.6 kN). The results indicate that the only case where a single loop of webbing does not meet a 10:1 SSSF is for tubular webbing with an NFPA defined rescue load.
It is interesting to note that a loop of 8 mm cord (tied with a double overhand bend) just barely meets a 10:1 SSSF for this application with a BCCTR defined rescue load, but certainly does not with an NFPA defined rescue load. Mountain rescue teams commonly use a loop of 8 mm cord as the DCD jumper, but, they also define a rescue load as 2 kN.
Given this, it might be more useful to consider the tensile strength of the 8 mm ratchet Prusik of your haul system. If the 8 mm ratchet Prusik is acceptable for holding the load during resets, why would you need to worry about a single loop of flat webbing which has an SSSF of 12 for this appplication for an NFPA defined rescue load?
Adequate redundancy is maintained by using two-rope technique, not by doubling (tripling, quadrupling etc) components of the system that have SSSFs already exceeding 10:1 on their own...
05-11-2011, 02:23 PM #14
The more I read through these posts the more it makes me think. A lot of great points were made and it has changed my outlook somewhat.....
I still think redundancy for the reason of safety in some occasions is needed...but redundancy all the time could get a bit out of control. I think to some (including myself) it becomes a mind game....a thinking challenge if you will, to see if you can build onto your current rigging system for possible "what if" happenings.
I knew this would be a hot button topic (in a good way) and being there are a hand full of guys in this forum that do tree work or climbing the viewpoints always cover a wide spectrum of the thread topic.
I'm glad I started this thread because it did tweak my outlook a bit...not completely though....I am a stubborn Irishmen
Great webbing info also!
Mike"Training Prepares You...For Moments That Define You
05-23-2011, 09:57 PM #15
Also another artical this past emag trescue.com #20 about anchors by James Fairfield.
Another thing about anchors when I am setting up my systems is I know that I am going to use two diffrent anchors (in order to stay compliant with rescue gods), but I see alot of crews putting the main hauling system onto the strongest anchor and the belay system onto the weaker/ the one that may need the back-up. I teach and do the opposite, my line of thinking is if there was to be a blow out on the main part, the belay side would one: have to catch and hold, and two: turn into the main part of the system with another point being found for a belay.
05-24-2011, 12:12 AM #16
- Join Date
- Feb 2011
You make a great point. I think that is one toughest ideas to convey to people new to rescue work. The stress that could be applied to the belay line would be much greater then a "normal rescue load". If that belay is ever needed due to a failure, I want to see the bomber or the best anchor you have used for that. I think sometimes new people forget about the belays importance and will use the weaker of the possible anchors.
05-24-2011, 08:28 AM #17
The other point I wanted to bring up was someone mentioned that they have never seen or heared of equipment having a failuer that led to braking of equipment. Keep in mind there has been a test that was done to see how much force would be needed for failuer, in the case that a Figure eight would become jammed up on a beiner (eight to beiner connection,happens all the time when not paying attention) and a load is applied at normal or shock speed. It was found that just by recreating this setup, the force you can apply by hand is enough to snap the beiner's gate appart.
I know a little off topic but wanted to point out the eaze it takes to cause a failuer. Sometimes it gets to easy to foucus on shoke loads causing all the problems.
05-24-2011, 11:08 AM #18
05-24-2011, 08:40 PM #19
05-26-2011, 06:42 PM #20
Do you have or know where to get the document or PDF of that test?
Mike"Training Prepares You...For Moments That Define You
05-27-2011, 11:42 PM #21
- Join Date
- Jul 2006
- Southern Illinois
Ok, since you specifically requested feedback, I'll "let a post fly". Just my opinion with no animus intended.
I'm not sure of your logic in your methodology Mike, because I am just not able to follow it or see it. You speak of being a fan of backing up the anchor system, but you're really only backing up one component of the system. But I guess you do then mention the components you're worried about- your hardware. To do what you're doing certainly does not sound clean and simple (or look to be based on what I saw in one of your video clips). It honestly looked... well... kind of quite messy and like an overuse and misplaced distrust of your gear. I'd probably get a little cranky if I had to be the guy who was safety checking that because it would about need to be somewhat undone in order to see what's going on.
Are you following your own example of this backing up of your hardware throughout the rest of your system? Wouldn't following this line of logic then also mean that you need 2 mains, twice the carabiners at all connections, and perhaps even 2 harnesses for the rescuer? I know you didn't mention feeling like you need to back up your rope in the given anchor, but since you're worried about some one-in-a-million chance of your hardware failing, shouldn't you also assign the random-based one-in-a-million odds on any of your gear having an acute case of vaporization? These are perhaps humorous questions, but with no tongue-in-cheek.
"...the safer the better right?" Where is the stopping point of that ideology? There has to be one somewhere. And wherever that point is, it should be across the board in the rigging, or else it becomes illogical.
But otherwise, the safer thing would ultimately be to not leave the house except maybe to go work behind a desk. Now that was tongue-in-cheek...
Mike, I appreciate your willingness to moderate the forum, as I suspect it's not exactly paying for cruises and the like. I hope you don't take my points as an offense, but I just don't agree with your practices. You're certainly not the first person I've seen do this. But you are the first one doing it who has openly asked for opinions. So now you have mine.
All the best to you from So. IL.
By the way, as for the terminology of a "bombproof" anchor, for me, that means that the anchor point being tied to can carry the day for both the main and the belay, with separate cord or webbing. Perhaps a big hickory tree, or a large concrete post in a parking garage, etc.
05-28-2011, 12:18 AM #22
Wow Eric that stung a little... Kidding.
I appreciate your kind words and your response. That "need to back up" mentality stems from the foundation of my rope training...old habits are hard to break I guess. The great thing or the feature I love the most about this forum is the ability to throw something out there a receive feedback from a dozen different angles. I'm of the mentality that you never stop learning and that you can learn something new from anyone. There's a lot of smart guys in this forum and I pick things up all the time. The ability to get in someone else's head and grab information is a priceless feature we have and share here.
As "blunt" as your post was you're 100% correct. Old habits are hard to break I guess but part of being a good rescuer is breaking habits and allowing yourself to grow and giving a pat on the back to someone or a group of guys that may have a better way of doing things. We're all in the same game so I'd hope its safe to say we've all experienced it.
So with that being said I'll give the guy's in our forum that responded a pat on the back for changing my point of view.
Job Well Done.
MIke"Training Prepares You...For Moments That Define You
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