Redundancy In Rope Systems

[ProgressiveRescue]

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....
Stay Safe,
Mike Donahue

[DCFDRescue2]

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

Two questions:

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>

[jmatthe2]

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!

Jeff Matthews
www.TrainingTECH1.com

[jmatthe2]

Darn you DC...You got me by 10 minutes....

Jeff

[FiremanLyman]

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.

[FiremanLyman]

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.

+2 awesome points

Jeff your entire post was fantastic. I quote this part because it is simply awesome. Well said.

[Engine4Cap]

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.

[TRT24]

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.

[stickboy42]

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.

-stick

[jdcalamia]

Anyone have a link to the redundancy article from Reed online?

[stickboy42]

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.

[jmatthe2]

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.

Flat webbing in a loop (with knot) gives about 8,000 lbs MBS, while tubular is around 5,600. Tubular is clearly not up to snuff if practicing a 10:1 SSF with a rescue size load. Our general teaching point is that we like to see 4 legs of webbing on all anchors. We use this rule during our introductory courses. The purpose is as students become aquainted with rope and rigging theory, it is an easy rule to remember for both tubular and flat webbing. Additionally, I like the comfort of having an anchor connection that is as strong as much of the hardware in the system. I don't consider this "redundancy" as, other than a longer piece of webbing, making a multiwrap doesn't require more manpower or "muck-up" the system.

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!

[servantleader]

webbing analysis

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...

[ProgressiveRescue]

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!
THanks,
Mike

[rescuedylan]

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.