Why does my 13000 lb Master-Pull winch rope have a 2T WLL hook? (1 Viewer)

[canman]

Believe it or not, but I just opened the package of my Master-Pull 5/16" x 100' Dyneema winch line I purchased a couple of years ago from Slee. It came attached with an orange sling hook with the following marking:

Yoke CE (one side)
7+8-8 YP LDD(other side)

A quick internet search gave me this link which appears to show the identical sling hook.

http://www.pwbanchor.com.au/files/Grade80_Chain_Fittings_Aug12.pdf

According to the catalogue, this sling hook (with latch) has a Working Load Limit (WLL) of only 2 tonnes.

Question: If this is correct, what is it doing on a synthetic rope rated for 13,000 lbs?

 

[Southeast Overland]

Argh. I just typed a ton with my thumbs and it didn't post. Ill post more later from the shop when I'm not sitting in my kitchen.

 

[Southeast Overland]

OK, let's see what I can type with my fingers instead of just my thumbs.

If you have the MasterPull 5/16" basic line then that is a Dyneema SK75 with a break strength (BS), which I'm assuming to be an average break strength (ABS), of 14,500 lbs. LINK

Your hook looks like it has a break strength of 18,000 lbs, which I'm again assuming is an ABS. LINK If the WLL you looked up is correct then a WLL of 2 tons = 4,000 lbs = a 4.5:1 safety factor between the WLL and BS but the catalog at your link states a 4:1 safety/design factor, so let's go with the more conservative 4:1.

So if your line has a BS of 14,500 lbs and your hook 18,000 lbs then the hook is stronger than the line - but - your hook does not have a BS and WLL and safety factor like a 3/4" Van Beest Green Pin shackle does at 62,000 lbs BS. That is why some go with a thimble that wraps the line all the way around it, and then a shackle. While the hook is more convenient to use, the thimble and shackle is more secure and stronger.

Another thing to consider is many of the products we use in off-road recovery come from the rigging industry which deals a lot with overhead lifting. There are more dangers involved with lifting a product overhead that can fall due to broken equipment and hit someone - versus a winch line that won't probably drop a vehicle but still could have consequences.

Synthetic winch line also has a WLL and maximum shock loading guidelines that are not often spoken of in the off-road industry. Again, this came from more so the lifting arena and not the pulling arena, but still is applicable to an extent. This muddies the waters even more.

If you are worried about the hook you can always cut it off, or if your hook has half a connector link built in just press the pin out and use the thimble in combination with a shackle.

I typically like to see a winch line with a 2:1 to minimum 1.5:1 safety factor between the winch's rating and the line ABS because you also have to factor in the weight of your vehicle in a dynamic loading situation. The thicker line you use though the less you can fit on your winch drum.

I like to have hardware that is upsized a bit. Synthetic line is much safer than steel cable when it comes to broken line recoiling and imparting it's store energy into your vehicle or yourself - but even so the hardware is still the last thing you want to break. With that being said, I've seen some pretty used and beat up hooks, even ones that I'd argue are undersized, but they are still in-tact and have not broken. I'm a pessimist when it comes to the loads involved with winching so I usually upsize. MasterPull are good people and know their stuff though. If you are worried I'd say cut the hook off to use the KISS method, or have a stronger hook spliced on.

 

[canman]

What then is the WLL of the MP 5/16" syn rope? It would seem to me a bit misleading to advertise it as 13K lbs if this in fact is the breaking strength and not the (safe) WLL. It is my understanding that the WLL should never be exceeded for any device - or am I missing something? I can foresee winching scenarios where the rope load could easily exceed 2T.

 

[landyNZ]

I'm not an expert but I think unlike the rigging/lifting community where WLL is the number used, in 4WD winching circles it is really break strain that is used in promotional materials.

Winching in 4WD run gear much closer to the limit due to size constraints. If we had the space we would all run 50k winches with 200k line, but we don't want to cart that everywhere, so sacrifices are made.

If you were rigging something to LIFT 13K there is no way the line would be 5/16. It would be bigger with a much greater safety margin.

 

[canman]

I'm not an expert but I think unlike the rigging/lifting community where WLL is the number used, in 4WD winching circles it is really break strain that is used in promotional materials.

Winching in 4WD run gear much closer to the limit due to size constraints. If we had the space we would all run 50k winches with 200k line, but we don't want to cart that everywhere, so sacrifices are made.

If you were rigging something to LIFT 13K there is no way the line would be 5/16. It would be bigger with a much greater safety margin.

Yes, this seems to be the prevailing approach in the recreational off-road market. I'm no rigging expert either, but I am a licensed professional mechanical engineer, and I suspect there are very good reasons why the (safe) WLLs were established in the first place. I'm not trying to be a smart a$$. I just want to understand the limitations of this "stuff" that I'm purchasing and installing on my vehicle, such that I don't injury or kill myself or others unnecessarily.

Check out these reports I came across on Dyneema rope:

http://www.barry.ca/publication/hig...rope-for-helicopter-longline-applications.pdf

http://www.barry.ca/publication/rt-inspection-dyneema-spectra-ropes-helicopter-products-jan-08.pdf

It's interesting that they note the actual breaking strength had been reduced by almost two thirds after use, and that the manufacturer cannot guarantee the specifications of used rope.

I think one of the most important and perhaps overlooked aspects, is the proper training, installation, use and maintenance of winches and associated equipment. I think most persons just go out and buy a winch and then install it, without giving it much thought.

 

[Southeast Overland]

LandyNZ is accurate, and canman is spot on regarding people installing and using a winch without any thought or training - I've seen it way too many times. Ill type more later when I'm at the shop and not pecking away with my thumbs.

 

[MAINEFJ40]

I dont claim to be an expert either but do work in the offshore oil industry where we do a lot of rigging and overhead lifting. I think a lot of these WLL compared to BS limits come from such industries where they are heavily regulated by governing bodies like the coast guard, ocea, ABS, DNV, etc etc etc. I know our company policy requires us to not use anything that does not have at least a 5:1 WLL to BS ratio. A lot of industries are under a lot of scrutiny when it comes to safety. The Oil Industry being one of them so we always air on the side of caution (regulation) and only operate based on WLL, even with this we still have failures, most of which are due to poor maintenance practice. We replace every sling, shackle, winch cable, and all other rigging gear annually regardless of condition. Most of the time this equals nearls a 1/2 million dollars annually just to be on the safe side.. In our case where we are recreational users we are not regulated by anyone so we can operate much closer to the BS but I still try not to push my limits too close to the max as there is no safety factor..

 

[canman]

...In our case where we are recreational users we are not regulated by anyone so we can operate much closer to the BS but I still try not to push my limits too close to the max as there is no safety factor..

Exactly. I guess knowing that a lot of these recovery ratings are actually the breaking strength puts things in an entirely different perspective for me.

 

[Southeast Overland]

Sorry it took a bit for me to get back in here. Been slammed at the shop.

So, BS (breaking strength) vs WLL.

WLL = BS / a safety factor.

Yes, WLL is used to provide a "safety factor" so a piece of equipment is not stressed to the point where there could be a failure which could = damage to equipment or worse, injury or death.

In off-road recovery gear BS is used often, and almost always if not always with winch lines. Samson's Amsteel Blue, which is a Dyneema SK75 fiber, and a very popular raw line material for splicing winch lines, has a WLL of 1/4 the BS. So, a 3/8" line with an average BS (ABS) of 19,600 lbs has a WLL per Samson of 4,900 lbs. To add to that, synthetic line should not be shock loaded, and Samson spec's a shock load to be a quick loading of the line at anything more than 10% of the WLL.

Now why not put a synthetic line on a winch that has a WLL that is equivalent to the rating of the winch? Let's look at the popular Warn M8000, or many other 8,000 lb winches that hold 100' of 5/16" line rated with an ABS of 13,700 lbs, or 85' of 3/8" line rated with an ABS of 19,600 lbs. To get a WLL on the line of 8,000 lbs you would need a line with an ABS of 32,000 lbs at Samson's 4:1 WLL/safety factor rating. An ABS of 32,000 lbs would necessitate 1/2" diameter line with an ABS of 34,000 lbs. Using 1/2" diameter line you would only be able to fit around 40' on the drum with about 10' of that reserved for leaving on the drum so the line attaches to the drum properly, which leaves you with around 30' of working line length. That's not very much.

So why do you often see WLLs in rigging gear and ABS/BS in off-road components such as winch lines and straps? With rigging/lifting gear if a failure occurs someone could very likely be injured or killed. In off-road if a failure occurs someone could also be killed or injured, but the likely hood is less. Using a WLL on winch line would take any of the modern and common winches and make them basically useless because there would be so little line available.

Now Southeast Overland recommends a 2:1 safety factor on winch line strength vs winch rating. This is to work in a safety factor. Winches often only work at a few thousand pounds of their rating, which effectively gives you your 4:1 WLL. You do need some safety factor because if you dynamically load your winch line you can cause a failure.

Also think about straps, especially snatch straps and kinetic recovery ropes. A polyester tow strap might only stretch a few percent, a nylon snatch strap 10-12 percent, and a kinetic recovery rope around 30%. A key point here that many don't realize is that 30% stretch for a kinetic recovery rope, or any strap, is at the BS/ABS. You don't get 30% stretch out of a 7/8" recovery rope if you pull on it with your hands, only if you yank on it with your vehicle. If it stretched so easy with your hands it would break way too soon.

Something else to think about is the use of rigging hardware in the off-road recovery industry. The shop uses Excel hooks on our winch lines and Van Beest shackles in our recovery bags because they are high quality. The hooks we use on our winch lines, both 5/16" and 3/8" have a BS of 25,200 lbs. The calculated WLL at a 4:1 safety factor is 3.15 tons or 6,300 lbs. Some only go up to a hook with this rating on a 3/8" line but we like to see a beefier hook used on both the 5/16" and 3/8" lines. We upsize the hook for 7/16" lines to a BS/ABS of 42,200 lbs, a calculated WLL of 10,600 at a 4:1 safety factor. This upsizing of hooks costs a significant bit more than the next step down in hooks, but we hate seeing undersized hardware, and especially hooks, on winch lines. Arguably, a smaller hook can be used on 5/16" line, especially synthetic which recoils less than steel cable, but we prefer to go beefier. You don't want a piece of hardware breaking on you and potentially recoil. Now - you could even argue to go with a heavier hook so the hook's WLL = the rating of a winch, plus an additional safety factor of 2-3 to account for dynamic loading of the line. I've been there when I was "getting funky" to get up a slick hill, had my winch spooling in, I overdrove the rate that the winch could spool in, gained ground, got "extra funky" and slid back hard on the line. Before the line went taught I called out to my passenger (who is my wife) that "the line is about to break." I was wrong, but was surprised that I was wrong. In that position there wasn't much that I could do to avoid that situation as it was a long winch, a steep slick hill, no good ground anchor, and there wasn't a good opportunity for a double line pull...

Speaking of steel line, take a look at some of the hooks, and their gates, that come on steel cable as stock equipment on some winches. In our judgement they are undersized.

So - with all that said - I absolutely do not think MasterPull was being underhanded, deceitful, <fill in the blank with a synonym) with how they spec their lines. MasterPull knows their stuff. They sell a ton more equipment than Southeast Overland does. I trust them and the shop sells their Superline and Superline XD lines.

The whole rating of WLL and safety factors pulled over into off-road gear is a bit different than how it is used in rigging, especially lifting, but we still need to be very careful. Too many people buy recovery gear and have no idea of how to use it. I've seen some horrible examples. I even tried to correct a neighbor of mine before but "he knew what he was doing!" and used a smaller than 1/2" shackle to set up a snatch strap. Since he wouldn't listen I made sure everyone else around was waaaaaaaaaaay clear. Winching is the same - too many people just hook up a line and spool in - bad things happen that way. I've been yelled down, even basically challenged to a fight, because someone was doing something so stupid winching they were putting many spectators at risk. Big Boy thought he knew better. Luckily nothing broke, but it so could have.

Whew - that was a lot to type! I'm sure I left some things out. Shoot any other questions at me you might have.

 

[canman]

I'm finally getting ready to install my Masterpull synthetic line onto my Superwinch EP9.0, and I have been doing a bit more reading. What I found interesting is the lack of info on how to properly install the syn line onto the winch drum. In my opinion, the Masterpull site provides only minimal technical info.

http://www.masterpull.com/how-to-install-a-synthetic-winch-line/

I found a youtube video made by Sampson Rope that has a great deal more critical technical info.



Additionally, I also discovered that there is an European standard, EU 14492-1, that also covers automotive winches, and according to one site from the UK, MY Superwinch EP9.0 is only rated at 2500 kg per the EU standard vs. the 4080 kg rated design load!

http://www.pwsacc.co.uk/pdf/superwinch/EP9.0 Pro Winch Information Sheet.pdf

 

[LFD2037]

Salt on the wound here but a Syn. winch rope that's sat on a shelf for 4 years and never used for lost 12% strength.

 

[canman]

Salt on the wound here but a Syn. winch rope that's sat on a shelf for 4 years and never used for lost 12% strength.

Thanks for reminding me. That sounds familiar...

 

[ChaseTruck]

...
I found a youtube video made by Sampson Rope that has a great deal more critical technical info.

Watching that video, I can't help thinking that things are getting a bit impractical here. Winches for 4x4 use don't have that many layers to have the luxury of leaving 2 layers of rope on the drum at all times. Same deal for the crossover wrap. That said, the majority of my pulls using my Ramsey typically happen with plenty of wire on the drum - it's been mostly recovery from being stuck in the rocks, and for the most part a short pull was sufficient to free the vehicle.

I've installed the rope on my HF12k in a 'line lock' pattern using 8 wraps. This is not universally accepted, as some feel it is safer to be able to let the rope slide off the drum in certain situations. I don't want that to happen, hence the line lock.

...and the links about durability of syn rope lead me to a place that looks like it sells rope.... just saying.

 

[e9999]

My Warn M12000, which is reportedly indeed capable of pulling with an actual 12,000 lbf and more did come from Warn with a 3/8" wire rope which -according to published specs I found for that type of wire rope- does likely have a Breaking Limit of only a bit more than 12,000 lbf. So, very little -if any- safety factor there, amazingly -and disturbingly- enough.
However, they do sell snatch blocks rated at 24,000lbs max load for use with winches up to 12,000 lbs, therefore implying a safety factor of 2 for those. (Although, IIRC -not sure-, they are stamped with a 9,000 lbs WLL rating, which would make the 12,000 lbs winch recommendation odd then...)
Don't know what the hook on that wire rope is rated at though.

That particular case aside, the use of disparate standards for advertising recovery gear out there makes it all messy and creates enough confusion to fill some of the marketers black little hearts with joy no doubt...