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Double, twin or single rope ...? 22-May-2004 At 1:43:55 PM M

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I have found some info on this topic from PMI. Although this provides evidence to the above statement perhaps the most relavent part to climbing is the last paragraph.

It was at the following webpage

http://mtncommunity.org/dcforum/DCForumID1/1142.html

the basic text is as follows

PMI's response:

Hello Bill,

I have tested and can say for certain that the impact forces on PMI's 8.1 and 8.6mm ropes are low enough to safely be used as twin ropes. We also purposely had the certifying lab test our 8.1mm as BOTH half and twin to the UIAA/CE tests so that we could legally dual-label them as twin and half.

I have NOT tested all brands of "half" (a.k.a "double") ropes. What I can say is that any other brand half rope that has a higher impact force rating than shown below will of course also have higher impact forces than shown below when two are used together as twins. Any such combo may still test out below the UIAA limit of 12 kN, but you'd have to get that info from the rope manufacturer or someone able to do such tests.

Here are some actual test results:

A) PMI Fusion 8.6mm half rope - UIAA "1/2" rope test - single strand of rope - 55kg test mass - 5.9 kN impact force - 17 falls held

B) PMI Fusion 8.6mm half rope - UIAA "1" rope test - single strand of rope - 80 kg test mass - 7.3kN impact force - 3 falls held - this is a FAILING result and why we can't/don't sell the 8.6mm rope as a "1" rope

C) PMI Fusion 8.6mm half rope - UIAA twin rope test - two strands of rope - 80 kg test mass - 8.7 kN impact force - stopped test after 19 falls held - perfectly safe result

For further comparison, the PMI Verglas 8.1mm rope tested as a twin (w/ 80kg mass) has impact force of 8.4 kN. This is a little less than our 8.6mm tested in the same manner, but equal to that of the PMI Cirque 10.6mm "1" rope. Hope all this helps you make safe climbing decisions.

Regards,

Chuck Weber
Quality Mgr. / ISO Coordinator
PMI
P.O. Box 803
LaFayette, GA 30728