Rope Grabs FAQ
Q: What is a rope grab and what types of rope grabs are available? What are the advantages and disadvantages of each?
A: To answer this question we must first define rope grabs. In rigging, a rope grab is a device that holds the rope in place or as a means of holding and pulling the rope. Not all rope grabs are rope stops. In other words rope grabs are not synonymous with belay or vertical fall arrest devices. Although, some devices might qualify for both functions under specific applications.
The term Progress Capture defines a function of a rope grab that is rigged to the mainline anchor.
- Example, the Petzl I’D is commonly used as a progress capture component of a haul system, it is therefore holding the rope (load) in place while allowing the haul team to re-set the system. The Petzl I’D also qualifies as an approved belay device simply by the activation of the same internal mechanisms under a shock load event.
The types of rope grabs available in today’s market are too numerous to count or list on this website. However, we can define two major divisions of rope grabs: 1) Soft rope grabs, and 2) Hard rope grabs.
- Soft rope grabs are made of rated textile products such as prusik loops tied or stitched 6mm-8mm cordage or less common, webbing loops. This loops are tied to the host rope using a prusik hitch or one of a number of other approved hitches.
- Hard rope grabs are manufactured devices such as the Gibbs Ascender, the Petzl Rescucender. There are many.
Advantages and disadvantages:
- Soft prusik loops and webbing loops are light weight and easily backpacked for wilderness use as well as some sport climbing applications and industrial applications as seen during tower work. These same loops (depending on their rating) may be used for quick and reliable anchorage. A basket hitch from a webbing loop is a quick and effective anchor point when atop a steel tower. Many of these stitched loops have ratings that are as strong, if not stronger than the carabiner that will be connected to them.
One disadvantage to soft loops is that they tend to really bite the host rope when used at the hauling position and need to be physically loosened to facilitate a re-set of the pulley system. Additionally, rope climbing with prusik loops is doable, however, due to the same biting effect, extremely cumbersome for most people. Some hitches such as the French Prusik or the Caver’s Helical Knot are used to provide a quicker release when used for climbing.
- Manufactured hard rope grabs are very reliable and extremely quick to release and reset. This reason alone is why mechanical hand ascenders and foot loops combined with a mechanical chest component such as a Petzl Croll is a must for any rope access job or any time rope climbing over a few feet is required.
There are not many disadvantages to hard rope grabs other than they might a bit more clinky hanging on your harness and they weigh a little more than those prusik loops. At no fault to the hard rope grab, some people thing that all hard rope grabs qualify as a belay device. This is a very dangerous assumption! Unless specifically approved by the manufacture as useable as a belay device, the vast majority of hard rope grabs are not designed to be shock loaded and should never be used as a belay.
Q: Will a rope grab work on any type of rope?
A: Yes, no, maybe. As it has been stated above, there are a million and one rope grab combinations out there. Each one has its own characteristics and design function. This question is highly dependent on the type of rope and the rope grab device. Soft rope grabs (hitches) tend to be more universal however there is the tendency for more slipping to occur the close the diameter of the prusik loop is to the diameter of the host rope.
Hard rope grabs are mostly universal when using ½ inch rope are 7/16 inch rope. Although a few rope grabs are specifically design for one diameter of rope only. Strict adherence to the recommendations of the manufacturer is required by all end users.
Q: Can a rope grab cut a rope if too much stress is applied?
A: Yes. Usually too much sudden stress is the result of a shock loading event. This is why most rope grabs are not designed for belay/fall arrest applications. When simply hauling or climbing, the potential of shock loading the host rope with the rope grab is exceedingly rare. Most rope grabs, soft and hard alike, will start to slip long before serious damage can occur to the host rope. This slippage of the rope grab can be equated to a fuse in an electrical system. When over-loaded, the fuse will slip and the system will lose power. When the haul prusik slips, this is a strong indication that the load is too big or the system has been rigged wrong. Figure it out and fix it!
Q: What are the advantages of sewn prusik loops compared with tied prusik loops?
A: Sewn prusik loops are manufactured and certified, tied prusik loops are not. Sewn prusik loops are choked together and at the point of the stitches using shrink tubing. This is a means when clipping the loop to a carabiner to choke the shrink tubing up tight to the spine of the carabiner thus eliminating any chance of side-loading the gate of the carabiner. This is more of a problem for traditional tied prusik loops where the carabiner loop is big and floppy and carabiner side-loading is a common occurrence.