Vertical caving terminology and methods > Personal SRT gear
A dedicated device designed to automatically catch an accidental fall, which can be used for self belaying, and is specifically designed to minimise the damage to the rope when catching a fall. Almost all of these are intended for rope access work, and the terms originate there. It is important to note that "rope grab" or "rope clamp" can also refer to ascenders, or anything that grips the rope to allow its position to be adjusted easily, and these are not designed for catching falls. "Fall arrester" can refer to a personal device used to grip a stationary lifeline (known as a backup line in rope access work) when a fall occurs, and this is the type that is most likely to be relevant to vertical caving. These are officially referred to as a "guided-type fall arrester". However, the term can also be used for an automatic belay device that feeds out or retracts a lifeline as long as movements are slow, and stops the lifeline from moving if motion is fast. This type may be known as a "fall arrester block", and is not relevant to vertical caving, but is similar to the devices sometimes installed at indoor climbing walls.
In rope access work, a guided-type fall arrester is typically connected to an attachment point on the chest or back of a full body harness, with the back often being preferred because it holds the body naturally below the attachment point, minimising the amount of flailing when catching a fall. However, these harnesses are not normally used by cavers, so the typical attachment point for a caver would be the D-ring attached to the sit harness. When catching a fall, fall arresters will take some distance to react, start to catch, and actually stop the falling motion. The fall distance will depend on the length of the tether used to attach the fall arrester, since the device could be that distance below the person at the start of the fall, and they will fall until they are that distance below the device, meaning that the tether adds double its length to the distance that the person falls. If the tether changes length during the fall, such as dynamic rope or a shock absorbing tether, that also will be added on to the fall distance. When the rope stretches to absorb the impact of the fall, that stretch amount is also added to the total fall distance. This total fall distance is the height below which the device cannot react fast enough to fully catch a fall before the person hits the ground. With many types of fall arrester, the shortest attachment that can be used is simply a carabiner that is clipped directly to the harness. A locking carabiner is essential, to prevent the device from loading an unlocked carabiner gate. A tether allows rotation, so that no matter whether the person rotates, the device can remain oriented correctly upwards. Cavers are likely to use a cows tail, and will need to have one with a locking carabiner. When using a longer tether, the typical advice is to run the tether over the shoulder so that the device is kept above the attachment point on the harness, reducing the total fall distance, as the tether is already pointing mostly upwards from the harness. This also makes it possible to keep the rope behind the back, out of the way.
Lever cam fall arresters function in the same way as lever cam ascenders, though they normally do not grip much until they are loaded. While it might therefore be assumed that a lever cam ascender could be used for this purpose, ascenders have not been specifically designed and tested for catching falls. Like many lever cam ascenders, some lever cam fall arresters have a spring forcing them to grip the rope, so while they work very well for ascending, they do not move downwards freely and need to be manually pushed downwards when descending. This limits their usefulness.
Fall arresters that are designed to freely allow motion up and down a rope, and only catch when a fall occurs, are typically designed for rope access, where the regulations are different. They are not normally designed to work with the thinner ropes used with caving and climbing. Some are designed to work with the kind of flexible backup lines used in rope access, which is similar to a lifeline used in caving and climbing. Since fall arresters and ascenders are often both sold simply as "rope grabs" is it important to check the device ratings, and see what PPE standards they are designed for, to see if they can actually be trusted as fall arresters. Fall arrester devices are covered by the standards EN 12841-A, relating to common rope access usage, and EN 353-2, which requires even better performance (and normally a thicker rope). Some are designed to be used with a rigid anchor line (often a cable) that is attached at both ends and kept under tension, often seen next to rigid ladders on masts (covered by EN 353-1, an approach only ever seen in caving as a tension traverse, but may be used in climbing for via ferrata). Devices that are designed only for EN 353-2 normally state that they require the thicker ropes, and do not give any details of what happens when used on thinner caving ropes, so they must be assumed to be unable to reliably activate on those ropes.
The vast majority run the rope between a rocker arm and a solid block when the device is hanging downwards from a carabiner, but when pulled downwards using the carabiner, the rope pulls the top edge of the rocker arm, pinching the rope between the bottom of the rocker arm and the solid block. These may be known as rockers, with a few of them using that as the name of the device. The catch is not instant, as it needs the user to be falling faster than the device naturally slides down the rope (which depends on the device's friction against the rope), causing the device to be rotated and pulled downwards. However the catch is usually fast enough not to notice (within 1-2 metres). Often, these will have a locking switch that can prevent them from moving downwards freely, resulting in a faster catch, though this then prevents them from freely moving down the rope when descending. This is an intentional feature intended to prevent high winds pulling rope upwards through the device when working on skyscrapers, a feature cavers are unlikely to care about, but it also makes some devices more useful as an ascender if needed. A couple have a sprung lever that dramatically improves the catching speed, so that they can start to react within just a few centimetres of freefall. Some can also be used as rope access ascenders (EN 12841-B), which may be useful when trying to get back off the rope after the device has caught a fall.
A number of reputable companies make these devices. Rockers with a locking switch include the ISC Rocker, Troll Rocker, SAR Rocker, Beal Monitor, G-Force AC080, Kratos Blocker and Singing Rock Locker. Rockers without a locking switch include the 3M Protecta Viper 2. (The Camp Lift also uses that design, but it is only rated as an ascender, not for catching falls.) Rockers with a more gently curved rocker arm, and without a locking switch, include the DMM Buddy. Rockers which also push the rope with an extra lever when the carabiner pulls downwards, so it catches more reliably, include the Kong Back-up. It also has a locking switch. Rockers with a sprung lever that pushes the rope into the rocker, so it catches much more quickly, which is lifted out of the way when the device is hanging from the carabiner, include the Camp Goblin and Climbing Technology Easy Speed/Move. Both also have a locking switch. Lever cam devices without a spring include the ISC Mini, 3M Protecta Viper LT, Kratos Olly and Kratos Lorel, of which only the Kratos Olly has a locking switch. Lever cam devices with a spring include the Climbing Technology SKR-2 and Kratos Niro. The Petzl ASAP uses a toothed wheel, which relies on a governor to lock the wheel when it moves too fast, and can damage the rope's sheath when catching hard falls. There is a version with a locking switch and a version without.
These devices all rely on moving parts that may not function as well when muddy. Some must only be used on very clean ropes. Some may only work on vertical ropes. Some may not work well on dynamic ropes, and may repeatedly engage and disengage due to bounce. Most require specific carabiner designs, typically an oval locking carabiner, with steel being suggested or required. Most must not be held during a fall, with the Petzl ASAP being the only exception. The Kong Back-up has a known failure if the carabiner rotates on top of the device during a fall. The Petzl ASAP and DMM Buddy explicitly state that they will only work on clean ropes, so they are not at all suitable for caving. The Petzl ASAP catches falls so abruptly that it requires a special shock absorbing tether or rope that cannot cope with multiple falls. Others may intentionally slip a little when catching severe falls, in order to reduce the force seen by the user, and shock absorbing tethers are optional. The Kratos Blocker does not state whether it is certified as an ascender or fall arrester under EN 12841, but is certified as a fall arrester under EN 353-2. The Troll Rocker, 3M Protecta Viper 2, DMM Buddy, ISC Mini, 3M Protecta Viper LT, Kratos Niro, Kratos Olly and Kratos Lorel are only certified under EN 353-2, which explains their thicker rope requirements. The Camp Goblin and Petzl ASAP can work on slightly thinner ropes than the other designs, with both being certified for use with 10 mm rope, but for high performance, they need the same thicker rope as most of the others. The Camp Goblin, Kong Back-Up and Climbing Technology Easy Speed/Move are also rated for use as ascenders. The author of this website cannot make any recommendations, but the Camp Goblin is the only device mentioned here that is certified for use with the 10 mm ropes common in British caving, while not having some other severe limitation. If it helps, Up and Under say that they can order them for you in Britain, since rope access suppliers may have limitations as to whether they can supply them. (There are also the Taz LOV2 and LOV3, which can also be used as a belay device and descender, and are sometimes recommended, but they do not run freely down the rope, so they do not serve the desired purpose. Many other devices, such as the Rock Exotica Silent Partner and Wild Country Revo have similar limitations.)
In personal testing, the sprung lever of the Camp Goblin improves the catching speed from about 1.6 metres of freefall without the sprung lever (like a basic rocker device) before it begins to catch the fall, to just 5-10 cm of freefall before it begins to catch the fall, a truly impressive improvement. As a result, its performance is far better than many other devices. It may then take another 30-40 cm to slow and stop the fall, like many other rocker devices. Meanwhile its locking switch (which is intended to switch it into ascender mode) causes it to need the weight of about 7 metres of rope below the device before it will slide upwards, which is a significant limitation when used that way. Cavers are unlikely to use it with the locking switch engaged, but it is much worse than an actual ascender, and a significant amount of bottom weighting would be required.
It should be noted that many of these devices are copied by brands without any reputation, sold on major online shopping sites (particularly Amazon and eBay), and are often said to work with much thinner ropes, normally claimed to be useful for climbing. The Rocker is by far the most common design copied this way, often without the locking switch. Many of these copies have falsified ratings stamped on them, and often have mistakes in the certification logos. Some may simply be labelled as complying with EN 567, which means they are only rated as ascenders, EN 341 or EN 12841-C, which means they are only rated as descenders, EN 358, which means they are only rated as belay belts or tethers, or EN 12275, which means they are rated as carabiners (!), even though the accompanying images and text may pretend that they can be used to catch falls. They may even have YouTube videos from people claiming to have used them that way, but just because somebody else risked their life with an uncertified knockoff brand, or got paid to pretend that they did, doesn't mean you should; you will never know until the moment it fails to catch you, by which time it is too late. If the manufacturer of a device does not trust their device enough to certify it for catching falls, then it should not be trusted for catching falls. The author of this website urges you to purchase only reputable brands, from trustworthy suppliers, and use them with appropriate ropes. Your life depends on it. If a brand is only ever sold online, not in dedicated physical shops, it is almost certainly not reputable enough.
The GrandWall Equipment uAscend earns a specal mention here, since some climbers recommend it for this purpose, and it is a very basic rocker without a locking switch, so it looks like it should be suitable. It is certified as a fall arrester under EN 353-2 and the Canadian manufacturer's website says that it is an ascender that can be used with 8-12 mm rope, as a rope grab for limited mountaineering applications. However, the website and marketing is hugely misleading, as the device is only rated as a fall arrester when used with 12 mm rope (not 8-11 mm rope), which nobody ever uses for mountaineering. The manufacturer does not state this on their website, and the device stamp says "ROPE 8-12mm" instead of 12 mm, which is not compatible with the EN 353-2 requirements. It does not move downwards freely on a rope, since it has a spring causing it to lock on the rope, so it is not useful for the situations where it would be needed. The device is not rated as an ascender at all, no matter what the manufacturer claims on their website, since it only has a single certification, and that is not as an ascender. The manufacturer does not trust their own device as a fall arrester, even though they certified it as one, as they say that it needs its own backup device. This type of misleading marketing is both shameful and downright dangerous, and really, any manufacturer that acts this way should not be trusted. Other markings on their device have mixed up the terms when specifying the minimum breaking strength, which suggests that the manufacturing organisation does not understand what they are writing, a mistake which is most common with knockoff brands. The device has been tested and it broke below 6 kN, while a device needs to cope with 15 kN static loading to pass the EN 353-2 certification testing. This device should be treated like any other knockoff brand, and avoided.
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