Petzl equipment is very popular amoung the Caving, Climbing and Rescue of the dry karst exploratory side of our National Speleological Society community...being personally involved only with the wet (cave diving) side I have no experience with the equipment. Though some 'sump' divers do use such equipment... Its use for mast climbing does show interesting possibilities...
I have used a petzl grigri for solo rock climbing. I'm not sure the differences between this device. I think the grigri is more rock climbing specific where this one has more industrial applications.
However, I trusted the grigri. It worked on the same principal and they still make it. It has teeth and the rope slides freely one way, even though with the grigri it snakes through, so you have to pull it through with each step up, and if you fall, the teeth engage and lock the rope.
It's how I imagine a seatbelt on a car works.
With this device would you be able to easily release it if you were alone. What if you swung away from the mast? The gri gri allows controlled descents if I remember right.
As a safety device, I use a figure 8 (with ears) on a second line that I handle, while being winched up. You can lock a figure 8, once at the top. It would be too hard to explain how in writing, but it's simple. However, it needs to be partially loaded to do so, or it can work it's way undone.
The modern automatic devices are probably much better. On the other hand, the real pros can do a safety harness with a prussic knot.
As a 30+ year rock and ice climber, it is a solid bet that I am familiar with all of the ascender, descender, and belay devise options.
The advantage of unit such as the ASAP is that no tending is required; it simply rides up and down the line. This and related units are commonly used in industry and construction for moving up and down un-guarded ladders and towers, and most commonly for roofing and building maintenance. They are not the means of support; there is always some other climbing means, whether it be steps or rope climber system, to hold the worker in place. However, this unit also has a lock function, which would be nice for some access methods.
I have seen this in use at a mega-yacht yard by riggers, generally being hoisted by halyard winch; if the belayer has a brain fart and the wraps come off or the tail is dropped, the climber will be caught in a short distance, without adding an extra distraction to his work.
Petzls self arresting, etc. gear is great; have used them a lot during mountain and high angle rescue. Problem is just like any such device ... you really need to PRACTICE with them to be sure and to be confident in their usage.
Being a longtime vertical caver and sailor, I might be able to offer some perspective. That Petzel thing looks complicated when it is nothing more than a fancy Gibbs Ascender. I'd not want to use something that looks like it'd jam with cave mud in a cave. Why not just buy a Gibbs? They work the same and I've long used them as described, they ride up the rope easily but jam when you fall or go back down. A Gibbs is easy to release and very simple.
I now have something that is even simpler that would be ideal for this purpose. I don't have it her so wait till I get home to get pics of it and the manufacturer but it is a simply thing like a cam cleat with teeth. You put a carabiner thru it and it'll ride up the rope easily but jams when pulled back down. The teeth make it questionable for muddy cave rope but it'd be great for use on halyards.
Yes, I have managed to combine sailing and caving.
RichH: Practice is everything. I'll be ice climbing tomorrow!
FrogWatch. I first used a Gibbs 30+ years ago. This is very different in function. It slides up and down the rope without tending, but catches a fall. In other words, it will not catch descending at normal speed, but will catch a fall.
Nope, I would not use this is a muddy environment and I would maintain it carefully in a marine environment. However, Petzel is well known for industrial fall arrest equipment, perhaps the premier vendor.