In confined space work it is imperative that we not only have trained workers, check the atmospheres and anticipate any hazards but to also have a way to remove entrants in the event something goes terribly wrong. It is not uncommon for us to have trainees tell us they will “tie a line to the worker and pull them up and out.” This simply will not work! Even if you have the strength and ability to pull a worker up to the top of the tank or vessel, how will you get them through the opening? Can you hold the rope with one hand and move the victims head or shoulders with the other? What happens if you cannot pull them up?
Unfortunately it is next to impossible to pull off a vertical rescue using hand over hand techniques and no mechanical advantage. I want to emphasize next to impossible. In trainings we commonly ask a volunteer to attempt this feat and have only had one success and they made it to the top of the tank and DID NOT make it through the opening. This technique is not only foolish but dangerous. In a horizontal entry, a manned rope will work as you “slide” the victim along the tank or pipe. A mechanical advantage is necessary to make any retrieval timely and successfully. Unfortunately not one piece of equipment will solve the problem in every confined space. Pre-planning your space and having different options is critical to a successful retrieval. The best case scenario, however, is to prevent retrieval need.
Let’s take a look at the top three systems and some of the pros and cons of mechanical advantage equipment.
Tripod:
Pros- Easily the most popular in the industry, fairly common and available, light weight, easy to set up, offers a self-supporting anchor point, designed for use as a man rated system.
Cons- Cannot be used in open top areas or wide openings, need at least 7 ft. of headroom typically, attachment point at top of tripod must be positioned directly over center of opening, only works on vertical entries without redirecting line.
Pre-engineered Haul System:
Pros- Can be used in horizontal and vertical entries, a basic system of mechanical advantage of 3:1 or 4:1, simple to setup as an anchor point for pulley is all that is needed, already rigged to go and requires no additional setup.
Cons- Rope must be taken care of as it is lifeline, subject to environmental abuse, requires a large amount of loose rope in a bag, cumbersome if taken apart entirely, intimidating look.
Davit Arm:
Pros- Similar to a tripod but works off of the side of the vessel, booms out over a large open area, fairly simple to set up as it is contained like a tripod, man rated.
Cons- Requires a sleeve or anchor device of some sort on the side of the tank or vessel to insert arm into, places worker at edge of vessel, somewhat bulky and heavy, only works in vertical entries.
As you can see, not one system will work in all applications. From our opinion, the rope haul system of mechanical advantage of 4:1 is by far the most easily adaptable system for use in a horizontal or vertical entry. We use it in training and highly recommend it for use in real applications. If you have any questions let me know. Anything you can do to assist with retrieving a worker is the best option. Plan for it and practice it!