I recently read a post on a social media site that began a spirited discussion. How to use, or whether to use, a common tool in geotechnical drilling. I’m speaking of course of the slip ring, used to quickly hoist geotechnical rods for sampling. Some drillers love ’em. Some drillers do not. But most geotechnical drillers have used them at some point of their career, or do use them, on a consistent basis.
Maybe you’re a guy who spent his entire career in the water well industry or doing oil and gas work, so maybe you don’t know what I’m talking about. A slip ring is a simple tool: a donut shaped piece of steel that has a tab on one side with a shackle to hook your hoist to. Rods used in geotechnical and environmental drilling are typically flush joint and have no slots machined for breakout. This leads to the use of the slip ring.
Slacking the hoist line allows the ring to slide down the rods if the drill string is secured below. If the drill string is not secured, the driller can run the ring down to the table, put tension with his hand on the hoist line and (when done properly) “lower” the rods into the borehole. Now, this is where the debate comes in. If the rods can slip through the ring without the proper tension, were they ever safely secured? And, furthermore, if you can move the ring down the rod to pick up a different point, it’s possible that you can accidentally move the ring below the center of gravity of the drill string. This, of course, would cause the string to become top heavy and possibly fall over.
So are they safe? The answer to that question comes back to the same conundrum that workers and owners struggle with daily: which is more important, production or drill crew safety? The easy answer to is that safety is paramount, so no one should ever use a slip ring. But in the “real world” things are not that black and white. (See what I think of the “real world” in my December 2019 column.)
In my career as a driller, I have used slip rings extensively and teach my apprentices their uses. “Safe” use of slip rings requires diligence from the drill crew in adhering to a several handling rules:
- Follow company safety policies. Are slip wings allowed?
- Require the driller to always maintain manual control of the rods. Helpers may only assist.
- Allow the driller to control the hoist, so he can coordinate movement to prevent accidental release.
- Keep the ring above the center of gravity of the hoisted drill sting.
- Keep the ring from making contact with anything during hoisting.
- If running rods through a “crow’s nest,” limit the drill string being hoisted to less than twice the tower height.
- If rods, while slipping back into the borehole, begin to “run,” do not use the hoist lever to attempt to catch them.
When used as stated above slip rings could and have been run without incident. We could also walk a balance beam across the Grand Canyon and as long as we keep our balance it’s not a problem. But even the best gymnast falls off once in a while. Look no further than the reason slip rings are used to determine if a mistake will happen. They increase production. Whenever production is the driving force of a job, the tendency is to cut a corner. This corner cutting almost always leads to a decrease in safety.
Drillers tend to be a pretty macho group. A few extra feet or completion of the job a little faster can tempt the best professionals. “I’ve got years of experience and I’m damn good,” runs through the mind of every driller worth their salt. I’ve been in this industry for a while and have rarely met a geotechnical driller that wasn’t “the best.”
Let’s look at other sectors of the industry: water well and oil and gas. How do they handle drill rods? Most water wall rigs either store rods in a carousel, or the rods are hoisted with a hoisting plug and stored horizontally in a rod box. The hoisting plug ensures the rods are suspended below the hook and secured by the “pin” of the plug being threaded in to the “box” of the rod. The oil and gas industry does use a “crow’s nest” built into the derrick of the rig but, the traveling block can get above the rods to place them into the hole. Again, the drill string is suspended below the hook. So the other sectors of the industry have no need for slip rings.
What do rig manufacturers say about the use of slip rings? They are all more than happy to sell you slip rings, but no geotechnical rig manufacturer will put a “crow’s nest” on their drill rig. This means that every crow’s nest installed on a geotechnical rig was either installed by the driller or company that bought the rig. No matter how stout they may be, there’s no engineering rating for what they would support. In addition, OSHA says friction is not an approved lifting device.
I think it’s pretty clear: Slip rings are commonly used, but that does not make them a best practice. Rods should not be hoisted above the height of your tower. We’re all human, so it’s not if an accident happens, but when.
I don’t see the use of slip rings going away anytime soon. Given that, I urge geotechnical manufacturers to build tool-handling capabilities into their rigs as standard equipment. I would also call on drilling contractors to include the cost of safely handling tooling into their bids. In this industry, contractors consistently underbid each other right out of advancing technology for both production and safety.
Until next month, stay safe and keep ’em turning clockwise (unless, of course, you use left-hand threaded tooling).