Ever sliced through a tree with a chainsaw?

Try again, but this time…underwater. With limited visibility.

Randy Busby is the Divers Institute of Technology (DIT) instructor for hydraulic tools, salvage theory and practical. He defines underwater chainsaws as “pretty unusual.”

“Using a power tool underwater is not something people see or do every day; it’s not something a lot of people know even exists.”

At DIT, training with the underwater chainsaws is an experience classes enjoy immensely. They apply their cutting skills on a tree trunk: the student who slices it thinnest is deemed the winner. It’s not an easy task, but it’s one of the many in their hydraulics and salvaging training module.

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Underwater Power: Hydraulic & Pneumatic Tools

Of course, a chainsaw doesn’t always cut it.

Commercial divers use a variety of hydraulic equipment and power tools on the job. Underwater construction that requires demolition or cleaning may require these types of tools. Especially if the job requires more than just brute strength.

How it Works: Power Tools’ Function & Application

“In my experience, underwater power tools are more used offshore, used to do everything from bolting up flanges, to drilling holes to plant explosives and scrubbing the hull of a boat. They are used more often offshore, but are also used for the same types of things in inland work on a smaller scale,” Randy says.

Here’s a few examples of jobs requiring underwater power tools:

River dam demolition

Vessel hull and propellor polishing

Cutting through coral blockage

Driving in bolts/rods

Creating holes in dock pillars

Flange pipes

Since divers use this equipment underwater, the equipment must have a tough exterior that can hold up under pressure and floating material. These tools are powered through hydraulics (fluids in pistons) and pneumatic (air pressure) application. Not electricity like underwater welding stingers.

These tools require large amounts of energy for small periods of time, and hydraulics and pneumatic power are perfect for applying this force in the wet.

Operation underwater versus topside is a bit different, as Randy explains.

“The main differences are the weight and leverage. Topside leverage is a lot easier than underwater leverage. If the tool gets away from you and starts to spin, it’s going to take you with it.”

Surface Team Responsibilities

In DIT’s course, students train with the underwater chainsaw, jackhammer, hammer drills, impact hammers, impact wrenches and hull scrubbers. And they don’t just train underwater. Surface operation is just as important to the proper application of hydraulic tools.

Randy points out that the responsibilities of surface teams are primarily focused on equipment maintenance, preparation and delivery:

Hooking up tools

Testing tools

Checking for safety guards

Proper Maintenance if needed

Sending tools up and down to the diver

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Meet Hydraulic Tools

Underwater Chainsaw: Precision is of the utmost importance in underwater use. Underwater chainsaws run off hydraulic power and cut through wood, plant growth or other entanglements.

Jackhammer: Underwater, divers use jackhammers in a variety of different positions, but always grip the handles securely, focusing pressure toward the end of the bit. Several different weights exist, ranging from light to heavy.

Hammer Drill: Used for much harder material like rock or cement, commercial divers often utilize hammer drills to clear out holes for bolts and other support systems. They use special carbide tips to get the job done.

Hull Scrubber: Wax on, wax off. Divers polish and clean away rust, coral and growth on submerged metal. They don’t have the power of most of their high impact cousins, but are just as effective.

Impact Hammer: Like the hammer drill, impact hammers chip away cement and masonry. They make use of various sizes and shapes of bits to cut, chip or break away debris.

Impact Wrench: Impact wrenches use a powerful swing-hammer movement to tighten or loosen bolts. They come with two handles, one for the back and a bottom handle on the business end.

Ins & Outs of DIT Hydraulics’ Module

Students train with these power tools in month five of their seven month training. The hydraulics portion lasts for two weeks.

Students learn all aspects of power tools’ application, maintenance and safety.

They also study the how diesel engines to supply power to diving equipment. Sending power to hydraulic tools works similar to underwater wet welding, in which power is controlled through a knife switch.

“The tools are not always “hot” (on) when they are sent to the diver, the diver will call topside to give power to the tool. There is not a knife switch, but there is something called a squash plate (topside) which is similar, it gives power from the hydraulic power unit to the tool underwater.”

Importance of Safety

Like all aspects of commercial diving, safety is the number one priority in operating underwater power tools. Randy emphasizes several actions when he covers this portion of the course:

“Make sure all safety guards are in place while you are hooking up equipment. Watch your hand placement; make sure your gear is not floating up into the tool; make sure you are standing clear when the tool comes down, so it doesn’t hit you.”

Written by Matt Smith, Creator of Water Welders