A little air pressure — say, 14.7 psi, the atmospheric pressure at sea level — doesn’t stir up anything. But crank it up to 1,000 or 2,000 psi, and the concentrated bursts of air can easily blow away compacted earth. Add water to slurry the obstructing soil and a vacuum hose to collect the muddy solution and — voila! — you have the modern hydro-excavator.
Mobile soft excavators — some of which eschew the water component — have been around for decades as an alternative to backhoes and other mechanized digging equipment. They are particularly handy for safely uncovering buried utility lines and pipes. Established best practices for using and maintaining the machines enhance their utility even more.
“The art of hydro-excavation remains the same. The speed with which you can do it is enhanced as the machines evolve,” says Dan Coley, President of Hi-Vac Corp., which makes the X-Vac brand of excavator. He adds that quicker excavation doesn’t lie in just blasting away, using higher and higher volumes of air and water. “There is no sense in using more water or pressure than needed to expeditiously dig. If you can do the job with 1,500 psi, it doesn’t make it much faster at 2,500 psi. And beyond that, you can damage what you are trying to reach.”
The machines do keep getting bigger, however, along with the rest of the mechanized world — think pickup trucks. However, Trevor Connolly, Vice President of Sales and Marketing at Vacmasters, cautions that the size of a machine doesn’t necessarily mean it poses more hazards for operators or the utilities being unearthed. “More powerful means more efficient, not more dangerous,” he says. “More horsepower means faster digging times and faster vacuum times.”
Vacmasters, incidentally, was for many years the only manufacturer of excavators using only air pressure. Some other industry manufacturers now offer customers a choice of hydro systems or air-only excavation units, but Vacmasters continues to promote the newer air-only technology as less potentially hazardous to buried lines and cables.
Speaking of protecting buried lines, Vactor Mfg. has released its “DigRight” technology, for which a patent is pending. The technology lets an operator select a maximum desired water pressure for a particular situation based on vacuum excavation best practices data. It limits the unit’s water pump from exceeding maximum pressures designated by a customer, recommended by the industry’s engineers and stipulated for a particular application. Selecting the proper pressure has the pleasing side-benefit of extending the life of Vactor HXX excavators.
What are some other best practice tools and recommendations to protect a machine, safeguard the operator holding the high-pressure wand and boost productivity?
Because operators are at risk of injury from the highly pressured air of digging wands and powerful vacuum suction of collection hoses, precautions are engineered in. Safety mechanisms on the Vacall AllExcavate hydro unit are typical of the industry’s efforts to protect the operator by putting safety in his hands. Emergency shutoffs are on the operating panel as well as on the remote tethered panel and the wireless remote. Punching the shutoff immediately returns the unit’s power plant to idle. A vacuum breaker also allows an operator to stop suction without interrupting the rest of the operation.
“Operators should always inspect the unit prior to leaving for the jobsite to ensure all required vacuum tubes, nozzles and accessories are loaded in the truck. Forgetting a nozzle or vacuum tube can bring a job to a halt,” says Ben Schmitt, Product Manager for Vactor. Aside from helping prevent forgetfulness, inspections contribute to safe operation, Schmitt says. “Vacuum excavation works on high pressure and vacuum, both of which are extremely dangerous.” To assure that such inspections occur, Coley suggests that operators inspect the excavator unit at the beginning of a shift with the same care taken for a CDL pre-trip inspection. “Your DOT inspection is a fantastic time to do your own hydro-excavator pre-trip inspection.”
Soil types can determine nozzle selection. “Using wands is quite an art. The wedge, the spike, the most accepted one is the rotating nozzle. They all have a suitable application,” says Vacall Vice President Bill Petrole. “The wedges work well in tough material when you are not worried about damaging cables. You can use it like a shovel.” In more sensitive digs, more care must be taken to avoid interruption of a utility. Because suction hoses also can pose dangers during cable and line digs, rubber booting generally is affixed to the probing end of the hoses.
How many operators are enough on a job? Some manufacturers say one person can safely operate a hydro-excavator. Unlike fire hoses, the air and water being spent into the ground does not produce too much back pressure for an operator to control. However, other manufacturers recommend that two people control the process. “We always recommend a minimum of two operators,” says Connolly. “Any fewer hands on a job and it could be unsafe because it is fairly difficult to manage both digging and vacuuming. The big reason we recommend two is because you are going to be operating more efficiently.” Coley agrees with that view: “There is no reason to have three people on a job, but having two people is safer and more productive.”
Hydro-excavators — as opposed to units employing high-pressure air only — need to keep tabs on the water they are using. Schmitt says more water is not always better. “Operators should try to minimize the amount of water used during the application. Minimizing water usage will allow more productive time on a job and more debris in the debris tank.” Furthermore, bad water can lead to deterioration of components in the hydro-excavator, says Petrole. “One of the top things that can be done to keep an excavator in top condition is to use as clean of water as you can. A lot of times operators will take water out of a creek, and a water pump is sensitive to dirt.”
Besides being familiar with the emergency switches that interrupt the flow of air, water and suction, operators should wear personal protective equipment, including gloves. Ears should be insulated against the noise of the operating machine and eyes protected from ricocheting materials. “The best is a full-face shield mounted to a hard hat,” says Coley. “It’s a good idea to wear it always.” Petrole says Vacall recommends grounding devices for its trucks and insulating placemats for operators to stand on. “I don’t know anyone who has been hurt like that, but you take all the precautions you can.”
Daily inspections and regularly scheduled maintenance are absolutely necessary to keep an excavator functioning reliably and well. Are recommended checks and maintenance schedules actually followed? “More often than not, the inspections are being done,” says Coley at Hi-Vac. “I think most operators recognize that what they are operating is very expensive, and they want to keep it in good shape. Successful companies and departments have successful people doing this.” When care isn’t taken, the neglect becomes obvious, in the view of Petrole. “A good indicator of poor maintenance is downtime. If you maintain these trucks, there is no reason they shouldn’t go out and operate every day.”
Giles Lambertson is a Freelance Writer for Utility Contractor.