Learning to effectively and safely use air or hydroexcavation means you can offer a wide variety of services.
Vacuum excavation is most commonly used for things like the safe exposure of underground utilities, but the added safety and precision that it provides means the applications are endless.
Adding vacuum excavation to your services opens the door to a wide range of jobs you can take on: excavate for onsite system installation in small lots or confined areas with confidence; bid on municipal work locating and excavating utilities, helping with main break repair or digging utility pole holes; or even building landfills.
There are so many opportunities, particularly in the winter when it’s more difficult to use traditional excavation equipment to break up frozen ground. However, with the diversity in size and capability of vacuum excavators, you need to know how to right-size a vacuum excavator and follow best practices to increase productivity.
A wide array of attachments can expand the applications of any vacuum excavator. Different size-reduction tools allow cleaning of smaller water-valve boxes and catch basins. A valve exerciser attachment, which mounts to the vacuum trailer, can save crews countless hours of exercising valves from one stationary location, eliminating the old-fashioned hand cranking method.
In today’s vacuum excavator market, there are two predominant methods. Hydroexcavation uses water to excavate the hole, and is particularly useful in fragmented soils or heavy clay conditions. It is very useful in congested or urban areas, as it limits the amount of particulate material in the air.
Even with the numerous proven benefits of hydroexcavation, there is a growing trend toward using air for excavation. Air excavation is typically more successful in sandy, dry or granular soils.
One of the advantages of air excavation is being able to put the soil back in the hole. If you are using air, you don’t get the soil wet and you can put the dry material back in and don’t have to haul material in and out.
Determining the correct size of a vacuum excavator is just as important as the excavation method. Excavator selection can often be predicated on tank and blower capacity, which frequently determines hose size and overall machine productivity. Most vacuum excavators tend to feature tanks between 500 and 800 gallons, however, contractors engaged in fluid management will use rigs up to a 1,200-gallon capacity. For contractors that typically work on smaller projects, smaller excavators are available with only 100- to 250-gallon capacities.
Operator best practices
Constant attention and adherence to training are necessary for safe and effective operation. Most manufacturers will set the water pumps on hydroexcavators below 3,000 psi, with 2,200 to 2,800 being the most popular range. Many of these machines have pumps capable of achieving pressures up to 4,000 psi, but it is this high pressure that can lead to issues if the operator is not careful.
When working around sensitive utilities or a mass of tree roots, experienced operators pay close attention to their water pressure as well as the distance between the rotary nozzle and the lines or roots to avoid damage.
Through proper maintenance and training, the potential for damage is alleviated. The aforementioned rotary nozzle is an important piece to this puzzle; being prepared and precise are also equally important when completing an excavation project.
With the weight, air pressure and suction factors that come with vacuum excavator units, being aware of the safety guidelines is critical for worker safety, as well as the protection of equipment and road surfaces.
Safety training should begin with a focus on the suction and off-loading capabilities of vacuum excavators. Hoses have positive connections for both off-loading and suction, and operators need to ensure that hoses are secured properly before performing any task.
There is a proper way to off-load a vac unit. First, if you’re using a trailer-mounted unit, always make sure to keep it attached to the tow vehicle. Next, open the gate valve on the bottom of the rear tank door and bleed all of the fluids out of the unit so you reduce the tank load and weight of the tank. Finally, open the rear door and elevate the tank to dump the spoils. Some vac units come with an in-tank washout system to assist in removing spoils, while others may include a liner to assist in releasing spoils.
Many of today’s vacuum units have the ability to put a small amount of pressure inside the vacuum tank to help off-load the fluids without ever having to open the rear door. In these situations, a strong banded coupler is needed to help create a positive connection to the hose. Substitutions like duct tape are never recommended in place of a quality, approved coupler.
Pressure can also help push rocks and other obstructions from the hose, but a good positive hose connection and integrity throughout the hose length is critical for this. If you’re using any kind of segmented hose, a positive cam lock style coupler is important. These couplers are ideal for positive connections when an operator is pressure off-loading or using reverse pressure in the tank to remove clogs.
Wear and tear
The rotary nozzle is the No. 1 wear item on hydroexcavators and is important to monitor for safe operation. It is constantly working in an abusive environment and too often becomes the digging tool itself. If the nozzle becomes damaged or inoperable — losing its rotary dispersion — the high water pressure can create risk of damaging a utility.
The suction hose is next in line. The hose can get worn down over time and often sees more rapid wear than other components. Daily job site checks should also be done on the air filter between the tank and blower. The filter should be free flowing and free of dust.
Cleaning the tank, vacuum float ball and full-tank shut-off mechanisms should also be included in the maintenance schedule. Full-tank shut-off mechanisms reduce the risk of overfilling the tank and passing material to the final filter and blower. Finally, dumping the tank at the end of the day limits the chance of dirt and dust drying and solidifying inside.
With trailer vacs that can weigh up to 24,000 pounds, it is also important to perform routine maintenance on the towing and transportation equipment. Regular inspection of the brakes on a trailer hauling the excavation unit is important for both safety and fleet maintenance.
Weight distribution is also crucial when towing vacuum excavation trailers. Having axles equally loaded and at proper hitch height is critical to the longevity of tires and axles, as well as the trailers themselves. If the hitch is too high you will put that entire load on the rear axle. If it is too low, the opposite will happen and the whole load will shift to the front. Either imbalance can lead to excessive tire wear or damage to either the front or back axle of a trailer.
Vacuum excavation is growing in popularity not only out of necessity, but also viability. The ability to quickly and effectively remove dirt and debris has enhanced the demand and role of vacuum excavators. Before starting out, however, you should compare the selection, safety and maintenance of each excavator to achieve the best possible results.