To Rent or Not to Rent: Vacuum Excavator Edition
The vacuum excavation market has really taken off over the last two years, especially in the Northeast — these trucks are the future of digging around utilities. Some people will argue that a mechanical excavator is faster and more efficient than a vacuum excavator, and to some extent that is true.
However, what is your employees’ safety worth? Or the time and money it will cost, if you puncture an electrical line, or an unknown water line? These things are less likely to happen when you are using a vacuum excavator.When a customer is considering renting a vacuum excavator, he or she should take a few things into consideration, first where will the unit be working. These trucks come single axle, tandem and tri axle. If you are working in the city, you want a smaller truck for better maneuverability. Another consideration is where will you be dumping the material and how often. Not only do the units come in different axle configurations, but the debris bodies are also different sizes as well; you can get them in 3, 9 or 12 cubic yards. Depending on how far your dump site is, you may want a 12 cubic yard debris body as opposed to a 9 cubic yard unit so you can be on site for longer before having to go dump.
Once you pick the size truck you are going to use, you will pick which way you feel will be best to excavate the material. You can use up to a 300-cfm air compressor, which is usually used when excavating around electrical lines or in a substation. This method is also nice because after you dig the hole, you can reuse the material in the debris body since it is dry material; therefore, eliminating the need for the contractor to bring a dump truck with clean fill onsite. The other option is to use water, where, depending on the size of your truck, you will have anywhere from 8 to 20 gpm to excavate. This is the most common way of vacuum excavating and the fastest. If you are working on a chilly day and the ground has frozen, you have a 400,000-btu boiler that you can switch on to heat the water and help you cut through the frost with ease; the heated water also comes in handy when trying to cut through thick clay regardless of the season.
Much like the water system, the size of the vacuum system all depends on the size of the truck you are using. All vacuum systems use positive displacement blowers and range from 2,200 to 5,200 cfm.
The market for these trucks is only growing and it is not going to slow down anytime soon as more and more utility companies are forcing contractors to include these types of trucks in their bids. We predict within the next five years every utility contractor will have at least one of these trucks in their fleet same as they have mechanical excavators and dump trucks.
The vacuum excavator market has seen major growth over the last 10 years as billions of dollars are being invested into expansion, rehabilitation and updating of the underground infrastructure systems in North America. These systems include water, sewer, natural gas, telecommunications, power distribution and transmission, as well as oil and oil byproducts pipeline installation and maintenance. With all the dollars being invested in the aging and undersized underground utility distribution grid, comes the need to protect these systems from accidental line strikes as well as increasing productivity by eliminating hand digging to locate the utilities.
Accurate above ground locating, coupled with the use of hydro-excavation equipment to pothole or daylight the existing utility has also become required by many of the utility owners and operators. This need has opened opportunity for contractors that already own and operate equipment that has hydro-excavation capabilities, as well as new contractors into the market. The demand for rental equipment has also grown as many of the larger prime contractors desire the ability to regulate their own progress schedules and not have to wait on a sub-contractor to mobilize to their site, as well as to pay the hourly rate for travel time, water, dump fees, minimum hourly charges, overtime and other charges typically included in hiring a contractor to perform hydro-excavation work.
The rental market has also seen growth due to the sheer amount of available work. The underground infrastructure has historically been neglected as an ‘out of sight, out of mind’ problem. With more public national attention, and multiple, long term, Federal government funding programs, the underground infrastructure construction industry should see steady growth for the foreseeable future.
With the increase in unit demand, the manufacturing sector has responded with major improvements with technological advances to improve productivity, safety and reliability as well as improvements in payload capacity to comply with local and federal weight restrictions. The later has been brought around primarily from the commercial market demanding units that are able to legally transport as much spoils as possible.
When considering a rental or purchase of a hydro-excavator, there are a few significant specifications that need to be looked at and decided. We can take the manufacturers branding out of the equation for this purpose, although service support is also a major factor. That aside, all units have some basic specifications to be considered, which are: debris body capacity and the legal weight capacity, fresh water capacity, how many gallons can the water tank hold, etc. These are two of the variables for every jobsite that will affect the production the greatest. If the material must be transported off-site, sometimes a considerable distance, and if a suitable water source is close by or not will dictate the productivity immensely. There are also other specs to consider, such as blower size and performance, boom size and reach and water pump flow and pressure to mention a few.
In general, though, most of the units produced today are comparable when lined up head-to-head and can be broken into four basic groups. Full size units with debris body ranges from 10 cubic yards up to 15 cubic yards and chassis axle configurations from tandem drive to tri-drive or tandems with air lift pusher and tag axles. These full-size units also typically carry 1,000 to 1,600 gallons of water, utilize large 5,000 to 6,000 cfm at 27 in. Hg positive displacement blowers and have 8-in. suction hose booms that are hydraulically manipulated via wireless remote control.
The next size down would be a mid-size unit. These typically have 6 cubic yard to 9 cubic yard debris bodies, carry approx. 600 gallons of fresh water and will be mounted on a smaller chassis with a tandem drive axle or possibly tandem with a pusher lift axle. Often these units will have a 6-in. diameter boom hose and a 3,000 to 4,500 cfm blower. They will still have many of the full-size unit features, just in a more compact, easier to maneuver configuration.
Next would be the compact size unit. These hydro-excavators will have 3 to 5 cubic yard debris bodies, 300- to 500- gallon water capacity tanks and typically a 6-in. boom system. The blower systems are often hydraulically driven as opposed to direct drive transfer case as they require less horse power to drive the blower. Again, the compact units will have many of the same features as the full and mid-size units. One big advantage is the ability for some manufacturers to mount their equipment for the compact size hydro-excavators on a non-CDL chassis. This has become a popular rental feature for contractors that don’t have a pool of CDL-licensed drivers/operators.
Lastly is the trailer mounted unit. These units typically range in size from 2 to 3 Cubic yard capacity debris bodies, 200 to 300 gallons of water and often utilize a 3- or 4-in. suction hose. While some manufacturers do offer a boom system, it’s also common to see units without any boom as the smaller hose is more easily handled with manpower. These units will typically be pulled with a one-ton size truck and require class A CDL drivers.
All the units discussed here have a large array of options, depending on the individual manufacturer. Some of these options include air compressors to perform air spade digging in lieu of using high pressure water, diesel fired burners to heat the water in frozen ground conditions, full opening rear doors, some units have hydraulic hoists to dump and others utilize sloped floors or pusher plates to eject the material out of the debris tank, pressure off load systems, hydro sludge pumps, winterization packages to insulate and protect the water systems from freezing during winter months, and many other options.
Steve Carbeck and Ed Walsh are regional sales representatives-commercial at Jack Doheny Co. Tags: September/October 2022 Print Issue, Vacuum Excavation
