Vacuum excavators have become one of the most common tools used to identify existing utility assets during underground construction projects. With new advances in technology, they are quickly becoming a must-have machine to support HDD rigs in trenchless projects, as well as projects that require the removal of spoil while minimising ground disruption and removing the risk of damaging assets.

20170413_160058There’s no one-size-fits-all solution for every excavation job, but there are a number of key differences between vacuum excavators that should be considered when selecting the best one for your project.

Here, Jeff Lawson, National Construction Equipment Sales Manager at Vermeer, discusses the key factors that should be considered when choosing the correct vacuum excavator for your specific job.

Displacing spoil with air and water

Vacuum excavators use pressurised water or air to displace the soil. Water digs through most types of material faster than air and is more effective on a wide variety of materials. As the materials will be wet, more spoil can also be held in spoil tanks. However, there is also a risk of spoil becoming contaminated and needing to be removed from the site.

“Air is not as fast as water, but it allows for a neater process as the materials are dry so they can be replaced to the site immediately. Using water, the material can’t be returned to the site unless it has dried out,” Mr Lawson said.

“Operators can also select the level of air or water pressure to use depending on the utility asset they are identifying. Low pressure should be used for gas and fibre lines, and high pressure for water pipes.”

Choosing the right vacuum blower

There are three distinct types of vacuum blower used in the industry that you should be aware of: liquid ring pumps, centrifugal fans, and positive displacement blowers. Mr Lawson said selecting the right blower for your application is an important step.

“Vermeer’s vacuum excavators use positive displacement blowers as they maintain constant volume and speed, and reduce loss of airflow,” Mr Lawson said.

“They also come in a range of power levels and hose diameters to suit each job site. The VX200 is particularly suited for big jobs. It has a large 6” (15.2cm) hose diameter with a 3200cfm (90.6 m3/min) blower at 457.2mm of mercury. At the other end of the scale, for smaller jobs the VSK100 has a 3” (7.6cm) hose diameter with a 573cfm (16.3 m3/min) blower at 254mm of mercury.”

Spoil tank size

Spoil tanks come in a variety of sizes, which will determine how much spoil you can remove during the day. Mr Lawson recommends that operators select a tank size that can hold a minimum of half a day’s worth of spoil, although a full day’s is ideal.

“The bigger the tank, the more material you can vacuum up and store. Another thing to keep in mind is that the size of the tank will also affect which tow vehicle or truck is required,” Mr Lawson said.

Vermeer has units with spoil tank capacity ranging from 500L to 11,000L. For larger projects, the VX200 has a spoil tank capacity ranging from 4000L to 11,000L, with a standard option of 3000L of fresh water shared between two self-equalising saddle tanks.

Small projects with restricted space are also catered to, with the smallest unit, the 100 gallon VSK100, fitting into the bed of a full size half-ton truck.

Strong seal and locking mechanism

Selecting a unit that has a hydraulic door with a strong seal and manual locking mechanism is a feature that contractors should consider.

This will not only prevent material from escaping the tank, but it reduces manual handling risk, making the process safer and boosting productivity.

For example, Vermeer’s VX200 has a cam-over auto-locking hydraulic rear door that provides a 360-degree positive seal without additional clamping requirements. The cam-over design also has no moving parts, so all maintenance is external.

“Having the hydraulic mechanism located on the outside of the tank is important, as if it is inside, it could potentially leak hydraulic fluid, causing the spoil to become contaminated,” Mr Lawson said.

“Contaminated spoil is a hazardous material which, if put back in the ground, could cause a variety of environmental issues to the area. It’s critical to prevent this contamination from occurring.”

Avoiding clogging with quality filtration systems

While the vacuum blower and spoil tank are the things that are front-of-mind for most people, Mr Lawson said it’s also important to select a filtration system that is able to filter the spoil and avoid clogging.

“Vermeer’s VX200 has a three-stage cyclone filtration system which has been designed specifically for 3200cfm blower systems. Three- stage cyclone filtration systems are one of the most effective filtration methods as they allow for both wet and dry vacuum excavation, while also prolonging filter life and keeping maintenance costs low.”

A variety of sites and applications

All job sites are different so choosing an excavator that is best suited to your work site will provide the most benefit.

Smaller sites demand less power, and therefore less equipment and labour. Larger sites, on the other hand, demand heavy-duty equipment, and harder-to-reach sites where there is uneven or rough terrain require heavy-duty trailer options.

To accommodate various site requirements, Vermeer’s VX200 can be mounted on either a new or repurposed truck chassis. The tank, power pack and water system all have a modular design, offering the versatility of mounting the unit in the configuration that best suits vehicle and operational needs.

As vacuum excavators can also be used with a wide range of attachments and tools, they are used for a variety of other projects, including cleaning catch basins, digging post holes, sewer jetting, and exercising water valves.

Vacuum excavators continue to gain popularity for projects that require minimal landscape disruption and a reduced risk of utility asset damage, and are saving contractors time and money on trenchless jobs.

This partner content is brought to you by Vermeer. For more information, visit www.vermeer.com.au

Elisa is an experienced industry journalist and is a regular contributor to a range of energy and infrastructure titles. She has a unique knack for quickly finding the angle in any story her audience is most interested in learning more about.

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