By Chris Thompson, vacuum excavation product manager for Ditch Witch.
As anyone in the utility construction industry can attest to, regulations that require exposing existing underground infrastructure have increased greatly over the last several years. This has led to a large increase in the demand for vacuum excavators. As any growing business segment, this has drawn a lot of new people into the vacuum excavation market. While it is great to see this critical tool of the underground jobsite become more mainstream, this can lead to some misunderstanding and misuse of the equipment that might be costing contractors money.
There are a few helpful reminders of note that will ensure owners and operators are working effectively. The goal is to get the job done as quickly as possible, with as little cost as possible, while following best practices to mitigate damages.
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Wrong Equipment
The first mistake commonly made by contractors is having the wrong vacuum excavator for the job. Oftentimes, the initial cost of a bigger vac is enough of a deterrent for contractors to make the investment. If a contractor is just wanting to stick their toe in the water and learn more about their vacuum needs, a smaller unit is a great place to start. However, for a more experienced contactor, or a contactor looking to bring in-house soft excavation work they are currently subbing out, a smaller vacuum excavator may cost more over the long haul.
An undersized machine may not have enough freshwater on board to complete a job, or multiple jobs in one day. Trips to get more water slows down the operation. The same is true for spoils tanks. Smaller vacs will obviously fill up faster and require more trips to the dump site, which equates to more time off the job and increased fuel costs and dumping fees.
Additionally, it’s important that contractors are buying the correct type of vacuum. Many equipment manufacturers have multiple types of vacuums. Two common types are hydroexcavator vacuums, meant for potholing, and mud vacs, which are designed as suction only machines, mainly for HDD spoils support. Contractors who try to dig with mud vacs are in for a long, unproductive day.
Wrong Nozzle
The nozzle contractors select to use on the end of the wand is another factor in how much money can be made on vacuum excavation jobs. The first consideration about nozzles should be the size. If a nozzle is too small, the contactor may not be getting the full benefit of the water system from the vacuum. If the nozzle is too big, it will have too much water coming out and will struggle to get enough pressure to cut.
Nozzles are rated by gallons per minute (gpm) and should be fit to the vac. Typically it is recommended to select a nozzle that has a gpm output that is slightly less than the maximum gpm the water system is rated to produce.
Now that you have the right size, you’ll need the right type. Fan nozzles increase the likelihood of damaging existing utilities. Oscillating nozzles should always be used, not only for the sanctity of the existing utilities, but also for production. It’s expensive and time consuming to have to deal with damaging utilities and using underperforming equipment.
Much like the vac itself, you get what you pay for when it comes to nozzles. Cheaper nozzles don’t perform as well, will typically wear out and need to be replaced faster, and can not be rebuilt. OEM equipment, like the Prospector nozzle, is rebuildable, oscillates and has multiple sizes that can be fit to any vacuum excavator.
Too Much Cutting
Costs can add up quickly on a vacuum excavation job. One of the quickest ways to add unnecessary expenses to the jobsite is over-cutting the size of the excavation. Contractors are strongly encouraged to start with the smallest possible hole, in diameter, and only go bigger when needed. By over-cutting, contractors will use more water, collect more spoils than necessary, and add time and costs to the job.
Vacuum excavator contractors should have already called 811 to locate existing utilities before beginning the job. However, there is an 18” tolerance zone on either side of the paint and/or flag they put down to mark the spot. These locates should be verified by the contractor. Not only does this go a step further in damage mitigation, but it also reduces the amount and size of holes the excavator will have to dig. The more precise an existing utility can be located, the less dirt an excavator will have to move to expose it.
When potholing, it is important to excavate to the depth of the bore, not just to the utility. If an HDD crew is coming in behind the vac to install new product, the vacuum excavator needs to dig deep enough to visibly see the new product passing under the existing. This step helps mitigate damage to utilities and equipment, resulting great time and cost savings for contractors.
Make More Money
Regular maintenance, like cleaning and changing filters, will go a long way in keeping vacuum excavators up and running. And operational tips, like always using a boiler in sticky soils, regardless of ambient temperature, can make contractors up to 30 percent more efficient.
There is a lot of work to be done in this space, and a lot more coming. By ensuring contractors have the right vacuum excavator, with the right nozzle, they’ll be well on their way to cashing in. With the proper operational procedures and following best practices, contractors will be set up for success.
