Maintenance on Vacuum Excavators Will Keep the Machine Profitable

Use these troubleshooting tips to keep your hydroexcavator out of the shop and on the job making money.

Maintenance on Vacuum Excavators Will Keep the Machine Profitable

Vacuum excavators handle a ton of work every year, but keeping up with maintenance on the machines can go a long way in ensuring they last for your company.

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No matter how well a hydroexcavator is engineered and built, the rigors of working under difficult and demanding conditions take their toll. As such, some downtime is inevitable.

But savvy operators with the ability to troubleshoot problems can get their machines up and working again, without suffering significant losses in revenue and job site productivity.

With that in mind, here are some common problems operators encounter while running hydroexcavators and what can be done to solve them and keep the productivity train rolling.

Mike Selby, southeastern regional sales manager for Vac-Con, and Dave Barr, sales manager at Presvac Systems, who have a combined 60 years’ experience in the industry, share their best tips for troubleshooting in the field. 

LOSS OF VACUUM

This is typically caused by debris clogging a hose, a tear in a hose or dirty filters. “Most machines have a vacuum gauge,” Selby explains. “If it shows elevated vacuum while it’s not working, you have a hose restriction. If you have low pressure while working, you usually have some kind of tear or hole in the hose. Or the suction filters that protect the blower from carry-over contamination are clogged.”

To fix clogged hoses, booms or turrets, shut down the machine and check out each one. “Blockages are most likely to occur where the hose has vertical to horizontal to vertical transitions,” Barr says. “Prioritize the most likely location of the problem and move down to the least likely location. When you find the clog, move the hose out and give it a shake to loosen the debris.”

To help prevent clogged hoses, Barr suggests using the following rule of thumb regarding hose diameter: The hose should be three times the size of the material being vacuumed. If it’s 2-inch-diameter gravel, for instance, use a 6-inch-diameter hose.

If the hose, boom and turret are clear, then examine the cyclone separators. If they’re clogged, lighter materials remain in the airstream longer and carry over into the filter, which is final protection for the blower. The remedy for this is to clean or replace the cyclones and/or filter, Barr says.

Selby recommends having several extra separators on hand. While one is getting cleaned and washed, another can replace it and the truck can keep working. “If the cyclonic separators get full, material can’t settle out,” he explains. “So you need to keep the separators clean. Some have a removable receptacle at the bottom that can be pulled out and dumped.”

Operators should also carry extra filters to replace clogged filters. To minimize downtime, consider cleaning filters in between dump cycles, Selby advises.

If a hose is torn, use duct tape to stop air leakage. “You have to remember that material is running through the hose at 150 to 200 mph, and sands and rocks can eventually abrade a hose,” Selby says. “Wrapping a hole with duct tape is a quick field fix that’ll at least get you through the day until you have time to replace the entire hose. Trying to keep working with just a duct-tape patch only delays the inevitable total-hose failure.”

NO WATER FLOW

Presvac hydroexcavators are equipped with triplex plunger water pumps, in which water first passes through a strainer. A clogged strainer will stop water flow, which results in a hammering or banging noise, Barr says.

“The solution is to shut down the system, then check the water-supply line and the strainer to make sure they’re clear. When you start up again, be sure to open the drain valve to make sure everything flows properly and that there’s no air in the water-supply line.”

Selby also points out that some nozzles are more fragile than others. As a result, they’re more prone to clogging with whatever material is being excavated.

Fixing that requires taking apart the nozzle, which isn’t always feasible out in the field. “So carry extra nozzles,” he suggests. “If something fails on a nozzle and you don’t have a replacement, then you’re done — dead in the water.” 

LOSS OF WATER PRESSURE OR FLOW

Several things typically cause loss of water pressure, including a worn or improperly sized nozzle tip or an unloader that’s stuck open or set improperly, Barr says.

Resolve the first two issues by replacing the nozzle tips. As for the unloader, which regulates water pressure, it needs to be disassembled and cleaned. “Usually there’s sand or particulate stuck inside the seats of the valve,” Barr says. “Because it’s a high-wear item, it’s designed to be maintained in the field.”

Furthermore, operators need to ensure the water pressure is set properly for the type of nozzle being used. “You have to size the nozzle according to the pressure. We have an adjustable unloader you can set from 1,200 to 3,500 psi.” 

BROKEN BLOWERS

There’s not much anyone can do in the field to repair a blower. But Barr points out that operators can minimize blower issues by not running the hydroexcavator at high vacuum while the engine is running at low revolutions per minute. This can occur when a hose gets clogged while cycle-loading heavy materials, such as sludge.

“As you create vacuum, the horsepower draw increases,” he explains. “But if you have high vacuum and low revolutions per minute, the torque goes up … and the drive shaft can only handle so much torque.”

To avoid this, Presvac hydroexcavators feature a velocity-control valve that allows the operator to reduce load velocities as needed, he says.

If the blower isn’t working because carry-over debris has locked it up, an operator can try to physically turn the blower backward to work the material out. To do this, turn off the machine, then manually turn the blower in the opposite direction than it normally rotates, Selby says.

“You need to put a big pipe wrench on the drive shaft in order to get it to spin backward. The drive shaft is easily accessible.”

MAINTENANCE MATTERS

Performing routine maintenance and listening for unusual noises can go a long way toward minimizing repairs and keeping small issues from becoming bigger issues.

“An ounce of prevention is worth a pound of cure,” Selby says. “If you do periodic maintenance as recommended by the manufacturer, the machine should at least last through its expected life cycle of roughly 10 years.”



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