May 2023 Vol. 78 No. 5
Rehab Technology
Rehab technology: 10 expert tips to ensure safe sewer cleaning
Del Williams | Technical Writer
(UI) — Municipalities must safely clean and maintain many miles of sewer line annually to eliminate blockages and prevent sanitary sewer overflows, which are regulated by the EPA. However, the use of high-pressure equipment in underground sewers can be dangerous, unless operators are well-trained and fully understand the hazards.
Understanding and correcting some of the typical operator mistakes in sewer cleaning can go a long way toward keeping everyone safe.
Dan Story, safety expert and operations manager at KEG Technologies, who has instructed operators for decades, provides 10 tried-and-true sewer cleaning safety tips that address the most-common errors he has observed.
As a national trainer of best-practice techniques, the company is a member of NASSCO.
Tip 1: Properly set up the area around the sewer vacuum truck to ensure operator safety in street traffic.
“To start sewer cleaning, when you park the vacuum truck in the middle of the road, you need to block off the traffic so it can pass in a safe manner. Set safety cones in front and behind the work zone and make sure the hazard flasher lights are functioning correctly,” said Story.
Tip 2: Keep equipment noise levels low enough to hear traffic.
Revving the sewer truck engine and running its vacuum pump can be noisy. Story advises keeping RPMs low enough so operators can hear, and avoid, approaching vehicles, and converse with co-workers, as needed.
One way to do this during engine operation is by only using the vacuum when needed and allowing the water to pass through as the solids remain.
“You can put the nozzle in the bottom of the sewer pipe and let the water run around it,” he explained. “The solids remain to vacuum as needed; you do not need to run continuously high RPMs.”
Another method is using more efficient nozzles, which enable sewer cleaning with lower pressure water, reducing engine RPMs.
Tip #3: Understand how your specific sewer truck boom operates.
There are differences in how sewer truck manufacturers configure, deploy and extend the booms that control the vacuum hose. Some deploy rapidly, some articulate, and some telescope. Operators must understand these differences before operating a boom in the field around their co-workers.
“Because you may go out in different vehicles from day to day, with different crew members, it is important that you understand your boom equipment. For everyone’s safety, do not rush the job; the boom can cause injuries if it is not used with full understanding and control,” cautioned Story.
Tip 4: Use Personal Protective Equipment (PPE) and practice good hygiene.
“Protect your hands and feet with waterproof gloves and work boots,” he said. “Protect your eyes with goggles or a face shield. Of course, protect your head with a hard hat to avoid injury from a swinging boom or a falling object.”
When cleaning sewers, operators exposed to sewage or human waste may be at increased risk of becoming ill from waterborne diseases. To reduce this risk and protect against illness, operators should wash their hands with soap and water immediately after cleaning sewers, before eating or drinking. Avoid touching the face, mouth, eyes and nose while handling sewage, and cover any open cuts, sores or wounds with clean, dry bandages.
In addition, Story points out that the CDC advises vaccination against Hepatitis A and B and other contagious diseases that could put operators at-risk when exposed to sewage or human waste. The CDC, in fact, also recommends vaccinations for tetanus, polio and typhoid fever in these environments.
Tip 5: Open the upstream sewer manhole first.
In underground sewers, operators can be at-risk from toxic inhalation. High concentrations of methane in enclosed areas can lead to hazards as large amounts of methane decrease the level of oxygen in the air. Oxygen deficiency can cause headache, nausea, dizziness and even unconsciousness.
There are precautions to note.
“For safety in sewer pipe, the first thing you always want to do is open your upstream sewer manhole.,” Story said. “That will allow the system to draw in fresh air. On the other hand, if the air were to be drawn directly from the homes, it could fill them with sewer gas, which is unsafe and unpleasant for homeowners.”
Tip 6: To avoid injury, do not start hydro jetting outside a pipe.
With hydro jetting, sewer cleaning nozzles are designed to direct water at exceedingly high rates of pressure. For typical cleaning, 1,000–1,500 PSI is normal. To remove a blockage, pressures as high as 5,000 PSI may be reached.
“Sewer cleaning nozzles at extremely high pressures should only be used in a pipe,” he explained. “If a nozzle is used outside of a pipe, it can whip around like a fire hose. I have seen sewer nozzle and hose go up and wrap around telephone wires. I have seen nozzles over 60 feet in the air.”
Tip 7: Use a hose with a robust safety factor to prevent bursting.
Since hose and nozzle pressures can be so high, it is important to utilize only robust hose of sufficient strength to ensure safe use over time.
“Most operators and municipalities overlook the possibility of burst hoses,” he said. “However, the hose is gradually cut going in and out of sewer pipe. The braided nylon weave remains, but every layer that is cut reduces hose strength and the corresponding PSI that can be run.”
Tip 8: Properly size the nozzle-to-hose connection to prevent nozzle “ricochet.”
If the nozzle-to-hose connection is not sized properly, it can lead to a dangerous, high-pressure “ricochet,” where the nozzle and hose can suddenly turn around and come back at the operator.
“As a rule of thumb, the distance from the tip of the nozzle to where the hose connects needs to be approximately one-and-a-half times the size of the pipe diameter you are cleaning. Sizing it in this way can help prevent the nozzle from turning around and coming back at you,” Story stressed.
He also advises against “free spooling” a nozzle up the sewer line.
“Any time you do that, you lose control of the nozzle – and it can ricochet back at you. To prevent this, use a nozzle skid and hold the nozzle back,” he added.
Tip 9 – Choose the right nozzle for the job to reduce turbulence and wear.
As is known throughout the industry, there are several tiers of nozzles, rated for water efficiency, from Tier 1 (about 30-percent efficient), Tier 2 (50-to-60-percent efficient), to Tier 3 (75-to-98-percent efficient).
What sets the most efficient Tier 3 nozzles apart from others in the category is fluid mechanics engineering on-par with the aerodynamics of race cars or jet fighters.
By more effectively containing, controlling, and directing high-pressure water with less turbulence, a Tier 3 nozzle can deliver more cleaning power at lower PSI. This eliminates the need for operators to compensate for the lack of power from Tier 1 or 2 nozzles by increasing the pressure to higher PSI on the way back through the line.
Ultimately, less PSI (with a better, faster result) makes for safer sewer cleaning, as outlined in many of the tips above.
Tip 10: Slow and steady wins the race – and is safer for operators.
The number-one mistake of most sewer cleaning operators that puts them at risk is rushing through the process, according to Story.
“Most operators run their nozzles way too fast. Rushing to clean more footage of sewer pipe is dangerous. To clean safely, keep the nozzle slow and steady, and let it do its job,” he said.
To stay safe and productive, he advises contractors to never outrun their water, or they risk losing control of the process and eventually running into a blockage.
“Sooner or later operators will run into a blockage of roots, grease, mineral deposits or cave-ins that will plug up their front jets. Then, they no longer have a penetrating tool but a battering ram – a nozzle with no forward jets trying to feed its way through the blockage,” he said.
“For greater operator safety, slow down even more to remove a blockage and let the nozzle do the work. The reason we put forward jets on the nozzles is to safely open the blockage before the nozzle arrives. Slow down and the water will open the blockage before the nozzle ever gets there.”
While there is much more to the practice of sewer cleaning, following these 10 tips will go a long way toward keeping operators safe and productive on the job for many years to come.
FOR MORE INFORMATION:
KEG Technologies, (866) 595-0515. kegtechnologies.net
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