Underground Infrastructure - May 2023 - 40

Rehab Technology
cient 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 nozzleto-hose
connection to prevent
nozzle " ricochet. "
To prevent free spooling the nozzle up the line and losing control, use a nozzle skid and hold the
nozzle back.
40 MAY 2023 | UndergroundInfrastructure.com
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 oneand-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.

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Underground Infrastructure - May 2023

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