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CATASTROPHIC
FAILURE
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Preventing Poly Tank Failures
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Purpose of this presentation is :
# 1 – Identify the problem
# 2 – Demonstrate what to look for
# 3 - Provide information to assist employers
and protect employers and employees
The Issue: Preventing CATASTROPHIC
Failure of Poly Tanks
• Poly tanks can fail:
– 0-30 years
– Many tanks are at the 12 year mark
– There are increasing failures in storage
• Failure is caused by:
– Improper use
– Sunlight breaking down the plastic
The GOAL
• Is to replace the
tanks prior to
FAILURE to
prevent serious
injuries,
economic &
environmental
costs.
Poly Tank
101
Two Types:
#1 – Vertical
Storage #2 - Transport
Tank Design
• Vertical tanks- also called stationary, upright,
or hockey puck tanks
• Horizontal tanks – side-to-side, transport,
application or leg tanks
• Significant design difference between the two
dictate how they should or should not be
used.
• Using a tank outside it’s design specs voids the
manufacturer’s warranty and increases odds
of a failure.
Follow the Manufacturer’s
Requirements
QUIZ:
Improper
Use
What does a
transport tank
have that the
storage tank
does not?
Do you see a
problem here?
Storage Tank Placement
• Level
• Tied down
• In a location that, when it goes, will have
minimal impact.
Proper Placement?
Proper Placement?
Factors that Influence Longevity
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High specific gravity rating
Infrequent refilling
Protection from UV radiation
Stationary placement
Not all tanks are the same
SPECIFIC GRAVITY
• A tank’s specific gravity rating is a
measurement of its ability to hold material.
The specific gravity of a substance is a
comparison of its weight per unit volume to
that of water.
• The weight of water is 8.334 pounds per
gallon
• Tanks are designed at 1.0 to 1.9 or more.
Specific Gravity, cont.
• A poly tank with a specific gravity of 1.0 is
designed to hold the weight of water or any
other liquid that weighs 8.334 pounds (or less)
per gallon.
• A poly tank rated at 1.5 is designed to handle
the weight of a liquid product 1.5 times the
weight of water (1.5 X 8.334); so a 1.5 s.g .tank
is build to withstand the internal forces of
liquids weighing up to 12.5 pounds per gallon.
Specific Gravity
• Important for grower to recognize the type
needed for his/her particular storage needs.
• Specific gravity is noted on the tank
Horizontal “Transport “Tanks
• Horizontal tanks are mounted to steel skids or
fastened to trailers
• If they have legs, each entire leg must rest on
the trailer.
• Those without legs must rest in a cradle that
supports them from end-to-end and
surrounds one-third of their circumference
Horizontal “Transport” Tanks
• Baffles
– Poly tank manufacturers recommend that
horizontal transportation tanks that hold more
than 1.000 gallons be mounted lengthwise on the
truck or trailer.
– If mounted across the width of the truck or trailer
the baffles would be out of position to control the
content as it surges forward and backward during
transit.
Horizontal “Transport” Tanks
• Metal Bands and Hoops
– Sometimes required for structural strength and
stabilization
– Bands often are made from sheet metal, which
has excellent tension strength, however the bolts
that hold the metal to the trailer or cradle can
become weakened.
– Hoops are made of structural steel tubing or pipe
and can withstand the powerful c\forces exerted
by liquid contents when a transport vehicle stops
quickly
Horizontal “Transport” Tanks
• Hoops & Bands must be tightened to remove
all gap between bands/hoops and tank before
filling and after filling but not causing tank
distortion.
• Improperly installed anchors can deform and
weaken tanks
• Metal bands can cut into the sides of the poly
tank
Poly Tank Attachments and Venting
• The manner in which attachments are placed
on poly tanks can decrease useful tank life
• Rigid systems such as stainless steel or solid
plastic pipe cause excessive stress in the valve
and bung area.
• Flexible connections are preferable.
• Make sure all connections allow the tank to
flex
• Improper of nonfunctional vent can cause
tanks to swell during loading or collapse.
Inspections - Transport
• Inspect tank before hauling for:
• Missing, broken and bent bolts on the hoops
or bands
• Leaks around valves, tank bungs or lids or
plumbing
• Cracks or splits in hoses
• Improperly secured hoses and covers
• Vents in the lid or tank that are obstructed or
clogged
Inspections – Vertical Storage
• Visual inspections should occur at each fill
• Inspect for physical damage such as holes,
dents, and abrasions
• Make sure that the base remains solid
• Check fittings for leaks
Tank Inspections
• Scratches are open to the surface; displaced
material is evident on the tank’s surface;
fingernail catches
• Crazing is displayed as a patchwork of fine
lines
• Cracking causes no displaced material; very
abrupt lines may run parallel or cross at right
angles; UV cracking has a dry-rot or alligatorskin look in advanced stages; fingernail way
catch
Inspection Techniques
• Writing with water-soluble ink
• Candling with light
• Louisville slugger
• Now, for the visual demonstration….
Resources
Dr. Fred Whitford, Purdue University
1-888-EXT-INFO
http:www.ces.purdue.edu/new
Publication # PPP-77