2. VasilyevAlexandrstephankerkhofs
Third Quarter 2016 | P E I J O U R N A L | 5 5
ombine two atoms of hydrogen with one
atom of oxygen, and you have one of the
greatest potential sources of cost and
exposure for the petroleum industry.
Water ingress in fuel storage systems usually
leads to microbial bacteria growth, which devas-
tates product quality and tank health.
If left untreated, microbial bacteria can lead to
significant equipment replacement costs, damaged
brand reputation, revenue loss and potential envi-
ronmental impact.
Unfortunately for underground storage tank (UST)
operators, the problem is getting worse. Changes
in fuel formulas, more awareness and better educa-
tion throughout the industry have led to increased
inspections.Those performing inspections include
regulatory agencies that collect fuel samples for
quality assessment and marketers that try to control
By Mike Thornton
3. costs of pumping system maintenance and frequent dis-
penser filter changes.
Water in tanks persists partly because few tank owners
are developing or subscribing to preventative maintenance
programs.
Automatic tank gauges (ATGs) provide many benefits;
however, few users pay much attention to water indications
from ATGs until water alarms activate. ATGs cannot mea-
sure water levels less than half an inch in tanks, and many
ATGs can measure only higher water levels.
New fuels — particularly diesel — are more susceptible
to water than fuels from the past because they can hold more
moisture entrained in the fuel. Reduction in sulphur content
has resulted in more tolerable environments for microbes,
which allow them to grow at higher rates and in parts of
tanks left unaffected by high-sulphur content fuels. Other
petrol grades are at risk, too, especially with the introduction
of ethanol-blended grades, which attract acetobacteria that
feed on ethanol.
Microbial contamination from water ingress nearly al-
ways corrodes metal tank parts and dispensing equipment,
and it often leads to sludge in tanks. New tank systems are
equally as susceptible as old ones. New sites have experi-
enced problematic levels of rust and sludge in their tank
systems in as little as 12-18 months because of microbial
contamination. Aggressive corrosion has occurred in as few
as 90 days where water remained in a tank, resulting in the
loss of an STP motor to the tank.
If not proactively managed and treated effectively, water
ingress can lead to costly replacement of pumps, filters, pipes,
dispensers and whole tank systems. In recent studies and lab
experiments, microbial-induced corrosion (MIC) on mild
steel has been measured as high as 1 millimeter per year,
meaning that if ignored, a new steel tank could be compro-
mised in less than seven years, depending on wall thickness.
What’s more, rust debris and sludge in tanks and dis-
pensing equipment can cause other significant problems,
such as dispenser filter blocking, malfunctioning pumps
and ATGs, slow flow and errors with preset volume delivery,
all of which can result in lost customers and revenue.
Contaminated fuel also has been linked to reduced
life of engine parts and environmental pollution, creating
additional exposure.
HOWWATERGETSINTANKS
Water enters USTs and aboveground storage tank systems
various ways. The most common include:
• Loose or damaged drop tube fill caps and adaptors.
These allow rain and water runoff paths into tanks
and fuel.
• Drop tube spill buckets (sumps) with faulty drain
valves. Spill buckets are intended to catch and contain
small spills during bulk deliveries. They’re also good at
catching rain or wash water if the lids are damaged or
the covers are not raised. Faulty drain valves or the use of
drain valves can allow water into tanks and fuel.
5 6 | P E I . O R G | Third Quarter 2016
Regulatory agencies and marketers frequently collect fuel samples for quality assessment.
4. • Compromised ancillary piping attached to tank tops.
These provide paths into tanks and fuel.
• Tank vents. Tanks are vented to the atmosphere. As fuel is
sold, moisture enters tanks with the air as the tank pres-
sure balances with the atmosphere. Unfortunately, this is
unavoidable.
• Bulk fuel deliveries. Bulk fuel comes from
storage tank systems that are subject to the same
threats as retail tank systems. Hence, water can
be transferred inadvertently from one system to
another. Improper or inadequate flushing of trans-
port tanker compartments between deliveries also
can introduce water and other contaminates into
tank systems.
WHATTODO
Even in the best-kept tank systems, microbial con-
tamination can be a problem. Any water is a problem,
and water gets into tank systems. The key is to control the
environment microbes need to multiply.
Good preventative maintenance and housekeep-
ing practices are the first line of defense. Adopting or
developing a program to control water ingress plus
incorporating practices such as those found in PEI/
RP900, “Recommended Practices for the Inspection and
Maintenance of UST Systems,” is a great start. Other
routine measures to manage water ingress include:
• Inspecting spill buckets for standing liquid, drain
valve operation and intact lid gaskets.
• Inspecting fill cap gaskets for dryness, cracking and
loose seals.
• Dipping the tank for water using the appropriate
water-finding paste designed for the fuel stored.
• Dipping the tank for water after any bulk delivery.
• Investigating ATG indications of any water even if there
5 8 | P E I . O R G | Third Quarter 2016
Microbial contamination led to corrosion and blockage of filters at this site 18
months after it opened.
Water ingress is responsible for this bacterial sludge removed from a
tank system.
5. is no alarm, then taking the appropriate steps for correction.
• Collecting fuel samples from the tank from multiple
openings and performing visual inspections first. If needed,
having the sample analyzed by a laboratory.
• Performing an ullage tightness test to ensure tank top integ-
rity is not compromised.
• Testing for free water frequently (at least weekly and after
any bulk delivery).
When it comes to water ingress and microbial contamina-
tion, prevention is best.
Mike Thornton is vice president of U.S.
operations at Leighton O’Brien and heads the
company’s tank and fuel cleaning business.
Thornton has served the petroleum sector
for 32 years in roles ranging from senior field technician,
service manager, operations manager, sales engineer and
product specialist to equipment design. Reach Thornton at
michaelthornton@leightonobrien.com.
Third Quarter 2016 | P E I J O U R N A L | 5 9
Flooded dip points pose another problem in keeping water out
of tanks.
