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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

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.

HOW WATER GETS IN TANKSWater 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.

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Regulatory agencies and marketers frequently collect fuel samples for quality assessment.

• 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.

WHAT TO DOEven 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

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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.

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.