Water Management in ULSD Storage Systems

Water management is key to keeping ULSD storage systems running smoothly.  Anyone who owns an underground fuel storage system knows that keeping water out of that system is of the utmost importance. This is especially true in ULSD storage systems. Because ULSD is a bio-fuel, it is highly susceptible to damage from bacteria which feed on the organic compounds found within the fuel, causing a myriad of problems.

Problems Caused by Water in ULSD Storage Systems

When water contamination of ULSD storage systems occurs, it impacts more than just the storage system. When ULSD is contaminated by water it leads to decreased vehicle performance and an increase in sludge accumulation in the bottom of tanks. In addition to these factors, any salts in the water can cause degradation of the fuel chemical structure itself, degrading the ULSD into components that are potentially damaging to the storage system itself. This, in turn, can lead to ground water contamination due to leakage and a costly clean up job. On it’s own, water is a major problem in fuel storage systems. In ULSD strorage systems, water contamination is only the first part of the problem. Water is like a floating petri dish in ULSD storage systems. In fact, lest than one-quarter of an inch of water can promote microbial growth. These microbes live in the space where the fuel and water meet, feeding on the organic compounds found within ULSD.

Maintenance Issues Associated with Microbial Buildup

  • Plugged Filters
  • Pump and Injector Trouble
  • Water Monitor Malfunction
  • Sludge Accumulation Within the Tank Itself.

Symptoms of ULSD Water Contamination

Normally, dispenser flow reduction of 50 percent indicates a need for filter replacement, however dispenser flow reduction coupled with persistent filter problems can be a sign of a systemic storage system problem rather than a lack of timely or correct maintenance procedures.

Major Signs of Fuel and/or Storage System Issues:

  • Clogged Fuel Lines
  • Inconsistent Gauge Readings
  • Sulfurous Odor
  • Consistent Failure of Valves, Rubber Seals, Hoses, and the Like

Types of ULSD Contamination Caused by Water

One of the easiest ways to determine if your ULSD storage system has a contamination issue is to examine the contents of a clogged fuel filter. To do this, simply cut open the filter. The two major types of contaminants caused by water infiltration into the ULSD storage system are solid or semi-solid and microbial. Both of these can be detected via the naked eye.

Symptoms of Solid or Semi-Solid Contamination

  • Corrosion: Rough, gritty red to orange metal “silt”
  • Degraded Fuel: Black or brown particulates

Symptoms of Microbial Contamination

  • Sulfurous smell in the fuel or the filter
  • Tank bottom sample presenting an inversion rag layer
  • Corroded metal filter components
  • Filter covering is not uniform
  • Leopard spotted water coalescing filter

Preventing Microbial Growth in ULSD Systems

  • Watch for increased fuel times
  • Remove detected water in excess of one inch immediately
  • Check tanks every four to six months for microbial growth and treat with an EPA approved biocide
  • Periodically contract examination and maintenance of tank interior

ULSD Fuel Delivery and System Management

Proper fuel delivery and system management is key to keeping your ULSD storage system running smoothly and efficiently and to reduce the likelihood of water contamination of the system. A few simple can help ensure that your system runs optimally.

ULSD Delivery and System Management Recommendations

  • Nominal 5 micron filter installation on dispensers
  • Gauge and check for water in all storage tanks, removing water which exceeds one inch before and after normal operation hours
  • Gauge all tanks, checking for water before and after delivery of fuel
  • After delivery, ensure fill and gauge caps are tight and stick tank a second time after it has settled out
  • If fuel has been delivered overnight, check gauge caps and storage tank water levels
  • Inspect tanks, piping, valves, pumps, meters, and dispensers daily for any leaks or other damages
  • Test all fuel tanks a minimum of once per month and conduct extended quarterly analysis of the system when fuel is not consumed within 90 days

Monitoring for and Managing Water Contamination in ULSD Systems

How Water can Infiltrate Storage Tanks

  • Condensation due to high humidity in the air and wide variation in fuel temperature
  • Transportation of fuel from the refinery to the storage system
  • Leakage due to damaged fill pipes, vents, spill buckets, or fill cap gaskets and fittings or plugs that have become loose
  • Accidental drainage of spill buckets back into the storage tank
  • High output in fuel distribution and delivery infrastructure resulting in insufficient time for water to settle out of the fuel
  • Water runoff from storms

Checking ULSD Systems for Water

ATG systems are best for monitoring the amount of water in a ULSD system, provided the sensors are properly maintained. Often, it’s suggested that manual tank gauge readings be compared to ATG readings, as differences in these readings can be indicative of water in the system.

Basic Water Sampling Guidelines

  • Take fuel samples from the low end of the tank whenever possible
  • Do not take samples from the fill tube if it can be avoided.
  • Take samples from under the submersible turbine pump if possible
  • Take multiple samples in varying tank locations
  • In cold weather, use a field detection kit if the fuel appears waxy or hazy

Prevention of Water Infiltration

  • Ensure that all ULSD storage system openings are sealed and maintained
  • Remove and dispose of any debris or water around tank openings before accessing the tank
  • Minimize water entry with cap and screen vents, regulations permitting
  • Use manufacturer’s recommendations for suctioning levels
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