EQUIPMENT DEGRADATION and CORROSION ISSUES in SECONDARY CONTAINMENT SUMPS and SMALL LOW PRESSURE FUEL STORAGE TANKS

Provide and present enough information gained from education and experience to inform customers and others concerned (tank owners, tank operators and regulators) with enough information to prevent and or resolve aggressive corrosion issues now being found in secondary containment sumps and fuel storage tanks.

First I reiterate that adding chemically formulated surface corrosion control treatments and or amines to treat microbial of fungal conditions found in fuel storage tanks as part of a normal or regular tank maintenance routine is if conditions warrant recommended. When regimentally adding chemicals to a fuel storage tank that is thought problematic with regards to corrosion or exhibiting fuel quality, fuel stability or system integrity issues understand symptoms and not the possible underlying problem is being treated.

For the benefit of the tank owner/operators, storage tank inspectors and regulating inspection agencies, understand that corrosive conditions effecting tanks, a tanks associated secondary containment or associated fueling system product delivery components is a problem worth worrying about.

Addressing ONLY corrosion symptom effects in present day fueling systems will inevitably lead only to eventual doom of fuel storage infrastructures.

Prompting this issue editorial the analogy being used is a tank owner asking why components in a secondary containment sump seemingly all of a sudden are failing due to corrosion. Logically one being asked has to say saturated hydrocarbon vapors or low PH tank empty space atmospheres are leaking under pressure from a tank(s) associated into the sump that more or less has a moist and oxygen rich atmosphere normally resident therein. The saturated hydrocarbon and or acidic vapors then mix in the sump creating an ideal low or lower PH environment for corrosion attack on exposed soft metal component(s) surfaces.

A realization and matter of fact for tank owner/operators, third party tank testers and regulating agency inspectors is that if you find corrosion in the sump The Tank top or an associated fueling system component Is Leaking.

“My tank testing contractor says that the tank is not leaking”

?“My line testing contractor says that the associated product piping is not leaking”

“My sump testing contractor says that the associated sumps are not leaking”

Where might you think the saturated hydrocarbon vapors mixing with atmospheric moisture and air in a sump is coming from?  Vapors are migrating from the associated tank(s) into the sump and or through secondary containment piping connecting to the dispenser fueling points. The (a) tank is leaking when over pressurized during a bulk fuel delivery (loading) and or liquid is leaking and vaporizing somewhere within the secondary containments boundary. The sump “caldron effect” corrosion causing constituent can’t logically be explained or sourced originating anywhere else. Ironically there are still people designing, building, servicing, testing, regulating, inspecting and operating fuel dispensing facilities with little or no understanding of just how tanks, associated piping and connected system components are supposed to work under normal, adverse or in poorly maintained condition. “It just has to be coming from somewhere else now doesn’t it?”

There seems to be misconceptions and misunderstanding for atmospheric corrosion causing issues being seen in sumps and fuel storage tanks. One who knows something about fuel and the dynamics by which it is refined, before or thereafter transported and stored understands that diesel and gasoline fuels are dramatically different in formulation. The first misconception is that corrosive low PH atmospheres being seen in a fueling sites diesel or gasoline tank or sump can be attributed solely to ULSD and ULSG reformulation, terminal or transport cross contamination with added amines or gasoline containing ethanol. While there may be some validity in the cross contamination theory it doesn’t explain why corrosion issues were not noticed or points of concern when percentages of ethanol as oxygenates in gasoline were first (1980’s) introduced. Further understanding and examination of fueling systems today interestingly shows that a corrosion condition in a diesel tank doesn’t necessarily correlate to corrosion conditions found in a gasoline tank or on component surfaces in its associated secondary containment sump. More simply explained as probable and likely is the need to understand and address two different corrosion causing issues.

The common corrosion causing denominating factors are moisture and oxygen. Saturated hydrocarbon vapors under pressure migrating from a gasoline fuel storage tank and mixing in a moist oxidizing atmosphere will in a fueling system associated containment sump(s) likely produce a low PH (acidic) atmosphere. Corrosion in an associated sump does not necessarily mean there are combined, contributing or corrosive conditions in an associated tank. Without moisture and oxidization contributing to the effect corrosion likely will not exist.

The common problem in a fueling system in all likelihood is that somewhere in the system a tank is leaking under pressure. Corrosive condition constituent(s) migrating throughout the fueling system are combining to create a low PH “Cauldron Effect” Understanding that regardless of where the degradation and corrosion effects are seen a serious system integrity problem may exist.

Tanks where storage tank atmospheres under pressure migrate out of tanks are highly susceptible for water ingress when tank pressures become negative during normal dispensing operation.

Leaking tank vapor migration paths unrecognized can make a source of an actual vapor leak(s) difficult to identify. Migrating vapor causing issues often will follow low voltage electrical and secondary piping conduits between tanks, dispenser and sumps.

As well it is important to realize that corrosion conditions in a diesel tank may not produce corrosion in a diesel associated sump. Reasoning being that diesel tanks typically are not equipped with pressure vacuum valves and over pressurization. Corrosion in a diesel sump might very well be caused by gasoline vapor migration leaking somehow and through unrecognized conduit from another tank(s) or associated sump on the fueling site.