managing liquid fuel cleanliness

8/10/2019 Managing Liquid Fuel Cleanliness

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Managing Liquid Fuel Cleanliness


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TABLEOFCONTENTS

Why the Need for Clean Fuel? ..............................................................................1

The Operating Environment ................................................................................. 2

Clean Fuel Standards .......................................................................................... 3

Types of Contaminants ........................................................................................ 3

Solids

Water

Fuel Based

Fuel Storage

Failure Modes ...................................................................................................... 4

What is Clean Fuel? ............................................................................................. 5

Clean Fuel Awareness ......................................................................................... 6

Fuel Supply .......................................................................................................... 7

Storage ................................................................................................................ 7

Filtration

............................................................................................................... 9

Monitoring .......................................................................................................... 10

Summary ............................................................................................................11

Getting the Most Cost-Effective Solution .............................................................11


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WHYTHENEEDFORCLEANFUEL?

INCREASING EFFICIENCY WHILE DECREASING EMISSIONS

CALLS FOR SIGNIFICANT TECHNOLOGICAL CHANGES.

Since the 1980s, dry low emissions (DLE) technology has reduced NOx emissions by a factor of five.

Such a dramatic improvement has been facilitated by an increasingly more sophisticated combustion system,

and is contingent upon both clean fuel, and rigorous adherence to maintenance proceduresoutlined by the

original equipment manufacturer (OEM) for prolonged performance and durability.

This document is intended to raise your level of awareness of, and appreciation for clean fuel. After reading it,

you should understand:

Clean fuel standards are internationally recognized by such organizations as the International

Organization for Standardization (ISO) and the American Society for Testing and Materials (ASTM).

The types of fuel-bound contaminants and their corresponding failure modes in gas turbine equipment.

Typical ways by which fuel contaminants are introduced during transportation and within on-site storage.

The recommendations Solar Turbines makes to protect your equipment, leveraging the experience

that comes from successfully placing more than 3,500 units running on liquid fuel into

commercial operation.

Regardless of whether your specific application requires gas turbines or reciprocating engines; and irrespective

of manufacturer, the need for clean fuel remains the same.

Poor quality fuel can lead to extensive damage of

internal hot section components, and lost production time.

M A N A G I N G L I Q U I D F U E L C L E A N L I N E S S - 1 -

Design Conplexityinmodern-day fuel injectors has

increased significantly placing

more emphasis on requirements

for clean fuel.

Stringency of Emissions Regulations

Design Complexity

1993 1996 2001 2006 Future

NOxEmissions

Conventional

Combustion Dry Low Emissions Technology

>

>

1980

>

LOW CONTAMINATION LEVELS IN THE FUEL IN THE TURBINES IN-PLANT FUEL SYSTEM

ARE REQUIRED TO MINIMIZE CORROSION AND OPERATING PROBLEMS.

ASTM D2880-03; X2.3.1


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THEOPERATINGENVIRONMENT

Gas turbines are designed to operate in some of the harshest environments in the world.

Whether offshore, or at a land-based industrial site, the threat of contamination is present.

Taking steps towards the proper storage and handling of liquid fuel ensuring only clean

fuel enters the gas turbine package is critical to mitigating the risk of contamination.

These steps prolong the useful life of your equipment.


CONTAMINATION LEVELS IN THE FUEL ENTERING THE COMBUSTOR(S)

MUST BE LOW FOR IMPROVED TURBINE LIFE.

ASTM D2880-03; X2.3.1


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CLEANFUELSTANDARDS

Clean fuel is a rather arbitrary term, and subject to interpretation. National standards, such as ASTM D2880,

and international standards, such as ISO 4261, were developed to clarify the definition by setting forth the

properties of fuels at the time and place of custody transfer to the user. Similarly, manufacturers will develop

specifications to clarify definitions. Solar Turbines, for example, publishes Engineering Specification 9-98

(ES9-98) which establishes the quality requirements for fuel, air and water (or steam), for use in its line of gas

turbine products. The purpose of these specifications is to ensure reliability and availability expectations,

while meeting environmental and emissions reduction goals.

TYPESOFCONTAMINANTS

SOLIDS Solids include items such as rust, scale, weld slag, sand, dirt, grit blast, and other debris. The intro-

duction of solid contaminants into the gas turbine package components can cause excessive wear and erosion-of fuel valves, fuel injectors, turbine hot section components, and blockage of small passageways.

WATER Stagnant water promotes bacteria and algae growth. Water can also contain contaminants like sodium,

potassium, calcium, and magnesium. Contaminated water in the fuel can lead to excessive plugging of fuel filters

and severe corrosion of fuel system components.

FUEL-BASED CHEMICAL CONTAMINANTS Chemical contaminants in the fuel can, by themselves, or through

interaction with each other, adversely affect the gas turbine, particularly the hot section life. Significant contami-

nants include:

Sulfurin the presence of sodium and potassium in the combustion environment, will react to form sodium

and potassium sulfates. These salts have melting points in the operating range of the gas turbine and will

result in severe hot corrosion degradation.

Vanadiumcan form low melting point compounds, such as vanadium pentoxide. These compounds

can cause severe corrosion on all of the high temperature alloys in the gas turbine hot section.

Sodium and Potassiumcan combine with vanadium to form eutectic compounds, and can combine with

sulfur to yield sulfates with melting points in the operating range of the gas turbine. These compounds

cause severe corrosion in the turbine hot section.

Other Contaminantssuch as mercury, cadmium, bismuth, arsenic, antimony, phosphorous, boron, gallium,

and indium, are unlikely to be present except under unusual or accidental circumstances. If present,

these contaminants can cause significant corrosion to both engine and package components.

FUEL STORAGE CONTAMINANTS Liquid fuels will start to drop out contaminants in the form of waxes as the

temperature of the fuel decreases. The temperature at which this starts to occur is known as the cloud point.

Fuel temperatures must be maintained at least -12C (10F) above the cloud point to avoid problems with

gas turbine operation and filter plugging.


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Photo 1- shows an injector tip with

degradation attributed to sulfidation, an

accelerated form of oxidation. The presence

of sulfur affects the nature of the inherent oxide

layer that forms, causing it to be less resistant

to further oxidation.

Photo 2-illustrates Stage 1 turbine bladesdamaged by hot corrosion. Sodium and/or

potassium, in the presence of sulfur, can form

sodium sulfate or potassium sulfate. These salts

have melting points at typical turbine operating

temperatures, resulting in severe corrosion to

hot section components.

Photo 3- is an example combustion liner

damage by oxidation. The cause of this damage

is likely an indirect result of fuel contamination. As

liquid passages in the injector become plugged,

non-uniform combustion downstream manifests

itself through localized over-temperature.

Photo 1

Photo 2

Photo 3


FAILUREMODES

These photos show various hot section components damaged as a result of contaminated fuel.


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WHATISCLEANFUEL?

In its simplest terms, clean fuel contains no solid particles or liquid contaminants, and minimal, but acceptable

levels of fuel-based contaminants, such as sulfur consistent with its respective refined fuel specification. Prop-

erly refined fuels dont contaminate themselves, they need help from other sources.

Contamination can be introduced at three different stages:

Production Fuel-based contaminants not reduced to acceptable

levels during the refining process.

Transportation/Distribution

Fuel is introduced to a variety of

potential contaminants during the shipping process, including dirt,

metal particles and liquid contamination from trucks, pipelines,

and shipping vessels.

Storage/Handling Water from condensation can be present in

both free and dissolved states; metals (rust) from storage vessels

and steel pipes, as well as dirt from unfiltered vent air.

The contaminants of primary interest are foreign materials introduced subsequent to the manufacture of

specification quality fuel. They are materials introduced in the distribution system, or in the end users storage and

handling system. This is especially true in remote areas of the world including offshore locations.

Because fuel represents the largest operating expense, it is frequently supplied by the lowest bidder, with little

regard for quality or cleanliness. In most cases, the chemical composition, energy content, and lubricity of the

fuel is acceptable. Its the unintended contaminants that arrive in the fuel that can cause accelerated wear, even

failure, of engine and package components.

By investing in clean fuel, customers can avoid downtime, lost revenue, and costly repair bills;

and enjoy reliable performance of their respective gas turbine products.

THE CONTAMINANTS OF PRIMARY INTEREST ARE FOREIGN MATERIALS INTRODUCED

SUBSEQUENT TO THE MANUFACTURE OF SPECIFICATION QUALITY FUEL.

ASTM D2880-03; 3.1.1.1


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CLEANFUELAWARENESSFROMREFINERY

TOTHEGASTURBINEPACKAGE

FUEL SUPPLY

>

STORAGE

FILTRATION/MONITORING

GAS TURBINE PACKAGE

>

>



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FUELSUPPLY

Protection against fuel contamination begins with fuel supply. The fuel supplied to the site should be inspected

and tested to ensure that the contaminant levels are below those detailed in Solars ES 9-98 fuel specification

(reference Section 9.0, and Appendix D: Liquid Fuel Suitability form).

Most transportation systems will introduce excessive contamination by the time the fuel is delivered. This

problem only gets worse as the distance and storage time increase between the refinery and the end user.

If the levels are above the recommended values in the specification, then further action should be taken.

SOLUTION Mix the fuel in the fuel tank with low contaminant fuels, introduce additives to react with the

contaminant, or return the fuel to the supplier.

STORAGEProper tank design is an essential component of the on site liquid fuel system. First and foremost,

storage tanks should be sized to allow adequate settle time. For applications where prolonged operation of

equipment on liquid fuel is anticipated, multiple tanks may be required.

Condensation from daily heat/cool cycles may generate gums, sediments, and significant amounts of water in the

fuel. Normal tank breathing draws in dust and moisture through vents and exacerbates the problem. This water

and sediment is heavier than the fuel and settles to the bottom of the tank, where it must be drained regularly to

a sludge tank.

Water is a breeding ground for bacteria that can cause corrosion damage to tanks.

Water is heavier than fuel.

Properly designed storage tanks allow water and other contaminants to settle on the bottom over time.

SOLUTION A well-designed fuel storage tank should have the following key features:

Floating Suction

Non-Corrosive Tank Lining

Storage Tank Design

Water/Sediment Drain

Desiccant Vent Filter

Inlet Diffuser

Sloped Tank Floor



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STORAGE(CONT.)

In addition to ensuring adequate settle time, tanks should be designed with the following four design features:

Sloped Tank Floor

Because water is heavier than fuel, water and other contaminants will settle at the

lowest point in the tank. A sloped tank floor with a bottom drain facilitates effective disposal of water and

sediment to a sludge tank. Tanks should be drained frequently to minimize the presence of water on the

tank floor, which provides a breeding ground for bacterial growth. Specific recommendations for tank drain

intervals vary from site to site, as settling times are dependent upon ambient temperature and humidity,

as well as contaminant levels of incoming fuel.

Floating Suction Pipe The suction pipe, unlike the drainage pipe, should be placed well above the tank

floor to ensure only clean fuel is drawn in, and other settled contaminants remain undisturbed. Most newer

designs incorporate a floating suction pipe one that rises and falls with the fuel level.

Desiccant (Drying) Vent Filters When fuel is drawn from a tank, air may enter. Depending on daily

temperature changes, this can cause condensation on the tanks interior. To trap and prevent moisture

from entering the tank, desiccant (drying) air filters should be used on the tanks vent. These vent filters do

wear out so they should follow a maintenance schedule.

Non-Corrosive Tank Lining Tank interiors should have a non-corrosive internal lining to prevent oxidation.


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FILTRATION

A major portion of a storage tanks contaminants can be removed during the settling and draining process.

Most of the remaining water and dirt can be removed by using either a filter/coalescer or a centrifuge.

Solars filter/coalescer system is illustrated below.

Filter/Coalescer SystemPositioned in the fuel supply line between the fuel storage tank and fueling station, filter/coalescer systems have

been a proven method of cleaning fuel in the airline industry for more than 50 years. These filtration units are

designed to remove water and solid particles from fuel in one pass, and to meet maximum flow requirements.

Each unit is skid mounted and includes the following features:

3-micron absolute particulate filter for solid removal capability

Filter Delta P transmitter to monitor the status of the filters

Water coalescer with an automatic drain for continuous water removal capability

Filter/Coalescer System

Automatic Water Drain

Delta P Transmitter

Coalescing Filter

3-Micron Absolute Particulate Filter

SOLUTION Solar Turbines offers a pre-engineered filter/coalescer unit for their portfolio

of gas turbine products.


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MONITORING

The most comprehensive liquid fuel system is only as effective as the maintenance procedures it follows.

Storage tanks must be inspected, sludge and water removed, centrifuges maintained, and filter elements

regularly replaced. Fuel that is kept clean along every step of the supply chain will save hundreds of thousands

of dollars in machinery repairs and replacements, fuel injector cleaning and replacement resulting in downtime,

which can last days and is the costliest source of lost revenue.

SOLUTION Every liquid fuel application project Solar Turbines delivers includes a monitoring system that

will alarm on the condition of high particulate matter or the presence of water. This serves to encourage

regular maintenance of the entire liquid fuel system.

CentrifugeA centrifuge mechanically separates different liquid phases and solids by exposing a liquid medium to as much

as 10,000 times the force of gravity. The force separates liquids from other liquids and solids efficiently and with

great accuracy, in a manner that is easy to control.

SOLUTION Solar Turbines offers centrifuges on a project-specific basis.

Each application is analyzed to allow Solar to properly design and configure

the centrifuge for the specific application.


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SUMMARY

Similar to a recommended series of preventive maintenance procedures, clean liquid fuel is critical to ensuring

the long-term health of your equipment. This document is presented to help you gain a better appreciation for

the steps required to achieve and maintain a clean fuel environment. This starts with the fuel supply chain,

and continues through to the regular inspection and maintenance of your on-site liquid fuel storage and

treatment system.

GETTHEMOSTCOST-EFFECTIVE

SOLUTIONFORYOURSITE

Solar Turbines has vast experience with liquid fuel operation, and leverages

this experience to help you develop the most cost-effective liquid fuel storageand treatment system for your application. To do so, Solar has developed

a Liquid Fuel System Assessmentform that is intended to make

recommendations consistent with the proposed fuel quality, and intended

philosophy of liquid fuel operation.

Accordingly, some of the areas addressed include:

Site environmental information (ambient conditions)

Assessment of existing fuel storage and treatment equipment

Analysis of proposed fuel sample

Modes of fuel transportation

For more information, please contact your local Solar sales representative.


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Clean Fuel

Increasing Efficiency

Lowering Emissions

Maximizing Machinery Life Cycle

Avoiding Costly Repairsand Downtime


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CONTACTINFORMATIONSolar has been a pioneer in the design, manufacture and packaging of gas turbine systems for more

than 50 years and is a world leader in the mid-range industrial gas turbine business. Customers in

96 nations spanning the globe know they can rely on Solar Turbines to provide rugged, reliable

turbomachinery systems, responsive service, technical assistance, and service parts availability,

with a worldwide, around-the-clock support network.

For more information, visit www.solarturbines.com or please contact:

Solar Turbines IncorporatedP.O. Box 85376

San Diego, CA 92186-5376

Tel: [+1] 619-544-5352

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+244 222-338070

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+32 7125-3000

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Mexico - Mexico City

+52 55-5442-2590

Cat and Caterpillar are registered trademarks of Caterpillar Inc. Turbomach is a wholly owned subsidiary of Caterpillar Inc. Specifications subject to change

without notice. Printed in U.S.A. 2008 Solar Turbines Incorporated. All Rights Reserved.

Anchorage, AK

+1 (907) 562-2440

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+1 (630) 527-1700

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+1 (202) 466-0655

Or your nearest Solar field office.

International Offices:

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+41 918 511 511

Sales @turbomach.com

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managing liquid fuel cleanliness

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