maximizing power plant efficiency

Technical DigesT

Maximizing Power Plant efficiencyMany power generation systems rely on liquid

fuel and oil. Clean, dry oil and liquid fuels

are essential to preserving equipment and

preventing shutdowns that could cost hundreds

of thousands of dollars. Proper filtration is

crucial to optimizing the performance of power

generation and emission control systems.

It reduces the cost of new oil purchases,

decreases disposal costs, reduces wear, cuts

downtime and mitigates environmental

contamination. Power plants operate more

efficiently using high-performance oil, gas,

carbon and gearbox filters. Given the harsh

operating conditions of a power plant,

maintaining reliability can be challenging.

Contamination control solutions can mitigate

failures and save power plants money by

reducing downtime and maintenance costs.

2 Is Your Gen-Set Engine Ready or Not? 11 Gas Turbine Air Filter

System Optimization 26 Keeping Fluid Systems Clean

sPonsoreD by:

the magazine of power generation

Reprinted with revisions to format from Power Engineering. Copyright 2015 by PennWell Corporation.

2

Power Engineering :: TECHNICAL DIGEST :: sponsored by

Originally published June 17, 2014

Is Your Gen-Set Engine Ready or Not?

Ensure your diesel engine will respond at a moment’s notice by focusing on preventive maintenance.

By Craig Purvis, John Deere Power Systems

generaTor-seT

Diesel engines

are trusted to

keep the power on

through the strongest storms

and in the most remote

locations on earth. Whether

they’re protecting hospital

operating rooms or providing

distributed power, these

engines must be ready when

called upon.

Proper preventive

maintenance is critical to

ensuring that gen-set diesel

engines deliver reliable power

in standby or prime-power

applications. By carefully

following the engine manufacturer’s maintenance recommendations, you can

optimize the performance, reliability and durability of your engine. Neglecting

preventive maintenance can lead to inefficient operation, component failures or

permanent damage to the engine - potentially costly consequences.

Generator-set diesel engines are trusted to keep the power on through the most powerful storms and in the most remote locations on earth. Proper preventive maintenance is critical to optimizing the performance, reliability and durability of generator-drive diesel engines. Photo courtesy: John Deere Power Systems



3

Your gen-set engine features integrated components working together to

provide fast response for standby situations and excellent load recovery in all

applications. The fuel, lubrication, air intake, cooling and electrical systems

require maintenance at various intervals. Observing the detailed service

recommendations in your engine operator’s manual will help ensure that the

engine stays healthy and responds when you need it most.

Gen-set engine maintenance recommendations vary from manufacturer to

manufacturer. It’s important that you adhere to all the service procedures

and intervals found in the operator’s manual for your specific engine. John

Deere Power Systems, which offers generator-set diesel engine models with

displacements from 2.9L to 13.5L and ratings from 31 to 563 kW (42 to 755 hp),

recommends the following system-by-system maintenance practices.

before you buy

The first step in properly maintaining your generator-set engine isn’t a procedure

performed at a given interval on a certain system. You can avoid many potential

service issues and promote longer engine life by appropriately sizing the engine

for the application during the selection process.

An oversized engine will operate inefficiently and could experience issues such

as slobbering unused fuel. If an engine is too small, it may overheat, stall or be

slow to respond to load changes, and have a shorter life. When choosing a gen-

set, carefully assess your standby or prime power requirements and properly size

the engine to the load you’ll be running. John Deere recommends working closely

with the gen-set manufacturer to determine the appropriate engine size for your

application.

Standby gen-set engines should be properly loaded in exercise mode. To ensure

that your standby gen-set engine will deliver efficient performance when needed,

John Deere recommends running the engine at rated speed with 50 to 70 percent

load for 30 minutes every two weeks. The engine shouldn’t be allowed to run for

extended periods of time with no load. John Deere advises that standby gen-set

owners work with the gen-set manufacturer to implement an automated solution

for appropriately loading the engine during exercise mode.



4

lubrication system

The first hours of an engine’s life

are important in determining

its performance, reliability and

longevity. It’s important to use the

right type of oil during this break-

in period to allow the engine parts

to wear properly.

New John Deere engines are filled

at the factory with John Deere

Break-InTM Plus engine oil, which

is formulated to work with the

specific alloys and part tolerances

used in John Deere engines. During

the recommended 100-hour break-

in period, the engine should be

operated under various conditions, particularly heavy loads with minimal idling,

to help seat engine components properly. The use of 10W-30 John Deere Break-In

Plus engine oil encourages rings and liners to set correctly to ensure a good wear

pattern and longer life.

If the engine has significant operating time at idle and/or light-load usage, or

makeup oil is required in the first 100-hour period, a longer break-in period may

be required. The oil and filter should be changed between a minimum of 100

hours and a maximum of 500 hours during the initial operation of a new engine.

With the introduction of exhaust filters in engines used to meet U.S.

Environmental Protection Agency Tier 4 diesel emissions regulations, the type

of engine oil used can have a significant impact on the proper functioning and

ash service life of these devices. John Deere recommends using only engine oils

meeting API CJ-4 and ACEA E9 standards, such as John Deere Plus-50TM II. These

oils are refined with a lower trace metal content, which reduces ash accumulation

and increases exhaust filter service life.

A PowerTech E 13.5L model, a standby engine. Photo courtesy: John Deere Power Systems



5

Lab and field tests reveal that the superior anti-wear additives in quality engine

oils can significantly reduce engine wear, increasing the productive life of the

engine. They also extend drain intervals and reduce piston deposits, which leads

to a cleaner engine that will last longer and provide consistent power.

Lubricants should be clean. Even the best lubricants cannot function properly if

they are dirty. When maintaining the engine, be sure to:

:: Change oil when recommended.

:: Keep all lubricant containers covered in an area protected from dirt and

moisture.

:: Remove all dust and grime from both the container and service points before

performing lubrication service.

Unfortunately, all lubricants gradually lose effectiveness during operation due

to chemical and physical changes in the lubricant. The deterioration process is

accelerated by contaminants from external and internal sources. That’s why

following manufacturer-recommended lubricant change intervals for normal

operating conditions is so important.

More frequent oil changes are recommended when operating in extreme

environments, such as in very hot or dusty conditions, or at high altitudes. Oil

analysis can be performed to ensure that the recommended service interval is

adequate for your application. Regularly scheduled oil sampling and analysis can

pay for itself by detecting potential problem-causing conditions before they turn

into performance issues or costly downtime.

Fuel system

Gen-set engines meeting Tier 4 diesel emissions regulations require the use of

ultra-low sulfur diesel (ULSD) - diesel fuel with a sulfur content of less than 15

ppm. Using diesel fuel with a sulfur content greater than 15 ppm can damage

the exhaust filter used to reduce particulate matter, leading to early replacement.

Some Tier 4 engines also operate efficiently with biodiesel blends, providing fuel-

choice flexibility.



6

John Deere recommends limiting biodiesel use with gen-set engines to prime-

power applications. Biodiesel is naturally biodegradable, and blends up to B20

should be used within 90 days of the date of biodiesel manufacture. Microbial

growth present in biodiesel used after 90 days could damage an engine’s fuel

system and result in the need for new components. Because standby generators

may not use a full tank of biodiesel fuel during a short time period, John Deere

recommends using only regular diesel fuel for standby gen-set applications.

To ensure the quality of regular diesel fuel in standby applications, John Deere

recommends replacing old fuel with fresh fuel every six months to a year.

If you opt to run biodiesel for your prime-power application, a 5 percent blend

(B5) is preferred, but a biodiesel concentration of up to 20 percent (B20) may be

used. Regardless of biodiesel blend level, verify with your fuel provider that the

biodiesel blend meets ASTM D6751 (U.S.) standards.

Regardless of which fuel you run, only fuel additives that are approved by the

engine manufacturer should be used. Frequent fuel sampling and analysis is a

sound practice that promotes engine performance, reliability and durability.

To help achieve an uncontaminated and unrestricted fuel flow, John Deere

recommends these practices when performing fuel system maintenance:

:: Check for leaks.

:: Check for bent, kinked or dented supply or return.

:: Inspect fuel filters for dirt, water or other foreign matter.

:: Use fuel that is not contaminated with water. Water in the fuel system is the

greatest cause of fuel injection system failure.

:: Check for water in the fuel filter. Daily inspection of the fuel filter and draining

the water from the fuel filter water separator and fuel tank as required will

ensure that the fuel system is protected.

:: Install a fuel storage tank water-separating filter to further protect engines by

filtering out dirt, rust and scale. To service the tank filter, install a shutoff valve

between the tank and filter. The filter element should be changed annually or

more often if fuel flow becomes restricted.



7

air-intake system

Making sure your engine receives an unrestricted flow of clean air is imperative

for proper operation and long life. For example, dust reaching your engine through

a leaking connector in the air-intake system - called “dusting the engine” -

can destroy an engine, even one with low hours of operation. Therefore, it is

important to:

:: Inspect the entire air-intake system for openings that could draw in unfiltered

air (loose clamps, cracked hoses, etc.).

:: Inspect dry element type filters and replace if clogged with dust or dirt.

Inspect for damaged seams and pleats. Replace if necessary. Cleaning the

elements with compressed air or by pounding them on a hard surface is not

recommended.

:: Highly efficient filters, such as Donaldson PowerCore filters, cannot be cleaned

and must be replaced when restricted.

cooling system

When performing maintenance on your engine’s cooling system, always use the

recommended class of coolant. It’s important to be selective with antifreeze/

coolants because not all of them provide the protection needed to operate

efficiently under extreme pressures and temperatures.

John Deere Cool-Gard II, for example, is a fully formulated antifreeze/summer

coolant designed and extensively tested to protect wet-sleeve-liner diesel engines

from cylinder-liner cavitation erosion.

Engine cooling systems should be thoroughly flushed and cleaned with a heavy-

duty cleaner and refilled with clean coolant and inhibitors per the recommended

intervals in your operator’s manual. In addition, it is important to visually

inspect the radiator and thermostats for any signs of corrosion, debris or physical

damage.



8

John Deere highly recommends coolant solution analysis, which will verify

the chemical composition of your coolant and include a written report with

maintenance recommendations for the coolant and cooling system. Regular

coolant analysis is particularly important in standby applications because coolant

heaters can deteriorate additive packages.

Also, John Deere recommends these maintenance practices:

:: Replace radiator hoses that are cracked, soft or swollen.

:: Clean all dirt and trash from between radiator fins and around the radiator

itself.

:: Check for bent radiator fins and straighten as needed.

:: Ensure baffles and fan shrouds are in place and functional.

:: Inspect the fan blades for damage and the fan belts for excessive wear. Replace

as needed.

electrical system

Maintaining the electrical system is often more complicated than maintaining

some of the engine’s other systems, so most electrical maintenance tasks should

be left to a certified mechanic. However, an engine’s electrical system is centered

on its battery, and it is always important to check the condition of your battery:

:: Verify batteries are fully charged and the electrolyte is at its proper level.

:: Remove battery cables and clean cable ends and posts.

:: Repair or replace the alternator if it isn’t keeping the battery fully charged.

:: Check all alternator wiring connections for tightness and corrosion. Correct as

needed.

:: Check all chassis grounding and bonding wires for corrosion and integrity.

:: Check condition and tension of alternator belt and adjust or replace as needed.

:: Check all starting motor connections for tightness and corrosion. Correct as

needed.



9

Facilities and locations around the world depend on diesel-powered generator sets

to provide worry-free service, often at a moment’s notice. By diligently following the

engine manufacturer’s preventive maintenance recommendations, gen-set owners

can optimize the performance, reliability and durability of their gen-set engine.

Craig Purvis is a senior field service representative specializing in generator sets

at John Deere Power Systems. He has 16 years of industry experience, including

positions as an electronics technician, heavy-duty diesel engine wire harness

designer and quality engineer in production engine testing.

The Hilliard Corporation100 West Fourth Street, Elmira, New York 14902-1504 USAPH: 607.733.7121 | FAX: 607.737.1108 | hilliardcorp.com | [email protected]

MK Electrically Released Caliper BrakesPowerful floating caliper design can be used on conventional disc or rail applications. The compact spring-applied design provides easy installation and maintenance. Spring force and air gap can be adjusted to match torque requirements. The patented Hilliard MK Guide Rail Brake is designed for use on elevators, conveyors, cranes, or other devices requiring a spring-applied

electromagnetically released brake. The patented MK brake can be applied to a guide rail or a brake disc.

As bulk material handling machinery designs become more powerful and increasingly efficient, braking system designs must also progress to satisfy the demand to control speed and stop machines in routine and, most importantly, during emergency stopping events.Brakes are no longer straightforward on or off mechanical devices. Sophisticated Smart Brake deceleration controls with system status monitoring, fault acknowledgement, and feedback are required to maintain system integrity under all stopping conditions. This is particularly crucial on belt conveyor systems, where tension management and personnel safety are of paramount importance.With these considerations in mind, Hilliard has developed a line of power units capable of controlling braking systems for a multitude of scenarios and applications.

BBH2: Railcar Positioners, Wind Turbines, Cable Winders, Escalators, Overland/Underground Conveyors

BBH3: Overland/Underground Conveyors, Conveyor Tension Winches, Marine Towing Winches

BBH4: Grinding Mills such as AG, SAG, and Ball Mills

Magna Torque (MT) for Backstopping & IndexingHilliard’s line of overrunning clutches is economically priced and ideally suited for backstopping and gearbox applications. Custom designs and rapid prototyping are available.

Magna Torque (MTR) for Clutch Couplings, Dual-Drive & Turning GearRoller-Ramp design for increased reliability and longer life.

An integral part of many Hilliard motion control products is our roller-ramp design. The use of hardened cams and precision-machined rollers maximizes service life.There is almost no wear during freewheeling operations because rollers are free to rotate between the outer member and the inner cam. When the rollers are engaged, the load falls at random positions on the rollers. The result is superior service life and reliability.The MTR is similar to the MT design except the cam surface is reversed allowing it to be used in multi-speed/dual drive applications.

Hilliard’s enclosed overrunning clutch incorporates superior MTR design in a totally enclosed package. Designed for power transmission operations, this clutch is totally contained in a stationary housing for constant protection from hostile environments or wash-downs.

Overrunning Clutches

Hilco Oil ReclaimersComprehensive Contamination Control for Hydraulic Systems

If your application involves oil with substantial amounts of water or volatile contaminants, an oil reclaimer may be the most cost-effective solution to your contamination problem. The addition of settling and clean-oil holding tanks, filters and controls converts the basic Hilco Oil Reclaimer into an extremely efficient reclamation system. The reclamation process uses a combination of filtration and vacuum distillation to purify the oil and return it to a like-new condition. Other contaminants best removed by this process include acids, solvents, dissolved gases — almost any volatile contaminant. Although most reclaimers are part of a permanently installed system, they can be made portable for the greatest flexibility in dealing with your application.

Supplemental Protection for Other Locations

A particular set of operating conditions may require contamination control in addition to that provided by the off-line loop. Examples include pressure-line filters for in-line protection of remotely mounted critical components, and reservoir air-breather filters to protect against ingestion of airborne contaminants in hostile atmospheres. Hilco products are available for these special applications, and Hilliard's applications specialists can advise and assist you in the selection of such equipment for supplementary locations.

11


Originally published January 21, 2015

Gas Turbine Air Filter System Optimization

By James DiCampli, P.E., and Jack Pan, GE Power and Water, and Mark Arsenault, American Air Filter

ProPer air FilTraTion is critical to the overall performance and

reliability of gas turbines. Fuel costs approach 80 percent of the life

cycle cost of electricity. Small gains in efficiency can mean huge

savings. With fuel costs of around $16.00/mmBTU and higher in certain

global regions, operational savings can be achieved through improved compressor

performance using High Efficiency (HEPA) air filters. Operators can see greatly

reduced maintenance costs as a result of a much cleaner engine, quantified

by less frequent inspections, fewer shutdowns, and higher availability. HEPA

filtration can maintain optimum GT efficiency throughout the life of the filter.

This article investigates the decision criteria required in selecting an optimum

air filtration solution, with the goal of maximizing gas turbine availability and

lowering operating costs. Through case studies and analysis, essential filter

parameters and their impact on gas turbine operations and maintenance are

reviewed.

air Filtration and conditioning overview

Aeroderivative gas turbine ventilation and combustion air filter systems are

designed to protect the gas turbine, generator, and equipment compartments

from the effects of air-borne dirt, contamination and foreign objects. A number

of inlet conditioning options are also available to maximize gas turbine

performance.

GE Distributed Power gas turbines use a three-section inlet air filter that mounts

directly above the turbine enclosure, conserving space and providing compact,

low-pressure loss ducting to the turbine inlet. Figure 1 provides an illustrative

example.


LM6000 Gas Turbine Generator Air Flow 1

Bolt-on Coil Section

CoilSection

CompositeFlter

Canisters

TurbineExhaust

Guard Filters

Drift Eliminator

Drift Eliminator

Combustion Air

VentilationAir

FanFanGeneratorEnclosure

TurbineEnclosure

Exciter Generator

EnclosureVentilationAir Exhaust

EnclosureVentilationAir Exhaust

AmbientAir In

AmbientAir In

Generator Cooling Air Exhaust

GearBox


12

The ventilation and combustion air system consists of a filter house structure,

roof-mounted silencers, fans, and associated ductwork all located on the turbine

and generator enclosures. The filter house is comprised of weather hoods, filter

elements, chiller or anti-icing coils, and plenum chamber assembly. Air from the

plenum assembly is ducted to the turbine engine intake for combustion and to the

turbine and generator compartments for cooling and ventilation. An external ladder

and walkway with access doors to the air filter structure enables filter servicing.

A temperature element in the air filter house combustion air section provides

inlet temperature information to the control system. Relative humidity sensors

measure moisture in the air before it enters the filter housing and activates an

alarm if icing conditions exist.

Pressure transmitters sense the pressure difference between the outside air

and the combustion air inlet plenum. For example, on a GE LM6000, if the



13

differential pressure reaches −5 in-Wg (-127 mm), the control system activates an

alarm, an indication of filter clogging. If the differential pressure reaches −8 in-

Wg (-203 mm), the control system activates a load reduction. Another pressure

differential transmitter monitors total pressure drop at the ventilation air plenum

and activates an alarm if the pressure differential reaches -5 in-Wg (-127 mm).

Ventilation air is ducted from the ventilation plenum directly into the turbine

compartment. One of the two turbine compartment fan assemblies draws air from

the inlet air filtration system through the turbine compartment and expels it to an

air exhaust stack that is equipped with a silencer limiting the transmitted noise.

component Description

Weather Hoods and Drift Eliminators

Air entering the filter house first passes through (optional) weather hoods, drift

eliminators and inlet screens. Weather hoods protect filters from rain, snow

and sun. Weather hoods are bolted to the inlet side of the left and right coil

assemblies (for dual inlet systems). Weather hoods prevent rain and snow from

entering the inlet filter house by drawing inlet air upward at lower velocities

than that of falling rain and snow. Snow hoods and tropical rain hoods are

available for snowy or tropical environments. Inertial moisture separators (vane

type separators) are also available to prevent heavy rain or heavy fog mist from

entering the filter house.

Filters

A multi-stage filtration system is available which includes a guard filter upstream

of the chiller coils and a set of composite canister “barrier” or panel-type filters

located downstream of the coils. The guard filters (also known as pre-filters)

keep the chiller coils clean for maximum heat transfer efficiency and provides

supplementary filtration to extend the service life of the composite fine filters.

The fine filter elements are mounted to the filter face of the inlet plenum and

extend into the clean air plenum. The elements have extended surface area, large

dirt-holding capacity and low-pressure drop.



14

Air passes through the fine filters and enters the clean air plenum. This

fabricated structure is the center section of the inlet filter assembly and separates

ventilation air from combustion air. Combustion air flows through a transition

duct from the clean air plenum to the combustion air inlet silencer. Ventilation

air flows through transition ducts to the turbine and generator compartment. The

inlet silencer is a low-pressure-drop device located in the combustion air stream

before the inlet volute. The silencer attenuates noise from the turbine and helps

maintain the unit’s low noise level.

Inlet Cooling and Heating

Air conditioning options include evaporative coolers or optional inlet air chiller

coils to maximize gas turbine performance on hot days. Conversely, coils can be

used for anti-icing and/or optimizing efficiency during partial power operations.

The evaporative cooling system uses the process of evaporation to create a

reduction in inlet air temperature. Water is pumped to a header that distributes

the water over media blocks that consist of corrugated layers of a fibrous

material. Air passing through channels comes into contact with the falling water

causing a portion of the water to evaporate, transferring heat from the air to the

water.

Static and Pulse Filter Options

The correct type of filter (pulse or static) should be used for the specific project

environmental conditions and specific contaminants.

In general, a pulse or self-cleaning type inlet air filter should be used when the

dust loading approaches 0.300 mg/m3 or higher, or when operating in conditions

where dust or sand storms can occur. The ambient air can be tested using a

direct read-out device, such as a laser photometer that counts particulates in the

air sample.

The American Air Filter ASC Pulse filter system utilizes a unique inertial

separation system that diverts over 90 percent of the dust particles from the gas

turbine inlet into a secondary air system, via negative pressure. The remaining

particles are captured on the surface of AAF’s PanelPak filter element, which



15

in turn is pulsed off the filters when required. The AAF system prevents re-

entrapment of the pulsed particles as they are expelled into the same separation

system during the pulse cycle. This allows for continuous operation of the GT

during the pulse cycle, while the design provides for a lower pressure drop of the

entire inlet system. AAF has over 900 of these units in operation to date, in many

industrial areas and locations with very poor air quality.

Pulse filters can and have been successfully used in very dusty environments,

such as steel mills, cement plants, Middle East environments, or areas where

sand or dust storms are prevalent, even with high humidity. The pulse controller

can be programmed to pulse as the loading requires (e.g., based on filter pressure

drop, ambient relative humidity, hourly, daily, or even continuously). For example,

a common recommendation for an installation in a cement factory, is to

minimize caking on the filters by automatically pulsing the filters whenever the

relative humidity is greater than 80 percent.

Pulse filters are also utilized when a turbine is being operated in an environment

with significant loading of snow or ice crystals. Although a static filter can be

used in these environments if there is a properly designed conditioning system

upstream (e.g., heating coils, bleed air or other hot air conditioning), pulse systems

are the most reliable for preventing filters plugging due to cold weather moisture.

Another advantage of pulse filter systems, particularly for peak loading turbines,

is that the filters can be pulsed when the unit is not in operation, which provides

maximum effectiveness to the pulse cleaning, so the filters can be “cleaned” and

ready for the next start-up.

Static filters can be fitted with inexpensive pre-filters that can be replaced and/or

cleaned to extend the life of the barrier elements. However, special pre-filters can

become a maintenance item and drive up costs over the life of the project. For

example, for areas with a high hydrocarbon loading or areas with cement dusts

and frequent high humidity, pleated composite type pre-filters, rather than the

more standard fibrous type, are often required to prevent short barrier filter life.

These pre-filters are less expensive and must be replaced (or possibly removed

and cleaned) at somewhat frequent intervals.



16

Water Wash

Fouling deposits on gas turbine compressor airfoils reduce engine performance

output. The water wash system provides a mechanism for cleaning engine

compressor blades. The aim is to recover power output and heat rate performance

by restoring the compressor’s flow capacity and efficiency.

There are many types of compressor fouling. The type and rate of fouling depend

on the environment in which the gas turbine operates and the efficiency level of

the inlet filtration. Among the most common types of contaminants are dirt or

soil, sand, coal dust, insects, salt, oil, and even turbine exhaust gas.

Salt also causes corrosion of blading and ductwork and subsequent ingestion of

rust and scale. Oil increases the ability of contaminants to cling to compressor

passages and airfoils. The type of material that is deposited on the compressor

blading influences the method of its removal.

Keeping the compressor internals clean can alleviate a number of problems before

they ever become apparent. Besides the obvious benefits of enhanced efficiency

(increased power output, lower compressor discharge temperatures, etc.), keeping

the compressor clean will help blades survive longer.

If the compressor is dirty, additional weight is added to the airfoil and this

increases the cyclic stress. Also, dirt in the dovetail slots will add to the existing

friction loading at the dovetail/slot interface and between the two mechanisms

making a blade dovetail failure more likely. Performing thorough water washes

with high quality ingredients on a regular basis with help combat these conditions.

Washing utilizes liquid detergents, a concentrated solution of water soluble,

surface active agents and emulsifiable solvents produced primarily for cleaning

gas turbine compressors, where the intent is to restore performance by removing

fouling buildup from compressor components.

Methods of Detection

The best method for detecting a fouled compressor is visual inspection. This

involves shutting the unit down, removing the inlet plenum inspection hatch,



17

and visually inspecting the compressor inlet, bellmouth, inlet guide vanes, and

early stage blading. If there are any deposits, including dust or oily deposits that

can be wiped or scraped off these areas, the compressor is fouled sufficiently to

affect performance. The initial inspection reveals whether the deposits are oily or

dry. For oily deposits, a water-detergent wash is required, followed by clean water

rinses. The source of the oil should be located and corrected before cleaning to

prevent recurrence of the fouling.

Another method for detecting a fouled compressor is performance monitoring.

Performance monitoring involves obtaining gas turbine data on a routine

basis, which in turn is compared to baseline data to monitor trends in the

performance of the gas turbine. The performance data is obtained by running

the unit at a steady base load and recording output, exhaust temperatures,

inlet air temperatures, barometric pressure, compressor discharge pressure and

temperature, and fuel consumption. The data should be taken carefully with the

unit warmed up. If performance analysis indicates compressor fouling, it should

be verified by a visual inspection.

The compressor cleaning operation is conducted after turbine shut down (crank-

soak cleaning) or while operating (on-line cleaning).

A consistent gas turbine water-wash strategy pays for itself many times over

in power and efficiency improvement. A crank-soak wash is typically the only

means to remove most deposits, including oily or tarry deposits which bind dirt

to the blades. Because crank-soak wash cleans the suction (convex) side of the

blade it has the greatest influence on compressor efficiency.

There are no hard and fast rules for when to crank-soak wash because the

schedule must be tailored based on type of atmospheric contaminants,

temperature, operational frequency, gas turbine health, and site economics.

In the absence of this information a prudent strategy would be to crank-soak

(off-line), wash every 2 weeks. High concentration of oily deposits and dust will

require more frequent crank-soak washing.



18

On-line washing serves primarily to maintain gas turbine performance between

crank-soak washes. The primary effect of on-line wash is to remove deposits

on the blade which adhere by impact. Also, dust and dirt are removed on the

pressure (concave) side of the blade but not on the suction side which has a lesser

influence on efficiency. For this reason, the use of water for on-line wash is often

as effective as a detergent solution. The higher the concentration of oil and tars,

the less effective on-line washing will be for improving performance.

In the absence of site-specific information, it would be beneficial to on-line wash

with water daily. Use of detergent should be based on testing which demonstrates

measurable benefits for the site. Visual inspection of the rinse water is effectively

used by some sites to set the wash schedule. If the rinse is mostly clear, the

interval can be extended.

Filter classification

Filtration systems are optimized to minimize foreign contaminants entering

the gas turbine, and are largely based on the operating environment. Seasonal

pollutants, rain, ice and snow, sand, dust, local industry exhausts, and other air

contaminants must be taken into consideration.

Filters are generally classified by several standard rating methods:

:: United States: American Society of Heating, Refrigerating, and Air-Conditioning

Engineers (ASHRAE) in standard 52.2: 2007.

:: Europe: European Standards EN 779: 2012 and EN 1822: 2009

(Parts 1 through 5).

High Efficiency Particulate Air filters ((H)EPA) filters are generally defined as

having an efficiency greater than 85% for particles greater than or equal to

a filter’s Most Penetrating Particle Size (MPPS). The MPPS for a filter varies

depending upon the media, media velocity, configuration along with other factors,

but is primarily between 0.07 and 0.2 microns for filters used in gas turbine inlet

applications.


Site Location Environment Engine Model Air Filter Filter Type

USA Continental Lm2500+G4 Static Air Filter; Additional Filter: Pre-Filter, Weather Hoods, Guard Filter Synthetic Panel

Russia Continental Lm2500+G4 Static Air Filter Synthetic Panel(F8)

ItalyIndustrial(Aerosol, Particles)

Lm2500+G4 Static Air Filter; Additional Filter: Pre-Filter, Weather Hoods, Guard Filter Synthetic Panel(F8)

Belgium Continental Lm2500+G4 Static Air Filter; wAdditional Filter: Pre-Filter, Weather Hoods, Guard Filter Synthetic Panel(F8)

China Site 1Heavy Industrial (Aerosol, Particles)

Lm2500+ Static Air Filter: Pre-Filter, Duracel Xl90, Hepa G4, F8, H12

China Site 2Heavy Industrial (Aerosol, Particles)

Lm2500+G4 Asc Pulse Filter, Hepa F8, H12

Summary For Investigated Sites 1


19

case studies

Six General Electric Distributed Power Lm2X gas turbine sites were investigated.

The environment of these sites ranged from continental, relatively clean air to

heavy industrial sites with significant amounts of hydrocarbon aerosols and

particulates. The air filter configurations are listed in Table 1. The usage of high

efficiency filters as a 3rd stage was installed at two of these sites, both with very

poor air quality.

The following sections summarize each case.

U.S. Site

This site is an urban area with an interstate highway nearby. There are two filter

stages in this system, a pre-filter and the AAF Duracel XL90N. The operator

changed the pre-filters at 4,000 hrs and primary filters at 8,000 hrs. Online water

washing was completed 1-3 times/week as a proactive measure to minimize off-

line washes.

Off-line water washing has been performed approximately every 3 months,

equivalent to 2,000 hrs of operation. Offline washing takes about one 8 hour shift,

although it usually is performed in conjunction with other work to maximize

overall availability. The operational history has shown ~1 MW power loss after

the three month period.



20

Russian Site

The plant has been operating since 2012 in a relatively clean environment and

uses only one stage filter, a static EU8.

Still, the HPC rotor blades and stator vanes have rust colored deposits on the

surface. Compressor residue samples should be taken and analyzed at a lab to

identify the corrosion mechanism. From this, changes to the filtration system

and/or wash detergent can be recommended.

Italian Site

This site is a small industrial area, but the air is generally clean. The unit is

running about half of the year.

There are 3 filter stages, two pre-filter stages and then the Duracel XL90N. The

pre-filter was changed at 7,000 hours because of high dP. Offline water wash is

performed every 3-4 weeks, or after 700-900 hours of operation.

The site does not perform any online water washing, but conducts off line water

washes frequently to keep the compressor efficiency high.

Belgium Site

The plant operates near a refinery. The refinery fumes can be ingested by the

gas turbine, causing oil contamination of the filters. Both pre-filters and fine

filters are changed every 18 months. Offline water washing is performed every 6

months unless the power loss exceeds 1MW, then an additional offline wash is

performed. On-line washing is generally performed every 2 days.

China Sites

The two China sites investigated are in areas with very poor air quality. The

particulate count and size are shown in Figure 2, taken at different times of the year.

The particulate count at the size level of 0.3um and 0.5um make up 99% of the

contamination. At this level the particulates are captured by the 2nd and 3rd

stage filters.


Filter Change & Water Wash Data (Unit 2) – China Site 1 3

10

9

8

7

6

5

4

3

2

1

0

Pres

sure

Dro

p (In

ch H

20)

Sep- 11 Nov- 11 Jan- 12 Mar-12 May- 12 Jul- 12 Sep- 12 Nov- 12 Jan- 13 Mar- 13 May- 13 Jul- 13 Sep- 13 Nov- 13 Jan- 14 Mar- 14

PreFilter Duracel X90 HEPA Filter Water wash

Particle Test Result at China Sites 2

Site 1 June 2011

Site 1 October 2011

Site 2 April 2011

1,200,000

1,000,000

800,000

600,000

400,000

200,000

0

Parti

cle

Coun

t

Particle Size0.3μm 0.5μm 0.7μm 1.0μm 3.0μm 5.0μm


21

China Site 1

There are 3 filter stages:

1st stage is a G4 pre-

filter, the 2nd stage is a

Duracel F8, and the 3rd

stage is a HEPA H12 filter.

The filter change cycles

and water wash cycle

are shown in Figure 3 for

Unit 2 at the site.

The 1st stage pre-filter change cycle is 3-4 months from March through October,

then typically less than once/month from October through March. The 2nd

stage Duracel change cycle is 4-8 months (Mar-Oct), and from 1 week-2 months


Filter Change & Water Wash Data – China Site 2 4

8

7

6

5

4

3

2

1

0

Pres

sure

Dro

p (In

ch H

20)

Unit 1 Unit 2 Unit 3 Water wash

Mar-13 Apr-13 May-13 Jun-13 Jul-13 Aug-13 Sep-13 Oct-13 Nov-13 Dec-13 Jan-14 Feb-14 Mar-14 Apr-14


22

(Oct-Mar). This is because of poor air quality in the winter months. The 3rd stage

HEPA filter change cycle is quite stable, every 6-9 months. Offline water wash is

performed at every 4,000 hours and requires 8-10 hours to complete.

China Site 2

The plant has a pulse filter system, and there are 2 filter stages. The 1st stage is an

ASC Panel Pak element (F8), and the 2nd stage is a HEPA filter (H12). The filter change

cycle and water wash cycles are shown in Figure 4 (Three gas turbines on site).

Both the pulsed filter and HEPA filter have not been changed, and have been

running almost one year.

Filter pulsing has proved very effective in removing particles. Offline water wash

is performed at every ~4,000-5,000 hours.

No on-line water washing has been conducted.


Project Location

Filter Change Cycle Water Wash Cycle

Pre-Filter Static/Pulse (H)EPA Online OfflineUSA 5.5 months 11 months No (H)EPA 1-3 times/week every 2-3 monthsRussia No change No change No (H)EPA No every 2 months

Italy 9.7 months No change No (H)EPA No every 3-4 weeks: 700-900 hours

Belgium every 18 months every 18 months No (H)EPA Every 2 days every 6 monthsChina Site 1 1 week-4 months 2 - 8 months 6 - 9 months No every 5.5 monthsChina Site 2 every 12 months every 12 months No every 5.5 months

Summary For Filter Change Cycle & Water Wash Cycles 2


23

Filter Change Cycle/ Water Wash Cycle Analysis

The filter change cycle and water wash cycle data is summarized in Table 2. Not

surprisingly, better air quality sites do not have to change the pre-filter as often.

The filters at China site 2 performed better than those in China site 1 due to the

effectiveness of the pulse cleaning mechanism. The water wash cycle, both on-

and off-line, at the site with no (H)EPA is more frequent, meaning more downtime

at the plant.

conclusions

The site analyses showed that (H)EPA filtration results in cleaner compressors,

longer cycles between water washing, and subsequently higher compressor

efficiency and plant availability.

To illustrate the savings, costs are normalized, and assumptions are based on the

site data summarized in this article. It is assumed that there is a 14 percent filter

house cost adder for (H)EPA filtration, and a negligible power loss due to higher filter

differential pressure. Further assume a 3 percent efficiency drop occurs linearly

over a 2 month period (non-(H)EPA) or 6 month ((H)EPA). Base natural gas price is

$16/MMBtu (Asia) and power sells for $15/MW-hr. Using (H)EPA filtration, the loss

of compressor efficiency is a rate 1/3 slower than without. For a 32MW turbine, the

net present value is >$550k for a base-load machine for one year and $3.7M over

15 years, as shown in Table 3. That is, a net benefit for (H)EPA filtration. Another

$200k/year could be assumed for increased operating time due to infrequent off-

line water washing. (H)EPA filtration yields higher compressor efficiencies over a

longer period saving fuel costs compared to non-(H)EPA filtration systems.


Variable Title Variable Value Year Power Loss Cashflow

Efficiency Raw Cashflow

Net Adj Annual Cashflow

3% Efficiency loss to wash 1 $0 $1,269,504 $1,103,917Fuel mmbtu/hr 330.6 2 $0 $1,269,504 $959,927MW 35.732 3 $0 $1,269,504 $834,719Fuel $/MMBtu 16 4 $0 $1,269,504 $725,843Sell price,$/(MW-hr) 15 5 $0 $1,269,504 $631,168# years 15 6 $0 $1,269,504 $548,842rate of return 0.15 7 $0 $1,269,504 $477,254run time, hr/yr 8000 8 $0 $1,269,504 $415,003

9 $0 $1,269,504 $360,872NPV w/o Cost $7,423,260 10 $0 $1,269,504 $313,802Equipment Cost Adder -$34,440 11 $0 $1,269,504 $272,871

12 $0 $1,269,504 $237,279NPV/3 $3,694,409.86 13 $0 $1,269,504 $206,330

14 $0 $1,269,504 $179,41715 $0 $1,269,504 $156,015

Fifteen Year Return For HEPA Filtration, Base Load 3


24

Proper filtration is essential for gas turbine peak performance. Selecting the

optimal filters and configuration is based on operating and environmental factors.

Subsequent data collected since the case studies shows 1 percent degradation

in power loss with HEPA over a year’s time. Improper filtration will degrade

turbine performance, including blade erosion, fouling, cooling passage plugging,

and corrosion. These and other factors should be discussed with your OEM

turbine manufacturer or filter supplier. Cost-benefit models for specific operating

environments can be applied and account for filter purchase price, fuel price,

power sale price, maintenance, inspections, wash cycles, power degradation, heat

rate increase, pressure loss, labor costs and down time.

A Division of THE HILLIARD CORPORATION

For info. http://powereng.hotims.com RS#31

1503PE_C3 3 3/6/15 9:00 AM

26


Originally published September 1, 2009

Keeping Fluid Systems Clean

Condensate and feedwater systems, turbine lube oil systems, electro-hydraulic control systems rely on fluid purity to operate optimally.

By Brad Buecker, Contributing Editor

Four years ago I wrote about the very successful application of

microfiltration for makeup water pretreatment at a former utility.1 The

machine replaced an aging clarifier and sand filters, where it greatly

reduced operating costs and vastly improved the quality of water being

fed to a downstream reverse osmosis (RO) unit. Obviously, however, power

generating units have many other fluid systems in which fluid purity is also very

critical. These include the condensate/feedwater system, turbine lube oil system,

electro-hydraulic control (EHC) system, and others. This article examines fluid

purity issues in these systems.

Power plant chemists and other plant personnel typically are aware that

contamination which enters steam-generator condensate can potentially cause

severe corrosion in the boiler and carryover of contaminants to the steam.

Condenser tube leaks are the worst culprit, but impurities may come from other

sources. Regardless, corrosion mechanisms in a boiler are exacerbated by the

presence of porous deposits, which can serve as concentration sites for impurities

that then directly attack the base metal of waterwall tubes.

During normal steam generator operation, condensate/feedwater piping and

boiler waterwall tubes develop a layer of iron oxide, which, while being a

corrosion product, protects the underlying base metal against further corrosion.

Even in the normal course of operation, this corrosion layer will gradually

increase in depth, but during periods of chemistry upsets, thermal transients



27

and forced outages, additional corrosion products are generated. And, during

the major work often performed at times of scheduled maintenance outages,

literally hundreds to thousands of pounds of loose particulates may lodge in the

condenser hotwell, condensate and feedwater systems.

Some plants have the capability to remove at least a portion of this debris at

start-up. But in many cases particulate removal is inadequate at best, where

perhaps the only method is to withdraw material through the drum blowdown.

Particulates that cycle through the waterwall tubes will, as the temperature

increases to normal load condition, deposit on the tubes. These porous deposits

will subsequently influence heat transfer. More importantly, they serve as sites

for possible under-deposit corrosion and premature tube failure. Thus, at some

plants, and particularly those with once-through steam generators, start-up holds

are used to allow debris to be cleaned from the system. These holds may last for

days following a particularly intense maintenance outage. As plant personnel well

know, any delay in start-up can cost a utility tens to hundreds of thousands of

dollars, or more, in lost power production.

An equipment investment that can pay for itself several times over with just

the first use is a condensate particulate filter. These straightforward mechanical

devices can be easily equipped with filter cartridges that remove particulates in

the single-digit micron range at very high efficiencies.

The common location for a particulate filter is just after the condensate pumps,

with the filter placed in a valved, bypass loop around the main condensate feed

line. The device need not be full flow, as at start-up the condensate circulation is

often restricted to half the full-load flow rate or perhaps even less. The devices

will remove iron oxide particulates and other “crud” within a short period of

time, allowing for potentially significant reductions in hold periods.

At one utility, we once started up a supercritical unit following a boiler chemical

cleaning. The only method to remove iron oxide and other particulates from the

condensate was filtration through the deep-bed condensate polishers. Not only

did this process significantly foul the polisher resin, but four days of filtration



28

were required to reduce the solids, whose original concentration was greater than

1 part-per-million (ppm), to the relatively low parts-per-billion (ppb) concentration

necessary to fire the boiler.

To alleviate this difficulty, we ordered a condensate particulate filter designed to

handle half of the full-load flow for installation ahead of the condensate polishers.

Plant personnel installed the unit and equipped it with 6-micron (absolute) filter

cartridges. The filter was first used in 2008 at start-up following another chemical

cleaning. Again, the initial particulate concentration was very high. As it turned

out, two filter replacements were required during the particulate cleaning

process. But the critical point is that the filtration time was reduced from four

days to one day. An extra three days of operation on a large supercritical unit

paid for the filter, the extra cartridges and the labor costs to install it several

times over just after the first use.

Turbine lube oil

In simplest terms, both steam turbines and combustion turbines are many tons

of machinery rotating at 3,600 rpm. Very tight tolerances are required at journal

or roller bearings, which in turn requires high-purity lubrication oil to prevent

bearing wear and premature failure. The most common contaminant in lube

oil is water. Water may enter through leaking steam seals, heat exchanger tube

failures, condensation in the main lube oil tank or other sources. Water can

cause corrosion and microbiological fouling in the main lube oil tank and other

locations, where the corrosion impurities will then travel to turbine bearings and

control valves, piping and so on.

Past equipment that has been used to remove water include gravity precipitation

systems with filter bags and settling chambers and centrifuges, which as the

name implies, ue circular motion to separate oil and water due to the difference

in density.

Typically, these older systems were somewhat efficient at removal of free water

but did not effectively remove emulsified or dissolved water from lubricating oils.

A more modern process that is capable of removing free water and up to 80 or

90 percent of dissolved water is mass transfer vacuum dehydration. The unit is



29

typically installed in a kidney loop on the main lube oil tank. It uses mild heating

of the oil slipstream followed by vacuum dehydration from a small, skid-mounted

unit to remove virtually all of the water in the oil. The tiny amount of dissolved

water that remains is at much too low a concentration to convert to free water in

the lube oil tank.

Varnish removal

Varnish formation in oil is a subject of great importance at both conventional

steam plants and those with combustion turbines. Power Engineering magazine

reported on this issue in February 20082 with an article that outlined many of the

fundamental varnish removal technologies. However, I have spoken with or heard

reports from a number of utilities, in which these conventional technologies gave

widely variable results. A process that has been recognized for some time but is

now beginning to grab headlines is that of adsorption to remove varnish. Varnish

occurs when oil and its additives oxidize and polymerize due to stresses placed

on the fluid, which include heat transfer from the equipment, microdieseling, and

electrostatic energy transfer from particulate filters.

Varnish polymers can reach high molecular weights, and due to their oxidized

nature, will settle on internal components, including servo valves. The latter has

become a very troublesome issue in many combustion turbines.

While varnish is only slightly soluble in oil, the fact that it has even some solubility

allows it to be removed from systems without the expense and headaches of

periodic off-line cleaning. Adsorption is proving to be an effective technology.

Adsorption is a film-forming mechanism, where the compound to be removed

exhibits an electro-chemical affinity for the surface of the collecting media.

The varnish removal compartment contains multi-layer media, whose surface

has been prepared to be especially attractive to the oxidized varnish particles. As

varnish comes out on the media, deposits within the lube oil system gradually

dissolve and are subsequently removed. Progress of this or other technologies can

be tracked via the QSA (Quantitative Spetrophotometer Analysis) test offered by

Analysts Inc. based in Los Angeles. The procedure involves filtration of oil samples

on a special filter media that collects dissolved varnish to produce a distinct color.

The color intensity can be directly related to varnish potential in Table 1.


TABLE 1 VARNISH POTENTIALVarnish Potential Rating (VPR) Condition

<35 Normal

38-58 Active monitoring should be implemented

60-79 Abnormal

>79 Critical. Immediate action needed.


30

A well designed and functioning varnish removal system should reduce the VPR

to well below the “normal” value of 35.

electrohydraulic control Fluid

Electrohydraulic control (EHC) fluids will also accumulate debris and varnish. A

malfunction of turbine control valves due to contaminated control fluid can be a

serious issue. The most common compounds utilized as EHC fluids are phosphate

esters, for example, organic compounds where the phosphate addition improves

fire resistance. A common method for filtering EHC fluid is to pass a slipstream

through material such as Fuller’s Earth. However, this process introduces

hardness ions to the fluid, which in turn can react with degraded EHC to produce

tenacious deposits such as calcium phosphate.

A technology to combat hardness-based deposit formation is to install an

ion exchange column on the slipstream, where the exchange media removes

the hardness ions. Use of ion exchange for phosphate ester treatment allows

the operator to selectively target both acidity and resistivity of the fluid by

combining different concentrations of anionic and cationic resins. The flow

rate required for these systems is relatively small, resulting in minimal resin

volume requirements, where the resin may last for several months before a

change-out is needed.

references1. B. Buecker, “Membrane Magic”; Power Engineering, pp. 26-30, September 2005.

2. F. Guerzoni, “Eliminating Varnish, Power Engineering, pg. 50, February 2009.



31

Brad Buecker is the Technical Support Specialist with AEC PowerFlow in Kansas

City, MO. He previously served as an air quality control specialist and plant

chemist for Kansas City Power & Light. Buecker has written many articles on

steam generation, water treatment, and FGD chemistry, and he is the author of

three books on steam generation topics published by PennWell Publishing. He

has an AA in pre-engineering from Springfield College in Illinois and a BS in

chemistry from Iowa State University. He is a member of the ACS, AIChE, ASME,

and NACE.



32

Company ProfileFounded in 1905, The Hilliard Corporation proudly marks its 110th anniversary in 2015. From the first product of the company, a friction disconnect clutch, to manufacturing oil reclaiming machines in 1925, Hilliard has continually evolved into becoming a leader in motion control and industrial filtration technology. HILCO has supplied thousands of liquid fuel filters, coalescers, and systems to OEM turbine and engine manufactures to maintain fuel cleanliness to their specifications. HILCO is able to offer our customer a customized and optimized solution to their liquid fuel filtration application that will ensure equipment reliability.

The Hilliard Corporation100 West Fourth StreetElmira, NY [email protected]

http://www.HilliardCorp.com

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