| Q. |
What are the methods of cleaning fouled GT compressors? |
| A. |
Offline cleaning
methods:
- Crank-soak chemical washing
using in-built chemical injection/water rinsing
systems
- Crank-soak chemical cleaning
using hand held hose or lance
- Partial hand cleaning (e.g.
Struts, IGV's, 1st stage rotor & stator
blading) using chemicals, rags, brushes and
water rinse
- Full hand cleaning with
compressor covers removed using chemicals,
various types of abrasives or even light
shotblasting techniques
- Steam cleaning
Online cleaning methods:
- Injection of abrasives (e.g.
crushed nutshells) into the compressor air
stream to displace blade deposits by high
velocity impingement
- Injection of plain water to
remove water soluble deposits
- Injection of special chemical
solutions (solvent & aqueous based) to
chemically dissolve and remove surface deposits
from the blades
<back to FAQ's>
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| Q. |
What is online compressor cleaning? |
| A. |
The compressor can be
chemically cleaned on a frequent basis while the gas
turbine remains in normal operation.
Again, if done properly, on-line cleaning can
be very effective in preventing - or at least
significantly reducing - the fouling of the
compressor with the additional and most vital
advantage being that there is no shut down involved
nor any interruption to operation or production of
the plant which it serves.
With
the continued development and improvement of on-line
cleaning processes and chemicals - which Rochem has specialized
in for over 20 years - one of the most
efficient and popular ways of maintaining compressor
efficiency is to now use a combination of on-line
and off-line washing procedures.
If
a properly designed on-line cleaning system and
chemical is used this procedure should, at the very
least, significantly reduce the rate of build up of
compressor fouling and thus considerably extend the
running time of the machine before shut down is
required for off-line cleaning.
<CLICK
HERE TO SEE A TECHNICAL PAPER ON THIS SUBJECT>
<back
to FAQ's>
|
| Q. |
What are the
advantages and disadvantages of online compressor
cleaning? |
| A. |
Lets start with the
disadvantages:
- Can have limited effect if
chemical is not properly formulated
- Can have limited effect if
chemical is not injected properly
- Some online cleaning chemicals
are quite expensive and results may not justify
the costs in some cases
- Some online cleaning systems
are very expensive and are priced against what
the customer may save in operation costs rather
than what it actually costs to develop and
manufacture the equipment
Now the advantages:
- No engine shutdown required
- Can arrest or slow down the
rate of compressor fouling while the gas turbine
remains in operation thus maintaining heat rate
and saving large amounts of money by avoiding
additional fuel burn
- Helps maintain power output to
avoid loss of production revenue and unnecessary
use of standby machines
- There is no interruption to
production or operation routines as washing can
be carried out at full speed and load
- The cleaning process usually
takes only a matter of minutes
- There is no waste chemical or
water to deal with after the wash
- Assuming the chemical is
properly formulated and injected it should not
contribute to any additional atmospheric
pollution
- By avoiding shutdowns for
offline washing thermal cycles are also
considerably reduced thus extending the life of
the engine
- No erosion, thermal shock,
bearing damage, cooling system blockage (if
properly designed system is used)
<CLICK
HERE TO SEE A TECHNICAL PAPER ON THE CASE FOR ONLINE
CLEANING>
<back to FAQ's>
|
| Q. |
What is offline compressor cleaning? |
| A. |
The
gas turbine can be completely shut down on a regular
basis for so-called crank-soak washing.
If done properly this form of cleaning can be
effective in restoring most of the lost performance.
However, as all turbine operators know, it is very
time consuming and laborious and, overall, a very
costly exercise - especially when the shut down of
the gas turbine means the total loss of revenue for
the whole period of the shutdown from the sale of
electricity and/or steam or costly interruption to
the production of the factory which the gas turbine
serves.
<back to FAQ's>
|
| Q. |
What are the
advantages and disadvantages of offline compressor
cleaning? |
| A. |
Let's start with the
disadvantages:
- Gas Turbine must be shut down
completely
- Time consuming process
- Labour intensive process
- Costly problems in disposing of
waste chemical and rinse water
- Lost power output cannot be
recovered
- Shutdown/Startup thermal cycles
for offline wash are damaging
- Extra wear and tear on starting
system during offline wash
- Can wash salt and corrosives
into inaccessible parts of the engine
- Only a short term cure and not
a prevention for compressor fouling
Now the advantages:
- When carried out correctly can
effectively clean compressor and restore
majority of lost performance
<back to FAQ's>
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| Q. |
What
are the direct effects of compressor fouling? |
| A. |
On day to day operating
costs:
- Higher fuel costs due to
increased heat rate
- Reduction in power output and
loss of related production revenue
- Use of more expensive external
power supplies to make up shortfall
- Higher cost of operating
standby plant to make up shortfall
On longer term operating and
maintenance costs:
- Reduction in life of all hot
section components due to higher EGT's
- Higher maintenance costs in
more frequent replacement of components
On safety
- Possibility of compressor stall
and subsequent engine damage
- possibility of rotor imbalance,
vibration and catastrophic breakup
On capital expenditure
- More frequent replacement of
expensive hot section components
- Greater investment in
non-productive standby plant and redundancy
- Shorter amortization periods
for gas turbine
<back to FAQ's>
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| Q. |
What
causes compressor fouling? |
| A. |
The typical causes of
GT compressor fouling are:
- Passage of oily vapours through
filtration system
- Ingestion of oily vapours
through breaches in air inlet plenum
- Leakage of lubrication oil
directly into compressor
- Leakage of oil form oil-bath
type filtration systems
- Passage of very fine
particulate matter through filter system
- Passage of larger particulate
matter through breaches in plenum
- Re-ingestion of exhaust gasses
through filtration system and breaches in air
inlet plenum casing
- Ingestion of saturated salt
droplets or dry salt crystals through filters
and/or breaches in plenum casings
- Ingestion of seasonal tree and
plant gums
- Ingestion of wide variety of
chemicals and other pollutants generated at site
of gas turbine operation
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FAQ's>
|
| Q. |
What are the
advantages and disadvantages of using plain water
for compressor cleaning? |
| A. |
The advantages of using
only plain water for compressor cleaning are:
- Can be used when gas turbine is
operating (if injected correctly)
- Simple to use
- Relatively inexpensive
- Can have some cleaning effects
if fouling is purely water soluble
The disadvantages of using only
plain water for compressor cleaning are:
- Not effective against
oily/greasy contamination
- Not effective against lacquered
or hard carbonaceous deposits
- May move deposits to hot
section of engine to cause corrosion
- May directly cause corrosion if
not inhibited
- May cause thermal shock/blade
stress if not injected correctly
- Not effective for offline
cleaning (unless the deposit is water soluble)
- Must be high quality water with
very low TDS and suspended solids
<back to
FAQ's>
|
| Q. |
How many installations have Rochem carried out? |
| A. |
In excess of 4000
nozzle manifold installations world wide on
practically every type of gas turbine
<back to
FAQ's>
|
| Q. |
What are the
questions to ask when selecting a compressor
cleaning system and/or chemical? |
| A. |
Questions to ask regarding the
cleaning system:
- How long has vendor been in
business
- An installation reference list
- Is the system known to engine
manufacturers. Do they approve it or have
no objection to its installation and use
- Is the system a recommended
option or installed as standard in new gas
turbines by any manufacturers/packagers
- Does the vendor design,
manufacture, install, service and guarantee the
system himself. (If not why not)
- Are the materials of the system
good quality
- How long does the vendor say it
should take to install the system. Some
can take a few hours to install, others can take
weeks to install if it involves drilling thick
castings etc
- Is the design safe? Could
it possibly damage the engine or injure those
using it
- Does the vendor have sufficient
liability insurance
Questions to ask regarding the
cleaning chemicals:
- Does the manufacturer also
manufacture special cleaning chemicals for use
with the system and are they tried, tested and
approved
- Was the chemical on offer
solely developed for online cleaning or was it
originally developed for some other application
not directly related to gas turbines
- Does the vendor offer a choice
of chemicals (i.e. solvent-based and water
based) to suit particular fouling and/or
environmental requirements
- Is the chemical supplied as a
concentrate to save storage and transportation
costs. Paying for water in ready-to-use
chemical solutions can be very expensive and
unnecessary
- Can the chemical offered also
be used safely and effectively for offline
compressor washing if need be
- Does the vendor offer
ex-warehouse availability of chemical
- If the vendor only supplies
chemicals are you sure it is safe to use them in
your injection system
Recommendation: Be very wary of
using any chemical especially for online, fired
washing, unless it has been properly tested and
approved and has a good long term safety record
behind it.
<back to
FAQ's>
|
| Q. |
Has there ever been a failure of a Rochem nozzle? |
| A. |
Never
in more than 25 years and millions of engine
operating hours in every environment
<back to
FAQ's>
|
| Q. |
What does the Rochem Fyrewash system consist of? |
| A. |
The system consists of
a uniquely formulated chemical and a specially
developed method of application. The cleaning
fluid is formulated to remove oil and grease,
carbon, salt and general atmospheric fouling from
the compressor whether axial or centrifugal
type. Complete compatibility with engine
materials, including special coatings, is assured by
the correct chemical formulation and proven over
many thousands of operating hours in a wide variety
of engine types. The cleaning fluid has been
tested and approved by many of the worlds leading
engine builders and also meets stringent U.S.
Military Specifications for compressor washing
fluids.
The Injection system is designed
to deliver the cleaning chemical into the air stream
in a highly atomized mist-like form and in every
case is specifically designed to suit the particular
engine type and air inlet trunking system. For
industrial engines a set of specially designed atomizing
nozzles connected by a common manifold
ring are normally permanently fitted to the air intake
plenum chamber and fed from a pressure injection
tank or pump system. In all cases the entire
system is designed for simple and low cost retrofit.
<back to
FAQ's>
|
| Q. |
How does the Rochem Fyrewash system compare in safety and
efficiency with other compressor cleaning methods? |
| A. |
Water washing is
generally ineffective because it has no power to
remove the oily/greasy contamination which is the
major problem affecting the loss of compressor
efficiency. Even for salt removal purposes -
an absolute necessity in marine and many helicopter
operations - plain water washing is often of no
benefit whatsoever since the salt is usually trapped
in and under the layer of oily deposit which the
water cannot remove. CRANK-SOAK SOLVENT
Cleaning can be effective but it require complete
shutdown, is labor intensive, contributes
significantly to wear and tear on starting systems,
and does nothing to solve the problem of power loss
and increased fuel consumption while the engine is
becoming fouled in normal operation. ABRASIVE
CLEANING METHODS can result in serious blade erosion
problems, bearing damage and the removal of very
costly blade coatings. Also since abrasive
cleaning can only dislodge the contamination back
into the air stream, rather than chemically dissolve
it, redeposition can occur in the latter stages of
the compressor and bearing system.
The Rochem Fyrewash system has
none of these disadvantages because it is used while
the engine remains in operation, it can be used as
frequently as necessary so contamination is not
allowed to build up so that output and specific fuel
consumption are not affected. The Fyrewash
chemical range will keep the compressor clean of any
salt, oily and greasy deposits and contamination
whilst being fully compatible with blade
coatings. It also leaves no residue in the
engine nor redesposition of the removed
deposits. The Fyrewash patented nozzles apply
the wash solution in a highly mist-like form at a
controlled flow rate so that there is no danger of
blade erosion.
<back to
FAQ's>
|
| Q. |
What about cost effectiveness? |
| A. |
The cost of installing
and operating a Rochem Fyrewash system is minimal
compared to the potential savings in fuel, engine
efficiency and output, and the avoidance of downtime
to be realized by keeping the compressor clean while
the engine remains in normal operation.
<back to
FAQ's>
|
| Q. |
How
much time is required to install or retrofit a
stationary engine? |
| A. |
This depends on to
which engine the system is being installed.
Some systems can be fitted in a matter of hours
whereas others can take a couple of days.
Generally the systems are fitted during an engine
overhaul or outage.
<back to
FAQ's>
|
| Q. |
How
much time is required for cleaning the gas turbine? |
| A. |
The time required to
clean a gas turbine is dependant upon the size of
it. A typical wash takes around 10-20 minutes
and consists of a chemical injection followed by a
soaking period to allow the chemical to break up
stubborn deposits. This is usually around 20
minutes and then will be followed by one or two
water only rinses.
<back to
FAQ's>
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| Q. |
Do
I need to use cleaning chemicals and detergents? |
| A. |
Rochem suggests the use
of cleaning chemicals and detergents for online and
offline compressor cleaning. The chemical
breaks up the carbonaceous deposits and particulate
matter that water alone cannot remove. Think
of it as trying to clean a greasy pan with no
washing up liquid!
<back to
FAQ's>
|
| Q. |
What
is the requirement for the water used in the washing
process? |
| A. |
The water must be of
high quality, i.e. Demineralised or Deionised water
<back to
FAQ's>
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| Q. |
Is
the cleaning procedure safe? |
| A. |
The Rochem Fyrewash
system has been designed with safety in mind from
conception to build. The patented nozzle
design allows for precise atomization of the spray
pattern to eliminate erosion to the engine.
<back to
FAQ's>
|
| Q. |
How
do I go about purchasing the Rochem Fyrewash
equipment? |
| A. |
All Rochem Fyrewash
systems are available for sale throughout the
world. In the first instance please contact
your nearest Rochem office. Alternatively you
may email sales@rochemltd.com
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FAQ's>
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