Mr Spaceman
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"Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 2:38 am

Hi guys.

I did a search, and there was nothing under "coke wash", so I'm sorry if this topic has already been discussed.

Here's the photographer's remarks ........

"This is a "coke wash" cleaning of a DC-10 engine in progress. Running the engine at idle, a technician will direct a spray of mild abrasive into the engine to clean off deposits that can cause high heat (EGT)."


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Photo © Colin T. Ebert



I have a few questions about the procedure of "Coke Wash" cleaning a jet engine.

Is this cleaning only done if required after an inspection of deposits, or is it scheduled maintenance based on the amount of hours the engine has run?

Can a jet engine like the one on the DC-10 in the photo go it's entire life without needing this type of cleaning?

Regarding the mild abrasive that's used, how fine are the particles? Are they smaller than table salt for example?

How do deposits (which I assume means soot in the cumbustion chamber[s] and tailpipe) cause an increase in the engine's exhaust gas temperature (EGT)?

Finally, have any of you maintenance technicians ever done a Coke Wash cleaning?


Chris  Smile

[Edited 2005-02-22 18:39:09]
"Just a minute while I re-invent myself"
 
777wt
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 3:16 am

Coke wash is done to increase the efficiency and the life of the turbine. It could be water or crushed walnuts or an chemical for it.
When it goes through the engine, it cleans off the compressor blades by abrasive means and carries that out to the turbine section where it either gets burnt up or flys out straight back.

I'd like to see what comes out of the engine at night during a coke wash.
 
AvionicMech
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 3:34 am

I have not really seen what comes out the back of the engine at night during a coke wash but if you look in the front you can see where the spray is hitting the first stage of the compressor blades as it produces bright orange sparks. It really is quite a good show to watch but I don't think we do 'coke washes' at BY anymore, I don't know whether it is an airport policy or a company policy change that has stopped us doing this.

Avionic Mech
 
Mr Spaceman
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 3:46 am

Hi guys.

Thanks for your replies.

>> 777WT, OK, so I guess the efficiency and the life of the turbine at the back of the engine is increased by having deposits (of soot?) sprayed off the turbine blades by an abrasive product.

I guess the turbine blades must get coated with deposits pretty good after time, in order for this procedure to reduce EGT and increase efficiency.

>> AvionicMech, ..... "I don't think we do 'coke washes' at BY anymore."

That photo's 10+ years old, so maybe a coke wash isn't done to often anymore..... anywhere.


Chris  Smile
"Just a minute while I re-invent myself"
 
broke
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 3:53 am

A coke wash is used to clean the airfoils in the compressor section of the engine, not the turbine. Over time, the elements that cause air pollution tend to adhere to the blades and vanes in the compressor, resulting in a loss of compressor efficiency. The result is the requirement to increase fuel flow and turbine inlet temperature to get the needed N1 or EPR, and in doing this you shorten the life of the turbine.
In the early days of jet transport, crushed walnut shells used to be used to scour the compressor airfoils clean, but when engines with air cooled vanes and blades in the turbine arrived, this practice was stopped. The problem being that the crushed shells tended to plug up the cooling passages to the turbine, resulting in turbine failures due to overtemperature.
 
Mr Spaceman
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 4:25 am

Hello Broke.

Thank You, for your clear explanation.  Big thumbs up

Ok, so I understand now that this type of cleaning is/was for the blades & vanes in the compressor stage of the engine, and that by making the compressors more efficient, the turbine's life span benefits by being exposed to lower temps.

Question ...... Was the practice of coke washing stopped all together, or just the use of crushed walnut shells for the abrasive material?


Chris  Smile
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SlamClick
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 5:06 am

Ah yes, MIL-G-5634

That is walnut shell grit to you civilians. It was pretty spectacular when done at night.

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Photo © Michael Licko


On the Grumman OV-1 Mohawk it was said that you could immobilize the propeller blade and start the engine to do this, however, I think you would lose the effect on half the engine if you did that. It would also be a really good idea not to let the prop start moving AT ALL.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
Mr Spaceman
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 5:46 am

Hello SlamClick.

As a civilian (former riffleman in Canada's QOR regiment), let me guess what that code stands for .... MIL = Military, G = Grit, 5634 = Crushed Walnut Shells.  Laugh out loud

Anyhow, was the reason why immobilizing the propeller was a good idea because the intake between the cowling and prop spinner is so narrow, or simply because the walnut shells would just bounce off the spinning prop?

PS, did you fly those aircraft?

Chris  Smile
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CRJ200Mechanic
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 7:28 am

I have done several of these on the CRJ. Its a wet and smelly job. We use a soap called Zok 27 mixed with water and depending on the temperature, alcohol (to keep from freezing). On are engines there is a manifold behind the cowlings that we hook up to. We dry motor the engines. When N2 hits 24 percent we introduce the solution for about 30 seconds. We do one soap rinse and 2 water only rinses per engine. Then we do a dry out run after both engines have been washed. We fire them up and run them at about 75-80 percent for 10 minutes to dry the engines out. We run on a six month interval. So every six months from the last wash, its due again

I also forgot to mention that we have have to disconnect all bleed lines and cap them off so we don't get the solution in the packs and the coalscer bags

The foam that comes out the engine is pretty grimy. I tend to get it all over me because you are right under the engines with the pump and the wind always seems to be coming up the tail when I do it. Thanks Murphy  Smile
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Mr Spaceman
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 9:12 am

Hello CRJ200Mechanic.

Thanks for your excellent info. Your step by step explanation of how the procedure is done was neat to learn about.  Big thumbs up

Now I know that some airlines do this procedure on a set time basis. In your company's case, at six month intervals.

I have 2 questions for you ......

Does the Zok 27 soap that you use have any abrasive material in it at all, such as a very fine silica sand to help scour clean the compressor blades and vanes? Or is it only strong soap?

Also, on a side note, I've learned a lot about the environmental control system on airliner jets from both this forum & the internet. Thus I've learned about all the parts of the system (so I thought Big grin ), from the N1 & N2 bleed air ports to the Cabin Pressure Control Valve (and all the parts in between ... ozone converters, ram air inlets, heat exchangers, mix manifolds, ducting, etc, etc), but I've never heard of coalscer bags.

What do these bags do?


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PS, welcome to the forum! Big grin

Chris  Smile
"Just a minute while I re-invent myself"
 
gocaps16
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 12:43 pm

Whenever we finish running an engine in the cell, we spray water directly into the intake to cool the engine quicker. It also cleans the interior as well. Also, it removes the salt when we're deployed. After running for 5-6 hours straight, salt deposit builds up big time. At night, it becomes a white stream of mist or whatever coming out of the exhaust nozzle...pretty cool.

Kevin
 
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 1:10 pm

CRJ200mech hit the nail on the head. We use a solution called Cee Bee or something along those lines. It has a milky color to it.We cap off the 10th stage and 14th stage bleed ports with blanking plates. We then dry motor the engine like he said, and pump the solution through. We normally do two wash cycles followed by two rinse cycles. Every cycle is seperated by 5 minutes in order to let the starter cool down. If the engine is especially dirty, we will continue with the wash cycles until the fluid is clean exiting the engine. You can actually see the dirt coming out the jetpipe during washing. The fluid first exits brown or grey, and then becomes white as the deposits are cleaned.

I had a "comp wash" the other night on one of my planes. Running it up to near takeoff power in the hush house was a bit 'interesting.' Seeing as there was fresh snowfall and we were light on fuel, I knew there might be trouble. Sure enough, as I was bringing #2 engine up to 80% N2 or so, the plane started sliding sideways to the left. Needless to say I ended up goosing up #1 to strike a balance during the run. We still slid, but at least it was forward. That put a few gray hairs on me Big grin
 
tbanger
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 5:06 pm

ZOK 27 isn't abrasive to feel, but if you stand over it and take a big whiff, you'll burn the hairs right off from your nostrils to your arse.........lol
 
CRJ200Mechanic
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 5:24 pm

Quoting Mr Spaceman (reply 9):
Does the Zok 27 soap that you use have any abrasive material in it at all


Quoting Mr Spaceman (reply 9):
I've never heard of coalscer bags.


To answer your questions. The soap is just soap. No abrasives in it. Obviously we all know how the compressor section works on the engine. When you pump the soap solution into the engine, the soap is compressed to the compressor blades through each stage. Thats how the cleaning action works. You can see the foam come out dirty at first then it turns white once its clean

To answer your next question. The coalescer bag is installed in the water separator of the pack. The pressurized air that comes from the air conditioning pack enters the water separator it expands. This causes moisture. The coalescer bag causes the moisture to condense and drain to the bottom of the water separator (hence the name, moisture bad). The water will then drain overboard I believe. The coalescer bag will also help prevent damage from ice or debris that may be present. In simpiler terms you might consider it a water filter of sorts

Replacing the bag can be a disgusting job. Its wet and smelly. I have also heard that in the days when smoking was allowed it was even worse. Those were before my days so I don't know. I hope this answers your questions

ps The picture you have tail number 8794. I worked on it the night I typed this reply. Pretty cool huh!
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CRJ200Mechanic
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 6:06 pm

Quoting Tbanger (reply 12):
ZOK 27 isn't abrasive to feel, but if you stand over it and take a big whiff, you'll burn the hairs right off from your nostrils to your arse


Yeah its some pretty ugly stuff. Who knew soap could be so nasty
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Mr Spaceman
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 6:37 pm

Hi guys.

>>GOCAPS16, UAL Bagsmasher, Tbanger & CRJ200Mechanic, Thanks for your answers & info.

"you'll burn the hairs right off from your nostrils to your arse"... hehehe, that sounds like some pretty wicked soap! The words "Chemical Suit" come to mind.  Laugh out loud

Ok, so now I know what a coalescer bag is, where it's located, and how it works.

Also, I understand that the soap used for cleaning jet engines doesn't have any abrasive material in it, it's just soap that cleans as it's being compressed.

>> CRJ200Mechanic, that is pretty cool. I chose that photo on purpose because the CRJ is landing in Tulsa ....where you are. Big grin


Chris  Smile
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CRJ200Mechanic
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Feb 23, 2005 6:53 pm

Quoting Mr Spaceman (reply 15):
I understand that the soap used for cleaning jet engines doesn't have any abrasive material in it,


I don't know if thats true for all soaps. I just know its true for the stuff we use

And the soap is actually non hazardous believe it or not. It does become hazardous when it leaves the engines for obvious reasons.
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777wt
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Thu Feb 24, 2005 9:34 am

Quoting Mr Spaceman (reply 3):

Turbine section doesn't get much deposits on them due to the high temp they get to while operating. It's the compressor section that gets the cleaning.

On the other hand, Southwest doesn't do cleaning of their engines which is against their policy. Someone on here did it and didn't know it.
Why? I don't know, either it's for safety reasons or it's left to the engine overhaul shop.
 
futureuapilot
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Thu Feb 24, 2005 9:58 am

Hey, this might be a silly question, but is there a mechanic or Pilot in the cockpit while this is going on to raise the throttles or can you do it without someone in the cockpit?

-Sam
The Pilot is the highest form of life on Earth!
 
777wt
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Thu Feb 24, 2005 11:16 am

Quoting FutureUApilot (reply 18):


Sure there has to be someone in there, no one is gonna let a plane run by itself without anyone in the cockpit.
 
DC10GUY
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Thu Feb 24, 2005 4:21 pm

I've done that several times, Scheduled most of the time. High EGT trends first required a "boroscope inspection" if "splattered" was found in the compressor a "coke" cleaning would be done. The "coke" is coke that's ground very fine. That stuff will kill you if you breath it in. The picture shows a #1 engine being cleaned .... The #2 was sooo much fun to do .....NOT!
Next time try the old "dirty Sanchez" She'll love it !!!
 
CRJ200Mechanic
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Thu Feb 24, 2005 4:38 pm

Quoting FutureUApilot (reply 18):
but is there a mechanic or Pilot in the cockpit while this is going on to raise the throttles or can you do it without someone in the cockpit?


You shouldn't have to advance the throttles, because you are only doing a dry motor, no fuel pumps, no ignition, you don't even touch the throttles. just the start/stop buttons

I know this is how we do it. I'm sure there are other places that do it different
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HAWK21M
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Thu Feb 24, 2005 8:45 pm

Quoting 777WT (reply 19):
Sure there has to be someone in there, no one is gonna let a plane run by itself without anyone in the cockpit.


Ditto.
regds
MEL
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Mr Spaceman
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sat Feb 26, 2005 2:09 am

Hi guys.

>> 777WT, I was tricked into thinking that the black smoke blowing out the back of the DC-10's engine in the first photo was being caused by soot that was deposited on the turbine blades, etc.

Thanks for mentioning that the high heat in the turbine section prevents a build up of deposits. That makes perfect sense Big grin .... which I didn't think of.

So, obviously the black smoke in the DC-10 photo is caused by the coke material itself.

Here's an excerpt from a Google search about coke.........

"The coke is crushed and screened and transported to the blast furnace. The oversize coke is returned to the crusher while the undersize coke, known as coke breeze, is recycled to the coke ovens, used as fuel in a sinter plant, or sold."

I guess one of the places that undersize "coke breeze" is sold to is the aviation industry!

>> DC10GUY, Thanks for your good info. I'm sure you would die if you inhaled to much coke!  Laugh out loud


Chris  Smile
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SlamClick
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sat Feb 26, 2005 2:28 am

Happiness is not seeing another trite Ste. Maarten photo all week long.
 
PW100Testpilot
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Tue Mar 29, 2005 6:02 am

When the engine (PW-100 Turboprop) needs it, we'll perform a compressor wash in the testcell. Just in front of the LP impeller a compressor wash nozzle is installed. We clean the impellers with a mixture of water and soap (I believe something like 'turboclean'). We'll dry-motor the engine for about 1-2 minutes at a speed of 5000 RPM NH, and after that we will let the soap do it's work for a couple of minutes, followed by another dry-motoring run for injecting pure water to wash the soap away.
It's only for cleaning the 2 impellers for a better effectivity of the impellers. So we don't have sparks out of the exhaust, but bubbles  Smile
No info
 
Mr Spaceman
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Tue Mar 29, 2005 6:25 am

Hello PW100Testpilot.

Thanks for your info. A jet engine blowing out bubbles would be great to catch in a photo! Big grin

>> SlamClick, Thank You, for that link ...... I know it's been a while since you posted it.  Silly

Chris  Smile
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UAL Bagsmasher
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Tue Mar 29, 2005 11:15 am

Our CRJ-200 comp. washes are many times done on a "trend" basis. We download engine data everyday from the IAPS (Integrated Avionics Processing System). When the MX planners detect a loss of performance in the engine, a compressor wash is scheduled to get things back to normal.
 
AR1300
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Tue Mar 29, 2005 2:15 pm

Quoting DC10GUY (Reply 20):
The "coke" is coke that's ground very fine. That stuff will kill you if you breath it in.

Coke as cocaine? uh???sounds weird...it's gotta be something else.

Mike
You are now free to move about the cabin
 
CaptOveur
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Tue Mar 29, 2005 3:57 pm

Quoting AR1300 (Reply 28):
Coke as cocaine? uh???sounds weird...it's gotta be something else.

I think they mean coke as in highly refined coal.
Things were better when it was two guys in a dorm room.
 
AvionicMech
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Wed Mar 30, 2005 4:26 am

We have changed back to doing coke washes at BY as it was found that the soap method didn't seem to do as good a job. But I am not sure if this was down to lack of experience of the guys doing the soap wash so therefore it was not done that well or whether the soap just doesn't do as good a job as a good old coke wash.
 
jeb94
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sat Jun 25, 2005 8:02 pm

Coke is just carbon build ups in the case of jet engines.
 
MD11Engineer
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sat Jun 25, 2005 9:09 pm

When LH still operated B737-200s with JT8D engines (during my apprenticeship), we used to do turbine water washes in the hangar to remove sulphidous deposits on the turbine blades. With the ignitor plugs removed, we would install spray nozzles in the combustor through the ignitor plug holes. Then, with the engine being motored by the starter a water / soap mix was sprayed into the turbine (the water supply was a fire hose, so a lot of water). This was followed by several rinsing steps with clear water.

Jan
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PW100Testpilot
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sat Jun 25, 2005 9:16 pm

I'm not experienced with turbine washes, but I was just asking myself: what do you do with the fuelnozzles in the combustor? A lot of water and soap don't do them any good, I guess... Or doesn't it matter?
No info
 
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HAWK21M
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sun Jun 26, 2005 12:13 am

Quoting PW100Testpilot (Reply 33):
I'm not experienced with turbine washes, but I was just asking myself: what do you do with the fuelnozzles in the combustor? A lot of water and soap don't do them any good, I guess... Or doesn't it matter?

Its a dry motoring.
regds
MEL
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MD11Engineer
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sun Jun 26, 2005 1:54 am

Obviously you do a dry motoring, when you wash the engine. You don't want to have fuel mixed in. The spray nozzles are poining after, towards the nozzle guide vanes and you have a powerfull flow of air blowing all the water towards the turbine.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
PW100Testpilot
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sun Jun 26, 2005 2:27 am

I know you perform a tubinewash during a dry motoring run, but because you have to handle the tips of the fuelnozzles with care, I was wondering if such an amount of water doesn't harm the fuel nozzles
No info
 
VC-10
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sun Jun 26, 2005 2:43 am

Quoting CRJ200Mechanic (Reply 21):
Quoting FutureUApilot (reply 18):
but is there a mechanic or Pilot in the cockpit while this is going on to raise the throttles or can you do it without someone in the cockpit?


You shouldn't have to advance the throttles, because you are only doing a dry motor, no fuel pumps, no ignition, you don't even touch the throttles. just the start/stop buttons

A DC-10 coke wash was done at Flight Idle with a run certified engineer in the cockpit.

When the CF6 is new or the compressor is overhauled the inside if the casing is sprayed with aluminum to reduce the rotor blade tip clearences to improve efficiency. With centrifugal force the comp blades would stretch and cut into the Al layer (by design) to reduce the tip clearence. The side effect is that the blades get covered with Al splatter.

To remove the splatter at a predetermined interval after fitment a coke wash would be carried out.

Further washes are carried out whenever the EGT start to trend to the upper end of the limit.

Hot water washes are carried out on CFM56's when engine start to look like it would soon become EGT limited.

I have also done water washes on JT9's
 
DeltaGuy
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sun Jun 26, 2005 7:05 am

Whenever we'd have the T-45's come in for the Carrier Dets, they'd come back from a few days at the boat, and be thouroughly rinsed down as soon as they returned from their last trip at the boat. The airframe would be hosed off real well, and a special hose and tank with a solvent would be sprayed down the intakes to clean out the engine from the salt spray. Left a little bit of junk on the tarmac, but better there than on the airframe.

Took this shot when they were washing one of em down...
http://img.photobucket.com/albums/v610/flydeltajets/000_0144.jpg

DeltaGuy
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EMBQA
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sun Jun 26, 2005 7:58 am

Keep in mind.... Compressor Washes and Coke Cleaning are two VERY different things....

'Compressor Washes' are done on a fixed interval established by the engine manufacture. You spray into the engine intake a warm soap and water mixture which removes all the film build up inside the engine. The soap is actually a degreasing agent that reminds me of 'Gunk' engine degreaser. Compare it to washing your car.

'Coke Cleaning' is done only when engine tread data shows the need to do so. With the engine running an abrasive agent is injected into the engine. It is used to remoave hard build up forming on the inner engine parts. On the down side, most engine only allow you to do this once or twice before the engine must be completely overhauled. Compaire this to sand blasting a rusty part.
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
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HAWK21M
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Sun Jun 26, 2005 6:13 pm

Quoting PW100Testpilot (Reply 36):
I know you perform a tubinewash during a dry motoring run, but because you have to handle the tips of the fuelnozzles with care, I was wondering if such an amount of water doesn't harm the fuel nozzles

As Jan said the Fuel nozzles tips face Aft.Hence damage from water due to its location is not a proiblem.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
Mr Spaceman
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RE: "Coke Wash" Cleaning Of A Jet Engine?

Mon Jun 27, 2005 1:07 am

Hi guys.

I just want to say Thanks for all the additional info since my last post for this topic on March 28th! I must have been unconscious  zzz  the next few days to miss the 4 posts on the 29th. I wasn't aware that this thread became active again.

>> DeltaGuy, that's a cool photo & Thanks for your info. Big grin

I read an excellent article about the T-45 Goshawk years ago in FLYING magazine (which I still have). The January 1998 issue of the magazine has a cover photo of what "short final" to the USS Saratoga looks like. The article inside has cool photos too and is an 8 page story that's written by a young Navy pilot named LTJG Morgan K. Hamon. He explains the training & emotions, etc, he experienced that led up to making his first carrier landing. The boat was the USS Eisenhower.

Chris  Smile
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