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"Coke Wash" Cleaning Of A Jet Engine?  
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Posted (9 years 1 month 4 weeks 1 day 2 hours ago) and read 18988 times:

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"
41 replies: All unread, showing first 25:
 
User currently offline777WT From United States of America, joined Jan 2005, 874 posts, RR: 1
Reply 1, posted (9 years 1 month 4 weeks 1 day 1 hour ago) and read 18943 times:

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.


User currently offlineAvionicMech From United Kingdom, joined Jan 2005, 315 posts, RR: 3
Reply 2, posted (9 years 1 month 4 weeks 1 day 1 hour ago) and read 18889 times:

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


User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 3, posted (9 years 1 month 4 weeks 1 day 1 hour ago) and read 18857 times:

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"
User currently offlineBroke From United States of America, joined Apr 2002, 1322 posts, RR: 3
Reply 4, posted (9 years 1 month 4 weeks 1 day 1 hour ago) and read 18865 times:

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.


User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 5, posted (9 years 1 month 4 weeks 1 day ago) and read 18796 times:

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



"Just a minute while I re-invent myself"
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 6, posted (9 years 1 month 4 weeks 1 day ago) and read 18749 times:

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.
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 7, posted (9 years 1 month 4 weeks 23 hours ago) and read 18657 times:

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



"Just a minute while I re-invent myself"
User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 8, posted (9 years 1 month 4 weeks 21 hours ago) and read 18601 times:

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



Always remember the responsibilies you hold with an A&P license
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 9, posted (9 years 1 month 4 weeks 19 hours ago) and read 18535 times:

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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Photo © Ralph Duenas



PS, welcome to the forum! Big grin

Chris  Smile



"Just a minute while I re-invent myself"
User currently offlineGOCAPS16 From Japan, joined Jan 2000, 4334 posts, RR: 21
Reply 10, posted (9 years 1 month 4 weeks 16 hours ago) and read 18457 times:

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


User currently offlineUAL Bagsmasher From United States of America, joined Sep 1999, 2143 posts, RR: 10
Reply 11, posted (9 years 1 month 4 weeks 15 hours ago) and read 18449 times:

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


User currently offlineTbanger From Australia, joined Jul 2004, 266 posts, RR: 0
Reply 12, posted (9 years 1 month 4 weeks 12 hours ago) and read 18399 times:

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

User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 13, posted (9 years 1 month 4 weeks 11 hours ago) and read 18396 times:

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!



Always remember the responsibilies you hold with an A&P license
User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 14, posted (9 years 1 month 4 weeks 11 hours ago) and read 18379 times:

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



Always remember the responsibilies you hold with an A&P license
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 15, posted (9 years 1 month 4 weeks 10 hours ago) and read 18373 times:

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



"Just a minute while I re-invent myself"
User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 16, posted (9 years 1 month 4 weeks 10 hours ago) and read 18358 times:

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.



Always remember the responsibilies you hold with an A&P license
User currently offline777WT From United States of America, joined Jan 2005, 874 posts, RR: 1
Reply 17, posted (9 years 1 month 3 weeks 6 days 19 hours ago) and read 18226 times:

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.


User currently offlineFutureUApilot From United States of America, joined May 2004, 1365 posts, RR: 4
Reply 18, posted (9 years 1 month 3 weeks 6 days 19 hours ago) and read 18219 times:

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!
User currently offline777WT From United States of America, joined Jan 2005, 874 posts, RR: 1
Reply 19, posted (9 years 1 month 3 weeks 6 days 17 hours ago) and read 18200 times:

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.


User currently offlineDC10GUY From United States of America, joined Feb 2000, 2685 posts, RR: 6
Reply 20, posted (9 years 1 month 3 weeks 6 days 12 hours ago) and read 18150 times:

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 !!!
User currently offlineCRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2
Reply 21, posted (9 years 1 month 3 weeks 6 days 12 hours ago) and read 18144 times:

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



Always remember the responsibilies you hold with an A&P license
User currently offlineHAWK21M From India, joined Jan 2001, 31573 posts, RR: 57
Reply 22, posted (9 years 1 month 3 weeks 6 days 8 hours ago) and read 18125 times:

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



Think of the brighter side!
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 23, posted (9 years 1 month 3 weeks 5 days 3 hours ago) and read 17944 times:

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



"Just a minute while I re-invent myself"
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 24, posted (9 years 1 month 3 weeks 5 days 2 hours ago) and read 17944 times:

Good basic info here:
http://www.zok.com/products/whywash.htm



Happiness is not seeing another trite Ste. Maarten photo all week long.
25 Post contains images PW100Testpilot : 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 nozzl
26 Post contains images Mr Spaceman : Hello PW100Testpilot. Thanks for your info. A jet engine blowing out bubbles would be great to catch in a photo! >> SlamClick, Thank You, for that lin
27 UAL Bagsmasher : 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
28 AR1300 : Coke as cocaine? uh???sounds weird...it's gotta be something else. Mike
29 CaptOveur : I think they mean coke as in highly refined coal.
30 AvionicMech : 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 do
31 Jeb94 : Coke is just carbon build ups in the case of jet engines.
32 MD11Engineer : 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 d
33 PW100Testpilot : 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 d
34 HAWK21M : Its a dry motoring. regds MEL
35 MD11Engineer : 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 nozz
36 PW100Testpilot : 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 su
37 VC-10 : 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 insid
38 Post contains links and images DeltaGuy : 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 th
39 EMBQA : Keep in mind.... Compressor Washes and Coke Cleaning are two VERY different things.... 'Compressor Washes' are done on a fixed interval established by
40 HAWK21M : As Jan said the Fuel nozzles tips face Aft.Hence damage from water due to its location is not a proiblem. regds MEL
41 Post contains images Mr Spaceman : 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 the next
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