Mr Spaceman From Canada, joined Mar 2001, 2786 posts, RR: 9 Posted (8 years 9 months 3 weeks 3 days 21 hours ago) and read 18113 times:
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)."
777WT From United States of America, joined Jan 2005, 874 posts, RR: 1 Reply 1, posted (8 years 9 months 3 weeks 3 days 20 hours ago) and read 18063 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.
AvionicMech From United Kingdom, joined Jan 2005, 315 posts, RR: 3 Reply 2, posted (8 years 9 months 3 weeks 3 days 20 hours ago) and read 18011 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.
Broke From United States of America, joined Apr 2002, 1322 posts, RR: 3 Reply 4, posted (8 years 9 months 3 weeks 3 days 20 hours ago) and read 17986 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.
Mr Spaceman From Canada, joined Mar 2001, 2786 posts, RR: 9 Reply 5, posted (8 years 9 months 3 weeks 3 days 19 hours ago) and read 17918 times:
Thank You, for your clear explanation.
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?
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 From Canada, joined Mar 2001, 2786 posts, RR: 9 Reply 7, posted (8 years 9 months 3 weeks 3 days 18 hours ago) and read 17779 times:
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.
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?
CRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2 Reply 8, posted (8 years 9 months 3 weeks 3 days 16 hours ago) and read 17723 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
Always remember the responsibilies you hold with an A&P license
Mr Spaceman From Canada, joined Mar 2001, 2786 posts, RR: 9 Reply 9, posted (8 years 9 months 3 weeks 3 days 14 hours ago) and read 17658 times:
Thanks for your excellent info. Your step by step explanation of how the procedure is done was neat to learn about.
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 ), 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.
GOCAPS16 From Japan, joined Jan 2000, 4314 posts, RR: 22 Reply 10, posted (8 years 9 months 3 weeks 3 days 11 hours ago) and read 17580 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.
UAL Bagsmasher From United States of America, joined Sep 1999, 2134 posts, RR: 10 Reply 11, posted (8 years 9 months 3 weeks 3 days 10 hours ago) and read 17572 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
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
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.
DC10GUY From United States of America, joined Feb 2000, 2685 posts, RR: 7 Reply 20, posted (8 years 9 months 3 weeks 2 days 7 hours ago) and read 17275 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 !!!
Mr Spaceman From Canada, joined Mar 2001, 2786 posts, RR: 9 Reply 23, posted (8 years 9 months 3 weeks 21 hours ago) and read 17069 times:
>> 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 .... 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!