Comp wash in the cab?

[g-mady]

With the 206 comp wash often leaks into the cab as heating is taken from the compressor stages.
Is comp wash "nasty stuff" and not to be breathed in???

Now its getting colder again and we're starting to use the heating all the summer's crud in the pipes blows into the cabin on first use. Have also had it splashing over the console!!!

MADY

[MightyGem]

I love the smell of comp wash fluid in the morning! Only ever had the smell though, never got splashed.

[nodrama]

The air bleeds on an Allison 250 should be blanked off during compressor washing. It means that the comp wash will take a little longer, but all that 'crud' that you are seeing coming out of your heating ducts is also getting into the engine's compressor bleed valve air filter (which can effect the bleed valve operation), is clogging up your heating bleed air valve and if it's a Bendix FCU, it's getting into the Pc air filter which could possibly effect your engine fuel governing.

Breathing comp wash fumes won't kill you, but is very unpleasant.....see link for Zok 27 safety data sheet.

ZOK 27

[[email protected]]

What is important is to carry out drying out runs after the comp wash to ensure that all the residue evaporates and doesn't get left on the compressor. Rolls-Royce recently made us change our procedure form drying out at ground idle to drying out rotors running at flight idle. We exercise the air bleeds during the drying out run to ensure they are clear.

[nodrama]

It is important to rinse the cleaning agent out of the engine with clean water before the drying run.
If not, whatever dirt etc that was on the compressor blades is then in solution with the cleaning agent and will just re-deposite itself onto the blades when the agent dries/ evaporates....defeating the object of the whole exercise. The cleaning agent will also leave a film on the blades that will attract even more dirt.

The drying run is not only to dry the compressor blades but to also prevent the onset of internal corrosion due to pooling water, blow through all the Pc air bleeds and prevent water from finding its way through labyrinth seals and into the oil and bearings.

I've got to say that if you've got cleaning agent coming out of your heating vents, it doesn't sound as if the cleaning procedure is being carried out correctly.

[Nubian]

Our washing procedure was:

With agent (broulin) Mechanic required.
First disconnect the PC line on the FCU, blank it off. Close the bleed-valve, with a choke. Pull the circiut-braker for the ignitor.
Monitor starter at 10% for 10 seconds while injecting the wash.
After the excess fluid has drained off, then repeat the procedure twice but only with clean water.

For drying.
After it has drained off, unblock the bleedvalve, connect the PC-line and ignitorbreaker and do a normal start, run for 3 min. at flight idle, open the heatervalve, and shutdown.
The reason for disconnecting the PC-line, is to prevent the agent from wearing on the membrane of the bleed-valve, almost impossible to rinse completely.

Waterwash:
Block the bleed-valve, pull ignitor breaker, rinse twise, then do a start as above. No need for a tech./mech.

In this way, I have never had water or cleaning agent entering the cabin the way you describe.

Only through the normal stardard-issue leaks provided by Bell.

Hope it helps.

[g-mady]

nodrama,

I have seen compwash used from a nozzel on a long arm directly into the intake while the engine is running.
Compared to the other method I have seen of inserting comp wash in the hangar and then wipeing up the mess that comes out the exhausts on first start???

MADY

[nodrama]

Allisons aren't washed (with cleaning agent) whilst running.... rinsed with just water maybe... but not washed.

This is for all the reasons I've mentioned above.

The second method you've seen is the right one. Washed by motoring over the engine, just as Nubian described.
Yes, it does chuck a load of dirty water out of the exhaust on first start that has pooled in the combustion chamber during the washing procedure.

[that chinese fella]

The Rolls Royce C20 (or later variants) Maintenance Manual explicitly details the full and correct procedure to use for rinse and/or wash. Sadly none of the 'methods' mentioned below are accurate and/or fully explain it - especially the 'while engine is running' method.

1 of the important details to note are the fluid should be injected for 3 seconds before engaging the starter to prevent the N1 accelerating too much and atomising the water and keep the water injecting for 3 seconds after the engine stops. There are more gems of this nature in the procedure.

Anyway, its all in the MM, have a read, it will make clear and concise sense, follow it and we will all remove yet another 'chinese whispers' screwed-up technique/myth.

[nodrama]

You're absolutely right That CF....

I was just trying to highlight to Mady (without copying and pasting the MM) that there are alot of things that should be done when washing an Allison that obviously aren't being done with his 206.

[Chris P Bacon]

A useful tip when doing a chemical wash is to note the TOT before cleaning. If the TOT is lower after cleaning, do another clean until the TOT stops dropping. You then know the compressor is as clean as you are going to get it.

[nodrama]

Or you could do an engine trend check and compare it to the previous ones.....it then takes into account OAT and P Alt.