Compressor rinsing

[Droopy]

This is really an engineering question but is particularly relevant to helicopter operations and it refers to the rinse not the chemical soak; does anyone use anything other than ordinary mains tap water for engine rinsing?

[Tynecastle]

Droopy,
I would not use tap water for anything these days, I am out in S.E. Asia and the only way to go for any engine wash/ rinse is bottled water.

[SilsoeSid]

Perhaps not in SE Asia etc, but normally tap water is better than bottled.

Is there really a difference? Apart fom cost! :hmm:

In the military the comp wash fluid smells god awful. (Whatever it was called). In the Gazelle for example, if the heater wasn't put on during the dry out run, the next time it was used made for an unpleasant cockpit environment. :ugh:

Tap water for us. :ok:

:8
SS

[Letsby Avenue]

I know where you're coming from Droopy - £1500 is the answer....:eek:

[Recuperator]

I was told NEVER to use just ordinary tap water or bottled water or similar.

The water for compressor rinses is supposed to be distilled water ONLY, as to prevent build up of calcuim and other unwanted chemicals etc on the compressor blades.

Any back-up on this out there?

[Hilife]

You’re spot on recuperator.

[18greens]

Interesting, I've never heard of this, why do you rinse compressors? Do they do the same with Aeroplane compressors.

[aeromys]

I think this has come about through Turbomeca "recommending" a daily Comp Wash if the engine is used in proximity of the coast. And their definition of Coastal seems to cover most of the UK....

[SilsoeSid]

Why Wash Compressors?

When gas turbine engines are run, they become fouled with airborne contaminants such as oil, soot, unburned fuel, soils and salt which encrust compressor components. Power loss follows as the compressor loses efficiency and degrades the performance of the engine, leading to higher operating temperatures, increased fuel consumption and shorter component life.

Some engines are more prone to fouling than others – low flying over land or sea, or operating in contaminated air, have led to helicopter engines and industrial engines traditionally needing cleaning – but nowadays it is recognised that all engines foul to some extent; for example, oil leakage and subsequent fouling can happen on any engine type. Contamination can also be caused by ingestion of exhaust gases from other aircraft during prolonged waits for takeoff clearance.
Source (http://www.zok.com/products/whywash.htm)

:8
SS

[Hidden Agenda]

RR advises operators of Model 250 series engines that “Salt laden humidity and chemicals will corrode the engine and cause it to fail.”

RR states that engines subjected to salt water contamination or other chemically laden atmosphere shall undergo water rinsing after shutdown following the last flight of the day.

RR reminds operators that salt laden air may be encountered up to 150 miles inland under certain conditions, and that all islands are considered a severe area.

The use of the highest quality water available, distilled or demineralized is recommended.

Source: Rolls Royce Commercial Service Letter

[diginagain]

There was me thinking it was a conspiracy, originated by some French mineral water company.

[Tynecastle]

Recuperator.
Your right, but it all depends on your location, the distilled water we used in the batteries had more impurities in than the bottled variety.
For offshore ops, the # 1 priority is a daily wash with the cleanest water available.

[MightyGem]

Having been told that we will need to do daily comp washes using 7 litres of distilled/de-ionised water a go(for Turbomeca engines), I subsequently discovered that our neighbours who fly an Explorer(Prattt and Witney) can use tap water.

So why the difference?

[Droopy]

Interestingly, we used to use tap water daily on a previous model of the same engine series, with the full knowledge of the contracted maintenance organisation which is also an accredited agent of the engine supplier. For 8 years we never had a contamination problem despite operating low level close to the sea.

When we replaced the old aircraft with one powered by a later model of the same engine we asked if we could continue that practice and were told we couldn't; not because of the water but because it's technically more complex so chemical washes every 50 hours would be acceptable. In hindsight it would seem that this was actually because they hadn't anticipated needing to supply the wash kits in that quantity.

Now that the UK fleet is showing signs of contamination the manufacturer has decided a daily wash with distilled or deionized water is the only way.

I can quite see the point about mineral content of domestic water, but what is annoying me at the moment is 1] if tap water was OK for so long why is it suddenly not, and 2] it can't be beyond the wit of a major engine manufacturer to specify a minimum water quality, and if our local supply is better than that surely we don't have a problem.

I washed many an engine on offshore operations and I have to admit I never asked what was in the rinse tank; what do the North Sea and other operators use?



How spooky is this - literally minutes after I posted this lot an email arrives to state that the manufacturer is looking again at the question of local water analysis. :hmm:

[Thomas coupling]

Any other operator using daily comp washes?

I'd buy shares in rinsing rigs if I were a UK operator if I were you :{

Definition of saline atmosphere: within 150 miles of a coastline, up to 1500'...that means the whole of the UK.

[NickLappos]

Most manufacturers that I know of allow clean drinkable water to be used, and they prefer the cleanest water available. If you are in doubt, just pour a glass and set it aside to evaporate (unless you are in England, where the glass will get MORE water in it with time! ;-) )

In any case, the amount of water used in a wash is small, and the encrustation from that water would be small, especially as compared to the enormous mineral content of the salt air and spray that are the reasons why you rinse.

[TeeS]

In days of old BIH had a load of engine problems in Shetland on the S61's. This was put down to daily water washes with tap water. Distilled from then on, problem sorted from what I remember.

TeeS

[kopter]

In reality, when landing at last light, how many people wait a further 45-mins for things to cool down before doing a wash / rinse and then start the aircraft up again??? (I even open up the cowls to assist in cooling, but still looking at an extra hour or so before completing paperwork and then going home)... In my case, (being totally honest), around 40% of the time - I might add that I have PC taps fitted and conduct a wash/rinse (with Zok) 3 to 4 times per week, not always at the end of the day though...

I do worry (feel guilty) though on the times that I've flown and then put the helicopter away for the evening without doing a wash or straight rinse... (Maybe it has just been a big day and the family is waiting etc)...

Obviously, doing a wash/rinse the next day is not as good as the salt has already done its work...

I always start the helicopter after the wash/rinse... Any thoughts here on doing the start the next day??? Not good I'd imagine as the fluid contains all the crap and would sit there overnight!

Just looking for ideas/input on doing it better!

(PS - Operate a B206 near the coast).

[Droopy]

I'd agree that washing the next day isn't ideal but it's better than not at all; the point is you're preventing build up if not keeping the engine scrupulously clean. We typically have a very quiet period around the handover between the day and night shifts where the engines are cool enough 99% of the time.

I don't know of any manufacturer that allows a wash without a dry, typically no more than 1 - 2 hours later.

[Brian Abraham]

We religiously washed T53 (205), PT6 (212,412), C20 (76A) and Turbomeca (76C). Difference with the 76C was the rinse is done at 70% N1. We had three catastrophic engine failures with the 76C one of which will be found at www.atsb.gov.au search the aviation site for VH-EXX engine failure. Is accompanied by an extensive technical analysis of the engine strip part of which says,

"The internal and external surfaces of the diffuser assembly showed significant levels of general and localised corrosion. The inside surfaces of the diffuser housing showed extensive pitting corrosion in many locations. The coincidence of several longitudinal cracks with large corrosion pits suggested the contribution of pitting to the initiation of fatigue cracking. Localised corrosion is known to increase the risk of fatigue damage and can appreciably lower the limiting stress levels required to initiate cracking.

The bulk of the scale-type deposit found over the inside surfaces of the diffuser housing was shown by analysis to be compounds of calcium, sulphur and oxygen, with iron, silicon, sodium and chromium also present in significant quantities. The iron and chromium most likely originated from the diffuser parent material, whereas the calcium, sulphur, sodium, silicon and oxygen are elements most likely entrained from external sources. The washing procedure adopted for the periodic maintenance of gas-turbine units commonly uses water introduced into the airflow path. In the presence of dissolved solids within the water (known as 'hardness'), resilient scales can form, particularly if the water is introduced into an operating or hot engine. Soluble elements can be readily precipitated from hard water when being exposed to hot surfaces.

Scale accumulations can also exacerbate corrosion problems by trapping corrosive compounds against metallic surfaces. The corrosion damage to the diffuser housing is evidence of this process, with chloride compounds (known promoters of pitting corrosion attack) being detected on the scaled surfaces."

We were using tap water at the time but after this went to demineralised/deionised water.

[TheStormyPetrel]

The actual report is here (http://www.atsb.gov.au/aviation/occurs/occurs_detail.cfm?ID=368) (just to save people search time)

[Droopy]

And strangely enough our local water is particularly soft and low in other contaminants..... but we knew that before we started using tap water.
I've hot washed the Turmo iv and the Makila; interesting to see that TM are still offering hot wash options on our Arrius [not that we're going to do it] if research shows that this leads to more contamination. Brian, do you know what the calcium content/hardness of the water was in your incident?

[trackdirect]

Does anyone have any thoughts on rinsing with filtered water, There seem to be quite a few brands of charcoal filters and the like on the market, would these remove enough of the contaminents to provide satisfactory rinse water???

[Thud_and_Blunder]

Our customers fleet had a particular problem. Out of the 4 Arrius 2B1 engines they have, 3 had to be rejected at 1300 hours (tbo 3000 hours) because of compressor erosion. The 4th passed the inspection but has noticeable wear on the compressor.

The reaction has been to bring in a programme of daily rinses (Turbomeca's manual talks about 3 separate processes: rinse, wash and clean), weekly washes and cleaning at 100 hours. The water used is de-ionised which is bought by the box from a local supplier. Each engine requires 3.5 litres per rinse, so that's 42 litres per week for the rinses plus whatever is needed in the weekly wash if you're calculating budgets.

It was also pointed out to the customer that when they've gone to the trouble of buying sand filters, it helps if you leave them switched on throughout the flight i.a.w the FLM. It also helps if you let the engineers fix them when they break, rather than just making it an Acceptable Deferred Defect.

[Thud_and_Blunder]

trackdirect,

Just seen your message. Charcoal/ other filters will remove contaminants but not minerals like the carbonates found in hard water (from limestone/chalk). You need salt-based water softeners to do that - cause as many problems as they cure.

[Brian Abraham]

Droopy,
Can only tell you that the water was HARD (bore water). Dont know what treatment it went through, or have an analysis, but was the domestic water used by the oil company in its gas plant, heliport etc. Some people thought it so unpalatable as to not drink the stuff.
blue skies,
Brian

[zorab64]

trackdirect - t & b is correct about the GAC (Granular Activated Carbon) filters, which will only remove chlorine and a few minerals. Similarly, a water softener won't do the job either - they work as ion exchange units, so you'll get other stuff you don't want instead.

There are filter systems (around £500) that will filter water to biological laboratory standards i.e. as pure and electrically resistive as you'll find. If it's good enough for scientific work, I can't believe it'll harm the engines, although we're waiting on the manufacturers to report on minimum quality, as mentioned by Droopy earlier.

t & b - I think you should check the maintenance manual (ref 71-01-01) where you'll find it's 7 litres per engine, administered by two rinses of 3.5 liters, followed by a drying run (with a 5-25 min gap in between each) . . . unless you do a hot rinse when the whole 7 litres goes in at once, albeit at a slower rate!

[SASless]

An un-named British subsidary of a large American helicopter company operating out of Warri, Nigeria had a problem with engines on S-76's. Seems they were changing engines faster than they did socks....which knowing some of our engineers would not mean much. Tear down analysis of the engines showed corrosion equivalent to old boat anchors raised from the sea floor after centuries.

Seems the "tap water" was a bit saline....and over a few months was enough to do in brand new engines. I wonder how many engines died an untimely death due to that small oversight?

I would suggest distilled....sparkling clear....pure...pure water for engine washes....any doubt....have your tap water tested before using it. You might be surprised at what you are feeding your engines.

[Thud_and_Blunder]

zorab64

Thanks for that - it's the final day of the weekend here so engineers not on duty (no sleeping overnight on the office floor for them - lucky tykes!). I'll check back with them after my rest day to see if it was me getting hold of the wrong end of the stick (as usual) or a mis-read on their part. Mind you, I did post those figures immediately after chatting with their head honcho, so I might have actually written exactly what they said...

(in other words, blame someone else - ideally the engineers... typical pilot, eh?)

[zorab64]

t&b - thanks. I would concur that a check of stick ends might be useful although, as with may things "TM", it's often a matter of interpretation.

Whilst your post was written after a "chat" with the engineers, I had the maintenance manual in front of me - although there's still plenty to get confused about. . .
If you're trying to determine how to follow the hot wash procedure, for instance, try this; Quote "Apply the washing procedure with the two engines in operation if the wind conditions make necessary to keep the rotor speed to the nominal rating (engine washed: select the GROUND IDLE mode; engine not washed: select the FLIGHT mode, fine full pitch)"

So, does that mean "engine to be washed" OR "engine that has been washed"? Likewise, "engine not yet washed" OR "engine not about to be washed"? :confused: My experience of comp-washing with engines running says that you tend to put the fire out if it's only at Idle but, as with many things translated, there's always room for improvement.:ok:

Ho hum.

[Thud_and_Blunder]

Hi again zorab64,

We always do the wash with the engine at idle - fire's not gone out yet. Big pain in the butt, as we can't keep the aircon on :hmm: (although we leave the sandfilter running). When the wind around the hangars has the usual Kuwait-afternoon gust-spread we do follow the instructions in finest Minglish - ie other engine to Flight while the engine being washed is at Ground, changing-over engines at Flight to minimise the vibration-band risk.

Another area where the 206/7s on the MD902 were far easier to look after than the 135T - comp-wash there is a single-person job during the daily, no fuss no bother.

Haven't heard anything back from Eurocopter about the fact that switching off the Gen to carry out the trend-monitoring in-flight checks involves the sandfilters going off, in direct contradiction to what the Sect 9 says about them remaining on at all times. On a previous type, if the EAPS blowers failed then all the crap that they were sweeping out of the way of the intakes was liable to get ingested in one big lump. Not exactly best practice.