Injection pump sticking problem in Wartsila 32 engines

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vkouroub
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Injection pump sticking problem in Wartsila 32 engines

Postby vkouroub » Wed Oct 08, 2014 1:31 am

Hello.

We are a power plant in Greece operating 2 Wartsila 32 12V engines using HFO 380 as the primary fuel. Ever since we turned to HFO 380 (from MDO) we are facing a very serious injection pump fuel rack stickiness problem. This problem happens randomly at a wide rang of loads but happens more frequently in low loads (approx. 10%) or when starting-stoping the engine.
As a solution the manufacturer has suggested to wash the lower part of the fuel injection pumps with diesel oil using an air pump, on a 500 operating hour basis.
While the results from the cleaning procedure are positive i.e. the pumps behave normally, this is only for a small amount of operation hours. There are many cases where cleaned and freshly repaired injection pumps get sticky just after a 48h period of operation.

From experience i can state with certainty that this problem has never been traced in the previous Vaasa Wartsila engines nor to many types of other engines (MAN, Mitsubishi and more) using the exact same fuel.

Therefore i would kindly like to ask all fellow colleagues who operate the same engines the following:

1. Are you facing similar problems?
2. What explanation do you give regarding the cause of this stickiness?
3. Is it the quality of the fuel or the deisgn of the pumps or both?
4. Has anybody found a more permanent and flexible solution of this issue rather than cleaning (almost everyday) the injection pumps?

Any help will be much appreciated.

BR,

Billy

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D Winsor
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Re: Injection pump sticking problem in Wartsila 32 engines

Postby D Winsor » Wed Oct 08, 2014 7:26 am

From you post you said that the engines first ran on diesel and were converted to run on IFO 380
If this is so, you are having problems with sticking fuel pumps at low load and after being shut down because there is insufficient heat being retained in the pumps to keep the fuel in the pumps and the injection lines at the proper viscosity temperature. This will cause the plunger to stick in the barrel and jam the fuel rack.
In order to prevent this you should either switch back to diesel before shutting down or running at low or no loads to reduce the viscosity of fuel in the pumps, investigate having a heat tracing system put around the pumps, increase the flow of fuel to the injection pumps with a larger booster pump or fit some sort of supplementary heater at the fuel rail to reduce the viscosity of the fuel being circulated while the engine is running at low load or stopped.
I would also suggest running on a lower viscosity fuel until the issue can be resolved (IFO 120 or IFO 180).
Troubleshooting 101 "Don't over think it - K.I.S.S. it"

Atlantic
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Re: Injection pump sticking problem in Wartsila 32 engines

Postby Atlantic » Sun Oct 12, 2014 8:06 am

I have had a similar problem on wasa 32. The fuel oil temp was to high @ 150 C. We lowered it to 125 C and the worked much better.

Vegman
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Re: Injection pump sticking problem in Wartsila 32 engines

Postby Vegman » Mon Oct 13, 2014 8:23 pm

My vessel had a similar problem sometime in the past( its an MAN med speed)-Not sure if the exact cause was ever determined , but we changed to the practice of always changing to diesel fuel for a at least 30 min before shut down, and the problem so far hasn't come back.

Rum Baron
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Re: Injection pump sticking problem in Wartsila 32 engines

Postby Rum Baron » Wed Oct 15, 2014 9:27 am

Agree with the comments above, although the manufacturer will state the engine can be started and stopped on HFO, it is always better to do so on diesel fuel to purge and pumps and injectors of heavy fuel. Are these L'Orange pumps? The newer tier 2 engines have a very late point of injection (about 6 deg BTDC) from memory, which looks very strange when viewed on a draw card! I've never seen these operate on HFO but assume they advance the timing somewhat to achieve the same effect.

Good luck
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vkouroub
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Re: Injection pump sticking problem in Wartsila 32 engines

Postby vkouroub » Thu Oct 16, 2014 4:25 am

Hello everybody and sorry for the late reply.
Fisrt of all thank you for your answers.
Now to the point:

Both engines are equipped with automatic viscosity controllers which maintain the fuel viscosity at the desired setpoint (16 cst according to Wartsila's instructions) by controlling a steam valve connected to the preheater.

There is also a temperature controller in case you suspect that the viscosity controller is not properly working. This temperature controller works by the same way meaning it will control the steam valve in such a way to maintain the fuel oil temp in the desired setpoint.
In our case we have crosschecked the functionality of our viscosity controllers, based on the viscosity of the HFO we use (around 380 cst@ 50oC) and corresponding HFO charts and they are working correctly (approx. 125 oC @ 16 cst).

These controllers work properly at any load and also when the engine is stopped (we never stop running the booster pumps) therefore the fuel is always at the correct temp+viscosity all the time.

Also accoriding to Wartsila's specs the viscosity limits before the injection pumps (L’ORANGE PEO-G057mV) are 16-24 cst and the max viscosity @ 50oC the pumps can withstand is 700 cst i.e. about 140 oC @ 16cst. Therefore we are totally in the limits concerning the viscosity and temps of the fuel used.

So we don't believe we have an insufficient heating issue in our case and stoping the engine to diesel fuel will not solve this problem (we have already tried this with no success).

Another problem is that whenever we stop the engine on diesel oil we have tremendous difficulties in starting up the engine. When we reported this problem to Wartsila they said that it's due to the weariness of the pump elements from the HFO operation in combination with the fact that the diesel oil is of lower viscosity causing difficulty to the weared pumps to inject the fuel properly!

After conducting some detailed chemical analysis of our HFO we have come to the conclusion that maybe the Asphaltenes are the cause for the stickiness although Wartsila's aspahaltene limit is 8% and our fuel has around 7.5%.
We are still working on it.
Any other reccomendations much appreciated.
BR,
Billy

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Big Pete
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Re: Injection pump sticking problem in Wartsila 32 engines

Postby Big Pete » Fri Oct 17, 2014 12:34 am

If you can't start the engine on MDO, that is because the clearance in the fuel pumps is so exceesive that all the MDO leaks out between the barrel and plunger rather than going to the injector.
If there is that much clearance the problem is unlikely to be caused by temperature differences between the barrel and plunger closing the clearance.
If the fuel is leaking out around the fuel racks where they enter the fuel pump body, when it cools on the outside of the pump it can cause the stickiness you describe, but the washing you describe should prevent that.

There is another problem, completely unrelated to the fuel, which can cause this stickiness.
I am not familiar with this particular engine, but if when the fuel pumps are fitted, the fuel racks are not exactly "square" or perpendicular to the operating shaft, they can mechanically sieze, because the rotation of the operating shaft, will push the racks forward or aft relative to the pumps. The rear face of the pump has to be exactly parralell with the operating shaft and the attachment of the fuel rack to the operating shaft positioned so that the rack is exactly at 90 degrees to the shaft and the face of the fuel pump.

Please let us know how you get on.

B.P.
It is always better to ask a stupid question than to do a stupid thing.

Rum Baron
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Re: Injection pump sticking problem in Wartsila 32 engines

Postby Rum Baron » Fri Oct 17, 2014 8:44 am

If the barrels and plungers are so badly worn that you cannot start on diesel fuel then this is likely to be your root cause. When did you last change/overhaul the pumps? On this particular engine they should be replaced at 12000 - 16000 hours although operation on HFO will reduce this somewhat. Pete, I have seen the problem you describe with the misaligned racks however this should not be a problem with the pumps on the 32 series as they are aligned with 4 studs/nuts.

This is what I would do: replace a proportion of the pumps (say one or two per bank) with overhauled or new units and continue to run on HFO to see if these units suffer the same problem. If the wear is the culprit then the reduced leakage of the good pumps will make a noticeable difference. When they are fitted ensure that the timing is set as per the manufacturers spec which in this pump is a dimension taken when the pump is removed. From experience, the shim at the bottom of the pump tappet does wear (often unevenly) and this retards the point of injection. Also be aware that not all cylinders will fire on this engine when at idle, you may have one or two drop out, this is normal.

I have had pumps incorrectly overhauled by the OEM which led to huge exhaust temp spread and loss of power. Not saying this has happened to you but just to prove a point that you should trust nobody. If you have any doubt, send one pump to an independent company and then assess the difference in performance afterwards. I have been forced to do this several times and can recommend some good companies if you need one.

I wish you all the best and please let us know how if goes.
Marine Power Systems - New Zealand's marine diesel and propulsion specialists [url]http://www.marinepower.co.nz[/url]

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Big Pete
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Re: Injection pump sticking problem in Wartsila 32 engines

Postby Big Pete » Sun Oct 19, 2014 11:51 pm

I totally agree that the fuel pumps should be replaced or overhauled, the costs will easily be saved by the reduced fuel consumption.

With regard to the alignement, unless the fuel pumps are dowelled to the engine there is always a clearance between the studs and the holes in the base flange which permits small amounts of misalignement.

I have often seen misalignement in the fuel racks where Engineers have unclamped the connection to the Governor output shaft in order to adjust the fuel delivery, and accidently retightened the clamp out of alignement with the pump.
With the fuel pumps so badly worn it is likely that they have been adjusted to try and balance the exhaust temperatures, peak pressures or power output.
HOWEVER, almost all Engine Makers say that the maximum permitted difference in the individual cylinder fuel rack settings is 1.0 m.m. from the average, for the entire engine. If the differences are greater, you should be changing injectors and fuel pumps not messing about with the fuel racks.

Big Pete.
It is always better to ask a stupid question than to do a stupid thing.


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