engine working hours

Discussion in 'Diesel Engines' started by urisvan, Aug 29, 2012.

  1. urisvan
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    urisvan Senior Member

    it is written in yanmar diesel engine manual that: engine can work at cruising speed which is under 2800 rpm for 9 hours of 10 hours working time. so what should we do? should we stop and rest the engine at least one hour after we use it 9 hours?

    regards
     
  2. gonzo
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    gonzo Senior Member

    It means that if you run the engine at the rated speed for 90% of the time, the engine life will be what the company claims. If you run it at top speed all the time, the life shortens dramatically. Cruising speed should be at 80-90% maximum RPM.
     
  3. urisvan
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    urisvan Senior Member

    ok, i know that you shouldn't force your engine to its maximum speed for a long time. Maybe i understand what is written in the manual wrong.
    it says in the manuel that you can use engine full speed 30 minutes of 10 hours working time and you can use your engine at 80-90% of maximum rpm for 9 hours of 10 hours working time. What i understand from this statement is: we can force the engine full speed 30 minutes in every 10 hours working time and we should close and rest the engine 1 hour after 9 hours working in cruising speed.
    is it wrong?
     
  4. BKay
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    BKay Junior Member

    urisvan, I take that to mean that you should reduce operating RPM's well below 2800 RPM's for at least 10% of your operating hours.

    If you run into and out of port at lower RPM (say 1800-2500) for a total of 1 hour, you can run at 2800 for 9 hours and have good engine life. It does not mean to shut down the engine after 9 hours of 2800 RPM (if you do that, you are running at 80-90% power 100% of the time).
     
  5. rxcomposite
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    rxcomposite Senior Member

    You can force the engine to its rated hp as long as you want but it shortens the time between overhaul (TBO). Engine manufacturers use a ratings for their engine, sometimes up to 5 categories and is usually expressed as a percentage of the operating hours. It is actually time based and manufacturers rely on the engine hours meter for warranty claims.

    For example, a continous duty rated engine can be used 100% of the time 24 hours a day for a year before overhaul while a leisure rated engine can be used only 30% of the time. If you have used up the hours because you are using the boat more than intended, it is time for overhaul. You cannot claim warranty. The manufacturers have a way of knowing it, even if you disable the engine hour meter. The last engine we installed for a commercial vessel has a black box. The manufacturers know when the engine is running whereever we are, At least that is what they say. What we know is when they plugged their laptop into the service port, they were able to retreive all the engine working data for the last several hours we were running the boat.
     
    Last edited: Aug 31, 2012
  6. jonr
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    jonr Senior Member

    At most. You can get better economy and engine life at far less than that.
     
  7. WestVanHan
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    WestVanHan Not a Senior Member

    Rx touched on it:

    If the engine has any electronic controls,all paramaters are stored: fuel burned,throttle position (how long),load,temperature, etc and if there's any warranty claim they hook it up and can see exactly what you've been up to.

    So if you run it at WOT for hours on end-they'll know.

    I'd follow the recommended use.
     
  8. urisvan
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    urisvan Senior Member

    Thank you for replies.
    yes i always follow recommended use. Never exceed the cruising speed if not really necessary. All i want to know is should i stop it to rest after some hours. but as i understand from this threat it is not necessary. Maybe reducing speed a little bit for example to 1500 rpm to let it take a breath for half an hour or so can be nice...
     
  9. Petros
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    Petros Senior Member

    That is an odd way of stating that requirement, must be something with the translation of your documents that does not make it clear.

    I would recommend to ALWAYS keep rpm below 90 percent at all times, unless it becomes necessary for safety reasons to go higher for short bursts of speed.
     
  10. rxcomposite
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    rxcomposite Senior Member

    Let us calculate. You say your Yanmar is to operate at full load 9 hours out of 10, therefore 9/10=0.9 or 90% of the time. This is typical of continuous duty ratings of 80% to 100% such as tugboats or trawlers. Let us find the operation profile.

    Operation Profile:
    Frequency: 5 times a week. (Assume the boat goes out only 5 x a week)
    Since there is (365 days/year)/ (7 days/ week) =52.14 week/year.
    Days of operation/year will be: 5x 52.14= 260 days
    Hours of operation per day= 10 hours (given)
    Hours of operation per year= (10 hours/day) x (260 days/year) =2,600 hours/year, the hours the boat is in use per year.

    Let us look at the boat usage profile (Assume you are a hot shot captain, does not happen in real life):
    Going out of harbor, Low cruising= 5% of the time (of 10 hours)
    Full load, max rpm= 90% of the time
    Going into the harbor= 5% of the time
    Total= 100%, 10 hours/day

    Engine load will be;
    50% partial load during low cruising going out 5% of the time
    100% Full load, max rpm 90% of the time
    50% partial load during low cruising coming in at harbor 5% of the time.

    That means, you can use max rated power 90% of the time. With an allotted 2,600 hours/year, you can run the boat at maximum rated power 2,600 x 90%= 2,340 hours before overhaul. You cannot use the 2,600 hours allotted to your engine. This is what ratings is all about. If your engine has a duty rating of only 50%, you can run the engine at max power at 2,600 x 50%= 1,300 hours only, the rest at reduced throttle settings. It is how the pie is cut.

    If you use a lower throttle setting, say 90% of max rpm, you will be using only 77%-80% of the max load (power) and will increase your engine life plus reduced fuel consumption. Fuel consumption goes up rapidly after 80%-85% power. That is the reason marine engineers design the boats cruising speed at 80% of power. To find the % loading, you need to get a copy of the engine performance curve.
     
  11. jonr
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    jonr Senior Member

    Without reference to any specific post, one of my pet peeves is using rpm, load and power/output interchangeably. Sometimes people even throw torque, time, throttle position and boat speed into the mix. They are all different.
     
  12. Petros
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    Petros Senior Member

    that is true, you can be at full throttle at 50 percent rpm. but for most boat installations the rpm is directly related to load because the prop is directly geared to the crankshaft. It is the simplest way for operators to gauge engine load.
     
  13. rxcomposite
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    rxcomposite Senior Member

    Sometimes the terms are interchanged for fluidity of thoughts. A trained person can easily shuttle their mind between power, rpm, and torque but someone would see it a different way.

    Say, "What if at Wide Open Throttle, I suddenly lost my propeller, if my tacho is reading max rpm, does that mean I am developing max hp?"

    Or "If I am at WOT, but the boat is so light because it has used up almost all the fuel, there is no longer FW on board, plus no catch (unlucky), am I loading the engine?"
     
  14. MechaNik
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    MechaNik Senior Member

    Operating profiles are needed to form a maintenance schedule and give an idea of TBO.

    However if you operate your engine at a consistent profile or cruising schedule the maintenance regime will become apparent. Then you can optimize service periods and component replacement schedules with the help of your dealer.

    For example, extended periods of continuous cruising operation are rewarded with reduced oil changes vs hours.
    Many small trips with lots of slow maneuvering and idle time can give an show extended TBO vs hours.
     

  15. pistnbroke
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    pistnbroke I try

    I think you miss read it or bad translation..by 9 of 10 hours they mean for a maximum 90% of the time keep it below 2800 rpm....so run it as long as you like below 2800 rpm


    30 min in 10 hrs is 5% of the time . so only run WOT for 5% of the time
     
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