Diesel generator ancillary systems power source 1

[chao_david]

Hi. I know for sure that the electronics of a diesel generator set are powered by a DC battery source. What about the radiator fan? Is it powered by the generator itself, and therefore reducing the actual output of the generator because some of the power goes to the fan? Or is it DC powered from the battery?

Thanks!

 

[waross]

Belt drive on most units.
If it is electric it will be powered by the starting battery which is charged by an automotive style alternator, independent of the main power alternator.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Not so fast Bill! The last generator I worked on used an electric motor driven by the prime-mover output. It was 480Vac3ph 20hp.

That said chao it doesn't really matter since either way the engine has to supply the power. Switching an electric fan over to engine driven buys you very little. Perhaps reduced dependability and possibly voltage regulator instability if the fan was used as a 'base load'.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[FreddyNurk]

Radiator fans can be belt driven as waross mentioned, although in my previous experience we didn't have a single belt driven or crankshaft driven fan at all.

All of the installations I'd been involved with had separate fans driven off the generator's AC output, although all of them also had remote mount radiators as well. Above a certain size there appears to be power savings in running a variable speed fan, although the economics can change wildly depending on the particular site. All of my applications were multiple parallel units as prime source of power, standby sets are likely to be different.

Only other thing to keep in mind is where the fan gets fed from if its an electric fan, there was much consternation about running fans off the main bus, and the risk of idling an engine for a period of time with no radiator cooling if the generator wasn't connected to the bus. Of course, such things are only relevant in an LV site.

EDMS Australia

 

[waross]

Yes I have seen a few of those Keith. Generally when the radiator is remote from the engine.
On our 300 kW and 600 kW sets we had about 3 HP each on the fans.
In your case the fan would be a 20 HP load that the generator would have to supply.A remote fan is generally a special design.
I have seen hundreds of generator specs over the years and have yet to see a standard unit come standard with a line powered fan.
I believe that we have both seen some unusual non-standard installations.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[catserveng]

There is a lot of "it depends" in that answer. Mainly what size unit are you talking about? Is it in an enclosure? Is there a noise reduction requirement? How about direction of hot air venting? More and more places don't want horizontal discharge of the radiator exhaust air because its hot enough to be a hazard and it requires room that a lot of places don't have these days.

While belt drive fans are common on a lot of units, more and more units are going to AC driven fans, and in a lot of cases multiple fans (usually 2-4 in the units I see) with staging control or VFD(s) to limit parasitic power and noise when the unit is running at less than rated load or when ambient conditions don't require as much air flow.

I have also worked on a number of units that used hydraulic drive fans, but don't see them much anymore except in some mining or hazardous location applications.

If the OP is just looking for general information, here are some good resources,

Caterpillar Application and Installation Guides,

http://s7d2.scene7.com/is/content/Caterpillar/CM20160713-53120-13199

Kohler has a print version of the Engineer's Guidebook, but also a lot of info here,

https://power.kohler.com/na-en/generators/industrial/engineers-toolbox

EGSA publishes the OnSite Power Generation Handbook, a nice reference that is pretty non-commercial,

http://www.egsa.org/Publications/OnSitePowerGenerationBook.aspx

Cummins has a lot of good info, their Power Suite is a good starting point for that,

https://powersuite.cummins.com/PSWEB/login.action

Hope that helps, MikeL.

 

[itsmoked]

That makes sense Bill. The radiator on the last one was 90 degrees to the engine.

Question: Staged fans seems a very reliable solution but brings me a question. If, say, only one fan is on what prevents it from sucking all its air from the fan side of the radiator via all the other neighboring fan holes?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Look at an automotive electric fan Keith. With twin fan units the fans are close enough to the radiator and somewhat shrouded to prevent that.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[TugboatEng]

Large marine diesel generator sets drive the cooling pumps off the AC output and that's a lot like driving a fan off the AC output. Big difference is that at least one of those pumps is backed up by an emergency diesel generator with a belt driven fan.

 

[racookpe1978]

Question about belt-driven diesel generator fans is a lot like the Main Feed Pump pumps in a steam-powered power plant.

Do you accept the simplified repair but greater expense of a very large (multi-Megawatt) electric motor to drive the main feed pump, or the piping and steam controls and maintenance headaches of a steam-driven pump that is a slightly more efficient use of the baseload steam already available? After all, if you use an electric motor you're accepting the steam-to-electric inefficiency of your turbine-generator power that you're trying to sell.

 

[TugboatEng]

In a marine plant the steam driven feed pump is not more efficient than an electric motor (about 600-700 hp). The pump is steam driven because as long as the boiler is hot it needs feed water. As long as the boiler is hot and has feed water there will be steam. As long as there is steam the feed pump can provide feed water. Regardless of the condition of the rest of the plant the feed pump needs to operate, it is a safety issue.

 

[GroovyGuy]

Howdy David,
It rally comes down to what type of (engine water jacket) cooling you intend employ.
The two major methods include;
1) Integral Radiator (ie engine driven)
2) Remote radiator
Your question involves the latter (Remote Radiator). The following 1-line clearly depicts how we facilitate powering the (remote radiator fan) motor. I this example the fan-motor was rated 75hp (on a 1500kW diesel generator).

FYI, The above 1-line is normally supplied as part of the tender docs when buying a standby-power gen-set.
GG


"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

 

[waross]

Hi groovy.

75 HP seems a little harsh for a set that size.
Did you mean 7 1/2 HP?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

Standby Deutz Diesel unit at one site where I worked had a separate station service supplied AC-driven radiator fan, with one big soft-start but constant-speed drive motor and recirculating air dampers. Reported rationale was that fan could be run post shutdown to cool out the engine, something that made no sense to me since there were no auxiliary non-engine-driven after-run pumps to circulate the coolant through the engine block...and I didn't make any friends when I pointed out that fact [thermosyphoning was of negligible value, due to the small size of the cooling piping and the numerous flow restrictions caused by including more flow monitoring gauges than necessary].

Strangely enough, the rad cooling fan had originally been supplied directly from the generator terminals, but connection to station service supply instead was made after the unit tripped a number of times at full load and the engine suffered damage due to overtemperature; thinking was as described above...then generator tripped at full load during a power outage, still had no cooling, more damage...you get the idea. My druthers would have been to have a DC-driven after-run coolant pump that would have at a minimum equalized the temperature of the block post shutdown, even in the event of failure during black-out; combined with fail-open air admission and exhaust dampers and fail-closed recirc dampers, there would at least still have been some cooling for long enough to preclude engine damage...but apparently I didn't know anything; don't you hate it when that happens?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[FreddyNurk]

crshears, your discussions around the feed for the generator fan are similar to what I experienced, albeit with a lot less equipment damage.

The arguments I've seen for running off station services are to facilitate space cooling rather than attempt to cool the block. A couple of sites I'd seen had the highest temperatures hit 5 minutes after the set shut down, with no further ventilation into the enclosure, and most of the time the interest was to cool the space to allow better conditions for servicing personnel than anything else.

I would have thought that if a standby set is running, there's no point in feeding off a station panel anyway, if the set trips off in that case wouldn't the site have no power in that context?

EDMS Australia

 

[waross]

My theory has been that a set is best cooled by running at no load for about 5 minutes before shutdown. As well as better cooling it allows the turbo to spool down with full lubrication.
I don't like the idea of the thermal shock if the hot engine has to be restarted with a cool radiator.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[GroovyGuy]

Howdy Bill,
No, the motor was rated 75hp, 1200rpm. Other Bidders has similar sized motors (although one or two were a tad smaller).
GG


"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

 

[waross]

Thanks for the clarification, GG. Was there a lot of duct-work involved? I used to be responsible for some 350 kW and 600 kW sets with remote radiators. The fan motors were very much smaller. (By more than the 600kW/1500kW ratio).


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

I would have thought that if a standby set is running, there's no point in feeding off a station panel anyway, if the set trips off in that case wouldn't the site have no power in that context?

Quite correct, FreddyNurk; the problem being experienced in the instance cited was that for reasons I can no longer recall the set was tripping during full load tests, not while running as the only supply. Rationale of supplying from a station panel was to allow the fan to continue to run to cool out the engine if any more trips occurred; strategy was in my view of questionable value for the reasons already stated.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[GroovyGuy]

Hi Bill,
With a remote radiator there is no ductwork at all. That is the main reason for a remote rad. ie the rad sits outside usually on a platform. Obviously the heat radiated from the engine needs to be removed from the room, but that is usually handled by a few small fans. On a recent project these small fans (ie four x 5hp) were provided to remove heat radiated from a CAT G3612 900prm engine-generator set rated 2.6MW. All of these fans were inlet-blower type, rated 30,000cfm each. Exhaust air was via a ridge-vent (in the roof) as well as exhaust louvers (high on the walls). Each fan was ASD controlled with an integral TIC within the ASD. I think the scheme worked rather well, as I didn't hear of any complaints from OPS.
GG
ps As far as the motor size for the engine radiator fan, it appears to be the wild-west out there. There seems to be little consistency from one job to the next wrt fan motor size. If I recall correctly the rad fan motors for the 2.6MW project included two (2) x 30hp. On another project the rad fan motors were rated three (3) x 10hp for a 2.3MW gen-set. All of theses rads were sized and supplied by the engine OEM and/or the bldg packager.

"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)