Non-rail GEVO applications

[Allen Hazen]

(This might become the first post of a regular string if other people have things to report!)

The May 2015 issue of "Professional Mariner" (a magazine of water-borne transportation) has an article on New York City's three new sewage tankers. (Apparently a tanker fleet to ship … "product" is what the crews call it … from one sewage treatment plant to another is more economically feasible than upgrading plants.) Each is powered by a pair of General Electric "6L250" diesel engines: "250" (= cylinder bore in millimetres) is what GE calls the GEVO engine when they are selling it for non-locomotive applications), and these would be 6-cylinder inline engines: the engine which would power a new generation U23B/B23-7 analogue if only some railroad would get around to ordering a batch. Total horsepower is stated as 3500 and something, so these engines are rated somewhat lower than GEVO engines in locomotives.

[MEC407]

Interesting that they're rated so conservatively.

[mtuandrew]

I'd read that the 250 series is more directly based on the HDL than the GEVO - perhaps the horsepower limitation is partly due to the inferior engine design?

[Allen Hazen]

For the moment (it's part of the "current issue," so may go away soon) the "Professional Mariner" article is available on-line at the magazine's website:
http://www.professionalmariner.com/May- ... e-tankers/" onclick="window.open(this.href);return false;

The engines are described as IMO Tier II L250. (The GETS website currently talks about Tier III L250, with news about the imminent introduction of Tier IV.) The article says the combined horsepower is 3,652. I don't know why it's so low: GE website gives a minimum power rating for the L250 series -- I assume this is for the 6-cylinder version -- as something over 1500 KILOWATTS for one engine, suggesting that the NYC Sanitation department's new (2014 build) ships are rated at about 70% of what they ought to be.

The possibility of error in the article has occurred to me. But I don't know.

[EDM5970]

Not to get too far off topic, but NY City has an older 'product' tanker for sale. IIRC correctly from the online article a month or so ago, it is 300 odd feet long, was built in the '60s and has Cooper-Bessemer diesels. We all know that the FDL is a C-B design; looks like the City has some loyalty to C-B and/or GE.

[litz]

It's not uncommon for marine or generator (e.g., a "stationary" application) to be more conservatively rated ... it helps with longevity of the powerplant; removing one of these beasts for major maintenance is not trivial in the last.

These engines, unlike bigger marine diesels (the Wartsilas, for example) are not anywhere near as modular in their disassembly.

It's always interesting to see where these things end up, though ... one of the best (and least known) example is the Alcos that power NASA Crawler/Transporter.

[Allen Hazen]

(Still compulsively scratching the itch of "Why the low power rating?")

The first of these ships (the Red Hook -- they seem to be named for landmarks in New York City waters) entered service in early 2014, so we can assume a 2013 iteration of the GEVO/250 design.

A GE brochure on the L250 for marine applications (I found it at some marine engineering site: couldn't find it on the GETS website) gives a variety of power outputs for the 6L250: continuous or "maximum" at three different operating speeds (900, 1000 and 1050 rpm). The continuous rating at 900 rpm is 1498kW: 2,000 hp. The article says the combined power of the two diesels is 3,652 hp, so we've got 350 horsepower to account for. (Assuming the engines are run at 900 hp. Article doesn't say. Main propulsion is by two propellors, running at a maximum of 300rpm.) Propellors don't like to go around as fast as diesel engines, so the engines have to be geared (or, I suppose, run generators for electric final drive?), so
--First Question: if the power rating in the article is power to the propellors, is 8% or 9% a plausible loss in the transmission?
Another possibility is parasitic losses. Any guesses? (This would be less than the transmission loss in a diesel-electric locomotive, after all.)
The article doesn't say anything about auxiliary power, so the main engines may have to handle a lot besides the propellors. For manoeuvring, there are steerable water jets fore and aft. And there are lots of pumps for cargo handling.
The take-offs for these other purposes have got to be fairly complicated.
--Second Question: Are power losses because of this a plausible explanation?
There are some pretty engineering-savvy people who frequent these forums.
--Third Question: Can someone explain the conventions for rating marine engines in a way that would allow easy comparison with locomotive ratings?

(PS. Continuous rating at 1000rpm is 2232 hp. Continuous rating at 1050 is 2344 hp. I think the last of these may be equivalent to what GE rates the GEVO-12 at in locomotive applications. Given the reliability of the engine in very demanding railroad service, I think it might be reasonable to run it at one of these higher ratings as a marine engine… particularly since the ships involved operate only in the protected waters of New York city, and not on the stormy ocean.)

[v8interceptor]

As far as marine diesel ratings from my reading that they go by BHP ;in some cases converted to Kilowatts.
I do occasionally purchase "Professional Mariner" magazine; particularly the yearly "American Tug Review" and "American Ship review" special yearbook issues and the engine specifications published definitely show Brake Horse Power.
Is there a simple way to derive a locomotive's BHP rating from the North American RR industry type power ratings (I say that because I find that many of the European OEM Diesel locomotive builders list Gross engine output in their specifications) that GE and EMD use?