[blueprint2002]

Chevron Gas Turbine Tankers
A recent thread entitled simply “Gas Turbines” mentioned the fate of the half-dozen or so gas turbine ships built in Australia in the mid-seventies, which is the first I heard of the (mostly) untimely end of that boldly innovative experiment. (Unlike the Sealand and Seatrain GT container ships, whose history has been widely reported, and accessible to anyone who might be interested).
Also less known, as far as I am aware, is the history of the five gas turbine powered product tankers built for Chevron, again in the mid-seventies, and employed on the US West coast and Hawaii. About all I am sure of is that all five ships had their control systems upgraded during the mid-nineties, which means that they had already served for around 20 years without needing re-engining. This perhaps means that they were the only successful commercial gas turbine ships (apart from some ferries), and that they went on to give many more years of service.
Does anyone have personal knowledge of the ships, or know of any published record of their history/experience, such as a magazine article or a technical paper? Some points of particular interest include:
a) The fuel used (HFO would likely be the most economical) and whether experience showed this needed to be changed.
b) Average annual running hours of the gas turbines.
c) Average TBO for the GE main gas turbines. Being of the rugged industrial type, this should have been a long time. And which parts needed replacement more often than might have been expected.
d) Experience with the Ruston auxiliary gas turbines. As these were rather highly rated for the auxiliary power demand that one might expect of these ships (about 35000 DWT), low loading and hence high fuel consumption may have resulted.
Thanks in advance.

 

[Thors Twins]

I know of the Chevron GT tankers, never worked on them but did visit and a tour aboard one of them about 15yrs ago (Overseas Integrity):
a) They used diesel oil fuel their entire careers, uncertain if Chevron experimented with HFO or other fuel types
b) An average of 240 running days per year is fairly standard for opex budgeting, perhaps Chevron did this as well.
c) Average TBO for the GE main gas turbines > dont know. The one i toured had both the original main and auxiliary GT's. I dont expect either were 'virgin' except for perhaps, the main rotor and some other robust ancilliaries.

My take-aways from the tour:
1. everywhere you walked in the Engine Room, was on top of a fuel tank.
2. the Engine Room arrangement was not at all typical to that of a steam or motor engine room. The machinery spaces were compartmentalized mostly on a single deck. Imagine if you can, entering the fwd end of the stbd side machinery space, then walk aft past all the machienry. Enter the door to Steering Gear space (very small space), walk over to port then thru door, walk fwd thru port machinery space. Now, the Main GT was above the main machinery space deck and centerline in a modestly spaced and insulated compartment. The Aux GT was in a separate compartment (think it was on the main deck level) located port side.
3. CCR and ECR in same room, in the Accommodation, A-deck
4. There was no SW cooling for any of the machinery. The Funnel and Engine Casing block was essentially one big cooling tower for the Cooling FW.
5. The vessels did not have FW Generators, however the 2 vessels sold to Maritrans, had been retrofitted later on with flash evaps.
6. These vessels were all-electric. Think the main propulsion motor was AC type. The orig operating concept was to have the Aux GT online during port stays for cargo and ballast system operations, then switch over to Main GT for maneuvering and steaming between ports. On the vessel i toured, the Aux GT was not used but only the Main GT for everything. Don't think it was fuel efficient this way.
7. These vessels were an early double hull design.
8. IG came from a dedicated IG generator plant, not GT exhaust.
9. Cargo Pumps were all electric motor-driven, each had the motor on top of main deck.
10. Don't think Chevron ever traded these vessels outside US waters, only between dedicated load/discharge ports with all amenities and services regularly available (bunkers, FW, spares, stores, provisions, misc. services, etc).

Maritrans purchased 2 GT's in the 90's, refitted them for dedicated lightering service at Big Stone, Delaware. The suezmax crude carriers with draft restrictions, brought in west african crude, discharged approx 750k-1M bbls via STS to the GT's which in turn shuttled the oil to the terminals.

 

[blueprint2002]

chevron gt tankers

Many thanks, Thors Twins, for your very detailed and clear response. Sorry I didn't reply earlier: I'd almost given up looking as there had been no response for so long. I do appreciate the time and trouble you have taken.
I have experience of Naval gas turbines, and always remember how little maintenance work they needed, by contrast with the diesels, to say nothing of steam. So it's nice to know that at least one class of commercial GT ships was profitable to run; they'd have been re-engined or scrapped if not.

 

[Edub]

Hello:

I sailed on all five of these vessels (GT Washington, Oregon, Colorado, Louisiana & Arizona). They were delivered over a two year time period from Dec 75 to Dec 77 by FMC (now Gunderson) in Portland, Oregon. There were plans for a sixth (Nevada) but the order was canceled, despite the ship being at least partially constructed. The Oregon and Louisiana were dedicated to carrying crude, while the Arizona and Colorado were product carriers. The Washington could carry both.

The Main Gas Turbine (MGT) powered the entire ship under normal conditions. It was an 8.8MW GE Frame 3 model... not a marinated aeroderivative such as the LM2500. They burned diesel, and to the best of my knowledge there was never any experimentation with heavy fuel. It would have been impossible and the turbine needed to run on clean oil to keep the compressor turbine blades clean.

The Auxiliary Gas Turbine (AGT) was indeed a Ruston. It was located on the port side, one deck below the main deck. The joke about these units was that the control panel meters generally showed more start attempts than running hours. They were, in my mind, highly unreliable. We used them generally only when in port and we needed to shut the MGT down for maintenance, about once per month. Normally we kept the MGT on. There was a strange method where you could, in an emergency, run the propulsion motor at a reduced speed on the AGT in the event the MGT was down at sea. I saw it done often, mostly as a test.

When I first started sailing on the vessels in the early 90's, the weak link was the original GE control systems for the MGT. They were getting old, weren't very well "marinized" and were the source of too many incidents of losing the main engine. Cuing a radio near the units would trip the MGT. Around 92 through 94 the control systems were upgraded to a solid-state PLC-type system. Most times trouble-shooting the MGT meant connecting a laptop to the controller. Lots of on the job learning.

The MGT had a very interesting control methodology. The MGT was twin-shaft, with the power end turning at a constant speed to produce 4160V at 60hz. The propulsion motor was a large, synchronous motor that ran at a constant speed of 100rpm. Speed (and direction) of the vessel was controlled by a CPP - controllable pitch propeller. When the prop motor was started, the lights would briefly dim, almost go out completely, then slowly come back on as the main engine responded to increased load.

The vessels also had a CAT diesel generator that acted as an emergency generator, but since it was located on the weather deck, was technically insufficient in that role in the eyes of the USCG. So there were two large 24v battery banks that powered emergency lighting and a few other essentials.

The GE frame 3 turbines were quite robust. As I recall, the "weak" area of the turbine unit itself was likely the compressor turbine blades which bore the brunt of the combustion gas. Every PO period some part of the turbine case would be cracked open for inspection.

Regarding profitability, it's hard to say. The vessels, particularly the Arizona, had fixed runs. Some acted as a pipeline connecting the two Chevron refineries in CA (Richmond and El Segundo). I think Chevron was willing to pay a price to keep a few tankers they could put their hand to immediately if necessary.

The strangest thing about these ships was the "PCC" - Port Control Center. It was basically a combination Engine Control Room and Cargo Control Room. In port, the engineer and mate on watch sat across a desk from each other, looking at two control panels that were behind the other person. This was located on A deck.

The ships weren't regularly traded outside the US, but I've been on one them in Canada, Mexico (both coasts), through the Panama Canal as well as Alaska and Hawaii.

Yes, the main engines required far less maintenance than a diesel, but I wouldn't say the vessels were low maintenance by any means. Plus, the culture on Chevron's vessels was that the engineers handled all on-deck repairs and maintenance (there were no pumpmen), so we were busy 12hrs/day.

Hope this helps...

 

[blueprint2002]

A long long wait, but it was worth it. Thank you Edub, for taking the time and trouble to write out that excellent description of your experiences and impressions of the ships. I couldn’t have asked for better. Together with the earlier reply from Thors Twins, I now have what must surely be the best, most authentic response to my appeal for information. Your contribution is deeply appreciated!